[{"issue":"4","type":"journal_article","intvolume":" 545","year":"2026","PlanS_conform":"1","status":"public","oa":1,"date_published":"2026-02-01T00:00:00Z","date_created":"2026-01-25T23:01:39Z","publication":"Monthly Notices of the Royal Astronomical Society","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication_status":"published","arxiv":1,"fulldoi":"https://doi.org/10.1093/mnras/staf2131","quality_controlled":"1","file":[{"creator":"dernst","file_size":5600366,"success":1,"file_id":"21220","content_type":"application/pdf","checksum":"52ba7d7b5b80af0c50f57e4c2acc3930","relation":"main_file","date_updated":"2026-02-12T12:44:33Z","file_name":"2026_MonthNoticesRAS_Chang.pdf","access_level":"open_access","date_created":"2026-02-12T12:44:33Z"}],"OA_type":"gold","article_type":"original","volume":545,"license":"https://creativecommons.org/licenses/by/4.0/","OA_place":"publisher","day":"01","author":[{"last_name":"Chang","full_name":"Chang, Seok Jun","first_name":"Seok Jun"},{"last_name":"Gronke","first_name":"Max","full_name":"Gronke, Max"},{"full_name":"Matthee, Jorryt J","first_name":"Jorryt J","last_name":"Matthee","orcid":"0000-0003-2871-127X","id":"7439a258-f3c0-11ec-9501-9df22fe06720"},{"last_name":"Mason","full_name":"Mason, Charlotte","first_name":"Charlotte"}],"acknowledgement":"The authorsthank the anonymousreferee for constructive comments, which improved the clarity of this paper. SJC acknowledges support from the ERC synergy grant 101166930 – RECAP. MG thanks the Max Planck Society for support through the Max Planck Research Group, and the European Union forsupport through ERC-2024-STG 101165038 (ReMMU). JM acknowledges funding by the European Union (ERC, AGENTS, 101076224). CAM acknowledges support\r\nby the European Union ERC grant RISES (101163035), Carlsberg Foundation (CF22-1322), and VILLUM FONDEN (37459). Computations were performed on HPC systems Freya and Orion at the Max Planck Computing and Data Facility.","external_id":{"arxiv":["2508.08768"]},"_id":"21038","publisher":"Oxford University Press","date_updated":"2026-02-12T12:56:33Z","ddc":["520"],"title":"Impact of resonance, Raman, and Thomson scattering on hydrogen line formation in Little Red Dots","citation":{"ieee":"S. J. Chang, M. Gronke, J. J. Matthee, and C. Mason, “Impact of resonance, Raman, and Thomson scattering on hydrogen line formation in Little Red Dots,” Monthly Notices of the Royal Astronomical Society, vol. 545, no. 4. Oxford University Press, 2026.","ista":"Chang SJ, Gronke M, Matthee JJ, Mason C. 2026. Impact of resonance, Raman, and Thomson scattering on hydrogen line formation in Little Red Dots. Monthly Notices of the Royal Astronomical Society. 545(4), staf2131.","short":"S.J. Chang, M. Gronke, J.J. Matthee, C. Mason, Monthly Notices of the Royal Astronomical Society 545 (2026).","chicago":"Chang, Seok Jun, Max Gronke, Jorryt J Matthee, and Charlotte Mason. “Impact of Resonance, Raman, and Thomson Scattering on Hydrogen Line Formation in Little Red Dots.” Monthly Notices of the Royal Astronomical Society. Oxford University Press, 2026. https://doi.org/10.1093/mnras/staf2131.","ama":"Chang SJ, Gronke M, Matthee JJ, Mason C. Impact of resonance, Raman, and Thomson scattering on hydrogen line formation in Little Red Dots. Monthly Notices of the Royal Astronomical Society. 2026;545(4). doi:10.1093/mnras/staf2131","mla":"Chang, Seok Jun, et al. “Impact of Resonance, Raman, and Thomson Scattering on Hydrogen Line Formation in Little Red Dots.” Monthly Notices of the Royal Astronomical Society, vol. 545, no. 4, staf2131, Oxford University Press, 2026, doi:10.1093/mnras/staf2131.","apa":"Chang, S. J., Gronke, M., Matthee, J. J., & Mason, C. (2026). Impact of resonance, Raman, and Thomson scattering on hydrogen line formation in Little Red Dots. Monthly Notices of the Royal Astronomical Society. Oxford University Press. https://doi.org/10.1093/mnras/staf2131"},"doi":"10.1093/mnras/staf2131","file_date_updated":"2026-02-12T12:44:33Z","publication_identifier":{"eissn":["1365-2966"],"issn":["0035-8711"]},"abstract":[{"lang":"eng","text":"Little Red Dots (LRDs) are compact sources at z > 5 discovered through James Webb Space Telescope spectroscopy. Their spectra exhibit broad Balmer emission lines (>~1000 km s^−1), alongside absorption features and a pronounced Balmer break – evidence for a dense, neutral hydrogen medium, in which the n = 2 state is significantly populated. When interpreted as arising\r\nfrom active galactic nucleus broad-line regions, inferred black hole masses from local scaling relations exceed expectations given their stellar masses, challenging models of early black hole–galaxy co-evolution. However, radiative transfer effects in dense media may also impact the formation of hydrogen emission lines. We model three scattering processes shaping hydrogen\r\nline profiles: resonance scattering by hydrogen in the n = 2 state, Raman scattering of ultraviolet (UV) radiation by ground-state hydrogen, and Thomson scattering by free electrons. Using 3D Monte Carlo radiative transfer simulations, we examine their imprint on line shapes and ratios. Resonance scattering produces strong deviations from Case B flux ratios, clear differences\r\nbetween Hα and Hβ, and encodes gas kinematics in line profiles but cannot broaden Hβ due to conversion to Paα. While Raman scattering can yield broad wings, scattering of the UV continuum is disfavoured given the absence of strong full width at half-maximum variations across transitions. Raman scattering of higher Lyman-series emission can produce Hα/Hβ wing\r\nwidth ratios of >~1.28, agreeing with observations. Thomson scattering can reproduce the observed >~ 1000 km s^−1 wings under plausible conditions – e.g. Te ∼ 10^4 K and Ne ∼ 10^24 cm^−2 – and lead to black hole mass overestimates by factors 10. Our results provide a framework for interpreting hydrogen lines in LRDs and similar systems."}],"DOAJ_listed":"1","article_processing_charge":"Yes","has_accepted_license":"1","department":[{"_id":"JoMa"}],"project":[{"grant_number":"101076224","_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization"}],"article_number":"staf2131","oa_version":"Published Version","scopus_import":"1","language":[{"iso":"eng"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","month":"02"},{"tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication":"Astronomy & Astrophysics","fulldoi":"https://doi.org/10.1051/0004-6361/202556597","arxiv":1,"publication_status":"published","date_published":"2026-02-01T00:00:00Z","oa":1,"date_created":"2026-02-22T23:01:35Z","type":"journal_article","PlanS_conform":"1","year":"2026","status":"public","intvolume":" 706","day":"01","author":[{"first_name":"Gauri","full_name":"Kotiwale, Gauri","last_name":"Kotiwale","id":"1438afc8-1ff6-11ee-9fa6-cd4a75d66875"},{"orcid":"0000-0003-2871-127X","id":"7439a258-f3c0-11ec-9501-9df22fe06720","last_name":"Matthee","full_name":"Matthee, Jorryt J","first_name":"Jorryt J"},{"first_name":"Daichi","full_name":"Kashino, Daichi","last_name":"Kashino"},{"last_name":"Vijayan","first_name":"Aswin P.","full_name":"Vijayan, Aswin P."},{"full_name":"Torralba Torregrosa, Alberto","first_name":"Alberto","id":"018f0249-0e87-11f0-b167-cbce08fbd541","last_name":"Torralba Torregrosa","orcid":"0000-0001-5586-6950"},{"id":"2d002343-372f-11ef-98ec-a164d20427cb","last_name":"Di Cesare","full_name":"Di Cesare, Claudia","first_name":"Claudia"},{"full_name":"Iani, Edoardo","first_name":"Edoardo","last_name":"Iani","id":"4053390a-6b68-11ef-9828-a3b8adef8d0a","orcid":"0000-0001-8386-3546"},{"last_name":"Bordoloi","first_name":"Rongmon","full_name":"Bordoloi, Rongmon"},{"first_name":"Joel","full_name":"Leja, Joel","last_name":"Leja"},{"first_name":"Michael V.","full_name":"Maseda, Michael V.","last_name":"Maseda"},{"full_name":"Tacchella, Sandro","first_name":"Sandro","last_name":"Tacchella"},{"full_name":"Shivaei, Irene","first_name":"Irene","last_name":"Shivaei"},{"last_name":"Heintz","first_name":"Kasper E.","full_name":"Heintz, Kasper E."},{"last_name":"Danhaive","first_name":"A. Lola","full_name":"Danhaive, A. Lola"},{"id":"edaf889c-c7cd-11ef-ab1b-bb28c431bd29","last_name":"Mascia","first_name":"Sara","full_name":"Mascia, Sara"},{"last_name":"Kramarenko","id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4","orcid":"0000-0001-5346-6048","full_name":"Kramarenko, Ivan","first_name":"Ivan"},{"full_name":"Navarrete, Benjamín","first_name":"Benjamín","last_name":"Navarrete","id":"aa14a535-50c9-11ef-b52e-e0c373d10148"},{"last_name":"Mackenzie","first_name":"Ruari","full_name":"Mackenzie, Ruari"},{"last_name":"Naidu","first_name":"Rohan P.","full_name":"Naidu, Rohan P."},{"first_name":"David","full_name":"Sobral, David","last_name":"Sobral"}],"OA_place":"publisher","volume":706,"file":[{"success":1,"file_id":"21355","content_type":"application/pdf","creator":"dernst","file_size":6531719,"file_name":"2026_AstronomyAstrophysics_Kotiwale.pdf","date_created":"2026-02-24T07:46:47Z","access_level":"open_access","date_updated":"2026-02-24T07:46:47Z","relation":"main_file","checksum":"6f5849d29ad43bee32f90152f6fc0294"}],"quality_controlled":"1","article_type":"original","OA_type":"diamond","department":[{"_id":"JoMa"},{"_id":"GradSch"}],"has_accepted_license":"1","corr_author":"1","abstract":[{"lang":"eng","text":"We aim to characterise the mass-metallicity relation (MZR) and the 3D correlation between the stellar mass, metallicity, and star formation rate (SFR) known as the fundamental metallicity relation (FMR) for galaxies at 5 < z < 7. Using ∼800 [O III] selected galaxies from deep NIRCam grism surveys, we present our stacked measurements of direct-Te metallicities, which we used to test recent strong-line metallicity calibrations. Our measured direct-Te metallicities (0.1–0.2 Z⊙ for M★ ≈ 5 × 107 − 9 M⊙, respectively) match recent JWST/NIRSpec-based results. However, there are significant inconsistencies between observations and hydrodynamical simulations. We observe a flatter MZR slope than the SPHINX20 and FLARES simulations, which cannot be attributed to selection effects. With simple models, we show that the effect of an [O III] flux-limited sample on the observed shape of the MZR is strongly dependent on the FMR. If the FMR is similar to the one in the local Universe, the intrinsic high-redshift MZR should be even flatter than is observed. In turn, a 3D relation where SFR correlates positively with metallicity at fixed mass would imply an intrinsically steeper MZR. Our measurements indicate that metallicity variations at fixed mass show little dependence on the SFR, suggesting a flat intrinsic MZR. This could indicate that the low-mass galaxies at these redshifts are out of equilibrium and that metal enrichment occurs rapidly in low-mass galaxies. However, being limited by our stacking analysis, we are yet to probe the scatter in the MZR and its dependence on SFR. Large carefully selected samples of galaxies with robust metallicity measurements can put tight constraints on the high-redshift FMR and help us to understand the interplay between gas flows, star formation, and feedback in early galaxies."}],"publication_identifier":{"eissn":["1432-0746"],"issn":["0004-6361"]},"doi":"10.1051/0004-6361/202556597","file_date_updated":"2026-02-24T07:46:47Z","citation":{"chicago":"Kotiwale, Gauri, Jorryt J Matthee, Daichi Kashino, Aswin P. Vijayan, Alberto Torralba Torregrosa, Claudia Di Cesare, Edoardo Iani, et al. “Rapid, out-of-Equilibrium Metal Enrichment Indicated by a Flat Mass-Metallicity Relation at z ∼ 6 from NIRCam Grism Spectroscopy.” Astronomy & Astrophysics. EDP Sciences, 2026. https://doi.org/10.1051/0004-6361/202556597.","short":"G. Kotiwale, J.J. Matthee, D. Kashino, A.P. Vijayan, A. Torralba Torregrosa, C. Di Cesare, E. Iani, R. Bordoloi, J. Leja, M.V. Maseda, S. Tacchella, I. Shivaei, K.E. Heintz, A.L. Danhaive, S. Mascia, I. Kramarenko, B. Navarrete, R. Mackenzie, R.P. Naidu, D. Sobral, Astronomy & Astrophysics 706 (2026).","ama":"Kotiwale G, Matthee JJ, Kashino D, et al. Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy. Astronomy & Astrophysics. 2026;706. doi:10.1051/0004-6361/202556597","ieee":"G. Kotiwale et al., “Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy,” Astronomy & Astrophysics, vol. 706. EDP Sciences, 2026.","ista":"Kotiwale G, Matthee JJ, Kashino D, Vijayan AP, Torralba Torregrosa A, Di Cesare C, Iani E, Bordoloi R, Leja J, Maseda MV, Tacchella S, Shivaei I, Heintz KE, Danhaive AL, Mascia S, Kramarenko I, Navarrete B, Mackenzie R, Naidu RP, Sobral D. 2026. Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy. Astronomy & Astrophysics. 706, A165.","mla":"Kotiwale, Gauri, et al. “Rapid, out-of-Equilibrium Metal Enrichment Indicated by a Flat Mass-Metallicity Relation at z ∼ 6 from NIRCam Grism Spectroscopy.” Astronomy & Astrophysics, vol. 706, A165, EDP Sciences, 2026, doi:10.1051/0004-6361/202556597.","apa":"Kotiwale, G., Matthee, J. J., Kashino, D., Vijayan, A. P., Torralba Torregrosa, A., Di Cesare, C., … Sobral, D. (2026). Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy. Astronomy & Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202556597"},"DOAJ_listed":"1","article_processing_charge":"No","title":"Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy","external_id":{"arxiv":["2510.19959"]},"acknowledgement":"We thank the anonymous referee for the insightful comments that helped improving this paper. This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Associations of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations were taken under programmes # 1243, # 1933 and # 3516. Funded by the European Union (ERC, AGENTS, 101076224). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. GK acknowledges support from the Foundation MERAC. APV acknowledge support from the Sussex Astronomy Centre STFC Consolidated Grant (ST/X001040/1).","ddc":["520"],"date_updated":"2026-02-24T07:49:42Z","publisher":"EDP Sciences","_id":"21341","scopus_import":"1","month":"02","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","language":[{"iso":"eng"}],"oa_version":"Published Version","article_number":"A165","project":[{"name":"Young galaxies as tracers and agents of cosmic reionization","_id":"bd9b2118-d553-11ed-ba76-db24564edfea","grant_number":"101076224"}]},{"volume":9,"article_type":"original","OA_type":"diamond","quality_controlled":"1","author":[{"first_name":"Rohan P.","full_name":"Naidu, Rohan P.","last_name":"Naidu"},{"last_name":"Oesch","first_name":"Pascal A.","full_name":"Oesch, Pascal A."},{"first_name":"Gabriel","full_name":"Brammer, Gabriel","last_name":"Brammer"},{"full_name":"Weibel, Andrea","first_name":"Andrea","last_name":"Weibel"},{"last_name":"Li","full_name":"Li, Yijia","first_name":"Yijia"},{"full_name":"Matthee, Jorryt J","first_name":"Jorryt J","orcid":"0000-0003-2871-127X","id":"7439a258-f3c0-11ec-9501-9df22fe06720","last_name":"Matthee"},{"first_name":"John","full_name":"Chisholm, John","last_name":"Chisholm"},{"last_name":"Pollock","first_name":"Clara L.","full_name":"Pollock, Clara L."},{"last_name":"Heintz","full_name":"Heintz, Kasper E.","first_name":"Kasper E."},{"first_name":"Benjamin D.","full_name":"Johnson, Benjamin D.","last_name":"Johnson"},{"first_name":"Xuejian","full_name":"Shen, Xuejian","last_name":"Shen"},{"first_name":"Raphael E.","full_name":"Hviding, Raphael E.","last_name":"Hviding"},{"last_name":"Leja","first_name":"Joel","full_name":"Leja, Joel"},{"full_name":"Tacchella, Sandro","first_name":"Sandro","last_name":"Tacchella"},{"last_name":"Ganguly","full_name":"Ganguly, Arpita","first_name":"Arpita"},{"first_name":"Callum","full_name":"Witten, Callum","last_name":"Witten"},{"last_name":"Atek","first_name":"Hakim","full_name":"Atek, Hakim"},{"last_name":"Belli","full_name":"Belli, Sirio","first_name":"Sirio"},{"full_name":"Bose, Sownak","first_name":"Sownak","last_name":"Bose"},{"last_name":"Bouwens","first_name":"Rychard","full_name":"Bouwens, Rychard"},{"last_name":"Dayal","full_name":"Dayal, Pratika","first_name":"Pratika"},{"full_name":"Decarli, Roberto","first_name":"Roberto","last_name":"Decarli"},{"first_name":"Anna","full_name":"De Graaff, Anna","last_name":"De Graaff"},{"last_name":"Fudamoto","full_name":"Fudamoto, Yoshinobu","first_name":"Yoshinobu"},{"last_name":"Giovinazzo","full_name":"Giovinazzo, Emma","first_name":"Emma"},{"last_name":"Greene","first_name":"Jenny E.","full_name":"Greene, Jenny E."},{"last_name":"Illingworth","full_name":"Illingworth, Garth","first_name":"Garth"},{"last_name":"Inoue","full_name":"Inoue, Akio K.","first_name":"Akio K."},{"last_name":"Kane","first_name":"Sarah G.","full_name":"Kane, Sarah G."},{"first_name":"Ivo","full_name":"Labbe, Ivo","last_name":"Labbe"},{"last_name":"Leonova","full_name":"Leonova, Ecaterina","first_name":"Ecaterina"},{"full_name":"Marques-Chaves, Rui","first_name":"Rui","last_name":"Marques-Chaves"},{"full_name":"Meyer, Romain A.","first_name":"Romain A.","last_name":"Meyer"},{"full_name":"Nelson, Erica J.","first_name":"Erica J.","last_name":"Nelson"},{"first_name":"Guido","full_name":"Roberts-Borsani, Guido","last_name":"Roberts-Borsani"},{"last_name":"Schaerer","full_name":"Schaerer, Daniel","first_name":"Daniel"},{"last_name":"Simcoe","first_name":"Robert A.","full_name":"Simcoe, Robert A."},{"full_name":"Stefanon, Mauro","first_name":"Mauro","last_name":"Stefanon"},{"last_name":"Sugahara","first_name":"Yuma","full_name":"Sugahara, Yuma"},{"first_name":"Sune","full_name":"Toft, Sune","last_name":"Toft"},{"full_name":"Van Der Wel, Arjen","first_name":"Arjen","last_name":"Van Der Wel"},{"last_name":"Van Dokkum","first_name":"Pieter","full_name":"Van Dokkum, Pieter"},{"last_name":"Walter","full_name":"Walter, Fabian","first_name":"Fabian"},{"full_name":"Watson, Darach","first_name":"Darach","last_name":"Watson"},{"last_name":"Weaver","full_name":"Weaver, John R.","first_name":"John R."},{"last_name":"Whitaker","first_name":"Katherine E.","full_name":"Whitaker, Katherine E."}],"day":"30","OA_place":"publisher","date_created":"2026-02-22T23:01:35Z","date_published":"2026-01-30T00:00:00Z","oa":1,"status":"public","PlanS_conform":"1","year":"2026","intvolume":" 9","type":"journal_article","fulldoi":"https://doi.org/10.33232/001c.156033","arxiv":1,"publication_status":"published","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication":"The Open Journal of Astrophysics","project":[{"_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224"}],"language":[{"iso":"eng"}],"month":"01","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","scopus_import":"1","main_file_link":[{"url":"https://doi.org/10.33232/001c.156033","open_access":"1"}],"oa_version":"Published Version","title":"A cosmic miracle: A remarkably luminous galaxy at zspec = 14.44 confirmed with JWST","date_updated":"2026-06-16T10:47:41Z","ddc":["520"],"publisher":"Maynooth Academic Publishing","_id":"21342","external_id":{"arxiv":["2505.11263"]},"acknowledgement":"We thank the two anonymous referees for their insightful comments that have strengthened this work. “Mirage or Miracle” is but the latest link in a long chain of surveys that have built COSMOS into a premier extragalactic legacy field. We are thankful to all the teams who have contributed to this legacy, particularly those mentioned in §3 for leading recent JWST programs whose imaging\r\nwe have incorporated in our analysis. We are grateful to Vasily Belokurov for help in compiling the Milky Way reference sample featured in Fig 8. We thank Danielle Berg for sharing a highly complete, highly decimalized NUV vacuum line list. We are grateful to our program’s NIRSpec reviewer, Dan Coe, and program coordinator, Allison Vick, for valuable input on our MSA design. We acknowledge illuminating conversations with Risa Wechsler and Chao-Lin Kuo about early reionization. RPN thanks Neil Pappalardo and Jane Pappalardo for their generous support of the MIT Pappalardo Fellowships in Physics, and for their enthusiasm and encouragement for seeking galaxies at the highest redshifts. RPN acknowledges funding from JWST program GO5224. Support for this work was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51515.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. This work has received funding from the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number MB22.00072, as well as from the Swiss National Science Foundation (SNSF) through project grant 200020 207349. Funded by the European Union (ERC, AGENTS, 101076224 and HEAVYMETAL, 101071865). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of\r\nthe European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant DNRF140. This work has also been supported by JSPS KAKENHI Grant Number 23H00131. HA acknowledges support from CNES, focused on the JWST mission, and the Programme National Cosmology and Galaxies (PNCG)\r\nof CNRS/INSU with INP and IN2P3, co-funded by CEA and CNES. HA is supported by the French National Research Agency (ANR) under the project FIRSTGAL, grant number ANR-24-CE31-0838. SB is supported by the UK Research and Innovation (UKRI) Future Leaders Fellowship [grant number MR/V023381/1]. R.D. acknowledges support from the INAF GO 2022\r\ngrant “The birth of the giants: JWST sheds light on the build-up of quasars at cosmic dawn” and by the PRIN MUR “2022935STW”, RFF M4.C2.1.1, CUP J53D23001570006 and C53D23000950006. Computations supporting this paper were run on MIT’s Engaging cluster. This publication made use of the NASA Astrophysical Data System for bibliographic information. Some of the data products presented herein were retrieved from the Dawn JWST Archive (DJA). DJA is an initiative of the Cosmic Dawn Center (DAWN), which is funded by the Danish National Research Foundation under grant DNRF140. Software used in developing this work includes: matplotlib (Hunter 2007), jupyter (Kluyver et al. 2016), IPython (P´erez & Granger 2007), numpy (Oliphant 2015), scipy (Virtanen et al. 2020), TOPCAT (Taylor 2005), and Astropy (Astropy Collaboration et al. 2013).This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space\r\nTelescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with program # 5224.","department":[{"_id":"JoMa"}],"has_accepted_license":"1","article_processing_charge":"No","abstract":[{"text":"JWST has revealed a stunning population of bright galaxies at surprisingly early epochs, z > 10,\r\nwhere few such sources were expected. Here we present the most distant example of this class yet – MoM-z14, a luminous (MUV = −20.2) source in the COSMOS legacy field at zspec = 14.44+0.02−0.02 that expands the observational frontier to a mere 280 million years after the Big Bang. The redshift is confirmed with NIRSpec/prism spectroscopy through a sharp Lyman-α break and ≈ 3σ detections of five rest-UV emission lines. The number density of bright zspec ≈ 14 − 15 sources implied by our “Mirage or Miracle” survey spanning ≈ 350 arcmin2 is > 100× larger (182+329 −105×) than pre-JWST consensus models. The high EWs of UV lines (≈15−35˚A) signal a rising star-formation history, with a ≈10× increase in the last 5 Myr (SFR5Myr/SFR50Myr = 9.9 +3.0 −5.8). The source is extremely compact (circularized re = 74+15\r\n−12 pc), and yet elongated (b/a = 0.25+0.11−0.06), suggesting an AGN is not the dominant source of UV light. The steep UV slope (β = −2.5 +0.2 −0.2) implies negligible dust attenuation\r\nand a young stellar population. The absence of a strong damping wing provides tentative evidence that the immediate surroundings of MoM-z14 may be partially ionized at a redshift where virtually every reionization model predicts a ≈ 100% neutral fraction. The nitrogen emission and highly supersolar [N/C]> 1 hint at an abundance pattern similar to local globular clusters that may have once hosted luminous supermassive stars. Since this abundance pattern is also common among the most ancient stars born in the Milky Way, we may be directly witnessing the formation of such stars in dense clusters, connecting galaxy evolution across the entire sweep of cosmic time. ","lang":"eng"}],"publication_identifier":{"eissn":["2565-6120"]},"doi":"10.33232/001c.156033","citation":{"ama":"Naidu RP, Oesch PA, Brammer G, et al. A cosmic miracle: A remarkably luminous galaxy at zspec = 14.44 confirmed with JWST. The Open Journal of Astrophysics. 2026;9. doi:10.33232/001c.156033","chicago":"Naidu, Rohan P., Pascal A. Oesch, Gabriel Brammer, Andrea Weibel, Yijia Li, Jorryt J Matthee, John Chisholm, et al. “A Cosmic Miracle: A Remarkably Luminous Galaxy at Zspec = 14.44 Confirmed with JWST.” The Open Journal of Astrophysics. Maynooth Academic Publishing, 2026. https://doi.org/10.33232/001c.156033.","short":"R.P. Naidu, P.A. Oesch, G. Brammer, A. Weibel, Y. Li, J.J. Matthee, J. Chisholm, C.L. Pollock, K.E. Heintz, B.D. Johnson, X. Shen, R.E. Hviding, J. Leja, S. Tacchella, A. Ganguly, C. Witten, H. Atek, S. Belli, S. Bose, R. Bouwens, P. Dayal, R. Decarli, A. De Graaff, Y. Fudamoto, E. Giovinazzo, J.E. Greene, G. Illingworth, A.K. Inoue, S.G. Kane, I. Labbe, E. Leonova, R. Marques-Chaves, R.A. Meyer, E.J. Nelson, G. Roberts-Borsani, D. Schaerer, R.A. Simcoe, M. Stefanon, Y. Sugahara, S. Toft, A. Van Der Wel, P. Van Dokkum, F. Walter, D. Watson, J.R. Weaver, K.E. Whitaker, The Open Journal of Astrophysics 9 (2026).","ista":"Naidu RP, Oesch PA, Brammer G, Weibel A, Li Y, Matthee JJ, Chisholm J, Pollock CL, Heintz KE, Johnson BD, Shen X, Hviding RE, Leja J, Tacchella S, Ganguly A, Witten C, Atek H, Belli S, Bose S, Bouwens R, Dayal P, Decarli R, De Graaff A, Fudamoto Y, Giovinazzo E, Greene JE, Illingworth G, Inoue AK, Kane SG, Labbe I, Leonova E, Marques-Chaves R, Meyer RA, Nelson EJ, Roberts-Borsani G, Schaerer D, Simcoe RA, Stefanon M, Sugahara Y, Toft S, Van Der Wel A, Van Dokkum P, Walter F, Watson D, Weaver JR, Whitaker KE. 2026. A cosmic miracle: A remarkably luminous galaxy at zspec = 14.44 confirmed with JWST. The Open Journal of Astrophysics. 9.","ieee":"R. P. Naidu et al., “A cosmic miracle: A remarkably luminous galaxy at zspec = 14.44 confirmed with JWST,” The Open Journal of Astrophysics, vol. 9. Maynooth Academic Publishing, 2026.","apa":"Naidu, R. P., Oesch, P. A., Brammer, G., Weibel, A., Li, Y., Matthee, J. J., … Whitaker, K. E. (2026). A cosmic miracle: A remarkably luminous galaxy at zspec = 14.44 confirmed with JWST. The Open Journal of Astrophysics. Maynooth Academic Publishing. https://doi.org/10.33232/001c.156033","mla":"Naidu, Rohan P., et al. “A Cosmic Miracle: A Remarkably Luminous Galaxy at Zspec = 14.44 Confirmed with JWST.” The Open Journal of Astrophysics, vol. 9, Maynooth Academic Publishing, 2026, doi:10.33232/001c.156033."}},{"fulldoi":"https://doi.org/10.1126/science.adz8603","publication_status":"published","publication":"Science","date_created":"2026-03-01T23:01:39Z","date_published":"2026-02-19T00:00:00Z","year":"2026","status":"public","intvolume":" 391","type":"journal_article","issue":"6787","author":[{"full_name":"Matthee, Jorryt J","first_name":"Jorryt J","orcid":"0000-0003-2871-127X","id":"7439a258-f3c0-11ec-9501-9df22fe06720","last_name":"Matthee"}],"day":"19","page":"767-768","volume":391,"pmid":1,"OA_type":"closed access","article_type":"comment","quality_controlled":"1","corr_author":"1","department":[{"_id":"JoMa"}],"article_processing_charge":"No","publication_identifier":{"eissn":["1095-9203"]},"abstract":[{"lang":"eng","text":"There may be a newly identified early phase of supermassive black hole growth"}],"citation":{"ama":"Matthee JJ. Black holes disguised as little red dots. Science. 2026;391(6787):767-768. doi:10.1126/science.adz8603","short":"J.J. Matthee, Science 391 (2026) 767–768.","chicago":"Matthee, Jorryt J. “Black Holes Disguised as Little Red Dots.” Science. AAAS, 2026. https://doi.org/10.1126/science.adz8603.","ista":"Matthee JJ. 2026. Black holes disguised as little red dots. Science. 391(6787), 767–768.","ieee":"J. J. Matthee, “Black holes disguised as little red dots,” Science, vol. 391, no. 6787. AAAS, pp. 767–768, 2026.","apa":"Matthee, J. J. (2026). Black holes disguised as little red dots. Science. AAAS. https://doi.org/10.1126/science.adz8603","mla":"Matthee, Jorryt J. “Black Holes Disguised as Little Red Dots.” Science, vol. 391, no. 6787, AAAS, 2026, pp. 767–68, doi:10.1126/science.adz8603."},"doi":"10.1126/science.adz8603","title":"Black holes disguised as little red dots","date_updated":"2026-03-02T09:15:45Z","publisher":"AAAS","_id":"21371","external_id":{"pmid":["41712710"]},"acknowledgement":"The author acknowledges the support from the European Union (European Research Council, AGENTS, 101076224).","month":"02","language":[{"iso":"eng"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","scopus_import":"1","oa_version":"None","project":[{"grant_number":"101076224","_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization"}]},{"article_number":"A75","project":[{"grant_number":"101076224","name":"Young galaxies as tracers and agents of cosmic reionization","_id":"bd9b2118-d553-11ed-ba76-db24564edfea"}],"scopus_import":"1","month":"03","language":[{"iso":"eng"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","oa_version":"Published Version","title":"The warm outer layer of a little red dot as the source of [Fe ii] and collisional Balmer lines with scattering wings","acknowledgement":"We thank the scientific referee for useful and constructive comments. We thank Ylva Götberg and Zoltan Haiman for insightful discussions about the physics of gaseous envelopes and accretion into black holes. Funded by the European Union (ERC, AGENTS, 101076224). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. This work is based in part on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with program #5664. This work has received funding from the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number MB22.00072, as well as from the Swiss National Science Foundation (SNSF) through project grant 200020_207349.","external_id":{"arxiv":["2510.00103"]},"_id":"21451","publisher":"EDP Sciences","date_updated":"2026-03-16T10:59:16Z","ddc":["520"],"has_accepted_license":"1","department":[{"_id":"JoMa"}],"corr_author":"1","file_date_updated":"2026-03-16T10:57:49Z","citation":{"chicago":"Torralba Torregrosa, Alberto, Jorryt J Matthee, Gabriele Pezzulli, Rohan P. Naidu, Yuzo Ishikawa, Gabriel B. Brammer, Seok Jun Chang, et al. “The Warm Outer Layer of a Little Red Dot as the Source of [Fe Ii] and Collisional Balmer Lines with Scattering Wings.” Astronomy & Astrophysics. EDP Sciences, 2026. https://doi.org/10.1051/0004-6361/202557537.","short":"A. Torralba Torregrosa, J.J. Matthee, G. Pezzulli, R.P. Naidu, Y. Ishikawa, G.B. Brammer, S.J. Chang, J. Chisholm, A. De Graaff, F. D’Eugenio, C. Di Cesare, A.C. Eilers, J.E. Greene, M. Gronke, E. Iani, V. Kokorev, G. Kotiwale, I. Kramarenko, Y. Ma, S. Mascia, B. Navarrete, E. Nelson, P. Oesch, R.A. Simcoe, S. Wuyts, Astronomy & Astrophysics 707 (2026).","ama":"Torralba Torregrosa A, Matthee JJ, Pezzulli G, et al. The warm outer layer of a little red dot as the source of [Fe ii] and collisional Balmer lines with scattering wings. Astronomy & Astrophysics. 2026;707. doi:10.1051/0004-6361/202557537","ieee":"A. Torralba Torregrosa et al., “The warm outer layer of a little red dot as the source of [Fe ii] and collisional Balmer lines with scattering wings,” Astronomy & Astrophysics, vol. 707. EDP Sciences, 2026.","ista":"Torralba Torregrosa A, Matthee JJ, Pezzulli G, Naidu RP, Ishikawa Y, Brammer GB, Chang SJ, Chisholm J, De Graaff A, D’Eugenio F, Di Cesare C, Eilers AC, Greene JE, Gronke M, Iani E, Kokorev V, Kotiwale G, Kramarenko I, Ma Y, Mascia S, Navarrete B, Nelson E, Oesch P, Simcoe RA, Wuyts S. 2026. The warm outer layer of a little red dot as the source of [Fe ii] and collisional Balmer lines with scattering wings. Astronomy & Astrophysics. 707, A75.","mla":"Torralba Torregrosa, Alberto, et al. “The Warm Outer Layer of a Little Red Dot as the Source of [Fe Ii] and Collisional Balmer Lines with Scattering Wings.” Astronomy & Astrophysics, vol. 707, A75, EDP Sciences, 2026, doi:10.1051/0004-6361/202557537.","apa":"Torralba Torregrosa, A., Matthee, J. J., Pezzulli, G., Naidu, R. P., Ishikawa, Y., Brammer, G. B., … Wuyts, S. (2026). The warm outer layer of a little red dot as the source of [Fe ii] and collisional Balmer lines with scattering wings. Astronomy & Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202557537"},"doi":"10.1051/0004-6361/202557537","abstract":[{"lang":"eng","text":"The population of the little red dots (LRDs) may represent a key phase of supermassive black hole (SMBH) growth. A cocoon of dense excited gas is emerging as a key component to explain the most striking properties of LRDs, such as strong Balmer breaks and Balmer absorption, as well as the weak IR emission. To dissect the structure of LRDs, we analyzed new deep JWST/NIRSpec PRISM and G395H spectra of FRESCO-GN-9771, one of the most luminous known LRDs at z = 5.5. These spectra reveal a strong Balmer break, broad Balmer lines, and very narrow [O III] emission. We revealed a forest of optical [Fe II] lines, which we argue are emerging from a dense (nH = 109 − 10 cm−3) warm layer with electron temperature Te ≈ 7000 K. The broad wings of Hα and Hβ have an exponential profile due to electron scattering in this same layer. The high Hα : Hβ : Hγ flux ratio of ≈10.4 : 1 : 0.14 is an indicator of collisional excitation and resonant scattering dominating the Balmer line emission. A narrow Hγ component, unseen in the other two Balmer lines due to outshining by the broad components, could trace the ISM of a normal host galaxy with a star formation rate of ∼5 M⊙ yr−1. The warm layer is mostly opaque to Balmer transitions, producing a characteristic P Cygni profile in the line centers suggesting outflowing motions. This same layer is responsible for shaping the Balmer break. The broadband spectrum can be reasonably matched by a simple photoionized slab model that dominates the λ > 1500 Å continuum and a low-mass (∼108 M⊙) galaxy that could explain the narrow [O III], with only a subdominant contribution to the UV continuum. Our findings indicate that Balmer lines are not directly tracing the gas kinematics near the SMBH and that the BH mass scale is likely much lower than virial indicators suggest."}],"publication_identifier":{"issn":["0004-6361"],"eissn":["1432-0746"]},"article_processing_charge":"No","DOAJ_listed":"1","volume":707,"quality_controlled":"1","file":[{"success":1,"file_id":"21460","content_type":"application/pdf","creator":"dernst","file_size":2510157,"file_name":"2026_AstronomyAstrophysics_Torralba2.pdf","access_level":"open_access","date_created":"2026-03-16T10:57:49Z","checksum":"fcab9cb3dcf1d68612e1fdc8191643c1","relation":"main_file","date_updated":"2026-03-16T10:57:49Z"}],"article_type":"original","OA_type":"diamond","day":"01","author":[{"orcid":"0000-0001-5586-6950","id":"018f0249-0e87-11f0-b167-cbce08fbd541","last_name":"Torralba Torregrosa","full_name":"Torralba Torregrosa, Alberto","first_name":"Alberto"},{"orcid":"0000-0003-2871-127X","id":"7439a258-f3c0-11ec-9501-9df22fe06720","last_name":"Matthee","full_name":"Matthee, Jorryt J","first_name":"Jorryt J"},{"full_name":"Pezzulli, Gabriele","first_name":"Gabriele","last_name":"Pezzulli"},{"full_name":"Naidu, Rohan P.","first_name":"Rohan P.","last_name":"Naidu"},{"first_name":"Yuzo","full_name":"Ishikawa, Yuzo","last_name":"Ishikawa"},{"last_name":"Brammer","first_name":"Gabriel B.","full_name":"Brammer, Gabriel B."},{"last_name":"Chang","first_name":"Seok Jun","full_name":"Chang, Seok Jun"},{"last_name":"Chisholm","first_name":"John","full_name":"Chisholm, John"},{"first_name":"Anna","full_name":"De Graaff, Anna","last_name":"De Graaff"},{"full_name":"D’Eugenio, Francesco","first_name":"Francesco","last_name":"D’Eugenio"},{"last_name":"Di Cesare","id":"2d002343-372f-11ef-98ec-a164d20427cb","full_name":"Di Cesare, Claudia","first_name":"Claudia"},{"full_name":"Eilers, Anna Christina","first_name":"Anna Christina","last_name":"Eilers"},{"last_name":"Greene","full_name":"Greene, Jenny E.","first_name":"Jenny E."},{"first_name":"Max","full_name":"Gronke, Max","last_name":"Gronke"},{"id":"4053390a-6b68-11ef-9828-a3b8adef8d0a","last_name":"Iani","orcid":"0000-0001-8386-3546","first_name":"Edoardo","full_name":"Iani, Edoardo"},{"full_name":"Kokorev, Vasily","first_name":"Vasily","last_name":"Kokorev"},{"last_name":"Kotiwale","id":"1438afc8-1ff6-11ee-9fa6-cd4a75d66875","full_name":"Kotiwale, Gauri","first_name":"Gauri"},{"id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4","orcid":"0000-0001-5346-6048","last_name":"Kramarenko","first_name":"Ivan","full_name":"Kramarenko, Ivan"},{"first_name":"Yilun","full_name":"Ma, Yilun","last_name":"Ma"},{"last_name":"Mascia","id":"edaf889c-c7cd-11ef-ab1b-bb28c431bd29","first_name":"Sara","full_name":"Mascia, Sara"},{"id":"aa14a535-50c9-11ef-b52e-e0c373d10148","last_name":"Navarrete","full_name":"Navarrete, Benjamín","first_name":"Benjamín"},{"first_name":"Erica","full_name":"Nelson, Erica","last_name":"Nelson"},{"first_name":"Pascal","full_name":"Oesch, Pascal","last_name":"Oesch"},{"last_name":"Simcoe","first_name":"Robert A.","full_name":"Simcoe, Robert A."},{"last_name":"Wuyts","full_name":"Wuyts, Stijn","first_name":"Stijn"}],"OA_place":"publisher","oa":1,"date_published":"2026-03-01T00:00:00Z","date_created":"2026-03-15T23:01:36Z","type":"journal_article","intvolume":" 707","status":"public","PlanS_conform":"1","year":"2026","publication":"Astronomy & Astrophysics","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication_status":"published","arxiv":1,"fulldoi":"https://doi.org/10.1051/0004-6361/202557537"},{"title":"The slope and scatter of the star-forming main sequence at z ∼ 5: Reconciling observations with simulations","acknowledgement":"We thank the anonymous referee for the insightful comments that helped improving the manuscript. We thank Romain. A. Meyer for valuable discussion, Pierluigi Rinaldi for his help with data handling and Luca Graziani and William McClymont for providing the dustyGadget and\r\nTHESAN-ZOOM data, respectively. Funded by the European Union (ERC, AGENTS, 101076224). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with program # 3516. We acknowledge funding from JWST program GO-3516. Software used in developing this work includes: matplotlib (Hunter 2007), numpy (Oliphant 2007), scipy (Virtanen et al. 2020), TOPCAT (Taylor 2005), and Astropy (Astropy Collaboration 2013).","external_id":{"arxiv":["2510.19044"]},"publisher":"EDP Sciences","_id":"21452","ddc":["520"],"date_updated":"2026-03-16T10:52:44Z","has_accepted_license":"1","department":[{"_id":"JoMa"},{"_id":"GradSch"}],"corr_author":"1","doi":"10.1051/0004-6361/202557790","file_date_updated":"2026-03-16T10:48:07Z","citation":{"apa":"Di Cesare, C., Matthee, J. J., Naidu, R. P., Torralba, A., Kotiwale, G., Kramarenko, I., … Tacchella, S. (2026). The slope and scatter of the star-forming main sequence at z ∼ 5: Reconciling observations with simulations. Astronomy & Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202557790","mla":"Di Cesare, Claudia, et al. “The Slope and Scatter of the Star-Forming Main Sequence at z ∼ 5: Reconciling Observations with Simulations.” Astronomy & Astrophysics, vol. 707, A129, EDP Sciences, 2026, doi:10.1051/0004-6361/202557790.","ista":"Di Cesare C, Matthee JJ, Naidu RP, Torralba A, Kotiwale G, Kramarenko I, Blaizot J, Rosdahl J, Leja J, Iani E, Adamo A, Covelo-Paz A, Furtak LJ, Heintz KE, Mascia S, Navarrete B, Oesch PA, Romano M, Shivaei I, Tacchella S. 2026. The slope and scatter of the star-forming main sequence at z ∼ 5: Reconciling observations with simulations. Astronomy & Astrophysics. 707, A129.","ieee":"C. Di Cesare et al., “The slope and scatter of the star-forming main sequence at z ∼ 5: Reconciling observations with simulations,” Astronomy & Astrophysics, vol. 707. EDP Sciences, 2026.","ama":"Di Cesare C, Matthee JJ, Naidu RP, et al. The slope and scatter of the star-forming main sequence at z ∼ 5: Reconciling observations with simulations. Astronomy & Astrophysics. 2026;707. doi:10.1051/0004-6361/202557790","short":"C. Di Cesare, J.J. Matthee, R.P. Naidu, A. Torralba, G. Kotiwale, I. Kramarenko, J. Blaizot, J. Rosdahl, J. Leja, E. Iani, A. Adamo, A. Covelo-Paz, L.J. Furtak, K.E. Heintz, S. Mascia, B. Navarrete, P.A. Oesch, M. Romano, I. Shivaei, S. Tacchella, Astronomy & Astrophysics 707 (2026).","chicago":"Di Cesare, Claudia, Jorryt J Matthee, Rohan P. Naidu, Alberto Torralba, Gauri Kotiwale, Ivan Kramarenko, Jeremy Blaizot, et al. “The Slope and Scatter of the Star-Forming Main Sequence at z ∼ 5: Reconciling Observations with Simulations.” Astronomy & Astrophysics. EDP Sciences, 2026. https://doi.org/10.1051/0004-6361/202557790."},"publication_identifier":{"eissn":["1432-0746"],"issn":["0004-6361"]},"abstract":[{"lang":"eng","text":"Galaxies exhibit a tight correlation between their star formation rate (SFR) and stellar mass over a wide redshift range known as the star-forming main sequence (SFMS). With JWST, the SFMS can now be investigated at high redshifts down to masses of ∼106 M⊙, using sensitive star formation rate tracers such as the Hα emission, which allow us to probe the variability in the star formation histories. We present inferences of the SFMS based on 316 Hα-selected galaxies at z ∼ 4 − 5 with log(M★/M⊙) = 6.4 − 10.6. These galaxies were identified behind the Abell 2744 lensing cluster with NIRCam grism spectroscopy from the survey All the Little Things (ALT). At face value, our data suggest a shallow slope in the SFMS (SFR ∝ M★α, with α = 0.45). After we corrected this for the Hα-flux limited nature of our survey using a Bayesian framework, the slope steepened to α = 0.59+0.10−0.09, whereas current data on their own are inconclusive on the mass dependence of the scatter. These slopes differ significantly from the slope of ∼1 that is expected from the observed evolution of the galaxy stellar mass function and from simulations. When we fixed the slope to α = 1, we found evidence for a decreasing intrinsic scatter with stellar mass (from ∼0.5 dex at M★ = 108 M⊙ to 0.4 dex at M★ = 1010 M⊙). This difference might be explained by a (combination of) luminosity-dependent SFR(Hα) calibration, a population of (mini)-quenched low-mass galaxies, or underestimated dust attenuation in high-mass galaxies. Future deep observations with different facilities can quantify these processes, which will enable us to achieve better insights into the variability of the star formation histories."}],"DOAJ_listed":"1","article_processing_charge":"No","article_number":"A129","project":[{"grant_number":"101076224","name":"Young galaxies as tracers and agents of cosmic reionization","_id":"bd9b2118-d553-11ed-ba76-db24564edfea"}],"scopus_import":"1","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","language":[{"iso":"eng"}],"month":"03","oa_version":"Published Version","oa":1,"date_published":"2026-03-01T00:00:00Z","date_created":"2026-03-15T23:01:36Z","type":"journal_article","intvolume":" 707","status":"public","year":"2026","PlanS_conform":"1","publication":"Astronomy & Astrophysics","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication_status":"published","arxiv":1,"fulldoi":"https://doi.org/10.1051/0004-6361/202557790","volume":707,"quality_controlled":"1","file":[{"file_size":1821411,"creator":"dernst","file_id":"21459","content_type":"application/pdf","success":1,"checksum":"c056b00ce7324849754521fde10fb7ca","date_updated":"2026-03-16T10:48:07Z","relation":"main_file","access_level":"open_access","date_created":"2026-03-16T10:48:07Z","file_name":"2026_AstronomyAstrophysics_DiCesare.pdf"}],"article_type":"original","OA_type":"diamond","day":"01","author":[{"last_name":"Di Cesare","id":"2d002343-372f-11ef-98ec-a164d20427cb","first_name":"Claudia","full_name":"Di Cesare, Claudia"},{"full_name":"Matthee, Jorryt J","first_name":"Jorryt J","id":"7439a258-f3c0-11ec-9501-9df22fe06720","last_name":"Matthee","orcid":"0000-0003-2871-127X"},{"last_name":"Naidu","full_name":"Naidu, Rohan P.","first_name":"Rohan P."},{"last_name":"Torralba","first_name":"Alberto","full_name":"Torralba, Alberto"},{"last_name":"Kotiwale","id":"1438afc8-1ff6-11ee-9fa6-cd4a75d66875","first_name":"Gauri","full_name":"Kotiwale, Gauri"},{"orcid":"0000-0001-5346-6048","id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4","last_name":"Kramarenko","first_name":"Ivan","full_name":"Kramarenko, Ivan"},{"full_name":"Blaizot, Jeremy","first_name":"Jeremy","last_name":"Blaizot"},{"full_name":"Rosdahl, Joakim","first_name":"Joakim","last_name":"Rosdahl"},{"last_name":"Leja","full_name":"Leja, Joel","first_name":"Joel"},{"first_name":"Edoardo","full_name":"Iani, Edoardo","orcid":"0000-0001-8386-3546","id":"4053390a-6b68-11ef-9828-a3b8adef8d0a","last_name":"Iani"},{"full_name":"Adamo, Angela","first_name":"Angela","last_name":"Adamo"},{"last_name":"Covelo-Paz","first_name":"Alba","full_name":"Covelo-Paz, Alba"},{"first_name":"Lukas J.","full_name":"Furtak, Lukas J.","last_name":"Furtak"},{"full_name":"Heintz, Kasper E.","first_name":"Kasper E.","last_name":"Heintz"},{"first_name":"Sara","full_name":"Mascia, Sara","last_name":"Mascia","id":"edaf889c-c7cd-11ef-ab1b-bb28c431bd29"},{"id":"aa14a535-50c9-11ef-b52e-e0c373d10148","last_name":"Navarrete","first_name":"Benjamín","full_name":"Navarrete, Benjamín"},{"last_name":"Oesch","first_name":"Pascal A.","full_name":"Oesch, Pascal A."},{"last_name":"Romano","first_name":"Michael","full_name":"Romano, Michael"},{"last_name":"Shivaei","first_name":"Irene","full_name":"Shivaei, Irene"},{"last_name":"Tacchella","first_name":"Sandro","full_name":"Tacchella, Sandro"}],"OA_place":"publisher"},{"project":[{"_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224"}],"article_number":"A184","oa_version":"Published Version","language":[{"iso":"eng"}],"month":"03","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","publisher":"EDP Sciences","_id":"21481","date_updated":"2026-03-23T15:46:31Z","ddc":["520"],"acknowledgement":"We thank the anonymous referee for the insightful comments that helped improve the manuscript. We also thank Thibault Garel, Pascal Oesch, Irene Shivaei, Charlotte Simmonds, Andrew Hopkins, Daniel Schaerer, and Rashmi Gottumukkala for useful comments and productive discussions. We gratefully acknowledge support from the CBPsmn (PSMN, Pôle Scientifique de Modélisation Numérique) of the ENS de Lyon for the computing resources.\r\nFunded by the European Union (ERC, AGENTS, 101076224). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. This work made extensive use of several open-source software packages, and we gratefully acknowledge the efforts of their authors: numpy (Harris et al. 2020), astropy (Astropy Collaboration 2022), matplotlib (Hunter 2007), ipython (Perez & Granger 2007), and scikit-learn (Pedregosa et al. 2011).","external_id":{"arxiv":["2509.05403"]},"title":"H α as a tracer of star formation in the SPHINX cosmological simulations","article_processing_charge":"No","DOAJ_listed":"1","file_date_updated":"2026-03-23T15:44:09Z","citation":{"chicago":"Kramarenko, Ivan, J. Rosdahl, J. Blaizot, Jorryt J Matthee, H. Katz, and Claudia Di Cesare. “H α as a Tracer of Star Formation in the SPHINX Cosmological Simulations.” Astronomy & Astrophysics. EDP Sciences, 2026. https://doi.org/10.1051/0004-6361/202557114.","short":"I. Kramarenko, J. Rosdahl, J. Blaizot, J.J. Matthee, H. Katz, C. Di Cesare, Astronomy & Astrophysics 707 (2026).","ama":"Kramarenko I, Rosdahl J, Blaizot J, Matthee JJ, Katz H, Di Cesare C. H α as a tracer of star formation in the SPHINX cosmological simulations. Astronomy & Astrophysics. 2026;707. doi:10.1051/0004-6361/202557114","ieee":"I. Kramarenko, J. Rosdahl, J. Blaizot, J. J. Matthee, H. Katz, and C. Di Cesare, “H α as a tracer of star formation in the SPHINX cosmological simulations,” Astronomy & Astrophysics, vol. 707. EDP Sciences, 2026.","ista":"Kramarenko I, Rosdahl J, Blaizot J, Matthee JJ, Katz H, Di Cesare C. 2026. H α as a tracer of star formation in the SPHINX cosmological simulations. Astronomy & Astrophysics. 707, A184.","mla":"Kramarenko, Ivan, et al. “H α as a Tracer of Star Formation in the SPHINX Cosmological Simulations.” Astronomy & Astrophysics, vol. 707, A184, EDP Sciences, 2026, doi:10.1051/0004-6361/202557114.","apa":"Kramarenko, I., Rosdahl, J., Blaizot, J., Matthee, J. J., Katz, H., & Di Cesare, C. (2026). H α as a tracer of star formation in the SPHINX cosmological simulations. Astronomy & Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202557114"},"doi":"10.1051/0004-6361/202557114","publication_identifier":{"eissn":["1432-0746"],"issn":["0004-6361"]},"abstract":[{"text":"The Hα emission line in galaxies is a powerful tracer of their recent star formation activity. With the advent of JWST, we are now able to routinely observe Hα in galaxies at high redshift (z ≳ 3) and thus measure their star formation rates (SFRs). However, using classical SFR(Hα) calibrations to derive the SFRs leads to biased results because high-redshift galaxies are commonly characterized by low metallicities and bursty star formation histories, affecting the conversion factor between the Hα luminosity (LHα) and the SFR. We developed a set of new SFR(Hα) calibrations that allowed us to predict the SFRs of Hα-emitters at z ≳ 3 with very little error. We used the SPHINX cosmological simulations to select a sample of star-forming galaxies representative of the Hα-emitter population observed with JWST. We then derived linear corrections to the classical SFR(Hα) calibrations that took variations in the physical properties (e.g., stellar metallicities) among individual galaxies into account. We obtained two new SFR(Hα) calibrations that compared to the classical calibrations reduce the root mean squared error (RMSE) in the predicted SFRs by ΔRMSE ≈ 0.04 dex and ΔRMSE ≈ 0.06 dex, respectively. Using the recent JWST NIRCam/grism observations of Hα-emitters at z ∼ 6, we show that the new calibrations affect the high-redshift galaxy population statistics: (i) the estimated cosmic SFR density decreases by ΔρSFR ≈ 12%, and (ii) the observed slope of the star formation main sequence increases by Δ∂logSFR/∂logM★ = 0.08 ± 0.02.","lang":"eng"}],"corr_author":"1","has_accepted_license":"1","department":[{"_id":"JoMa"}],"OA_type":"diamond","article_type":"original","quality_controlled":"1","file":[{"file_size":904565,"creator":"dernst","content_type":"application/pdf","file_id":"21492","success":1,"checksum":"7429076b381dd498084f40ffd199e714","relation":"main_file","date_updated":"2026-03-23T15:44:09Z","access_level":"open_access","date_created":"2026-03-23T15:44:09Z","file_name":"2026_AstronomyAstrophysics_Kramarenko.pdf"}],"volume":707,"OA_place":"publisher","author":[{"id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4","last_name":"Kramarenko","orcid":"0000-0001-5346-6048","first_name":"Ivan","full_name":"Kramarenko, Ivan"},{"last_name":"Rosdahl","first_name":"J.","full_name":"Rosdahl, J."},{"last_name":"Blaizot","first_name":"J.","full_name":"Blaizot, J."},{"id":"7439a258-f3c0-11ec-9501-9df22fe06720","orcid":"0000-0003-2871-127X","last_name":"Matthee","full_name":"Matthee, Jorryt J","first_name":"Jorryt J"},{"first_name":"H.","full_name":"Katz, H.","last_name":"Katz"},{"last_name":"Di Cesare","id":"2d002343-372f-11ef-98ec-a164d20427cb","full_name":"Di Cesare, Claudia","first_name":"Claudia"}],"day":"05","intvolume":" 707","status":"public","PlanS_conform":"1","year":"2026","type":"journal_article","date_created":"2026-03-23T14:58:03Z","oa":1,"date_published":"2026-03-05T00:00:00Z","publication_status":"published","arxiv":1,"fulldoi":"https://doi.org/10.1051/0004-6361/202557114","publication":"Astronomy & Astrophysics","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"}},{"author":[{"last_name":"Greene","first_name":"Jenny E.","full_name":"Greene, Jenny E."},{"first_name":"David J.","full_name":"Setton, David J.","last_name":"Setton"},{"full_name":"Furtak, Lukas J.","first_name":"Lukas J.","last_name":"Furtak"},{"full_name":"Naidu, Rohan P.","first_name":"Rohan P.","last_name":"Naidu"},{"last_name":"Volonteri","full_name":"Volonteri, Marta","first_name":"Marta"},{"full_name":"Dayal, Pratika","first_name":"Pratika","last_name":"Dayal"},{"last_name":"Labbe","full_name":"Labbe, Ivo","first_name":"Ivo"},{"last_name":"Van Dokkum","full_name":"Van Dokkum, Pieter","first_name":"Pieter"},{"last_name":"Bezanson","first_name":"Rachel","full_name":"Bezanson, Rachel"},{"last_name":"Brammer","full_name":"Brammer, Gabriel","first_name":"Gabriel"},{"first_name":"Sam E.","full_name":"Cutler, Sam E.","last_name":"Cutler"},{"first_name":"Karl","full_name":"Glazebrook, Karl","last_name":"Glazebrook"},{"last_name":"De Graaff","full_name":"De Graaff, Anna","first_name":"Anna"},{"last_name":"Hirschmann","first_name":"Michaela","full_name":"Hirschmann, Michaela"},{"last_name":"Hviding","first_name":"Raphael E.","full_name":"Hviding, Raphael E."},{"last_name":"Kokorev","first_name":"Vasily","full_name":"Kokorev, Vasily"},{"last_name":"Leja","full_name":"Leja, Joel","first_name":"Joel"},{"last_name":"Liu","full_name":"Liu, Hanpu","first_name":"Hanpu"},{"last_name":"Ma","full_name":"Ma, Yilun","first_name":"Yilun"},{"full_name":"Matthee, Jorryt J","first_name":"Jorryt J","id":"7439a258-f3c0-11ec-9501-9df22fe06720","last_name":"Matthee","orcid":"0000-0003-2871-127X"},{"full_name":"Nanayakkara, Themiya","first_name":"Themiya","last_name":"Nanayakkara"},{"first_name":"Pascal A.","full_name":"Oesch, Pascal A.","last_name":"Oesch"},{"full_name":"Pan, Richard","first_name":"Richard","last_name":"Pan"},{"full_name":"Price, Sedona H.","first_name":"Sedona H.","last_name":"Price"},{"last_name":"Spilker","full_name":"Spilker, Justin S.","first_name":"Justin S."},{"last_name":"Wang","first_name":"Bingjie","full_name":"Wang, Bingjie"},{"last_name":"Weaver","full_name":"Weaver, John R.","first_name":"John R."},{"last_name":"Whitaker","first_name":"Katherine E.","full_name":"Whitaker, Katherine E."},{"full_name":"Williams, Christina C.","first_name":"Christina C.","last_name":"Williams"},{"first_name":"Adi","full_name":"Zitrin, Adi","last_name":"Zitrin"}],"day":"10","OA_place":"publisher","volume":996,"article_type":"original","OA_type":"gold","file":[{"relation":"main_file","date_updated":"2026-05-04T11:19:48Z","checksum":"7b3cb025d4bcaa35c6e52bd0c8fb6cf4","file_name":"2026_AstrophysicalJour_Greene.pdf","date_created":"2026-05-04T11:19:48Z","access_level":"open_access","creator":"dernst","file_size":684400,"success":1,"file_id":"21792","content_type":"application/pdf"}],"quality_controlled":"1","fulldoi":"https://doi.org/10.3847/1538-4357/ae1836","publication_status":"published","arxiv":1,"tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication":"The Astrophysical Journal","date_created":"2026-04-12T22:01:50Z","date_published":"2026-01-10T00:00:00Z","oa":1,"PlanS_conform":"1","year":"2026","status":"public","intvolume":" 996","type":"journal_article","issue":"2","language":[{"iso":"eng"}],"month":"01","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","scopus_import":"1","oa_version":"Published Version","article_number":"129","project":[{"grant_number":"101076224","name":"Young galaxies as tracers and agents of cosmic reionization","_id":"bd9b2118-d553-11ed-ba76-db24564edfea"}],"department":[{"_id":"JoMa"}],"has_accepted_license":"1","article_processing_charge":"Yes","DOAJ_listed":"1","publication_identifier":{"eissn":["1538-4357"],"issn":["0004-637X"]},"abstract":[{"lang":"eng","text":"New populations of red active galactic nuclei (known as “little red dots”) discovered by JWST exhibit remarkable spectral energy distributions. Leveraging X-ray through far-infrared observations of two of the most luminous known little red dots, we directly measure their bolometric luminosities. We find evidence that more than half of the bolometric luminosity likely emerges in the rest-frame optical, with Lbol/L5100 = 5, roughly half the value for “standard” active galactic nuclei. Meanwhile, the X-ray emitting corona, UV-emitting blackbody, and reprocessed mid to far-infrared emission are all considerably subdominant, assuming that the far-infrared luminosity is well below current measured limits. We present new bolometric corrections that dramatically lower inferred bolometric luminosities by a factor of 10 compared to published values in the literature. These bolometric corrections are in accord with expectations from models in which gas absorption and reprocessing are responsible for the red rest-frame optical colors of little red dots. We discuss how this lowered luminosity scale suggests a lower mass scale for the population by at least an order of magnitude (e.g., ∼105–107 M⊙ black holes, and ∼108 M⊙ galaxies), alleviating tensions with clustering, overmassive black holes, and the integrated black hole mass density in the Universe."}],"file_date_updated":"2026-05-04T11:19:48Z","doi":"10.3847/1538-4357/ae1836","citation":{"chicago":"Greene, Jenny E., David J. Setton, Lukas J. Furtak, Rohan P. Naidu, Marta Volonteri, Pratika Dayal, Ivo Labbe, et al. “What You See Is What You Get: Empirically Measured Bolometric Luminosities of Little Red Dots.” The Astrophysical Journal. IOP Publishing, 2026. https://doi.org/10.3847/1538-4357/ae1836.","short":"J.E. Greene, D.J. Setton, L.J. Furtak, R.P. Naidu, M. Volonteri, P. Dayal, I. Labbe, P. Van Dokkum, R. Bezanson, G. Brammer, S.E. Cutler, K. Glazebrook, A. De Graaff, M. Hirschmann, R.E. Hviding, V. Kokorev, J. Leja, H. Liu, Y. Ma, J.J. Matthee, T. Nanayakkara, P.A. Oesch, R. Pan, S.H. Price, J.S. Spilker, B. Wang, J.R. Weaver, K.E. Whitaker, C.C. Williams, A. Zitrin, The Astrophysical Journal 996 (2026).","ama":"Greene JE, Setton DJ, Furtak LJ, et al. What you see is what you get: Empirically measured bolometric luminosities of Little Red Dots. The Astrophysical Journal. 2026;996(2). doi:10.3847/1538-4357/ae1836","ieee":"J. E. Greene et al., “What you see is what you get: Empirically measured bolometric luminosities of Little Red Dots,” The Astrophysical Journal, vol. 996, no. 2. IOP Publishing, 2026.","ista":"Greene JE, Setton DJ, Furtak LJ, Naidu RP, Volonteri M, Dayal P, Labbe I, Van Dokkum P, Bezanson R, Brammer G, Cutler SE, Glazebrook K, De Graaff A, Hirschmann M, Hviding RE, Kokorev V, Leja J, Liu H, Ma Y, Matthee JJ, Nanayakkara T, Oesch PA, Pan R, Price SH, Spilker JS, Wang B, Weaver JR, Whitaker KE, Williams CC, Zitrin A. 2026. What you see is what you get: Empirically measured bolometric luminosities of Little Red Dots. The Astrophysical Journal. 996(2), 129.","mla":"Greene, Jenny E., et al. “What You See Is What You Get: Empirically Measured Bolometric Luminosities of Little Red Dots.” The Astrophysical Journal, vol. 996, no. 2, 129, IOP Publishing, 2026, doi:10.3847/1538-4357/ae1836.","apa":"Greene, J. E., Setton, D. J., Furtak, L. J., Naidu, R. P., Volonteri, M., Dayal, P., … Zitrin, A. (2026). What you see is what you get: Empirically measured bolometric luminosities of Little Red Dots. The Astrophysical Journal. IOP Publishing. https://doi.org/10.3847/1538-4357/ae1836"},"title":"What you see is what you get: Empirically measured bolometric luminosities of Little Red Dots","ddc":["520"],"date_updated":"2026-05-04T11:20:42Z","_id":"21715","publisher":"IOP Publishing","external_id":{"arxiv":["2509.05434"]},"acknowledgement":"We benefit from the following JWST programs: UNCOVER (JWST/GO #2561; Labbé & Bezanson); ALT (JWST-GO #3516; Naidu & Matthee); MegaScience (JWST-GO #4111; Suess); RUBIES (JWST-GO #4233; de Graaff & Brammer); PRIMER (JWST/GO #1837; Dunlop).\r\n\r\nWe acknowledge funding from NSF/AAG #2306950, JWST-GO-02561, JWST-GO-03516, and JWST-GO-04111, provided through a grant from the STScI under NASA contract NAS5-03127. I.L. acknowledges support from Australian Research Council Future Fellowship FT220100798. K.G. and T.N. acknowledge support from Australian Research Council Laureate Fellowship FL180100060. A.Z. acknowledges support by grant No. 2020750 from the United States-Israel Binational Science Foundation (BSF) and grant No. 2109066 from the United States National Science Foundation (NSF); by the Ministry of Science & Technology, Israel; and by the Israel Science Foundation grant No. 864/23. J.M. and I.K. are funded by the European Union (ERC, AGENTS, 101076224). Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. Y.F. acknowledges support from JSPS KAKENHI grant No. JSPS KAKENHI grant Nos. JP22K21349 and JP23K13149. This work has received funding from the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract No. MB22.00072, as well as from the Swiss National Science Foundation (SNSF) through project grant 200020_207349. The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant DNRF140. Support for this work for RPN was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51515.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. The work of CCW is supported by NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. J.M. acknowledges funding by the European Union (ERC, AGENTS, 101076224). R.E.H. acknowledges support by the German Aerospace Center (DLR) and the Federal Ministry for Economic Affairs and Energy (BMWi) through program 50OR2403 “RUBIES.”"},{"OA_place":"publisher","day":"10","author":[{"last_name":"Baggen","first_name":"Josephine F.W.","full_name":"Baggen, Josephine F.W."},{"last_name":"Scoggins","full_name":"Scoggins, Matthew T.","first_name":"Matthew T."},{"last_name":"Van Dokkum","first_name":"Pieter","full_name":"Van Dokkum, Pieter"},{"full_name":"Haiman, Zoltán","first_name":"Zoltán","id":"7c006e8c-cc0d-11ee-8322-cb904ef76f36","orcid":"0000-0003-3633-5403","last_name":"Haiman"},{"orcid":"0000-0001-5586-6950","last_name":"Torralba Torregrosa","id":"018f0249-0e87-11f0-b167-cbce08fbd541","full_name":"Torralba Torregrosa, Alberto","first_name":"Alberto"},{"first_name":"Jorryt J","full_name":"Matthee, Jorryt J","last_name":"Matthee","id":"7439a258-f3c0-11ec-9501-9df22fe06720","orcid":"0000-0003-2871-127X"}],"quality_controlled":"1","file":[{"access_level":"open_access","date_created":"2026-05-11T06:44:37Z","file_name":"2026_AstrophysicalJourLetters_Baggen.pdf","checksum":"8c31d8603cd6ad39c772a72d136dc3f8","date_updated":"2026-05-11T06:44:37Z","relation":"main_file","content_type":"application/pdf","file_id":"21851","success":1,"file_size":13359642,"creator":"dernst"}],"article_type":"original","OA_type":"gold","volume":1002,"publication":"The Astrophysical Journal Letters","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication_status":"published","arxiv":1,"fulldoi":"https://doi.org/10.3847/2041-8213/ae58a5","issue":"1","type":"journal_article","intvolume":" 1002","status":"public","year":"2026","PlanS_conform":"1","oa":1,"date_published":"2026-04-10T00:00:00Z","date_created":"2026-05-10T22:02:15Z","oa_version":"Published Version","scopus_import":"1","language":[{"iso":"eng"}],"month":"04","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","project":[{"_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224"}],"article_number":"L4","doi":"10.3847/2041-8213/ae58a5","file_date_updated":"2026-05-11T06:44:37Z","citation":{"apa":"Baggen, J. F. W., Scoggins, M. T., Van Dokkum, P., Haiman, Z., Torralba Torregrosa, A., & Matthee, J. J. (2026). Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner sources enabling direct-collapse Black Hole formation. The Astrophysical Journal Letters. IOP Publishing. https://doi.org/10.3847/2041-8213/ae58a5","mla":"Baggen, Josephine F. W., et al. “Connecting the Dots: UV-Bright Companions of Little Red Dots as Lyman–Werner Sources Enabling Direct-Collapse Black Hole Formation.” The Astrophysical Journal Letters, vol. 1002, no. 1, L4, IOP Publishing, 2026, doi:10.3847/2041-8213/ae58a5.","ista":"Baggen JFW, Scoggins MT, Van Dokkum P, Haiman Z, Torralba Torregrosa A, Matthee JJ. 2026. Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner sources enabling direct-collapse Black Hole formation. The Astrophysical Journal Letters. 1002(1), L4.","ieee":"J. F. W. Baggen, M. T. Scoggins, P. Van Dokkum, Z. Haiman, A. Torralba Torregrosa, and J. J. Matthee, “Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner sources enabling direct-collapse Black Hole formation,” The Astrophysical Journal Letters, vol. 1002, no. 1. IOP Publishing, 2026.","ama":"Baggen JFW, Scoggins MT, Van Dokkum P, Haiman Z, Torralba Torregrosa A, Matthee JJ. Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner sources enabling direct-collapse Black Hole formation. The Astrophysical Journal Letters. 2026;1002(1). doi:10.3847/2041-8213/ae58a5","short":"J.F.W. Baggen, M.T. Scoggins, P. Van Dokkum, Z. Haiman, A. Torralba Torregrosa, J.J. Matthee, The Astrophysical Journal Letters 1002 (2026).","chicago":"Baggen, Josephine F.W., Matthew T. Scoggins, Pieter Van Dokkum, Zoltán Haiman, Alberto Torralba Torregrosa, and Jorryt J Matthee. “Connecting the Dots: UV-Bright Companions of Little Red Dots as Lyman–Werner Sources Enabling Direct-Collapse Black Hole Formation.” The Astrophysical Journal Letters. IOP Publishing, 2026. https://doi.org/10.3847/2041-8213/ae58a5."},"abstract":[{"text":"We compile a sample of 83 little red dots (LRDs) with JWST imaging and find that a substantial fraction (∼43%, rising to ≳80% for the most luminous LRDs) host one or more spatially offset, UV-bright companions at projected separations of 0.5 kpc ≲ d ≲ 5 kpc, with median 〈d〉 = 1.0 kpc. This fraction is even higher when smaller spatial scales are probed at high signal-to-noise ratio: the two most strongly lensed LRDs, A383-LRD1 and the newly discovered A68-LRD1, both have UV-bright companions at separations of only d ∼ 0.3 kpc, below the resolution limit of most unlensed JWST samples. We explore whether these ubiquitous red/blue configurations may be physically linked to the formation of LRDs, in analogy with the “synchronized pair” scenario originally proposed for direct-collapse black hole formation. In this picture, UV radiation from the companions, with typically modest stellar masses (M∗ ∼ 108−109 M⊙), suppresses molecular hydrogen cooling in nearby gas, allowing nearly isothermal collapse and the formation of extremely compact objects, such as massive black holes, supermassive stars, or quasi-stars. Using component-resolved photometry and spectral energy distribution modeling, we infer Lyman–Werner radiation fields of J21,LW ∼ 102.5–105 at the locations of the red components, comparable to those required in direct-collapse models, suggesting that the necessary photodissociation conditions are realized in many LRD systems. This framework provides a simple and self-consistent explanation for the extreme compactness and distinctive spectral properties of LRDs and links long-standing theoretical models for early compact object formation directly to a population now observed with JWST in the early Universe.","lang":"eng"}],"publication_identifier":{"issn":["2041-8205"],"eissn":["2041-8213"]},"DOAJ_listed":"1","article_processing_charge":"Yes","has_accepted_license":"1","department":[{"_id":"ZoHa"},{"_id":"JoMa"}],"acknowledgement":"We thank Earl Bellinger, Fabio Pacucci, Andrea Ferrara, and Dale Kocevski for useful discussions. This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These imaging observations are associated with programs 1345, 1180, 1181, 1243, 6882, 2561, 1324, 4111, and 1895. The compiled dataset can be accessed at doi:10.17909/1m8f-9c47. The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant DNRF140. J.M. and A.T. acknowledge funding by the European Union (ERC, AGENTS, 101076224). This work was performed in part at Aspen Center for Physics, which is supported by National Science Foundation grant PHY-2210452. This work used the following Python packages: Matplotlib (J. D. Hunter 2007), SciPy (P. Virtanen et al. 2020), NumPy (S. van der Walt et al. 2011), AstroPy (Astropy Collaboration et al. 2022), colossus (B. Diemer 2018), and photutils (L. Bradley et al. 2025).","external_id":{"arxiv":["2602.02702"]},"publisher":"IOP Publishing","_id":"21846","ddc":["520"],"date_updated":"2026-05-11T06:48:33Z","title":"Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner sources enabling direct-collapse Black Hole formation"},{"project":[{"_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224"}],"month":"05","language":[{"iso":"eng"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","scopus_import":"1","oa_version":"Published Version","title":"Little Red Dot - Host Galaxy = Black Hole Star: A gas-enshrouded heart at the center of every Little Red Dot","date_updated":"2026-06-08T08:25:40Z","ddc":["520"],"_id":"21951","publisher":"Maynooth Academic Publishing","external_id":{"arxiv":["2601.20929"]},"acknowledgement":"We thank the two anonymous referees for their insightful comments that have strengthened this work.\r\nWQS and RPN acknowledge funding from JWST programs GO-3516, GO-5224, and the MIT Undergraduate\r\nResearch Opportunities Program (UROP). Support for\r\nthis work was provided by NASA through the NASA\r\nHubble Fellowship grant HST-HF2-51515.001-A awarded\r\nby the Space Telescope Science Institute, which is operated by the Association of Universities for Research in\r\nAstronomy, Incorporated, under NASA contract NAS5-\r\n26555. RPN thanks Neil Pappalardo and Jane Pappalardo for their generous support of the MIT Pappalardo Fellowships in Physics, and for their enthusiasm\r\nand encouragement for pursuing the earliest galaxies and\r\nblack holes. JM and AT acknowledge funding from the\r\nEuropean Union (ERC, AGENTS, 101076224). KEH\r\nacknowledges support from the Independent Research Fund Denmark (DFF) under grant 5251-00009B and cofunding by the European Union (ERC, HEAVYMETAL,\r\n101071865). Views and opinions expressed are, however,\r\nthose of the authors only and do not necessarily reflect\r\nthose of the European Union or the European Research\r\nCouncil. Neither the European Union nor the granting\r\nauthority can be held responsible for them. REH acknowledges support by the German Aerospace Center\r\n(DLR) and the Federal Ministry for Economic Affairs\r\nand Energy (BMWi) through program 50OR2403 ‘RUBIES’.\r\nThe data products presented herein were retrieved\r\nfrom the Dawn JWST Archive (DJA). DJA is an initiative of the Cosmic Dawn Center (DAWN), which is\r\nfunded by the Danish National Research Foundation under grant DNRF140. This work is based on observations\r\nmade with the NASA/ESA/CSA James Webb Space\r\nTelescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope\r\nScience Institute, which is operated by the Association\r\nof Universities for Research in Astronomy, Inc., under\r\nNASA contract NAS 5-03127 for JWST. Support for\r\nprograms #3516, #5224, #5664 was provided by NASA\r\nthrough grants from the Space Telescope Science Institute, which is operated by the Association of Universities\r\nfor Research in Astronomy, Inc., under NASA contract\r\nNAS 5-03127.\r\nThe spectra used in this paper are associated with programs 1180 (D’Eugenio et al. 2025d), 1181 (PI: D. Eisenstein), 1208 (Willott et al. 2022), 1210 (PI: N. Luetzgendorf), 1211 (Maseda et al. 2024), 1212 - 1215 (PI: N.\r\nLuetzgendorf), 1228 (Luhman et al. 2024b), 1229 (Luhman et al. 2024a), 1286 (PI: N. Luetzgendorf), 1287 (PI:\r\nK. Isaak), 1345 (Finkelstein et al. 2023), 1433 (Hsiao\r\net al. 2024), 1747 (PI: G. Roberts-Borsani), 2028 (Wang\r\net al. 2024c), 2073 (PI: J. Hennawi), 2198 (Barrufet\r\net al. 2025), 2282 (Bradley et al. 2023), 2561 (Bezanson\r\net al. 2024), 2565 (Nanayakkara et al. 2025), 2640 (PI:\r\nW. Best), 2750 (Arrabal Haro et al. 2023), 2756 (Mascia et al. 2024), 2767 (Williams et al. 2023b), 2770 (PI:\r\nM. McCaughrean), 3073 (Castellano et al. 2024), 3215\r\n(Eisenstein et al. 2025), 4106 (PI: E. Nelson), 4233 (de\r\nGraaff et al. 2025c), 4446 (Frye et al. 2024), 4557 (PI: H.\r\nYan), 5105 (Shen et al. 2024), 5224 (PIs: P.A. Oesch &\r\nR.P. Naidu), 6368 (PI: M. Dickinson), 6541 (DeCoursey\r\net al. 2025), 6585 (PI: D. Coulter), 6642 (PI: J. Muzerolle\r\nPage), and FRESCO IFU (Matthee et al. 2024; Torralba\r\net al. 2025b).\r\nSoftware used in developing this work includes:\r\nmatplotlib (Hunter 2007), jupyter (Kluyver et al.\r\n2016), IPython (P´erez & Granger 2007), numpy\r\n(Oliphant 2015), scipy (Virtanen et al. 2020), TOPCAT\r\n(Taylor 2005), Astropy (Astropy Collaboration et al.\r\n2013), msaexp (Brammer 2023).","department":[{"_id":"JoMa"}],"has_accepted_license":"1","DOAJ_listed":"1","article_processing_charge":"No","publication_identifier":{"eissn":["2565-6120"]},"abstract":[{"text":"The central engines of Little Red Dots (LRDs) may be “black hole stars” (BH*s), early stages of\r\nblack hole growth characterized by dense gas envelopes. So far, the most direct evidence for BH*s\r\ncomes from a handful of sources where the host galaxy is completely outshone as suggested by their\r\nremarkably steep Balmer breaks. Here we present a novel scheme to disentangle BH*s from their\r\nhost galaxies assuming that the [O III]5008˚A line arises exclusively from the host. Using a sample\r\nof 98 LRDs (z ≈ 2 − 9) with high quality NIRSpec/PRISM spectra, we demonstrate that the hostsubtracted median stack displays a Balmer break > 2× stronger than massive quiescent galaxies,\r\nwith the rest-optical continuum resembling a blackbody-like SED (Teff ≈ 4050 K, log(Lbol) ≈ 43.9\r\nerg s−1\r\n, Reff ≈ 1300 au). We measure a steep Balmer decrement (Hα/Hβ > 10) and numerous\r\ndensity-sensitive features (e.g., Fe II, He I, O I). These are hallmark signatures of dense gas envelopes,\r\nproviding population-level evidence that BH*s indeed power LRDs. In the median LRD, BH*s account\r\nfor ∼ 20% of the UV emission, ∼ 50% at the Balmer break, and ∼ 90% at wavelengths longer\r\nthan Hα with the remainder arising from the host. BH*s preferentially reside in low-mass galaxies\r\n(M⋆ ≈ 108 M⊙) undergoing recent starbursts, as evidenced by extreme emission line EWs (e.g.,\r\n[O III]5008˚A≈ 1100˚A, C III]≈ 12˚A), thereby favoring BH* origins linked to star-formation. We show\r\nV-shaped LRD selections are biased to high BH*/host fractions (≳ 60% at 5500˚A) – less dominant\r\nBH*s may be powering JWST’s blue broad-line AGN. We find BH*s are so commonplace and transient\r\n(duty cycle ∼ 1%, lifetime ∼ 10 Myrs) that every massive black hole may have once shone as a BH*.\r\n","lang":"eng"}],"doi":"10.33232/001c.162505","file_date_updated":"2026-06-08T08:23:37Z","citation":{"ista":"Sun WQ, Naidu RP, Matthee JJ, De Graaff A, Chisholm J, Greene JE, Oesch PA, Torralba Torregrosa A, Hviding RE, Brammer G, Simcoe RA, Bose S, Bouwens R, Dayal P, Eilers AC, Fei Q, Furtak LJ, Gottumukkala R, Goulding A, Heintz KE, Hirschmann M, Kokorev V, Leja J, Liu Z, Natarajan P, Santarelli AD, Setton DJ, Smith A, Tacchella S, Volonteri M, Walter F, Weibel A, Williams CC. 2026. Little Red Dot - Host Galaxy = Black Hole Star: A gas-enshrouded heart at the center of every Little Red Dot. The Open Journal of Astrophysics. 9.","ieee":"W. Q. Sun et al., “Little Red Dot - Host Galaxy = Black Hole Star: A gas-enshrouded heart at the center of every Little Red Dot,” The Open Journal of Astrophysics, vol. 9. Maynooth Academic Publishing, 2026.","ama":"Sun WQ, Naidu RP, Matthee JJ, et al. Little Red Dot - Host Galaxy = Black Hole Star: A gas-enshrouded heart at the center of every Little Red Dot. The Open Journal of Astrophysics. 2026;9. doi:10.33232/001c.162505","short":"W.Q. Sun, R.P. Naidu, J.J. Matthee, A. De Graaff, J. Chisholm, J.E. Greene, P.A. Oesch, A. Torralba Torregrosa, R.E. Hviding, G. Brammer, R.A. Simcoe, S. Bose, R. Bouwens, P. Dayal, A.C. Eilers, Q. Fei, L.J. Furtak, R. Gottumukkala, A. Goulding, K.E. Heintz, M. Hirschmann, V. Kokorev, J. Leja, Z. Liu, P. Natarajan, A.D. Santarelli, D.J. Setton, A. Smith, S. Tacchella, M. Volonteri, F. Walter, A. Weibel, C.C. Williams, The Open Journal of Astrophysics 9 (2026).","chicago":"Sun, Wendy Q., Rohan P. Naidu, Jorryt J Matthee, Anna De Graaff, John Chisholm, Jenny E. Greene, Pascal A. Oesch, et al. “Little Red Dot - Host Galaxy = Black Hole Star: A Gas-Enshrouded Heart at the Center of Every Little Red Dot.” The Open Journal of Astrophysics. Maynooth Academic Publishing, 2026. https://doi.org/10.33232/001c.162505.","apa":"Sun, W. Q., Naidu, R. P., Matthee, J. J., De Graaff, A., Chisholm, J., Greene, J. E., … Williams, C. C. (2026). Little Red Dot - Host Galaxy = Black Hole Star: A gas-enshrouded heart at the center of every Little Red Dot. The Open Journal of Astrophysics. Maynooth Academic Publishing. https://doi.org/10.33232/001c.162505","mla":"Sun, Wendy Q., et al. “Little Red Dot - Host Galaxy = Black Hole Star: A Gas-Enshrouded Heart at the Center of Every Little Red Dot.” The Open Journal of Astrophysics, vol. 9, Maynooth Academic Publishing, 2026, doi:10.33232/001c.162505."},"volume":9,"article_type":"original","OA_type":"diamond","file":[{"content_type":"application/pdf","file_id":"21952","success":1,"file_size":7591188,"creator":"dernst","date_created":"2026-06-08T08:23:37Z","access_level":"open_access","file_name":"2026_OpenJourAstrophysics_Sun.pdf","relation":"main_file","date_updated":"2026-06-08T08:23:37Z","checksum":"33c4a444f7c37b3f47ecbd53eb187c1b"}],"quality_controlled":"1","author":[{"last_name":"Sun","first_name":"Wendy Q.","full_name":"Sun, Wendy Q."},{"full_name":"Naidu, Rohan P.","first_name":"Rohan P.","last_name":"Naidu"},{"full_name":"Matthee, Jorryt J","first_name":"Jorryt J","id":"7439a258-f3c0-11ec-9501-9df22fe06720","last_name":"Matthee","orcid":"0000-0003-2871-127X"},{"last_name":"De Graaff","first_name":"Anna","full_name":"De Graaff, Anna"},{"full_name":"Chisholm, John","first_name":"John","last_name":"Chisholm"},{"last_name":"Greene","first_name":"Jenny E.","full_name":"Greene, Jenny E."},{"full_name":"Oesch, Pascal A.","first_name":"Pascal A.","last_name":"Oesch"},{"last_name":"Torralba Torregrosa","orcid":"0000-0001-5586-6950","id":"018f0249-0e87-11f0-b167-cbce08fbd541","full_name":"Torralba Torregrosa, Alberto","first_name":"Alberto"},{"last_name":"Hviding","full_name":"Hviding, Raphael E.","first_name":"Raphael E."},{"last_name":"Brammer","first_name":"Gabriel","full_name":"Brammer, Gabriel"},{"last_name":"Simcoe","first_name":"Robert A.","full_name":"Simcoe, Robert A."},{"last_name":"Bose","full_name":"Bose, Sownak","first_name":"Sownak"},{"full_name":"Bouwens, Rychard","first_name":"Rychard","last_name":"Bouwens"},{"full_name":"Dayal, Pratika","first_name":"Pratika","last_name":"Dayal"},{"last_name":"Eilers","full_name":"Eilers, Anna Christina","first_name":"Anna Christina"},{"last_name":"Fei","first_name":"Qinyue","full_name":"Fei, Qinyue"},{"last_name":"Furtak","first_name":"Lukas J.","full_name":"Furtak, Lukas J."},{"last_name":"Gottumukkala","full_name":"Gottumukkala, Rashmi","first_name":"Rashmi"},{"first_name":"Andy","full_name":"Goulding, Andy","last_name":"Goulding"},{"first_name":"Kasper E.","full_name":"Heintz, Kasper E.","last_name":"Heintz"},{"first_name":"Michaela","full_name":"Hirschmann, Michaela","last_name":"Hirschmann"},{"first_name":"Vasily","full_name":"Kokorev, Vasily","last_name":"Kokorev"},{"full_name":"Leja, Joel","first_name":"Joel","last_name":"Leja"},{"last_name":"Liu","full_name":"Liu, Zhaoran","first_name":"Zhaoran"},{"last_name":"Natarajan","first_name":"Priyamvada","full_name":"Natarajan, Priyamvada"},{"last_name":"Santarelli","full_name":"Santarelli, Andrew D.","first_name":"Andrew D."},{"full_name":"Setton, David J.","first_name":"David J.","last_name":"Setton"},{"first_name":"Aaron","full_name":"Smith, Aaron","last_name":"Smith"},{"full_name":"Tacchella, Sandro","first_name":"Sandro","last_name":"Tacchella"},{"full_name":"Volonteri, Marta","first_name":"Marta","last_name":"Volonteri"},{"full_name":"Walter, Fabian","first_name":"Fabian","last_name":"Walter"},{"first_name":"Andrea","full_name":"Weibel, Andrea","last_name":"Weibel"},{"last_name":"Williams","full_name":"Williams, Christina C.","first_name":"Christina C."}],"day":"25","OA_place":"publisher","date_created":"2026-06-07T22:01:36Z","date_published":"2026-05-25T00:00:00Z","oa":1,"status":"public","PlanS_conform":"1","year":"2026","intvolume":" 9","type":"journal_article","fulldoi":"https://doi.org/10.33232/001c.162505","arxiv":1,"publication_status":"published","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication":"The Open Journal of Astrophysics"},{"volume":705,"article_type":"original","OA_type":"diamond","file":[{"success":1,"file_id":"21224","content_type":"application/pdf","creator":"dernst","file_size":2259914,"file_name":"2026_AstronomyAstrophysics_Torralba.pdf","date_created":"2026-02-16T07:35:03Z","access_level":"open_access","date_updated":"2026-02-16T07:35:03Z","relation":"main_file","checksum":"3782e03bc0843438aae8487f6af779c5"}],"quality_controlled":"1","author":[{"full_name":"Torralba Torregrosa, Alberto","first_name":"Alberto","orcid":"0000-0001-5586-6950","id":"018f0249-0e87-11f0-b167-cbce08fbd541","last_name":"Torralba Torregrosa"},{"full_name":"Matthee, Jorryt J","first_name":"Jorryt J","last_name":"Matthee","orcid":"0000-0003-2871-127X","id":"7439a258-f3c0-11ec-9501-9df22fe06720"},{"last_name":"Pezzulli","first_name":"Gabriele","full_name":"Pezzulli, Gabriele"},{"last_name":"Urrutia","full_name":"Urrutia, Tanya","first_name":"Tanya"},{"full_name":"Gronke, Max","first_name":"Max","last_name":"Gronke"},{"id":"edaf889c-c7cd-11ef-ab1b-bb28c431bd29","last_name":"Mascia","first_name":"Sara","full_name":"Mascia, Sara"},{"full_name":"D’Eugenio, Francesco","first_name":"Francesco","last_name":"D’Eugenio"},{"full_name":"Di Cesare, Claudia","first_name":"Claudia","id":"2d002343-372f-11ef-98ec-a164d20427cb","last_name":"Di Cesare"},{"last_name":"Eilers","first_name":"Anna Christina","full_name":"Eilers, Anna Christina"},{"last_name":"Greene","full_name":"Greene, Jenny E.","first_name":"Jenny E."},{"last_name":"Iani","id":"4053390a-6b68-11ef-9828-a3b8adef8d0a","orcid":"0000-0001-8386-3546","full_name":"Iani, Edoardo","first_name":"Edoardo"},{"first_name":"Yuzo","full_name":"Ishikawa, Yuzo","last_name":"Ishikawa"},{"first_name":"Ruari","full_name":"Mackenzie, Ruari","last_name":"Mackenzie"},{"first_name":"Rohan P.","full_name":"Naidu, Rohan P.","last_name":"Naidu"},{"full_name":"Navarrete, Benjamín","first_name":"Benjamín","last_name":"Navarrete","id":"aa14a535-50c9-11ef-b52e-e0c373d10148"},{"last_name":"Kotiwale","id":"1438afc8-1ff6-11ee-9fa6-cd4a75d66875","first_name":"Gauri","full_name":"Kotiwale, Gauri"}],"day":"14","OA_place":"publisher","das_tickbox":"1","date_created":"2026-01-25T23:01:41Z","date_published":"2026-01-14T00:00:00Z","oa":1,"PlanS_conform":"1","status":"public","year":"2026","intvolume":" 705","type":"journal_article","fulldoi":"https://doi.org/10.1051/0004-6361/202555596","publication_status":"published","arxiv":1,"tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication":"Astronomy & Astrophysics","article_number":"A147","project":[{"grant_number":"101076224","name":"Young galaxies as tracers and agents of cosmic reionization","_id":"bd9b2118-d553-11ed-ba76-db24564edfea"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","month":"01","language":[{"iso":"eng"}],"scopus_import":"1","oa_version":"Published Version","title":"A weak Ly α halo for an extremely bright little red dot. Indications of enshrouded supermassive black hole growth","ddc":["520"],"date_updated":"2026-07-08T06:38:23Z","_id":"21045","publisher":"EDP Sciences","external_id":{"arxiv":["2505.09542"]},"acknowledgement":"We thank the anonymous referee for constructive and useful comments. We thank Sebastiano Cantalupo for comments on the draft. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 114.27M6.001. Funded by the European Union (ERC, AGENTS, 101076224). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. We acknowledge funding from JWST program GO-3516. This work is based in part on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with program #3516. MG thanks the Max Planck Society for support through the MPRG. FDE acknowledges support by the Science and Technology Facilities Council (STFC), by the ERC through Advanced Grant 695671 “QUENCH”, and by the UKRI Frontier Research grant RISEandFALL. TU acknowledges funding from the ERC-AdG grant SPECMAP-CGM, GA 101020943. GK acknowledges support from the MERAC foundation.","corr_author":"1","department":[{"_id":"JoMa"},{"_id":"GradSch"}],"has_accepted_license":"1","article_processing_charge":"No","abstract":[{"lang":"eng","text":"The abundant population of little red dots (LRDs), compact objects with red UV to optical colors and broad Balmer lines at high redshift, is revealing new insights into the properties of early active galactic nuclei (AGN). Perhaps the most surprising features of this population are the presence of Balmer absorption and ubiquitous strong Balmer breaks. Recent models link these features to an active supermassive black hole (SMBH) cocooned in very dense gas (NH ∼ 1024 cm−2). We present a stringent test of such models using VLT/MUSE observations of A2744-45924, the most luminous LRD known to date (LHα ≈ 1044 erg s−1), located behind the Abell-2744 lensing cluster at z = 4.464 (μ = 1.8). We detect a moderately extended Lyα nebula (h ≈ 5.7 pkpc), spatially offset from the point-like Hα seen by JWST by ≈1.6 pkpc. The Lyα emission is narrow (FWHM = 270 ± 15 km s−1), and faint (Lyα = 0.07Hα) compared to Lyα nebulae typically observed around quasars of similar luminosity. We detect compact N IV]λ1486 emission, spatially aligned with Hα, and a spatial shift in the far-UV continuum matching the Lyα offset. We discuss that Hα and Lyα have distinct physical origins: Hα originates from the AGN, while Lyα is powered by star formation. In the environment of A2744-45924, we identified four extended Lyα halos (Δz < 0.02, Δr < 100 pkpc). Their Lyα luminosities match the expectations based on Hα emission, and show no evidence for radiation from A2744-45924 affecting its surroundings. The lack of strong, compact, and broad Lyα and the absence of a luminous extended halo, suggest that the UV AGN light is obscured by dense gas cloaking the SMBH with a covering factor close to unity."}],"publication_identifier":{"eissn":["1432-0746"],"issn":["0004-6361"]},"file_date_updated":"2026-02-16T07:35:03Z","citation":{"mla":"Torralba Torregrosa, Alberto, et al. “A Weak Ly α Halo for an Extremely Bright Little Red Dot. Indications of Enshrouded Supermassive Black Hole Growth.” Astronomy & Astrophysics, vol. 705, A147, EDP Sciences, 2026, doi:10.1051/0004-6361/202555596.","apa":"Torralba Torregrosa, A., Matthee, J. J., Pezzulli, G., Urrutia, T., Gronke, M., Mascia, S., … Kotiwale, G. (2026). A weak Ly α halo for an extremely bright little red dot. Indications of enshrouded supermassive black hole growth. Astronomy & Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202555596","ieee":"A. Torralba Torregrosa et al., “A weak Ly α halo for an extremely bright little red dot. Indications of enshrouded supermassive black hole growth,” Astronomy & Astrophysics, vol. 705. EDP Sciences, 2026.","ista":"Torralba Torregrosa A, Matthee JJ, Pezzulli G, Urrutia T, Gronke M, Mascia S, D’Eugenio F, Di Cesare C, Eilers AC, Greene JE, Iani E, Ishikawa Y, Mackenzie R, Naidu RP, Navarrete B, Kotiwale G. 2026. A weak Ly α halo for an extremely bright little red dot. Indications of enshrouded supermassive black hole growth. Astronomy & Astrophysics. 705, A147.","chicago":"Torralba Torregrosa, Alberto, Jorryt J Matthee, Gabriele Pezzulli, Tanya Urrutia, Max Gronke, Sara Mascia, Francesco D’Eugenio, et al. “A Weak Ly α Halo for an Extremely Bright Little Red Dot. Indications of Enshrouded Supermassive Black Hole Growth.” Astronomy & Astrophysics. EDP Sciences, 2026. https://doi.org/10.1051/0004-6361/202555596.","short":"A. Torralba Torregrosa, J.J. Matthee, G. Pezzulli, T. Urrutia, M. Gronke, S. Mascia, F. D’Eugenio, C. Di Cesare, A.C. Eilers, J.E. Greene, E. Iani, Y. Ishikawa, R. Mackenzie, R.P. Naidu, B. Navarrete, G. Kotiwale, Astronomy & Astrophysics 705 (2026).","ama":"Torralba Torregrosa A, Matthee JJ, Pezzulli G, et al. A weak Ly α halo for an extremely bright little red dot. Indications of enshrouded supermassive black hole growth. Astronomy & Astrophysics. 2026;705. doi:10.1051/0004-6361/202555596"},"doi":"10.1051/0004-6361/202555596"},{"ddc":["520"],"date_updated":"2026-07-13T08:08:41Z","publisher":"IOP Publishing","_id":"22263","external_id":{"arxiv":["2603.28335"]},"acknowledgement":"IOP Science home\r\nThe Astrophysical Journal Letters\r\nThe American Astronomical Society, find out more.\r\n\r\nThe following article isOpen access\r\nA Black Hole Star at Cosmic Noon: Extreme Balmer Break, Photospheric Continuum, and Broad Absorption by Thick Winds in a Little Red Dot at z = 1.7\r\nAlberto Torralba, Jorryt Matthee, Andrea Weibel, Rohan P. Naidu, Yilun Ma, Aidan P. Cloonan, Aayush Desai, Anna de Graaff, Jenny E. Greene, Christian Kragh JespersenShow full author list\r\n\r\nPublished 2026 June 30 • © 2026. The Author(s). Published by the American Astronomical Society.\r\nThe Astrophysical Journal Letters, Volume 1005, Number 2\r\nCitation Alberto Torralba et al 2026 ApJL 1005 L37\r\nDOI 10.3847/2041-8213/ae7bfd\r\n\r\nPDFOpens in a new tab.ePub\r\nAuthors\r\nFigures\r\nTables\r\nReferences\r\nArticle data\r\nPDFOpens in a new tab.ePub\r\nArticle metrics\r\n122 Total downloads\r\n\r\nShare this article\r\nArticle information\r\nAbstract\r\nRecent studies at high redshift have revealed an enigmatic class of little red dots (LRDs) with extreme Balmer breaks, stronger than in any stellar atmosphere. However, it is unclear whether such objects exist at lower redshift, especially given the low number of LRDs reported at z ≲ 2. Here, we report the discovery of PAN-BH*-1, an LRD with an extreme Balmer break at z = 1.73, identified from JWST/NIRCam pure-parallel imaging taken by the PANORAMIC survey, and confirmed by deep VLT/X-Shooter spectroscopy. The rest-optical to near-infrared spectral energy distribution of PAN-BH*-1 is consistent with a photospheric continuum with effective temperature Teff ≈ 4800 K. The broad Hα emission line shows remarkably deep absorption, stronger than previously measured in any LRD. The absorption trough spans from −520 to +267 km s−1 with respect to the systemic redshift. The presence of blue- and red-shifted absorption suggests complex dynamics of the obscuring gas along the line of sight. We speculate that the absorption trough can be produced by a thick wind launched from a thick, rotating photospheric disk, the latter being the source of the red optical continuum. While the source is unresolved in the rest-optical JWST data (reff < 47 pc), the rest-near-UV Hubble Space Telescope imaging shows an extended morphology with \r\n kpc, which we interpret as a host galaxy with a stellar mass of ∼108 M⊙, in line with the narrow Hα emission. The discovery of this object at cosmic noon highlights the feasibility of systematic searches for extreme LRDs with wide-area facilities such as Euclid and Roman.\r\n\r\nExport citation and abstract\r\nBibTeXRIS\r\n\r\nPrevious article in issue\r\nNext article in issue\r\n\r\nOriginal content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.\r\n\r\n1. Introduction\r\nThe unprecedented sensitivity of JWST has enabled the discovery of a new, abundant population of objects at redshifts z ≈ 3–9 nicknamed the “little red dots” (LRDs). These are characterized by their compact rest-frame optical morphology, broad emission lines, and a characteristic rest-UV to optical “V-shape” in their spectral energy distributions (SED; e.g., D. D. Kocevski et al. 2023; V. Kokorev et al. 2024; J. Matthee et al. 2024; I. Labbe et al. 2025).\r\n\r\nThe nature of LRDs is highly debated (see K. Inayoshi & L. C. Ho 2025, for a recent overview) as the LRDs show systematic differences with respect to other types of active galactic nuclei (AGN), such as faintness in X-rays (e.g., T. T. Ananna et al. 2024; M. Yue et al. 2024), mid-to-far-infrared dust emission (e.g., G. C. K. Leung et al. 2025; C. C. Williams et al. 2024; I. Delvecchio et al. 2025; D. J. Setton et al. 2025; M. Xiao et al. 2025), and radio (e.g., G. Mazzolari et al. 2026; M. A. Latif et al. 2025; K. Perger et al. 2025, see A. J. Gloudemans et al. 2025).\r\n\r\nA recurring spectral feature of LRDs is the presence of a strong Balmer break (e.g., D. J. Setton et al. 2025; B. Wang et al. 2024; R. E. Hviding et al. 2025; W. Q. Sun et al. 2026), in some cases stronger than any star or stellar population can produce. The two most prominent examples known to date are The Cliff at z ≈ 3.5 (A. de Graaff et al. 2025a) and MoM-BH* at z ≈ 7.8 (R. P. Naidu et al. 2025). The joint appearance of strong Balmer lines as well as strong Balmer breaks has been modeled as being due to absorption by a dense, neutral gas with a high column density in the line of sight to a highly ionizing source (K. Inayoshi & R. Maiolino 2025; X. Ji et al. 2025; A. Sneppen et al. 2026; A. Torralba et al. 2026). These observations have sparked the development of new theoretical models, ranging from a spherical envelope analogous to stellar atmospheres (e.g., M. C. Begelman & J. Dexter 2026; D. Kido et al. 2025; H. Liu et al. 2025; D. Nandal & A. Loeb 2026) or a thick accretion disk (e.g., H. Liu et al. 2025, 2026; K. Inayoshi et al. 2025; Y.-X. Chen et al. 2026).\r\n\r\nBesides their spectral features, the evolution of the LRD number densities is also in stark contrast to other types of AGNs (e.g., K. Inayoshi 2025). At 4 ≲ z ≲ 7, LRDs represent a few percent of the galaxy population (e.g., D. D. Kocevski et al. 2023, 2025; J. E. Greene et al. 2024; V. Kokorev et al. 2024; X. Lin et al. 2024; R. Maiolino et al. 2024; J. Matthee et al. 2024), with number densities of ≳10−5 Mpc−3. The number density does not appear to drop quickly beyond z > 5 (e.g., J. Zhang et al. 2026), with various LRDs having been confirmed at z > 8 (V. Kokorev et al. 2023; A. J. Taylor et al. 2025; R. Tripodi et al. 2025), well beyond the quasar redshift record (F. Wang et al. 2021). Photometric LRD candidates exist beyond z > 10 (T. S. Tanaka et al. 2025). In turn, the number density of LRDs seems to decline steeply at z < 4 (e.g., Y. Ma et al. 2026), with estimates of a number density of ∼10−6 cMpc−3 at z ∼ 2 and even ∼10−10 cMpc−3 at z ≈ 0.3 (X. Lin et al. 2026). While it is challenging to ensure a uniform selection function across such a large redshift baseline and dedicated spectroscopic follow-up of such lower redshift candidates has only just started, it is challenging to attribute five orders of magnitude to such effects.\r\n\r\nMotivated by the discovery of rare objects with extreme Balmer breaks at z > 3 and the very small number of known LRDs at lower redshift, we performed a dedicated search for extreme Balmer break objects using a template-match approach on a large compilation of JWST NIRCam data over ≈0.3 deg2 and z ≈ 1.5–7.0. This survey is presented in A. Weibel et al. (2026a). As part of an ongoing ground-based spectroscopic campaign of LRD candidates at z ∼ 2 (Y. Ma et al. 2026), we followed up the most luminous candidate with a photometric redshift of z ≈ 2 with the X-Shooter spectrograph on the Very Large Telescope (VLT). In this Letter, we present the discovery and spectroscopic confirmation of PAN-BH*-1, a luminous LRD at z = 1.73 with an extreme Balmer break comparable to the strongest observed in any LRD (and, in general, any astrophysical source). The low redshift of this source enables high-resolution spectroscopy from ground-based observatories that is otherwise impossible to obtain at high redshift.\r\n\r\nThroughout this Letter, we use a ΛCDM cosmology with Ωm = 0.31, ΩΛ = 0.69, and h = 0.677 as described by Planck Collaboration et al. (2020). All the magnitudes are given in the AB system (J. B. Oke & J. E. Gunn 1983).\r\n\r\n2. Observations\r\n2.1. Photometry and Source Selection\r\nWe identified PAN-BH*-1 (ID: PAN-1115, RA, DEC: 40.015835, −1.659363 J2000) as part of a systematic search across ≈0.3 deg2 of JWST NIRCam legacy imaging comprising at least six filters of coverage (A. Weibel et al. 2026b). Notably, this dataset includes the Cycle 1 pure parallel survey PANORAMIC (PID: 2514, PIs: Williams & Oesch; C. C. Williams et al. 2025) that contributes 28 of the 35 independent lines of sight, thereby enabling the discovery of rare objects such as PAN-BH*-1 across diverse large-scale structure environments. Specifically, this source was identified in the footprint j024000m0142 of the PANORAMIC DR1,15 which is adjacent to the A370 field (G. O. Abell et al. 1989), where archival images by the Hubble Space Telescope (HST) are available from the BUFFALO survey (C. L. Steinhardt et al. 2020). The HST/ACS images were processed with grizli and also released as part of the PANORAMIC dataset.\r\n\r\nPAN-BH*-1 is in the outskirts of the A370 lensing cluster, but the magnification is only μ ≈ 1.05 according to the models from A. Niemiec et al. (2023). Throughout the rest of the paper, we report the uncorrected flux measurements, since the effect of magnification (∼5%) is negligible given the uncertainties in the observations and the lensing model.\r\n\r\nThe search strategy and full photometric selection are described in a companion paper (A. Weibel et al. 2026a). Briefly, that work presents a new selection of LRDs as a combination of a “black hole star” template (BH*; R. P. Naidu et al. 2025) embedded in a host galaxy, instead of the typically used “V-shaped” selections (e.g., D. D. Kocevski et al. 2025; V. Kokorev et al. 2024). The host galaxies are modeled using eazy’s blue_sfhz templates. The BH*s are modeled using a novel template set comprising empirical luminosity-based stacks constructed in W. Q. Sun et al. (2026), the cloudy template from R. P. Naidu et al. (2025), and by using spectra of prominent LRDs spanning the observed effective temperature range (I. Labbe et al. 2024; A. de Graaff et al. 2025a; B. Wang et al. 2026).\r\n\r\nPAN-BH*-1 stood out as one of the few sources where the BH* template effectively dominated all the light over the full wavelength range covered by NIRCam (hence the name). The redshift of PAN-BH*-1 was estimated to be zphot = 1.85. Follow-up VLT/X-Shooter spectroscopy confirmed the redshift as zspec = 1.731 (see Section 3.2).\r\n\r\nPAN-BH*-1 is also covered by archival data from the VLT with the HAWK-I camera in the Ks band (G. B. Brammer et al. 2016) and in data from the Spitzer Space Telescope in IRAC bands 1 and 3 (3.6 and 5.7 μm), and MIPS 24 μm (P. Capak 2019). PAN-BH*-1 is detected in the Ks band and in the two IRAC filters. Performing Spitzer photometry of this source is challenging due to the large point spread function (PSF) and a neighboring source, especially in the MIPS band. However, the NIRCam photometry of the neighboring source suggests it has a limited contribution to the IRAC fluxes. The details of the photometry extraction are described in Appendix A, and the measured magnitudes in Table 2.\r\n\r\n2.2. VLT/X-Shooter Spectroscopy\r\nPAN-BH*-1 was observed for 5.8 ks with the X-Shooter spectrograph (J. Vernet et al. 2011) on the VLT as a bright backup target for program 116.294D (PI: Matthee) in visitor mode on 2025 December 17. The main aim of this program was to confirm candidate LRDs at cosmic noon (Y. Ma et al. 2026). These observations confirmed the redshift through the detection of Hα at z = 1.731. A DDT program (ID 116.2AQ0; PI: Matthee) obtained additional follow-up data of PAN-BH*-1 in service mode for 26.2 ks during 2026 January 10–26, yielding a total exposure time of 8.9 hr. X-Shooter observes with three arms simultaneously, UVB, VIS, and near-infrared (NIR), covering rest-frame wavelengths of ≈0.14–0.9 μm, albeit hampered by skyline emission and telluric absorption, primarily in the rest-frame optical.\r\n\r\nThe observing conditions were clear, with a seeing ranging from 05 to 07 (median 06). The service mode observations were primarily conducted during dark nights, with some gray (FLI = 0.03–0.6, median 0.1), and a typical airmass of 1.35. We used UVB, VIS, and NIR slits with widths 10, 09, and 09, yielding a nominal resolution of R = 5400, 8900, and 5600, respectively (FWHM ∼53 km s−1 for NIR). The target acquisition was done using blind offsets from a reference star, due to the target being too faint for direct acquisition. We used a standard nodding on the slit pattern, with 4″ nod throws in an ABBA pattern, and 1″ jitters in the NIR arm to improve the sky subtraction. In each observing block of ≈1 hr, the exposure times were 700, 655, and (2×)365 s for the three arms at each nod position.\r\n\r\nThe reduction of the X-Shooter data uses a combination of EsoRex libraries16 and Python code based on the reduction pipeline employed in J. Matthee et al. (2021). Each observing block was reduced separately. We used standard stars taken during the observing night for a first-pass flux calibration. Telluric corrections were applied using the molecfit tool (A. Smette et al. 2015) implemented in the X-Shooter EsoRex pipeline. Telluric stars were observed during the visitor nights, but they were not always observed during the service mode observations in January. For those observations, we took the telluric star that was observed at the closest observing date. Based on the variation in telluric absorption among the reference stars taken during this period, we estimate the variation in the transmission and propagate the uncertainty in the telluric correction. For each observing block, we then extracted an optimally extracted 1D spectrum using the spatial profile of the Hα line, thus accounting for seeing variations and (more importantly) minor errors in the accuracy of the slit pointing. Before median combining these spectra, we normalize them by the median Hα flux of all observations to account for variations in slit losses and flux calibrations.\r\n\r\nBesides Hα (integrated S/N = 75) and Hβ (integrated S/N = 6; Section 3.2), we also detect continuum emission in the best regions in the H and K bands at 1.6 μm and 2.1 μm, respectively, with a low signal-to-noise ratio (S/N) of ∼1 per resolution element. Unfortunately, the [O iii] λλ4960, 5008 doublet is undetectable because the observed wavelengths are impacted by very strong telluric absorption. No other lines or continuum are detected in the X-Shooter spectrum.\r\n\r\n3. Properties of PAN-BH*-1\r\n3.1. Spectral Shape: A Photospheric Continuum with Strong Hα Emission\r\nThe photometric SED of PAN-BH*-1 has remarkable similarities with The Cliff (Figure 1): luminous in the rest optical, with a sudden drop toward the rest-UV around the Balmer limit, and very weak near-to-mid infrared continuum emission. With a rough extrapolation of the two HST photometric points using a power-law fit (fλ ∝ λβ), we obtain a UV slope of β = −0.1 ± 1.2, and MUV = −16.7 ± 0.7. For the rest-frame optical to NIR data, we fit a Planck blackbody law to the JWST data points, after subtracting the measured Hα flux (see Section 3.2) from the F200W photometry. The rest-optical and NIR photometry of PAN-BH*-1 is remarkably well described by a single temperature blackbody with T = 4204 K (with a best-fit ). We measure the strength of the Balmer break from the fν ratio F115W/F814W = 7 ± 1, in line with the Balmer break strengths of The Cliff (; A. de Graaff et al. 2025a)17 and MoM-BH* (7.8 ± 1.8; R. P. Naidu et al. 2025), measured from JWST/NIRSpec PRISM spectra as fν,4000–4100/fν,3620−3720. In Figure 2, we compare the Balmer break strength with the spectroscopic sample of A. de Graaff et al. (2025b), showing that out of 134 sources, only two have breaks significantly above 5. This suggests that PAN-BH*-1 has among the most extreme Balmer breaks known, although we caution that our value is derived from wide-band photometry with pivot wavelengths corresponding to 4212 and 3042 Å, respectively, rather than from spectroscopy.\r\n\r\nZoom InZoom OutReset image size\r\nFigure 1. SED of PAN-BH*-1 Top: cutouts from all the HST and JWST images in which PAN-BH*-1 is covered. It shows a remarkably compact morphology in all the wavelengths, resolved only in the HST F606W and F814W bands (Section 3.3). Bottom: photometry from JWST/NIRCam (blue squares), HST/ACS (purple pentagons), and Spitzer/IRAC+MIPS (red hexagons, and red triangle for the 5σ upper limit). The empty square is the F200W flux after subtracting the Hα flux measured from X-Shooter spectroscopy. We show the spectrum of The Cliff for comparison (gray line), shifted to z = 1.73 and normalized to the F150W flux of PAN-BH*-1. We also show the best-fitting blackbody spectrum (blue dashed line) and the best model from the synthetic LRD atmosphere models from H. Liu et al. (2026), shifted to z = 1.73 (green line), undersampled by a factor of 500 for clarity.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution image\r\nZoom InZoom OutReset image size\r\nFigure 2. Spectroscopic sample of LRDs by redshift and Balmer break strength. We plot the redshift and Balmer break strength of PAN-BH*-1, and the JWST sample from A. de Graaff et al. (2025b) (purple diamonds), and three local LRDs in X. Lin et al. (2026), for comparison. We also highlight three sources with a particularly strong Balmer break: The Cliff (A. de Graaff et al. 2025a), MoM-BH* (R. P. Naidu et al. 2025), and CAPERS-LRDz9 (A. J. Taylor et al. 2025). The Balmer break strength of the JWST spectroscopic sample is computed as fν,4000–4100/fν,3620–3720, whereas the value for PAN-BH*-1 is directly obtained from the F115W/F814W photometry.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution image\r\n3.2. Hα and Hβ Emission Lines\r\nThe Hα profile appears as a complex combination of a broad line with strong absorption close to the systemic redshift. We fit the Hα emission line with a similar model as the one used in A. Torralba et al. (2026) and J. Matthee et al. (2026). The Hα model consists of two Gaussian emission components (with narrow and intermediate line widths), and a broad symmetric exponential convolved with the intermediate profile and parameterized as in F. D’Eugenio et al. (2025a). The absorption is implemented as an opacity law defined as e−τ(λ), where τ(λ) also follows a single Gaussian velocity distribution (F. D’Eugenio et al. 2025a, 2025b; A. Torralba et al. 2026). For simplicity, we assume a covering factor of Cf = 1 for the absorbing gas. In previous works, the width of the narrow component is tied to that of [O iii], assuming both components come from the same region, often interpreted as the interstellar medium (ISM) of the host galaxy. In this case, we have no information about [O iii] due to this doublet falling in a wavelength range heavily affected by strong telluric absorption. We fit the Hα line after masking relevant skylines and strong telluric absorption bands. The fitted Hα parameters are listed in Table 1 and the best-fit model is shown in Figure 3. The absorption feature is notably strong, with an equivalent width of EWabs = −148 ± 12 Å with respect to the fitted continuum and 12.2 ± 0.2 Å if including the broad emission component. The absorption corresponds to a Balmer optical depth at the line center of , reaching roughly the continuum level. The FWHM of the single Gaussian fitted to the absorber is 283 ± 8 km s−1, and is offset from the systemic redshift by −94 ± 4 km s−1. We note that this parameterization is somewhat arbitrary, and we discuss in detail the absorber properties in Section 4.\r\n\r\nZoom InZoom OutReset image size\r\nFigure 3. Hα spectrum, and the best fit to our fiducial model. We show the X-Shooter R ∼ 5600 spectrum of the Hα line of PAN-BH*-1, along with the best-fit to the model described in Section 3.2; total model (red solid line) and individual components (discontinuous color lines). The red wing of the line is severely affected by telluric absorption, thus the large uncertainties.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution image\r\nTable 1. Properties of PAN-BH*-1\r\n\r\nParameter\tValue\tUnit\r\nWidth (FWHM; Hα)\r\nExponential\t1257 ± 27\tkm s−1\r\nIntermediate\t687 ± 43\tkm s−1\r\nNarrow\t184 ± 12\tkm s−1\r\nAbsorption\t283 ± 8\tkm s−1\r\nFlux (Hα)\r\nExponential\t643 ± 7\t10−18 erg s−1 cm−2\r\nIntermediate\t19 ± 5\t10−18 erg s−1 cm−2\r\nNarrow\t38 ± 3\t10−18 erg s−1 cm−2\r\nTotal\t522 ± 7\t10−18 erg s−1 cm−2\r\nGeneral properties\r\n(LHα/erg s−1)\t43.046 ± 0.006\t⋯\r\nEW0(Hα)\t520 ± 20\tÅ\r\nSFR(Hα, narrow)a\t2.1 ± 0.2\tM⊙ yr−1\r\nSFR(Hα, narrow)b\t3.3 ± 0.3\tM⊙ yr−1\r\nreff,UV (F606W+F814W)\t\tkpc\r\nreff,opt (F200W)\t<0.047\tkpc\r\nHα/Hβ (total)\t>9.4\t⋯\r\nHα/Hβ (narrow)\t5 ± 1\t⋯\r\nNotes. aCalibration from I. G. Kramarenko et al. (2026). bCalibration from R. C. Kennicutt & N. J. Evans (2012). SFR values calculated assuming no dust attenuation.\r\n\r\nDownload table as: \r\nASCIITypeset image\r\n\r\nThe Hβ line is marginally detected. After undersampling the spectrum by a factor 5, a hint of a weak narrow component can be identified (Figure 4), along with a tentative absorption at the same mean velocity as in Hα. We fit the best Hα model to the Hβ spectrum, only rescaling it by a multiplicative factor, and adding a flat continuum component. By doing this, we find an Hβ flux of (47 ± 8) × 10−18 erg s−1 cm−2 (S/N ≈ 6). Conservatively, we obtain a Balmer decrement of Hα/Hβ > 9.4 (at a 3σ confidence level), in line with the high decrements found for the LRD population (e.g., G. P. Nikopoulos et al. 2026; A. de Graaff et al. 2025b; J. Matthee et al. 2026). In Figure 5, we show the Hβ spectrum compared to the rescaled Hα model. By matching the best-fit Hα profile with the data at the expected observed wavelength for Hβ (±5000 km s−1), we obtain a better agreement (, BIC = 1537) than fitting a flat continuum only (, BIC = 1658) with ΔBIC = 121 ≫ 10, strongly favoring a detection of a broad Hβ emission line, and securing the spectroscopic redshift. Similarly, we fit a narrow Gaussian to Hβ with the same width and velocity as the Hα best-fit model, assuming a completely saturated absorption. We obtain a Balmer decrement for the narrow component of Hα/Hβ = 5 ± 1, which would imply a dust extinction of using a J. A. Cardelli et al. (1989) attenuation law, under the assumption of case B recombination. However, due to the low S/N of Hβ this result is only tentative, and compatible with a standard Case B value within ∼2σ.\r\n\r\nZoom InZoom OutReset image size\r\nFigure 4. X-Shooter spectrum of Hα and Hβ of PAN-BH*-1 (blue). We compare to the spectrum of The Cliff (gray; data from JWST DDT #9433), normalized in each panel to the flux of PAN-BH*-1 in the range v ∈ (−3000, −2000) km s−1. Due to the low S/N, the Hβ spectrum of PAN-BH*-1 is rebinned to a coarser grid by a factor 5, after masking the most relevant skylines.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution image\r\nZoom InZoom OutReset image size\r\nFigure 5. Hβ spectrum. The spectrum is rebinned by a factor of 10 with inverse variance flux weighting for visual clarity, due to the low S/N. We compare to the best-fit Hα model, scaled by a factor of 0.112. In the bottom panel, we show the χ residuals between the spectrum and the rescaled Hα model in black, and for only the continuum in pink (ΔBIC = 121 strongly favoring the presence of a broad Hβ line).\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution image\r\n3.3. Spatial Morphology\r\nIn order to assess whether PAN-BH*-1 is spatially resolved, we use the Bayesian profile fitting software pysersic (I. Pasha & T. B. Miller 2023)18 to fit a single Sérsic profile to the JWST and HST imaging data of PAN-BH*-1. For JWST/NIRCam, we choose F200W as the filter with the highest S/N in the short wavelength channel, benefiting from a high spatial resolution and probing rest-frame optical wavelengths. To model its PSF, we use version 2.2.0 of the stpsf software (formerly webbpsf, M. D. Perrin et al. 2014). For the two HST bands F606W and F814W, we instead construct empirical PSFs from public imaging data in the GOODS-S field following A. Weibel et al. (2024). In all three bands, we sample the posterior with the No U-turn sampler in two chains with 1000 warm-up and 2000 sampling steps each. We find that PAN-BH*-1 is unresolved with NIRCam in F200W where the effective radius converges toward the edge of the prior at 0.25 pixels. Using the 95th percentile of the posterior chains as an upper limit on the effective radius, we find a rest-optical size of reff < 47 pc.\r\n\r\nPAN-BH*-1 appears to be resolved in the HST images corresponding to rest-frame pivot 0.2 and 0.3 μm, respectively. Due to the low signal-to-noise of the F606W and F814W photometry, we fit both bands simultaneously fixing all the morphological parameters in both images. We measure physical effective radii of kpc (see Appendix B). The modest stretching by the foreground A370 lensing cluster could imply a correction of ∼10% to the measured radius (A. Niemiec et al. 2023), which we disregard given the uncertainties. These measured sizes are consistent with the typical sizes for galaxies with a stellar mass ≲ 109 M⊙ at z = 1.75 (A. van der Wel et al. 2014). These findings are consistent with the scenario of a compact LRD “engine” dominating the rest-optical light embedded in a host galaxy, whose contribution becomes significant blueward of the Balmer break (see A. P. Cloonan et al. 2026, for a relevant discussion).\r\n\r\n4. Absorber Kinematics\r\nAs described in Section 3.2, the velocity distribution of the absorber is empirically modeled with a Gaussian, which we find has a central velocity of −94 ± 4 km s−1 relative to the redshift of the narrow emission component (adopted as systemic). The absorption trough extends from negative to positive velocities with respect to the redshift of the narrow component, but also with respect to the center of the symmetric exponential wings. However, there are several degeneracies between the shape of the absorber and other components of the emission line, such as the narrow central emission (see Section 3.2). Furthermore, direct interpretation of the absorber center velocity shift is challenging in an optically thick gas with presumably complex dynamics, and it does not necessarily trace bulk motion. A more robust, physically motivated pair of quantities is the minimum and maximum absorber velocities. We define them as the values where the transmission of the Balmer absorber increases to 99%, km s−1 and km s−1. These values trace the largest velocities in the line of sight of gas with significant Balmer absorption. The absorbing trough extends over 787 ± 17 km s−1 under this definition. The values of and are relatively agnostic to the choice of the shape of the absorber, since they are determined by the wavelength where the line profile deviates from a broad, symmetric exponential profile. In Figure 6, we illustrate three proposed configurations of the velocity distribution of the absorbing gas that could explain the shape of the observed Balmer absorption, and we discuss these scenarios below.\r\n\r\nZoom InZoom OutReset image size\r\nFigure 6. Geometric configurations for the absorber. We illustrate three scenarios that could give rise to the observed Balmer absorption in PAN-BH*-1. In scenario (a), the obscuring agent is a thick screen of gas with a certain bulk velocity, and turbulent motions produce the broadening of the absorption trough. In (b), there are two (or more) absorbers with opposite velocities in the line of sight. These first two scenarios are dynamically unstable; therefore, variability is expected in the absorption. Lastly, in (c), we observed an extended source through a disk wind with a rotational component (vϕ) in addition to the poloidal (nonazimuthal) velocity (vp). In the last scenario, the redshifted absorption is produced by streamlines that oppose the observer when projected along the line of sight, despite the fact that the gas is outflowing from the central source.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution image\r\n4.1. Unstable Gas Flows?\r\nThe fact that there is significant absorption at both negative and positive velocities with respect to the systemic redshift cannot be simply explained by an axisymmetric outflowing or inflowing wind. In the case of observing a compact object through a spherically symmetric, nonturbulent bulk flow, a classical P Cygni profile is expected, with a purely blueshifted absorption (or redshifted if the wind is infalling). The fact that we also see redshifted absorption rules out this simple scenario. In principle, turbulent motions could also produce broadening of the absorbing medium (scenario a in Figure 6). However, the required turbulent velocity dispersion σturb ≈ 120 km s−1 (from the Gaussian fit in Section 3.2) is comparable to the mean velocity of the absorption trough, meaning that turbulence dominates the gas flow. In such a case, strong variability of the absorption profile would be expected, given the typical dynamical crossing times (see Sect. 4.1 in F. D’Eugenio et al. 2025b). For example, for a radius of 1016 cm (e.g., A. Torralba et al. 2026) and a mass of 106 M⊙, the dynamical freefall time is yr. Moreover, the turbulent velocity would be highly supersonic, and the dissipation timescale would be comparable to the dynamical time (e.g., M.-M. Mac Low 1999). Alternatively, in the context of a strong Balmer absorber at z ∼ 7, F. D’Eugenio et al. (2026) recently discussed a “breathing mode” scenario with cyclic inflows and outflows along the same line of sight, with the gas being in different phases at different depths (scenario b in Figure 6; see also K. Park et al. 2017). In this case, the same arguments regarding the stability of the absorber would apply, and absorber variability is expected on observed timescales of ∼5 yr (for a source at z = 1.7), which is testable with future observations.\r\n\r\n4.2. The Case for the Disk Wind Hypothesis\r\nAn alternative, dynamically stable scenario is a disk wind configuration (scenario c in Figure 6). Here, the wind would be launched from a thick disk near the central engine, which we speculate could be the source of the optical continuum emission (e.g., H. Liu et al. 2025, 2026; L. Zwick et al. 2025; Y.-X. Chen et al. 2026). A rotating disk would imprint to the wind an azimuthal velocity component (vϕ). Observations at specific lines of sight, particularly for high inclination angles (close to edge-on) where the rotational component dominates the poloidal velocity, can give rise to both blueshifted and redshifted absorption features (D. Proga et al. 2000; P. B. Hall et al. 2002, 2013; D. Proga & T. R. Kallman 2004; M. Giustini & D. Proga 2012). Most observed LRDs have blueshifted P Cygni–like absorbers (J. Matthee et al. 2026), which can be naively interpreted as a uniformly expanding shell. The low incidence of redshifted Balmer absorbers in LRD spectra (e.g., I. Labbe et al. 2024; A. de Graaff et al. 2025a; F. D’Eugenio et al. 2025b, 2026; Y. Ma et al. 2026) can therefore be explained by the requirement of high inclination angles to observe such features (see also A. Sneppen et al. 2026). Such a picture is broadly in line with disk wind models for AGN with broad absorption lines (e.g., P. B. Hall et al. 2002; H. Zhou et al. 2019) and around stars with circumstellar disks (e.g., J. Erkal et al. 2022), such as accreting T Tauri stars (S. Edwards et al. 2006) or cataclysmic variables (D. Proga 2003).\r\n\r\n4.3. Implications of Rotating Winds for the Emission Lines of LRDs\r\nThe disk wind hypothesis would imply that a photosphere in the shape of a rotating disk is the source of the optical continuum emission, and drives winds that can explain the observed absorption trough. Emission lines originating in a thin rotating disk would have a double-peaked profile in the idealized case (for most inclination angles), but this is not necessarily true if the disk is not sufficiently thin (e.g., N. Murray & J. Chiang 1997), for instance, in the case of a puffed-up disk associated with super-Eddington accretion (e.g., H. Liu et al. 2026). In addition, most line emission would not be produced directly at the base of the disk, but slightly outside (e.g., via collisional cooling or residual recombination; A. Torralba et al. 2026), where the rotational velocity is lower, and the dynamics are complex (e.g., G. A. Shields 1977).\r\n\r\nThe Balmer lines of most LRDs are dominated by broad, symmetric exponential components that are associated with broadening by electron scattering (e.g., V. Rusakov et al. 2026; J. Matthee et al. 2026). For PAN-BH*-1, the Hα line profile of PAN-BH*-1 is compatible with a broad exponential profile emerging through a dense wind where the absorption trough is produced. In dense gas with a large column density of neutral hydrogen, and optically thick to Balmer transitions (NHI,2s ≳ 1014 cm−2), resonant scattering effects become important. Crucially, resonant scattering impacts Hα and Hβ differently (e.g., S.-J. Chang et al. 2026), hence the 3D radiative transfer and photon redistribution of both lines may produce different profiles (see, e.g., Figure 2 in D. Proga 2003). Therefore, the empirical fitting and interpretation of the absorption profiles becomes nontrivial. Dedicated radiative transfer modeling is necessary to study such effects, and they can be tested in other emission lines with high optical depth, such as He i λ10830 Å, or resonant lines like C iv λ1550.\r\n\r\n5. Implications for the Galaxy and Black Hole Masses\r\n5.1. Properties of the Host Galaxy\r\nAssuming that the narrow component of Hα corresponds to ISM emission in the host galaxy, we compute the associated star formation rate using the local calibration from R. C. Kennicutt & N. J. Evans (2012) and assuming no dust attenuation. We obtain SFR(Hα) = 3.3 ± 0.3 M⊙ yr−1. A somewhat lower value of SFR(Hα) = 2.1 ± 0.2 M⊙ yr−1 is obtained using the high-redshift (z ≳ 4) calibrations in I. G. Kramarenko et al. (2026), which might be more appropriate for a young dwarf galaxy with a bursty star formation history. The star formation rates are low, but in line with a main-sequence galaxy with (extrapolating the relation from J. S. Speagle et al. 2014). Assuming zero dust attenuation, the UV absolute magnitude (MUV = −16.7 ± 0.7; Section 3.1) would imply SFR(UV) = 0.18 ± 0.12 M⊙ yr−1 (R. C. Kennicutt & N. J. Evans 2012). The discrepancy between the UV and Hα inferred star formation rate suggests there is some amount of dust attenuation in the host galaxy.\r\n\r\nWe derive a dynamical mass from the width of the narrow component Hα line and the estimated UV size as , adopting the empirical virial correction K(n)K(q) from A. van der Wel et al. (2022), where K(n) and K(q) are functions of the best-fit ellipticity and Sérsic index (see Appendix B). Adopting a Mdyn/M* factor of 40 as found by A. de Graaff et al. (2024) for dwarf galaxies at high redshift, we infer a stellar mass of . However, the Mdyn/M* is very uncertain in this regime, and the uncertainty can span over 1 dex (A. Saldana-Lopez et al. 2025). We advise caution in interpreting this result, as there are large uncertainties in the measurements of the narrow Hα component, the HST morphology, and the empirical relations used.\r\n\r\nAs discussed in Section 4, the absorption profile is compatible with broadening by a rotating disk wind, and numerical modeling of such configurations often predicts a narrow component arising from increased transmission due to purely kinematic effects in the wind geometry (D. Proga et al. 2000; D. Proga 2003; D. Proga & T. R. Kallman 2004). This would be an alternative explanation for at least part of the narrow component flux. On the other hand, most LRDs present narrow [O iii] emission that is often associated with the host galaxy. Indeed, the ionized gas producing [O iii] emission should have associated emission in the Hα and higher-order Balmer lines. However, constraining this component largely depends on the assumptions on dust attenuation or ISM conditions, and requires very high S/N and resolution data. Deep, space-based follow-up observations of PAN-BH*-1 would be very constraining for the wind kinematics (e.g., by the joint analysis of Hβ) and to assess whether a narrow component comes from a host galaxy (e.g., by comparing to a narrow Hβ component or [O iii] λλ4960, 5008).\r\n\r\n5.2. Black Hole Mass From Photosphere Models\r\nThe general physical setup of LRDs is an open debate, and their masses are a major unknown. Due to the multiple differences with respect to the classical AGN population, the validity of standard virial calibrations has been questioned (e.g., V. Rusakov et al. 2026; J. E. Greene et al. 2026; A. Sneppen et al. 2026; A. Torralba et al. 2026, although see, e.g., M. Brazzini et al. 2025, 2026; J. Scholtz et al. 2026 for an alternative interpretation).\r\n\r\nOne can obtain a mass estimate assuming a system in radiative equilibrium with Lbol/LEdd = 1 (e.g., H. Umeda et al. 2026); this yields a total mass of ≈106 M⊙, using the bolometric luminosity from integrating the best-fit blackbody in Section 3.1. Recently, H. Liu et al. (2026) developed a synthetic spectral library of LRD atmosphere models. In these models, the density of the photosphere is regulated by the net surface gravity of an optically thick atmosphere, enabling constraints on the mass of the system. We fit the JWST photometry of PAN-BH*-1 using the models from H. Liu et al. (2026), assuming a negligible contribution from a host galaxy to the optical continuum. The best-fit model has effective temperature Teff = 4800 K, surface gravity , and metallicity (; see Figure 1). The best-fit implies a total mass of the system (BH plus gas) of (Equation (6) in H. Liu et al. 2026, assuming hydrostatic equilibrium). For the second and third best fits, we obtain and −2, respectively (, respectively; with the same metallicity and effective temperature), which would imply lower limits to the system mass between and 4. The bolometric luminosity of PAN-BH*-1 (from the integral of the best-fit green curve in Figure 1) implies an Eddington luminosity ratio of L/LEdd ≲ 13, assuming the best-fit mass from the H. Liu et al. (2026) models. The elevated Eddington ratio is in line with the hypothesis of a radiation-driven wind discussed in Section 4, and allows for somewhat larger system masses. The low masses obtained with this model, combined with the stellar mass inferred from dynamical arguments for the host galaxy (Section 3.3) set lower limits to the BH-to-stellar mass ratio of MBH/M* ≳ 10−4–10−2, which are compatible with the relations observed in the Local Universe, within the large uncertainties (A. E. Reines & M. Volonteri 2015).\r\n\r\n6. Conclusions\r\nIn this Letter, we presented the discovery and spectroscopic confirmation of PAN-BH*-1, an LRD with an extreme Balmer break at z = 1.731. The strength of the Balmer break (F115W/F814W = 7 ± 1) is comparable to the most extreme LRDs known, The Cliff (A. de Graaff et al. 2025a) and MoM-BH* (R. P. Naidu et al. 2025). We summarize the observations and our main conclusions as follows.\r\n\r\n\r\n1. \r\nWe obtained deep VLT/X-Shooter spectroscopy of PAN-BH*-1. The Hα emission line is luminous and broad (LHα = 1043 erg s−1), and has an unusually strong absorption. Hβ is detected with an S/N ≈ 6, and we conservatively estimate a lower limit for the Balmer decrement of Hα/Hβ > 9.4 (at a 3σ confidence level), in line with other LRDs in the literature (e.g., A. de Graaff et al. 2025b; G. P. Nikopoulos et al. 2026).\r\n2. \r\nThe absorption trough spans from −520 to 267 km s−1 (at a transmission level of 99%). We interpret the presence of blue- and redshifted absorption as produced by a disk wind, analogous to those analyzed in the context of broad absorption line quasars or accreting stars. This hypothesis would imply that the source of the optical continuum is likely a thick photospheric disk.\r\n3. \r\nWe detect a narrow Hα component (FWHM = 184 ± 12 km s−1), which we interpret as probing a host galaxy with M* ≈ 108 M⊙ and SFR = 2–3 M⊙. This interpretation is in line with the extended rest-NUV morphology measured in the HST bands (\r\n kpc).\r\n4. \r\nBy fitting the synthetic atmosphere models of H. Liu et al. (2026), we estimate a system mass (BH+envelope) of 104–106 M⊙. The inferred masses, together with the stellar mass inferred from morphology and narrow emission line dynamics, imply BH-to-stellar mass ratios of 10−2–10−4, close to the extrapolated trend in the local Universe (A. E. Reines & M. Volonteri 2015).\r\n5. \r\nThe confirmation of this source at cosmic noon (magnitude of ≈22 in the K band, Hα flux ≈5 × 10−16 erg s−1 cm−2) proves the feasibility of detecting extreme LRDs at such epochs with wide-area spectroscopic surveys like Euclid or the forthcoming Nancy Grace Roman Space Telescope.\r\n\r\nAcknowledgments\r\nA.T. thanks Debasish Dutta and Tamara Bogdanović for useful conversations about stellar and AGN winds.\r\n\r\nWe thank the scientific referee for the useful and constructive feedback, which helped improve the quality of this paper.\r\n\r\nJ.M. and A.T. acknowledge funding by the European Union (ERC, AGENTS, 101076224). The work of CCW is supported by NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. A.P.C. warmly acknowledges the support of the National Science Foundation through the NSF Graduate Research Fellowship Program. A.d.G. acknowledges support from a Clay Fellowship awarded by the Smithsonian Astrophysical Observatory.\r\n\r\nBased on observations made with ESO Telescopes at the Paranal Observatory under program IDs 116.294D and 116.2AQ0.\r\n\r\nThis work is based in part on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with programs #2514 and #9433. C.C.W. gratefully acknowledges support for program JWST-GO-2514 provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127. The authors acknowledge the team led by co-PIs R. Maiolino and F. D’Eugenio for developing their observing program with a zero-exclusive-access period.\r\n\r\nThis research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555. These observations are associated with program #15117.\r\n\r\nThe JWST and HST data presented in this article were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations analyzed can be accessed via doi:10.17909/ydwx-st06.\r\n\r\nThis work is based in part on observations made with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. The Spitzer data used in this work can be found in doi:10.26131/IRSA3.\r\n\r\nThis work was supported by the International Space Science Institute (ISSI) in Bern, through ISSI International Team project #25-659 “Little Red Dots, Big Open Questions.”\r\n\r\nJWST cartoon in Figure 6, credit: NASA.\r\n\r\nFacilities: VLT:Kueyen - Very Large Telescope (Kueyen) (X-Shooter), VLT:Yepun (HAWK-I), JWST - James Webb Space Telescope (NIRCam, NIRspec), HST - Hubble Space Telescope satellite (ACS), Spitzer - Spitzer Space Telescope satellite (IRAC, MIPS) - .\r\n\r\nSoftware: astropy (Astropy Collaboration et al. 2013, 2018; Astropy Collaboration et al. 2022), NumPy (C. R. Harris et al. 2020), SciPy (P. Virtanen et al. 2020), pysersic (I. Pasha & T. B. Miller 2023), stpsf (M. D. Perrin et al. 2014), lmfit (M. Newville et al. 2014), EsoRex (ESO CPL Development Team 2015), Claude (used for Python coding; https://claude.ai/), SEP (K. Barbary 2016).","title":"A black hole star at cosmic noon: Extreme Balmer break, photospheric continuum, and broad absorption by thick winds in a Little Red Dot at z = 1.7","DOAJ_listed":"1","article_processing_charge":"Yes","abstract":[{"lang":"eng","text":"Recent studies at high redshift have revealed an enigmatic class of little red dots (LRDs) with extreme Balmer breaks, stronger than in any stellar atmosphere. However, it is unclear whether such objects exist at lower redshift, especially given the low number of LRDs reported at z ≲ 2. Here, we report the discovery of PAN-BH*-1, an LRD with an extreme Balmer break at z = 1.73, identified from JWST/NIRCam pure-parallel imaging taken by the PANORAMIC survey, and confirmed by deep VLT/X-Shooter spectroscopy. The rest-optical to near-infrared spectral energy distribution of PAN-BH*-1 is consistent with a photospheric continuum with effective temperature Teff ≈ 4800 K. The broad Hα emission line shows remarkably deep absorption, stronger than previously measured in any LRD. The absorption trough spans from −520 to +267 km s−1 with respect to the systemic redshift. The presence of blue- and red-shifted absorption suggests complex dynamics of the obscuring gas along the line of sight. We speculate that the absorption trough can be produced by a thick wind launched from a thick, rotating photospheric disk, the latter being the source of the red optical continuum. While the source is unresolved in the rest-optical JWST data (reff < 47 pc), the rest-near-UV Hubble Space Telescope imaging shows an extended morphology with (formular displayed) kpc, which we interpret as a host galaxy with a stellar mass of ∼10^8 M⊙, in line with the narrow Hα emission. The discovery of this object at cosmic noon highlights the feasibility of systematic searches for extreme LRDs with wide-area facilities such as Euclid and Roman."}],"publication_identifier":{"issn":["2041-8205"],"eissn":["2041-8213"]},"citation":{"ista":"Torralba Torregrosa A, Matthee JJ, Weibel A, Naidu RP, Ma Y, Cloonan AP, Desai AA, De Graaff A, Greene JE, Jespersen CK, Kramarenko I, Mascia S, Oesch PA, Sun WQ, Williams CC. 2026. A black hole star at cosmic noon: Extreme Balmer break, photospheric continuum, and broad absorption by thick winds in a Little Red Dot at z = 1.7. The Astrophysical Journal Letters. 1005(2), L37.","ieee":"A. Torralba Torregrosa et al., “A black hole star at cosmic noon: Extreme Balmer break, photospheric continuum, and broad absorption by thick winds in a Little Red Dot at z = 1.7,” The Astrophysical Journal Letters, vol. 1005, no. 2. IOP Publishing, 2026.","ama":"Torralba Torregrosa A, Matthee JJ, Weibel A, et al. A black hole star at cosmic noon: Extreme Balmer break, photospheric continuum, and broad absorption by thick winds in a Little Red Dot at z = 1.7. The Astrophysical Journal Letters. 2026;1005(2). doi:10.3847/2041-8213/ae7bfd","short":"A. Torralba Torregrosa, J.J. Matthee, A. Weibel, R.P. Naidu, Y. Ma, A.P. Cloonan, A.A. Desai, A. De Graaff, J.E. Greene, C.K. Jespersen, I. Kramarenko, S. Mascia, P.A. Oesch, W.Q. Sun, C.C. Williams, The Astrophysical Journal Letters 1005 (2026).","chicago":"Torralba Torregrosa, Alberto, Jorryt J Matthee, Andrea Weibel, Rohan P. Naidu, Yilun Ma, Aidan P. Cloonan, Aayush A Desai, et al. “A Black Hole Star at Cosmic Noon: Extreme Balmer Break, Photospheric Continuum, and Broad Absorption by Thick Winds in a Little Red Dot at z = 1.7.” The Astrophysical Journal Letters. IOP Publishing, 2026. https://doi.org/10.3847/2041-8213/ae7bfd.","apa":"Torralba Torregrosa, A., Matthee, J. J., Weibel, A., Naidu, R. P., Ma, Y., Cloonan, A. P., … Williams, C. C. (2026). A black hole star at cosmic noon: Extreme Balmer break, photospheric continuum, and broad absorption by thick winds in a Little Red Dot at z = 1.7. The Astrophysical Journal Letters. IOP Publishing. https://doi.org/10.3847/2041-8213/ae7bfd","mla":"Torralba Torregrosa, Alberto, et al. “A Black Hole Star at Cosmic Noon: Extreme Balmer Break, Photospheric Continuum, and Broad Absorption by Thick Winds in a Little Red Dot at z = 1.7.” The Astrophysical Journal Letters, vol. 1005, no. 2, L37, IOP Publishing, 2026, doi:10.3847/2041-8213/ae7bfd."},"file_date_updated":"2026-07-13T07:46:22Z","doi":"10.3847/2041-8213/ae7bfd","corr_author":"1","department":[{"_id":"JoMa"},{"_id":"IlCa"},{"_id":"GradSch"}],"has_accepted_license":"1","project":[{"_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224"}],"dataavailabilitystatement":"Based on observations made with ESO Telescopes at the Paranal Observatory under program IDs 116.294D and 116.2AQ0.\r\n\r\nThis work is based in part on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with programs #2514 and #9433. C.C.W. gratefully acknowledges support for program JWST-GO-2514 provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127. The authors acknowledge the team led by co-PIs R. Maiolino and F. D’Eugenio for developing their observing program with a zero-exclusive-access period.\r\n\r\nThis research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555. These observations are associated with program #15117.\r\n\r\nThe JWST and HST data presented in this article were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations analyzed can be accessed via doi:10.17909/ydwx-st06.\r\n\r\nThis work is based in part on observations made with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. The Spitzer data used in this work can be found in doi:10.26131/IRSA3.\r\n\r\nThis work was supported by the International Space Science Institute (ISSI) in Bern, through ISSI International Team project #25-659 “Little Red Dots, Big Open Questions.”\r\n\r\nJWST cartoon in Figure 6, credit: NASA.\r\n\r\nFacilities: VLT:Kueyen - Very Large Telescope (Kueyen) (X-Shooter), VLT:Yepun (HAWK-I), JWST - James Webb Space Telescope (NIRCam, NIRspec), HST - Hubble Space Telescope satellite (ACS), Spitzer - Spitzer Space Telescope satellite (IRAC, MIPS) - .\r\n\r\nSoftware: astropy (Astropy Collaboration et al. 2013, 2018; Astropy Collaboration et al. 2022), NumPy (C. R. Harris et al. 2020), SciPy (P. Virtanen et al. 2020), pysersic (I. Pasha & T. B. Miller 2023), stpsf (M. D. Perrin et al. 2014), lmfit (M. Newville et al. 2014), EsoRex (ESO CPL Development Team 2015), Claude (used for Python coding; https://claude.ai/), SEP (K. Barbary 2016).","article_number":"L37","oa_version":"Published Version","language":[{"iso":"eng"}],"month":"07","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","scopus_import":"1","researchdata_availability":"yes","status":"public","year":"2026","intvolume":" 1005","type":"journal_article","issue":"2","date_created":"2026-07-12T22:02:17Z","date_published":"2026-07-10T00:00:00Z","oa":1,"fulldoi":"https://doi.org/10.3847/2041-8213/ae7bfd","publication_status":"published","arxiv":1,"tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication":"The Astrophysical Journal Letters","OA_type":"gold","article_type":"original","file":[{"content_type":"application/pdf","file_id":"22274","success":1,"file_size":5419071,"creator":"dernst","date_created":"2026-07-13T07:46:22Z","access_level":"open_access","file_name":"2026_AstrophysicalJourLetters_Torralba.pdf","relation":"main_file","date_updated":"2026-07-13T07:46:22Z","checksum":"7600db260d799ddea45cf3bd01effe41"}],"quality_controlled":"1","supplementarymaterial":"yes","volume":1005,"OA_place":"publisher","das_tickbox":"1","author":[{"id":"018f0249-0e87-11f0-b167-cbce08fbd541","orcid":"0000-0001-5586-6950","last_name":"Torralba Torregrosa","first_name":"Alberto","full_name":"Torralba Torregrosa, Alberto"},{"full_name":"Matthee, Jorryt J","first_name":"Jorryt J","orcid":"0000-0003-2871-127X","id":"7439a258-f3c0-11ec-9501-9df22fe06720","last_name":"Matthee"},{"first_name":"Andrea","full_name":"Weibel, Andrea","last_name":"Weibel"},{"full_name":"Naidu, Rohan P.","first_name":"Rohan P.","last_name":"Naidu"},{"last_name":"Ma","first_name":"Yilun","full_name":"Ma, Yilun"},{"full_name":"Cloonan, Aidan P.","first_name":"Aidan P.","last_name":"Cloonan"},{"full_name":"Desai, Aayush A","first_name":"Aayush A","last_name":"Desai","id":"502cfd30-32c1-11ee-a9a4-d8dad5c6739e"},{"last_name":"De Graaff","full_name":"De Graaff, Anna","first_name":"Anna"},{"full_name":"Greene, Jenny E.","first_name":"Jenny E.","last_name":"Greene"},{"last_name":"Jespersen","first_name":"Christian Kragh","full_name":"Jespersen, Christian Kragh"},{"first_name":"Ivan","full_name":"Kramarenko, Ivan","orcid":"0000-0001-5346-6048","last_name":"Kramarenko","id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4"},{"id":"edaf889c-c7cd-11ef-ab1b-bb28c431bd29","last_name":"Mascia","full_name":"Mascia, Sara","first_name":"Sara"},{"full_name":"Oesch, Pascal A.","first_name":"Pascal A.","last_name":"Oesch"},{"last_name":"Sun","first_name":"Wendy Q.","full_name":"Sun, Wendy Q."},{"full_name":"Williams, Christina C.","first_name":"Christina C.","last_name":"Williams"}],"day":"10"},{"type":"journal_article","issue":"2","status":"public","PlanS_conform":"1","researchdata_availability":"no","year":"2026","intvolume":" 1005","date_published":"2026-07-10T00:00:00Z","oa":1,"date_created":"2026-07-19T22:01:46Z","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication":"The Astrophysical Journal","fulldoi":"https://doi.org/10.3847/1538-4357/ae7b2c","arxiv":1,"publication_status":"published","file":[{"success":1,"file_id":"22375","content_type":"application/pdf","creator":"dernst","file_size":2267572,"file_name":"2026_AstrophysicalJour_Venditti.pdf","access_level":"open_access","date_created":"2026-07-20T13:05:27Z","checksum":"e783c9c10cf773482ac2f3b340ad130b","date_updated":"2026-07-20T13:05:27Z","relation":"main_file"}],"quality_controlled":"1","article_type":"original","OA_type":"gold","supplementarymaterial":"yes","volume":1005,"das_tickbox":"1","OA_place":"publisher","day":"10","author":[{"last_name":"Venditti","full_name":"Venditti, Alessandra","first_name":"Alessandra"},{"first_name":"Luca","full_name":"Graziani, Luca","last_name":"Graziani"},{"full_name":"Schneider, Raffaella","first_name":"Raffaella","last_name":"Schneider"},{"first_name":"Volker","full_name":"Bromm, Volker","last_name":"Bromm"},{"first_name":"Julian B.","full_name":"Muñoz, Julian B.","last_name":"Muñoz"},{"last_name":"Di Cesare","id":"2d002343-372f-11ef-98ec-a164d20427cb","full_name":"Di Cesare, Claudia","first_name":"Claudia"},{"last_name":"Valiante","full_name":"Valiante, Rosa","first_name":"Rosa"},{"last_name":"Calabrò","first_name":"Antonello","full_name":"Calabrò, Antonello"},{"first_name":"Roberto","full_name":"Maiolino, Roberto","last_name":"Maiolino"},{"last_name":"Finkelstein","full_name":"Finkelstein, Steven L.","first_name":"Steven L."},{"last_name":"Parente","full_name":"Parente, Massimiliano","first_name":"Massimiliano"},{"last_name":"Saggini","first_name":"Matteo","full_name":"Saggini, Matteo"},{"full_name":"Chisholm, John","first_name":"John","last_name":"Chisholm"}],"external_id":{"arxiv":["2603.27582"]},"acknowledgement":"We thank Elka Rusta and Stefania Salvadori for providing predictions of the He II line luminosities from the NEFERTITI model. A.V. acknowledges funding from the Cosmic Frontier Center and the University of Texas at Austin’s College of Natural Sciences. A.V., L.G., and R.S. acknowledge support from the PRIN 2022 MUR project 2022CB3PJ3—First Light And Galaxy aSsembly (FLAGS) funded by the European Union—Next Generation EU. J.B.M. was supported by NSF Grants AST-2307354 and AST-2408637, and by the NSF-Simons AI Institute for Cosmic Origins. This research was also supported in part by grant NSF PHY-2309135 to the Kavli Institute for Theoretical Physics (KITP). R.V. acknowledges support from PRIN MUR “2022935STW” funded by European Union-Next Generation EU, Missione 4 Componente 2 CUP C53D23000950006 and from Bando Ricerca Fondamentale INAF 2023, Theory Grant “Theoretical models for Black Holes Archaeology.\" C.D.C. acknowledges support from the European Union (ERC, AGENTS, 101076224).","date_updated":"2026-07-20T13:07:08Z","ddc":["520"],"publisher":"IOP Publishing","_id":"22364","title":"Catching the nebular needle in a polluted haystack: Line-emission signatures from population III-forming pockets around massive galaxies at the end of reionization","publication_identifier":{"issn":["0004-637X"],"eissn":["1538-4357"]},"abstract":[{"lang":"eng","text":"Finding the first generation of (Population III or Pop III) stars is one of the most ambitious and exciting challenges of astrophysics. JWST opened concrete prospects for their detection during the Epoch of Reionization, where increasing evidence suggests that residual Pop III formation may persist, even within pristine pockets of high-mass halos, due to inhomogeneous enrichment. However, the identification of Pop III stars within globally enriched environments will be challenging. We investigate the detectability of a subdominant Pop III component in/around massive (M⋆ ≳ 10^9 M⊙) galaxies at z ≈ 6.5–9 from the dustyGadget cosmological simulation suite, and the confusion arising from second-generation (Pop II) stars in their surroundings. We find that young (≲1 Myr), massive (MIII ∼ 6 × 10^5 M⊙) Pop III clusters forming within these galaxy environments are responsible for strong HeII1640 line emission (LHeII1640 ≳ 10^41 erg ^s−1), which would be detectable with ≈10(50) hr of medium-resolution observations with NIRSpec/IFU at z ≈ 6(10). These bright luminosities cannot be produced by standard Pop II populations alone. On the other hand, the dominant Pop II component within massive “hybrid” Pop III hosts powers strong metal line emission (L[OIII]5007 ≳ 10^42 erg s^−1), indicating that the detection of metal lines alone cannot exclude the presence of Pop IIIs in high-z galaxy environments. We further discuss candidate selection strategies based on Lyα, Hα, and Hβ emission, and how spatially resolved observations may enable the detection of isolated, pristine pockets in the outskirts of massive halos."}],"doi":"10.3847/1538-4357/ae7b2c","file_date_updated":"2026-07-20T13:05:27Z","citation":{"mla":"Venditti, Alessandra, et al. “Catching the Nebular Needle in a Polluted Haystack: Line-Emission Signatures from Population III-Forming Pockets around Massive Galaxies at the End of Reionization.” The Astrophysical Journal, vol. 1005, no. 2, 226, IOP Publishing, 2026, doi:10.3847/1538-4357/ae7b2c.","apa":"Venditti, A., Graziani, L., Schneider, R., Bromm, V., Muñoz, J. B., Di Cesare, C., … Chisholm, J. (2026). Catching the nebular needle in a polluted haystack: Line-emission signatures from population III-forming pockets around massive galaxies at the end of reionization. The Astrophysical Journal. IOP Publishing. https://doi.org/10.3847/1538-4357/ae7b2c","short":"A. Venditti, L. Graziani, R. Schneider, V. Bromm, J.B. Muñoz, C. Di Cesare, R. Valiante, A. Calabrò, R. Maiolino, S.L. Finkelstein, M. Parente, M. Saggini, J. Chisholm, The Astrophysical Journal 1005 (2026).","chicago":"Venditti, Alessandra, Luca Graziani, Raffaella Schneider, Volker Bromm, Julian B. Muñoz, Claudia Di Cesare, Rosa Valiante, et al. “Catching the Nebular Needle in a Polluted Haystack: Line-Emission Signatures from Population III-Forming Pockets around Massive Galaxies at the End of Reionization.” The Astrophysical Journal. IOP Publishing, 2026. https://doi.org/10.3847/1538-4357/ae7b2c.","ama":"Venditti A, Graziani L, Schneider R, et al. Catching the nebular needle in a polluted haystack: Line-emission signatures from population III-forming pockets around massive galaxies at the end of reionization. The Astrophysical Journal. 2026;1005(2). doi:10.3847/1538-4357/ae7b2c","ieee":"A. Venditti et al., “Catching the nebular needle in a polluted haystack: Line-emission signatures from population III-forming pockets around massive galaxies at the end of reionization,” The Astrophysical Journal, vol. 1005, no. 2. IOP Publishing, 2026.","ista":"Venditti A, Graziani L, Schneider R, Bromm V, Muñoz JB, Di Cesare C, Valiante R, Calabrò A, Maiolino R, Finkelstein SL, Parente M, Saggini M, Chisholm J. 2026. Catching the nebular needle in a polluted haystack: Line-emission signatures from population III-forming pockets around massive galaxies at the end of reionization. The Astrophysical Journal. 1005(2), 226."},"DOAJ_listed":"1","article_processing_charge":"Yes","department":[{"_id":"JoMa"}],"has_accepted_license":"1","project":[{"_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224"}],"dataavailabilitystatement":"Software: dustyGadget (L. Graziani et al. 2020), BPASSv2.2.134 (J. J. Eldridge et al. 2017; E. R. Stanway & J. J. Eldridge 2018), Yggdrasil35 (E. Zackrisson et al. 2011), Cloudy22.0136 (G. J. Ferland et al. 2017), NumPy37 (S. van der Walt et al. 2011; C. R. Harris et al. 2020), matplotlib38 (J. D. Hunter 2007), SciPy39 (Jones et al. 2001; P. Virtanen et al. 2020).","article_number":"226","oa_version":"Published Version","scopus_import":"1","language":[{"iso":"eng"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","month":"07"},{"title":"EIGER. VIII. First stars signatures in the connection between O I absorption and galaxies in the epoch of reionization","_id":"23115","publisher":"IOP Publishing","date_updated":"2026-10-14T07:58:57Z","ddc":["520"],"acknowledgement":"IOP Science home\r\nAccessibility Help\r\n\r\nJournals\r\nBooks\r\nPublishing Support\r\nLogin\r\nThe Astrophysical Journal\r\nThe American Astronomical Society, find out more.\r\n\r\nThe following article isOpen access\r\nEIGER. VIII. First Stars Signatures in the Connection between O I Absorption and Galaxies in the Epoch of Reionization\r\nJack Higginson, Rongmon Bordoloi, Robert A. Simcoe, Jorryt Matthee, Daichi Kashino, Ruari Mackenzie, Ivan Kramarenko, Simon J. Lilly, Anna-Christina Eilers, Rohan P. NaiduShow full author list\r\n\r\nPublished 2026 February 24 • © 2026. The Author(s). Published by the American Astronomical Society.\r\nThe Astrophysical Journal, Volume 999, Number 1\r\nCitation Jack Higginson et al 2026 ApJ 999 49\r\nDOI 10.3847/1538-4357/ae3e81\r\n\r\nPDFOpens in a new tab.\r\nePub\r\nAuthors\r\nFigures\r\nTables\r\nReferences\r\nArticle data\r\nPDFOpens in a new tab.\r\nePub\r\nArticle metrics\r\n626 Total downloads\r\n\r\n22 total citations on Dimensions.\r\nShare this article\r\nArticle information\r\nAbstract\r\nWe investigate the association between galaxies and neutral O i absorption systems at z ∼ 6, which trace metal-enriched gas during the epoch of reionization. We identify 40 galaxies across six quasar fields, residing in 15 overdensities within 300 kpc of the background sight lines. Five O i absorption systems are associated with five of these overdensities, yielding a covering fraction of \r\n within 300 kpc. The absorption occurs beyond typical virial radii, indicating that the gas traces extended overdensity environments rather than individual galaxy halos, unlike the z ∼ 0 circumgalactic medium (CGM), which is largely bound to halos. These galaxy-associated absorbers account for ∼35% of all O i systems seen in blind quasar surveys, implying the remainder arise in lower-mass galaxies below our detection threshold or in dense neutral intergalactic medium pockets. The CGM around these galaxies contains ≳ 2 × 106 M⊙ of oxygen, comparable to the interstellar medium oxygen mass of the galaxies themselves, suggesting that the surrounding environment holds as much metal mass as the galaxies. All five galaxy-associated systems show significantly higher \r\n ratios than absorbers lacking galaxy associations. Furthermore, relative abundance ratios ([Si/O], [C/O]) reveal that four of the five exhibit enrichment patterns consistent with Population III nucleosynthesis at the outskirts of galaxy overdensities. These rare systems offer a unique window into the role of first-generation stars in shaping the early metal enrichment of galaxies and their environments.\r\n\r\nExport citation and abstract\r\nBibTeX\r\nRIS\r\n\r\nPrevious article in issue\r\nNext article in issue\r\nRelated links\r\n\r\nOriginal content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.\r\n\r\n1. Introduction\r\nThe first generations of stars formed shortly after the Epoch of Recombination within dark matter overdensities, producing the first significant quantities of metals and enriching the intergalactic medium (IGM) while reionizing hydrogen and helium (e.g., R. S. Klessen & S. C. O. Glover 2023). These metals and gas eventually coalesced into the first galaxies, which over cosmic time evolved into Milky Way–like systems today. Studying these young galaxies and their environments provides critical insight into galaxy formation and evolution, constraining models of stellar feedback, gas accretion, and chemical enrichment (C.-A. Faucher-Giguère & S. P. Oh 2023; C. Peroux & D. Nelson 2024).\r\n\r\nAt low redshift, decades of observations using deep ground-based spectroscopy and Hubble Space Telescope (HST) data of background quasars and foreground galaxies have built a rich understanding of the circumgalactic medium (CGM) and its interplay with galaxies (e.g., J. Tumlinson et al. 2017). The CGM plays a crucial role in gas recycling, star formation regulation, and quenching; understanding its structure and composition informs galaxy growth models (Y. Peng et al. 2015; E. Zinger et al. 2020).\r\n\r\nHigh-redshift studies, leveraging ground- and space-based near-infrared (NIR) spectroscopy of quasars, reveal that the early Universe was already chemically enriched by the epoch of reionization (e.g., T. J. Cooper et al. 2019; L. Christensen et al. 2023; R. L. Davies et al. 2023a). Among tracers of neutral and low-ionization gas, O i has emerged as a key probe: surveys report an increase in O i number density at z ≳ 5–6 (G. D. Becker et al. 2019; L. Christensen et al. 2023; A. M. Sebastian et al. 2024; A. Sodini et al. 2024), while higher-ionization species like C iv and Si iv decline, consistent with a softer and evolving UV background at the end of reionization (T. J. Cooper et al. 2019; V. D’Odorico et al. 2022; R. L. Davies et al. 2023a, 2023b).\r\n\r\nHistorically, connecting absorption systems with their host galaxies was challenging due to the difficulty of obtaining deep, high-redshift galaxy spectroscopy. This has changed with the advent of JWST, providing unprecedented views of early galaxies and their impact on surrounding gas through surveys such as EIGER (D. Kashino et al. 2023) and ASPIRE (F. Wang et al. 2023). First systematic studies of cool, low-ionization CGM traced by Mg ii around z ∼ 6 galaxies suggest that high-redshift CGM differs significantly from its low-redshift counterpart: these galaxies typically have low masses, and strong stellar feedback can eject metals far beyond the halo’s gravitational potential (R. Bordoloi et al. 2024). Such pioneering studies now allow systematic investigations of the CGM in the early Universe.\r\n\r\nThe UV background during reionization was inhomogeneous and rapidly evolving (e.g., S. R. Furlanetto & S. P. Oh 2005; B. D. Oppenheimer et al. 2009; K. Finlator et al. 2013; G. D. Becker et al. 2015; S. E. I. Bosman et al. 2022), initially dominated by Population III stars (K. Nakajima & R. Maiolino 2022; K. Nakajima et al. 2025), then by early star-forming galaxies (L. Jiang et al. 2022; J. Matthee et al. 2022), with active galactic nuclei (AGN) contributing significantly by z ∼ 5 (A. D’Aloisio et al. 2017; G. Kulkarni et al. 2019; C.-A. Faucher-Giguère 2020). Modeling indicates that pockets of Population III star formation may persist throughout the Epoch of Reionization (L. Tornatore et al. 2007; R. H. Mebane et al. 2018; J. L. Johnson & A. Aykutalp 2019; A. Venditti et al. 2023; O. Zier et al. 2025).\r\n\r\nThe large reservoir of neutral O i observed in quasar absorption lines at high redshift is typically self-shielded, providing robust estimates of chemical abundances. Studying the association of these absorbers with galaxies offers unique insight into the CGM of early galaxies, and into potential contributions from Population III stars to early chemical enrichment.\r\n\r\nIn this work, we study the cool, neutral CGM around galaxies at z ∼ 6, traced by O i absorption from the EIGER survey (D. Kashino et al. 2023). We focus on O i absorbers associated with [O iii]5008-emitting galaxies at 5.875 150 kpc, an incidence of is measured. Within 300 kpc of the primary galaxy, the overall incidence is , with values of for 50 ≤ R ≤ 300 kpc and for 100 ≤ R ≤ 300 kpc. These rates are substantially weaker than the incidence of strong Mg ii absorption at z ∼ 6 (R. Bordoloi et al. 2024), indicating that neutral oxygen preferentially traces a different phase of the circumgalactic environment.\r\n\r\nPanels (b) and (d) reveal that O i absorbers are typically located at much larger R/Rvir than strong low-ionization tracers such as Mg ii. This distinction suggests that O i absorption at z ∼ 6 is not confined to the CGM of an individual galaxy but instead reflects the larger-scale gaseous environment of galaxy overdensities—what might be described as “cosmic ecosystems” rather than isolated halos.\r\n\r\nComparing the stellar mass distributions of overdensities with and without O i absorption, we find no statistically significant differences. The mean stellar mass of galaxies in overdensities with absorption is , compared to for those without.\r\n\r\nWe emphasize that at z ∼ 6, the large R/Rvir values of these halos imply that O i absorption typically arises at scales well beyond the typical CGM [R/Rvir ≲ 1] (J. Tumlinson et al. 2017) probed by low-ionization lines at lower redshift. Unlike the low-z CGM, where metal absorbers are closely tied to the halo of a single massive galaxy, the O i absorbers studied here appear to be linked to extended networks of low-mass, young galaxies embedded in shared overdensities. Over cosmic time, these small systems and their diffuse gaseous environments are expected to merge and evolve into more massive systems, eventually forming Milky Way–like galaxies by z = 0. Thus, neutral O i at reionization is best understood not as a tracer of isolated galactic halos, but as a probe of the extended environments that connect galaxies, gas, and structure growth in the early Universe.\r\n\r\nBecause O i absorption traces dense, neutral gas and requires only minimal ionization corrections, we can place a conservative lower limit on the total oxygen mass associated with the EIGER galaxies. These estimates are intended as simple, order-of-magnitude calculations to provide intuition about the amount of neutral oxygen relative to the observed galaxy properties. Following the formalism of R. Bordoloi et al. (2014), the oxygen mass contained in an annulus bounded by Rin and Rout is\r\n\r\nwhere Rin and Rout are the inner and outer radii of the annulus, fc is the covering fraction (the incidence of O i detections in that bin), 〈NOI〉 is the mean O i column density in the annulus, and mO = 16 mp is the mass of an oxygen atom, with mp being the mass of a proton. For a conservative lower limit, we adopt fion = 1, where fion is the ionization fraction (i.e., we assume that all of the oxygen mass is in the neutral phase). We justify this assumption as follows: O i is tightly coupled to H i through charge exchange, and in dense gas, the required ionization correction is minor, even under strong radiation fields such as the Fermi Bubbles (R. Bordoloi et al. 2017; T. Ashley et al. 2022). Under a typical metagalactic UV background, it is generally less than 10% and does not significantly alter the inferred oxygen abundance. In addition, oxygen does not deplete onto dust grains, unlike Si or C. For these reasons, we consider the approximation NO,total ≈ NOI to be valid for our analysis.\r\n\r\nWe compute masses in two radial bins: 0–100 kpc and 100–300 kpc, respectively. The total oxygen mass within radius is obtained by summing the masses of the constituent annuli. This yields a strict lower limit of ≳ 2 ×106M⊙ on the total oxygen mass within = 300 kpc.\r\n\r\nWe compare the inferred oxygen mass in the extended environment of our sample with the total oxygen content in the interstellar medium (ISM) of a typical z ∼ 6 galaxy. In computing this quantity, we make the following assumptions. First, we assume that all galaxies in this work lie on the typical z ∼ 6 mass–metallicity relation, derived by stacking [O iii] emitter galaxies (J. Matthee et al. 2022), and we adopt the gas-phase metallicity from this relation for each galaxy.\r\n\r\nBecause direct measurements of the total H2 and H i gas content are not available at these redshifts, we extrapolate the molecular gas fraction from L. J. Tacconi et al. (2018) to z ∼ 6 and adopt a conservative H i gas fraction based on local observations (S. Huang et al. 2012). We note that high-z galaxies are likely more gas-rich than their local counterparts; therefore, the inferred ISM gas masses should be considered lower limits.\r\n\r\nWith these caveats in mind, we estimate the total ISM oxygen mass as\r\n\r\nwhere we define . Here, XO is the gas-phase oxygen abundance derived from the mass–metallicity relation, and and MHI are the molecular and atomic gas masses derived as described above. For our galaxy sample, the mean stellar mass is , corresponding to an ISM oxygen mass of MO,ISM ≳ 6.8 × 105 M⊙. Remarkably, this indicates that the typical ISM oxygen content is comparable to the oxygen mass in the extended environment around these galaxies, implying that the circumgalactic or intergalactic medium at z ∼ 6 contains a substantial reservoir of oxygen. While these estimates depend on several specific assumptions, the inferred ISM and CGM oxygen masses appear to be of similar magnitude.\r\n\r\nAt low redshift, both L* and sub-L* galaxies similarly exhibit substantial metal content in their circumgalactic medium (CGM), with the CGM containing at least as much metal as the ISM of their host galaxies (J. Tumlinson et al. 2011; R. Bordoloi et al. 2014). A key difference is that, whereas the low-z CGM is typically gravitationally bound to its host galaxy, at high redshift much of the gas exists in the extended environment of galaxy overdensities rather than being bound to individual galaxies (see also R. Bordoloi et al. 2024).\r\n\r\n4.2. Expected Incidence of O i Absorbers\r\nIn this section, we report the expected redshift-path incidence of O i absorbers around [O iii] emitting galaxies detected in the EIGER survey. We define the number of O i absorbers associated with each galaxy overdensity per unit absorption distance above a detection threshold (WOI ≥ 0.05Å ) as\r\n\r\n\r\nHere, Rmax = 300 kpc is the survey radius adopted in this work, and is the mean O i absorber detection completeness (see Section 3.5; 91.4% for WOI ≥ 0.05 Å). nOD is defined as\r\n\r\n\r\nngal is the number density of [O iii] emitting galaxies per unit comoving volume, estimated from the [O iii] luminosity function at z ∼ 6. And 〈overdensity size〉 is simply the mean number of galaxies in each galaxy overdensity empirically measured to be 〈overdensity size〉 = 2.67. fc is the O i absorption covering fraction within 300 kpc for WOI ≥ 0.05 Å (). (The covering fraction within 300 kpc is independent of the definition of the primary member.)\r\n\r\nTo estimate the number density of galaxies per unit comoving volume (ngal), we integrate the z ∼ 6 [O iii] luminosity function derived from the EIGER survey, with a minimum luminosity of Lmin = 1042.2 ergs−1 (J. Matthee et al. 2022):\r\n\r\n\r\nwhere Φ(L) is the [O iii] luminosity function defined as\r\n\r\n\r\nHere, Φ* is the characteristic number density, L* is the characteristic luminosity, and α is the faint-end slope. We adopt Φ* = 10−4.02 Mpc−3, L* = 1043.33 ergs−1, and α = −1.92, values derived from detailed completeness calculations of the EIGER [O iii]-emitting galaxies (R. Mackenzie et al. 2026, in preparation). This results in ngal = 8.586 × 10−04 Mpc−3. Using these values in Equation (6) yields , for O i absorption around galaxies at a mean galaxy redshift of 6.001.\r\n\r\nAll calculations in this section are performed with a detection threshold of WOI > 0.05Å, since the survey is highly complete down to this equivalent-width limit and because most of the literature surveys we compare against adopt the same threshold.\r\n\r\nWe emphasize that this approach differs from blind QSO absorption-line surveys (e.g., G. D. Becker et al. 2006; L. Christensen et al. 2023; A. M. Sebastian et al. 2024; A. Sodini et al. 2024), where all O i absorption-line systems along the full quasar redshift path are counted to compute dN/dX directly, under the assumption that the absorber cross section is contributed by all galaxies. In contrast, our method begins by defining the absorber cross section around galaxy overdensities and then estimating the corresponding contribution to dN/dX from the galaxy overdensities under study. Comparing these two approaches constrains the fraction of O i (or other metal) absorption systems that arise in the extended halos of these galaxies. Figure 6 shows these literature measurements as colored circles, while the contribution to dN/dX around z ∼ 6 galaxy overdensities is indicated by an orange square. To quantify the relative contribution of galaxy overdensities, we fit a single power law to all literature values at z > 4 (blue dashed line with shaded region). Comparing the dN/dX inferred from quasar absorption-line surveys at z ∼ 6 to our measured value, we find that O i dN/dX around z ∼ 6 EIGER galaxy environments account for 35% ± 16% of all O i absorption-line systems detected in blind quasar surveys. This implies that [O iii] emitting galaxy environments at z ∼ 6 contribute roughly one-third of the O i absorption systems at that epoch. Although the EIGER QSOs were selected to have known absorption systems along their sight lines, the EIGER galaxy survey around these sight lines is highly complete and independent of this selection. Therefore, we can create an unbiased measurement of the absorption cross section (dN/dX) around these galaxy overdensities. We justify this comparison to blind absorption surveys in Section 2.\r\n\r\nZoom InZoom OutReset image size\r\nFigure 6. Incidence of O i absorbers per comoving path length, dN/dX. Values are derived from all O i absorption lines along high-z quasar sight lines. Literature measurements are shown from G. D. Becker et al. (2019; blue circles), L. Christensen et al. (2023; purple circles), and A. M. Sebastian et al. (2024; red circles). The blue dashed line shows a power-law fit to the z > 4 literature data, with the shaded region marking the 1σ uncertainty. The orange square gives the inferred dN/dX when including only O i absorption associated with host galaxies (see Section 4.2), indicating that only ∼35% of O i absorbers at z ∼ 6 arise in galaxy environments.\r\n\r\nDownload figure:\r\n\r\nStandard image\r\nHigh-resolution image\r\nThis in turn suggests that ∼65% of the O i absorption systems detected along quasar sight lines at the epoch of reionization are not associated with [O iii] emitter galaxy overdensities. Either the bulk of O i absorption resides in isolated pockets of neutral IGM gas outside extended galaxy halos, or it is contributed by even lower-luminosity, less massive galaxies () that fall below the EIGER detection limits. Such systems may also be detected in galaxy halos that are oxygen-poor or lack strong [O iii] emission features, since our galaxy identifications primarily rely on [O iii] and Hβ emission lines.\r\n\r\nSimulations suggest that O i absorption should primarily arise in galactic halos rather than in the diffuse IGM, since metals are not widely distributed and ionization fronts propagate more quickly than metals (B. D. Oppenheimer et al. 2009; K. Finlator et al. 2013). Very low-mass protogalaxies forming their first stars may blur the boundary between IGM and CGM, enriching their surroundings with metals, especially if their star formation is bursty and prolific. If sufficiently numerous, such systems could contribute a nonnegligible fraction of oxygen in the early Universe.\r\n\r\nRecent observations support this possibility. K. Nakajima et al. (2025) reported a strongly lensed (μ = 98) galaxy at z ≈ 6.6 with a stellar mass upper limit of only ∼2700 M⊙ and a dynamical mass ∼100 times larger. The source shows emission and may be dominated by Population III stars. This provides direct evidence of oxygen production in extremely low-mass systems. A population of such ultralow-mass dwarf galaxies could plausibly account for the ∼65% of O i absorbers detected along quasar sight lines that are not associated with galaxies in our survey. Our sensitivity limit of (J. Matthee et al. 2022) means such dwarfs remain undetected. However, these galaxies may lack a dense enough CGM to shield neutral O i from the UV background; thus, even if they produce oxygen, neutral O i may not survive (K. Finlator et al. 2013). Interestingly, simulations by S. Kušmić et al. (2024) showed that the contribution of metal ions, including O i, is only weakly correlated with the stellar mass of the galaxy, and the contribution is indistinguishable when comparing across galaxy luminosities. Additionally, they argue that due to the steep slope of the stellar mass function, lower-mass, lower-luminosity galaxies contribute the majority of absorbing metal ions in the CGM and IGM.\r\n\r\nLater simulation works by C. Doughty et al. (2018); C. Doughty & K. Finlator (2019) suggest that as the Epoch of Reionization continues, O i will reduce overall but be preferentially found in higher column density regions close to halos, as they have a better ability to self-shield from ionizing photons. In fact, C. Doughty & K. Finlator (2019) found that at z = 6 the majority of O i mass was located in the ISM of galaxies and only ∼30% of O i mass was found in the CGM and IGM. In contrast, in this work, we find that a substantial (comparable to ISM mass) oxygen mass exists outside galaxies; however, we stress that our mass measurements are order-of-magnitude estimates. A more direct comparison between these simulations and this work is the covering fraction. They report ∼5%–25% covering fraction at z = 6 for O i with out to 102 pkpc. In the EIGER survey, we report a covering fraction using a minimum threshold of WOI ≥ 0.05 Å (or approximately logNOI > 13.7 cm−2) out to 300 kpc. Given the large measurement uncertainties and different definitions of associated galaxies, the covering fractions are qualitatively consistent between the two works.\r\n\r\nThe simulations of K. Finlator et al. (2013) suggest that O i absorbers with are most likely associated with halos of mass ∼109 M⊙, where self-shielding is efficient. They further predict that only ∼13% of all O i absorption systems should reside in halos of 1010–1011.5 M⊙, the mass range of galaxies probed in this work. By contrast, we measure a higher dN/dX of ∼35%, but qualitatively our results remain consistent with the idea that roughly two-thirds of O i absorbers are associated with undetected ∼109 M⊙ halos. Future observations targeting lower-luminosity galaxies and higher redshifts will be essential to test these predictions.\r\n\r\nAfter the initial posting of this manuscript, G. Pruto et al. (2026) presented a simulation-based study that adopts the observational compilation shown in Figure 6 as a reference and explores the corresponding behavior in numerical models. Our minimum Wr threshold corresponds to ; therefore, the most appropriate comparison is with their sample. Qualitatively, the two sets of results are in agreement. A key distinction lies in the definition of galactic environment. We characterize environments in terms of galaxy overdensities, which we argue is the most appropriate description of where O i absorbers reside at z ≈ 6, whereas G. Pruto et al. (2026) define the CGM based on the virial radii of halos with . As a result, a direct quantitative comparison is not straightforward. Nevertheless, their inferred dN/dX corresponds to an incidence rate of O i absorbers of ∼58% ± 11%, which is consistent with our measurements within the uncertainties. This agreement may depend on their tighter constraints on absorber location and on the adopted minimum Wr or threshold. G. Pruto et al. (2026) further report that ∼80% of O i absorbers with are predicted to lie outside the CGM, also in qualitative agreement with our findings.\r\n\r\n4.3. Metal Abundances in O i absorber population\r\nIn this section, we examine the relative abundances and metal column density ratios of O i absorbers associated with galaxy overdensities, and compare them to O i absorbers without any associated galaxies. To enable a fair comparison, we restrict our analysis to the six quasar sight lines from the EIGER survey and identify all O i absorption systems in the redshift range where an [O iii]-emitting galaxy could be detected (5.9 ≤ zOI ≤ zQSO). We detect 10 O i absorption systems in total, 5 of which have associated galaxy overdensities (Table 1) and 5 are without any identified galaxy association.\r\n\r\nWe first compare the ionic column density ratios in these two populations. Figure 7 (top panels) shows the ratios of NSiII/NOI and NCII/NOI as functions of NOI. Systems located near galaxy overdensities (blue squares) systematically show higher Si ii/O i and C ii/O i ratios compared to systems without associated overdensities (green crosses). This offset could reflect differences in metallicity, or alternatively, the effects of ionization. However, since the majority of these O i systems lack detectable high-ionization transitions, it is reasonable to assume that neutral oxygen and singly ionized silicon and carbon dominate the elemental reservoirs (see also L. Christensen et al. 2023). In those cases, the observed ionic ratios provide direct tracers of relative abundances. Two exceptions are found along the J0100 and J1148 sight lines, which do exhibit Si iv and C iv absorption; for these systems, the degeneracy between chemical composition and ionization corrections cannot be resolved. It is plausible that, on average, O i absorption found near galaxy overdensities has higher elemental abundance ratios as the non-galaxy-associated absorbers either have significantly lower-luminosity and less massive galaxies, which would be expected to produce less metal, or there are truly no galaxies associated with this population.\r\n\r\nZoom InZoom OutReset image size\r\nFigure 7. Top panels: ion column density ratios of Si ii to O i (left) and C ii to O i (right) as a function of the detected O i column densities, shown in logarithmic units. Absorbers associated with galaxy overdensities (blue squares) and those not associated with galaxy overdensities (green crosses) exhibit clear variations in their column density ratios. One sight line with no detected Si ii absorption is indicated with a downward arrow, where a 2σ upper limit on the column density is assumed. Bottom panel: relative abundance ratios [Si/O] vs. [C/O] with respect to solar abundance. The background contours show the IMF-weighted abundance distributions from Population II and Population III SN models. Orange and pink circles indicate abundance ratios predicted by low-metallicity Population II SN models. The abundance ratios of several O i absorbers associated with galaxy overdensities are consistent with a significant contribution from Population III SNe.\r\n\r\nDownload figure:\r\n\r\nStandard image\r\nHigh-resolution image\r\nWe next compute the relative abundances [Si/O] and [C/O], presented in the bottom panel of Figure 7. These abundances are defined as\r\n\r\n\r\nwhere NSi,tot and NC,tot represent the summed ionic column densities. For systems with detected high-ionization absorption (C iv or Si iv), we include both low- and high-ionization states (NSiII + NSiIV and NCII + NCIV), marking these measurements as lower limits (blue upward arrows in the figure) since additional undetected ionization states may be present. We note that in the two systems (a and b) exhibiting high-ionization absorption (see Table 1), the low- and high-ionization absorption components are offset in velocity by Δv = –66 km s−1 and –69 km s−1, respectively. These offsets are within ≲1.5 resolution elements of the instrument, and therefore we cannot statistically distinguish whether the low- and high-ionization components are kinematically distinct. This is suggestive of a complex, potentially multiphase gaseous environment in the outskirts of these galaxies. For systems without detected high-ionization transitions, we adopt NSiII and NCII as the dominant contributions. We assume NO,tot ≈ NOI, as ionization corrections for O i are typically very small at high O i column densities (see Section 4.1 for discussion). We adopt solar reference abundances of = −1.18 ± 0.05 and (M. Asplund et al. 2021).\r\n\r\nFigure 7 (bottom panel) reveals a striking separation between O i absorbers associated with galaxy overdensities (blue squares) and those without galaxy associations (green crosses). Systems near galaxies are found in the upper left of the [Si/O]–[C/O] diagram, with two cases exhibiting high-ionization absorption (lower abundance limits, blue arrows), which will offset them even farther from the locus of nongalaxy absorbers.\r\n\r\nWe place these abundance patterns in the context of chemical enrichment models from different stellar populations (see also L. Christensen et al. 2023). The contours and colored circles in Figure 7 highlight predicted [C/O] and [Si/O] yields from representative Population II and Population III supernova (SN) models, weighted by a Salpeter IMF. The weighting by number of stars predicted by an IMF is done to represent the typical observational relative abundance distribution in these models. These are not exhaustive but span the dominant theoretical expectations.\r\n\r\nPopulation III pair-instability SNe (PISNe; 140–260M⊙; light green contours) predict narrow [C/O] ≃ –0.7 and high [Si/O] values, inconsistent with any of our observed systems. Such PISNe are also expected to produce substantial amounts of iron-peak elements, leading to elevated Fe/O ratios (J. Tumlinson et al. 2004). We will investigate Mg ii and Fe ii absorption associated with z ∼ 6 galaxies in an upcoming work (J. Higginson et al. 2026, in preparation). Models of massive Population III stars (10–100 M⊙) produce both hypernovae (gray contours; E > 1052 erg) and standard core-collapse SNe (light blue contours; A. Heger & S. E. Woosley 2010), spanning a broader region overlapping some of our measurements. We also consider Population II models: low-metallicity core-collapse SNe from M. Limongi & A. Chieffi (2018; orange contours, Population II SNe (L18)) occupy −0.25 ≲ [C/O] ≲ 0.5 and −0.4 ≲ [Si/O] ≲ 0.4, overlapping parts of the Population III range, while the C. Kobayashi et al. (2006) yields (pink and orange circles for hypernovae and SNe, respectively) tend toward lower [Si/O] and [C/O].\r\n\r\nAgainst these predictions, the contrast between the two absorber populations is clear. All nongalaxy O i systems (green crosses) fall at the lower left of the diagram, consistent with enrichment from both Population II and/or Population III SNe models. This regime also overlaps with ultra-metal-poor damped Lyman-α absorbers (DLAs) at z ∼ 3 (−0.5 ≲ [Si/O] ≲ 0, −0.5 ≲ [C/O] ≲ 0; R. Cooke et al. 2011; R. J. Cooke et al. 2017). By contrast, three of the five galaxy-associated absorbers lie well outside both the locus of Population II predictions and the locus of ultra-metal-poor DLA relative abundances. These systems are best explained if Population III enrichment played a major role, suggesting that they may represent a distinct population from ultra-metal-poor DLA host galaxies (see also A. Sodini et al. 2024).\r\n\r\nSimilarly, A. Sodini et al. (2024) found that the [C/O] and [Si/O] abundance ratios for high-redshift O i absorber systems are consistent with significant enrichment from Population III, with the majority explained by ≥ 30% contributions. They also find a large spread in the implied Population III contribution; several systems require ≥ 60% contributions, while others fall significantly below the average. This is a strong indication of heterogeneous chemical enrichment by Population III stars during the epoch of reionization.\r\n\r\nThe absorber toward J159 at z = 5.91 shows [C/O] = 0.20, [Si/O] = 0.55 (labeled c), and no evidence of high-ionization absorption. These abundance ratios are best explained by contributions from Population III SNe or hypernovae. The absorber toward J1030 at z = 6.07 ([C/O] = −0.38, [Si/O] = 0.65, labeled e) also shows no high-ionization absorption. The relative abundances in these two predominantly neutral systems are therefore quite robust. Interestingly, the J1030 system is not reproduced by any single Population II or Population III model, suggesting that it may have experienced multiple enrichment episodes, producing unusually high [Si/O] coupled with low [C/O].\r\n\r\nTwo cases require special mention. The absorber toward J0100 at z = 5.94 shows [C/O] ≥ 0.42 and [Si/O] ≥ 0.67 (labeled a), with strong C iv and Si iv absorption. Since these are lower limits, ionization corrections (for carbon and silicon) would push this system further upward, strengthening the case for Population III contributions. This observation is best explained by contributions from Population III hypernovae models. The J1148 absorber at z = 6.01 shows [C/O] ≥ 0.02 and [Si/O] ≥ 0.20 (labeled b), again with high-ionization lines; correcting for ionization would shift it diagonally upward in the diagram. Taken together, four of the five galaxy-associated absorbers show relative abundances that cannot be explained by Population II models alone, pointing instead to significant enrichment from Population III SNe or hypernovae.\r\n\r\nThus, most galaxy-associated O i systems carry signatures of Population III enrichment. These results suggest that O i systems tracing galaxy overdensities at z ∼ 6 carry chemical signatures of Population III enrichment, likely from multiple SNe events rather than a single explosion. The elevated [Si/O] and [C/O] ratios in these environments imply that [O iii]—emitting galaxies at this epoch may retain significant Population III contributions, and that metal-line absorbers around such overdensities provide a powerful probe of the first generations of stars.\r\n\r\n4.4. Comparison to the z ≈ 0 Universe\r\nAt z ∼ 6, we cannot directly detect the local environments where O i absorption systems arise. However, at z ∼ 0, there are instances where the environments giving rise to O i absorption are well understood. Here, we discuss several such instances and compare them with z ∼ 6 observations. Such comparisons can provide useful insights regarding the nature of local environments within which O i systems exist at high z. We focus on O i absorption associated with local blue compact dwarf (BCD) galaxies and the Magellanic Stream (MS), owing to their low metallicities and well-characterized local environments.\r\n\r\nThere is evidence that O i is found preferentially in the H ii regions of local BCDs, with their H i regions being pristine or showing very low levels of enrichment (D. Kunth et al. 1994; M. Pettini & K. Lipman 1995; T. X. Thuan & Y. I. Izotov 1997). In particular, T. X. Thuan & Y. I. Izotov (1997) report that, to varying degrees, low-ionization metal lines (e.g., O i and Si ii) reside in the ionized hydrogen regions of BCDs rather than the neutral hydrogen regions. They report . Compared to the z ∼ 6 measurements in panel (b) of Figure 7, the O i column density of the BCD is comparable, but the Si ii-to-O i ratio is inconsistent with the z ∼ 6 values. On the other hand, V. Lebouteiller et al. (2004) find that the H ii region of the BCD I Zw 36 has significantly higher metallicity than its H i region. However, inferred from velocity offsets, O i in that system is associated with the H i region. The reported O i column density of that BCD () is approximately 2 orders of magnitude higher than the z ∼ 6 sample. Given the available evidence, we conclude that the observed z ∼ 6 O i absorption systems are not similar to local BCD systems and are unlikely to originate in H ii regions.\r\n\r\nThe MS is a filamentary trail of gas in the Local Group. Multiphase absorption-line observations from A. J. Fox et al. (2013) and P. Richter et al. (2013) support the argument that the MS was tidally stripped from the Magellanic Clouds approximately 2 Gyr ago. Inferences from the abundance ratios of alpha elements in the MS are best explained by contributions from massive stars via Type II SNe when the MS was still part of the Magellanic Clouds, although the presence of significant dust depletion makes further inferences into enrichment history difficult. An additional study of the MS (N. Kumari et al. 2015) reports abundance ratios in a compact high-velocity cloud (CHVC) that is believed to be associated with the MS. They find [Si/O] = −0.04 ± 0.25 and [C/O] = −0.09 ± 0.23. When comparing these with the z ∼ 6 observations presented in panel (c) of Figure 7, we see that the CHVC abundance ratios occupy a different region of parameter space than the z ≈ 6 O i absorbers within identified galactic overdensities showing Population III enrichment signatures (points a, c, e). This discrepancy provides evidence that these z ∼ 6 O i absorbers with Population III enrichment signatures are unlikely to arise in environments similar to the MS. However, the ionic ratios of O i absorption systems not associated with galaxy overdensities (green crosses) are consistent with this measurement. With the caveat that MS measurements do contain dust depletion effects, it is plausible that such O i systems may trace IGM structures with densities comparable to those of the MS at high z.\r\n\r\n5. Conclusion\r\nWe have conducted a survey of neutral O i absorption systems associated with galaxies during the Epoch of Reionization in the EIGER survey, using six high-redshift quasars as background sight lines. Our study focuses on the distribution of neutral oxygen around -emitting galaxies within 300 kpc and their connection to galaxy overdensities. The main results are as follows:\r\n\r\n1. \r\nFive O i absorbers are detected among 15 galaxy overdensities, spanning z = 5.91–6.16 with a mean redshift 〈z〉 = 6.001.\r\n2. \r\nThe O i covering fraction within 300 kpc of the closest galaxy is , with for R ≤ 50 kpc and for 50 ≤ R ≤ 300 kpc, where the covering fraction is calculated using the galaxy in an overdensity with the lowest impact parameter.\r\n3. \r\nWe find ≳ 2 × 106 M⊙ of oxygen within 300 kpc, a mass comparable to the ISM oxygen content of z ∼ 6 galaxies—assuming minimal ionization correction (see Section 4.1 for justification)—suggesting that the circumgalactic environment already holds metal reservoirs rivaling those inside galaxies.\r\n4. \r\nO i absorbers are detected as far as ∼8 R/Rvir from galaxies, in sharp contrast to low-ionization tracers such as Mg ii, which are typically confined within ≲R/Rvir.\r\n5. \r\nThe incidence of galaxy-associated O i absorbers is \r\n \r\n. Comparison with blind quasar absorption-line surveys indicates that these systems represent only ∼35% of all O i absorbers at z ∼ 6, implying that the majority likely arise in lower-mass galaxies below current detection limits or in dense neutral IGM pockets that survived reionization.\r\n6. \r\nRelative abundance and ionization ratios ([Si/O], [C/O]) show that galaxy-associated O i systems are chemically enriched, with signatures in several systems consistent with contributions from Population III stars. In particular, we identify four galaxy overdensities whose outskirts exhibit absorption-line abundance ratios consistent with contributions from Population III nucleosynthesis.\r\n\r\nOverall, these results indicate that neutral O i at z ∼ 6 primarily traces extended overdensity environments rather than the CGM of individual halos. Moreover, the chemical abundance patterns of galaxy-associated O i systems suggest contributions from Population III stars, likely arising from multiple SNe events rather than a single explosion. The elevated [Si/O] and [C/O] ratios imply that [O iii]-emitting galaxies at this epoch may retain significant Population III enrichment. Consequently, metal-line absorbers around such overdensities offer a powerful probe of the first generations of stars, providing insight into early chemical enrichment and the role of primordial stellar populations in shaping galaxy evolution during the Epoch of Reionization.\r\n\r\nAcknowledgments\r\nThis work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with program #1243. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. This work was supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration (NASA) through the agency’s scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The JWST data presented in this article were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations analyzed can be accessed via DOI: 10.17909/y94q-h212. This work was partially supported by the National Science Foundation under grant No. AST-2108931. Jorryt Matthee and Ivan Kramarenko acknowledge funding from the European Union (ERC, AGENTS, 101076224).\r\n\r\nFacilities: JWST - James Webb Space Telescope (NIRCam), Magellan: Baade - (FIRE), VLT: Kueyen - (X-shooter), and Keck: I - (HIRES, MOSFIRE).\r\n\r\nSoftware: astropy (Astropy Collaboration et al. 2013, 2018, 2022), rbcodes (R. Bordoloi et al. 2025), rbvfit (R. Bordoloi & J. Higginson 2025).","external_id":{"arxiv":["2510.05220"]},"has_accepted_license":"1","department":[{"_id":"JoMa"},{"_id":"GradSch"}],"article_processing_charge":"Yes","DOAJ_listed":"1","file_date_updated":"2026-10-14T07:50:51Z","doi":"10.3847/1538-4357/ae3e81","citation":{"mla":"Higginson, Jack, et al. “EIGER. VIII. First Stars Signatures in the Connection between O I Absorption and Galaxies in the Epoch of Reionization.” The Astrophysical Journal, vol. 999, no. 1, 49, IOP Publishing, 2026, doi:10.3847/1538-4357/ae3e81.","apa":"Higginson, J., Bordoloi, R., Simcoe, R. A., Matthee, J. J., Kashino, D., Mackenzie, R., … Yue, M. (2026). EIGER. VIII. First stars signatures in the connection between O I absorption and galaxies in the epoch of reionization. The Astrophysical Journal. IOP Publishing. https://doi.org/10.3847/1538-4357/ae3e81","ieee":"J. Higginson et al., “EIGER. VIII. First stars signatures in the connection between O I absorption and galaxies in the epoch of reionization,” The Astrophysical Journal, vol. 999, no. 1. IOP Publishing, 2026.","ista":"Higginson J, Bordoloi R, Simcoe RA, Matthee JJ, Kashino D, Mackenzie R, Kramarenko I, Lilly SJ, Eilers A-C, Naidu RP, Yue M. 2026. EIGER. VIII. First stars signatures in the connection between O I absorption and galaxies in the epoch of reionization. The Astrophysical Journal. 999(1), 49.","short":"J. Higginson, R. Bordoloi, R.A. Simcoe, J.J. Matthee, D. Kashino, R. Mackenzie, I. Kramarenko, S.J. Lilly, A.-C. Eilers, R.P. Naidu, M. Yue, The Astrophysical Journal 999 (2026).","chicago":"Higginson, Jack, Rongmon Bordoloi, Robert A. Simcoe, Jorryt J Matthee, Daichi Kashino, Ruari Mackenzie, Ivan Kramarenko, et al. “EIGER. VIII. First Stars Signatures in the Connection between O I Absorption and Galaxies in the Epoch of Reionization.” The Astrophysical Journal. IOP Publishing, 2026. https://doi.org/10.3847/1538-4357/ae3e81.","ama":"Higginson J, Bordoloi R, Simcoe RA, et al. EIGER. VIII. First stars signatures in the connection between O I absorption and galaxies in the epoch of reionization. The Astrophysical Journal. 2026;999(1). doi:10.3847/1538-4357/ae3e81"},"publication_identifier":{"issn":["0004-637X"],"eissn":["1538-4357"]},"abstract":[{"lang":"eng","text":"We investigate the association between galaxies and neutral O I absorption systems at z ∼ 6, which trace metalenriched gas during the epoch of reionization. We identify 40 galaxies across six quasar fields, residing in 15\r\noverdensities within 300 kpc of the background sight lines. Five O I absorption systems are associated with five of\r\nthese overdensities, yielding a covering fraction of\r\n0.27 0.10\r\n+0.13\r\nwithin 300 kpc. The absorption occurs beyond typical\r\nvirial radii, indicating that the gas traces extended overdensity environments rather than individual galaxy halos,\r\nunlike the z ∼ 0 circumgalactic medium (CGM), which is largely bound to halos. These galaxy-associated\r\nabsorbers account for ∼35% of all O I systems seen in blind quasar surveys, implying the remainder arise in\r\nlower-mass galaxies below our detection threshold or in dense neutral intergalactic medium pockets. The CGM\r\naround these galaxies contains ≳ 2 × 106 M⊙ of oxygen, comparable to the interstellar medium oxygen mass of\r\nthe galaxies themselves, suggesting that the surrounding environment holds as much metal mass as the galaxies.\r\nAll five galaxy-associated systems show significantly higher\r\nlog NCII NOI ( / )\r\nratios than absorbers lacking galaxy\r\nassociations. Furthermore, relative abundance ratios ([Si/O], [C/O]) reveal that four of the five exhibit\r\nenrichment patterns consistent with Population III nucleosynthesis at the outskirts of galaxy overdensities. These\r\nrare systems offer a unique window into the role of first-generation stars in shaping the early metal enrichment of\r\ngalaxies and their environments."}],"article_number":"49","project":[{"_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224"}],"month":"02","language":[{"iso":"eng"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","scopus_import":"1","oa_version":"Published Version","date_created":"2026-10-12T12:15:27Z","oa":1,"date_published":"2026-02-24T00:00:00Z","intvolume":" 999","status":"public","year":"2026","PlanS_conform":"1","issue":"1","type":"journal_article","arxiv":1,"publication_status":"published","fulldoi":"https://doi.org/10.3847/1538-4357/ae3e81","publication":"The Astrophysical Journal","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"volume":999,"article_type":"original","OA_type":"gold","quality_controlled":"1","file":[{"creator":"dernst","file_size":2808503,"success":1,"content_type":"application/pdf","file_id":"23136","relation":"main_file","date_updated":"2026-10-14T07:50:51Z","checksum":"1b8caf640c32d0d27a078bfb27ffcf8a","file_name":"2026_AstrophysicalJour_Higginson.pdf","date_created":"2026-10-14T07:50:51Z","access_level":"open_access"}],"author":[{"full_name":"Higginson, Jack","first_name":"Jack","last_name":"Higginson"},{"full_name":"Bordoloi, Rongmon","first_name":"Rongmon","last_name":"Bordoloi"},{"full_name":"Simcoe, Robert A.","first_name":"Robert A.","last_name":"Simcoe"},{"first_name":"Jorryt J","full_name":"Matthee, Jorryt J","last_name":"Matthee","orcid":"0000-0003-2871-127X","id":"7439a258-f3c0-11ec-9501-9df22fe06720"},{"last_name":"Kashino","full_name":"Kashino, Daichi","first_name":"Daichi"},{"last_name":"Mackenzie","full_name":"Mackenzie, Ruari","first_name":"Ruari"},{"full_name":"Kramarenko, Ivan","first_name":"Ivan","orcid":"0000-0001-5346-6048","id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4","last_name":"Kramarenko"},{"first_name":"Simon J.","full_name":"Lilly, Simon J.","last_name":"Lilly"},{"last_name":"Eilers","full_name":"Eilers, Anna-Christina","first_name":"Anna-Christina"},{"first_name":"Rohan P.","full_name":"Naidu, Rohan P.","last_name":"Naidu"},{"full_name":"Yue, Minghao","first_name":"Minghao","last_name":"Yue"}],"day":"24","OA_place":"publisher"},{"tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication":"The Astrophysical Journal","fulldoi":"https://doi.org/10.3847/1538-4357/ae2799","arxiv":1,"publication_status":"published","type":"journal_article","issue":"2","year":"2026","PlanS_conform":"1","researchdata_availability":"no","status":"public","intvolume":" 997","date_published":"2026-01-28T00:00:00Z","oa":1,"date_created":"2026-10-12T12:17:25Z","das_tickbox":"0","OA_place":"publisher","day":"28","author":[{"first_name":"Daichi","full_name":"Kashino, Daichi","last_name":"Kashino"},{"first_name":"Simon J.","full_name":"Lilly, Simon J.","last_name":"Lilly"},{"orcid":"0000-0003-2871-127X","last_name":"Matthee","id":"7439a258-f3c0-11ec-9501-9df22fe06720","full_name":"Matthee, Jorryt J","first_name":"Jorryt J"},{"last_name":"Mackenzie","full_name":"Mackenzie, Ruari","first_name":"Ruari"},{"last_name":"Eilers","first_name":"Anna-Christina","full_name":"Eilers, Anna-Christina"},{"first_name":"Rongmon","full_name":"Bordoloi, Rongmon","last_name":"Bordoloi"},{"full_name":"Simcoe, Robert A.","first_name":"Robert A.","last_name":"Simcoe"},{"last_name":"Naidu","full_name":"Naidu, Rohan P.","first_name":"Rohan P."},{"last_name":"Yue","full_name":"Yue, Minghao","first_name":"Minghao"},{"last_name":"Liu","first_name":"Bin","full_name":"Liu, Bin"}],"file":[{"relation":"main_file","date_updated":"2026-10-14T08:09:31Z","checksum":"c33405da323cac352c0d751f0fe6f021","file_name":"2026_AstrophysicalJour_Kashino.pdf","date_created":"2026-10-14T08:09:31Z","access_level":"open_access","creator":"dernst","file_size":11393255,"success":1,"file_id":"23138","content_type":"application/pdf"}],"quality_controlled":"1","article_type":"original","OA_type":"gold","supplementarymaterial":"yes","volume":997,"publication_identifier":{"eissn":["1538-4357"],"issn":["0004-637X"]},"abstract":[{"lang":"eng","text":"We present a comprehensive analysis of the relationship between galaxies and the intergalactic medium (IGM) during the late stages of cosmic reionization, based on the complete JWST EIGER dataset. Using deep NIRCam 3.5 μm slitless spectroscopy, we construct a sample of 948 [O iii]λ5008-emitting galaxies with −21.4 ≲ MUV ≲ −17.2 spanning 5.33 < z < 6.97 along six quasar sight lines. We correlate these galaxies with Lyα and Lyβ transmission measured from high-resolution quasar spectra across multiple redshift intervals. We find clear redshift evolution in the correlation between galaxy density and transmission: it is suppressed in overdense regions at z < 5.50, while enhanced at 5.70 < z < 6.15. The intermediate range exhibits a transitional behavior. Cross-correlation measurements further reveal excess absorption within ∼8 cMpc of galaxies at low redshifts, and enhanced transmission at intermediate scales (∼5–20 cMpc) at z > 5.70. Statistical tests using mock catalogs with realistic galaxy clustering but no correlation with the transmission field confirm that the observed correlations are unlikely to arise by chance. The evolving signals can be explained by stronger absorption in overdense regions, combined with the competing influences of local radiation fields and the rising background radiation. While local radiation dominates ionization of the surrounding IGM at earlier times, the background becomes increasingly important, eventually surpassing the impact of nearby galaxies. These results support an inside-out progression of reionization, with ionized regions originating around clustered, star-forming galaxies and gradually extending into underdense regions."}],"citation":{"mla":"Kashino, Daichi, et al. “EIGER. VII. The Evolving Relationship between Galaxies and the Intergalactic Medium in the Final Stages of Reionization.” The Astrophysical Journal, vol. 997, no. 2, 280, IOP Publishing, 2026, doi:10.3847/1538-4357/ae2799.","apa":"Kashino, D., Lilly, S. J., Matthee, J. J., Mackenzie, R., Eilers, A.-C., Bordoloi, R., … Liu, B. (2026). EIGER. VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization. The Astrophysical Journal. IOP Publishing. https://doi.org/10.3847/1538-4357/ae2799","ieee":"D. Kashino et al., “EIGER. VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization,” The Astrophysical Journal, vol. 997, no. 2. IOP Publishing, 2026.","ista":"Kashino D, Lilly SJ, Matthee JJ, Mackenzie R, Eilers A-C, Bordoloi R, Simcoe RA, Naidu RP, Yue M, Liu B. 2026. EIGER. VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization. The Astrophysical Journal. 997(2), 280.","chicago":"Kashino, Daichi, Simon J. Lilly, Jorryt J Matthee, Ruari Mackenzie, Anna-Christina Eilers, Rongmon Bordoloi, Robert A. Simcoe, Rohan P. Naidu, Minghao Yue, and Bin Liu. “EIGER. VII. The Evolving Relationship between Galaxies and the Intergalactic Medium in the Final Stages of Reionization.” The Astrophysical Journal. IOP Publishing, 2026. https://doi.org/10.3847/1538-4357/ae2799.","short":"D. Kashino, S.J. Lilly, J.J. Matthee, R. Mackenzie, A.-C. Eilers, R. Bordoloi, R.A. Simcoe, R.P. Naidu, M. Yue, B. Liu, The Astrophysical Journal 997 (2026).","ama":"Kashino D, Lilly SJ, Matthee JJ, et al. EIGER. VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization. The Astrophysical Journal. 2026;997(2). doi:10.3847/1538-4357/ae2799"},"doi":"10.3847/1538-4357/ae2799","file_date_updated":"2026-10-14T08:09:31Z","DOAJ_listed":"1","article_processing_charge":"Yes","department":[{"_id":"JoMa"}],"has_accepted_license":"1","external_id":{"arxiv":["2506.03121"]},"acknowledgement":"We thank Enrico Garaldi, Rahul Kannan, Aaron Smith, and the THESAN team for providing us with their simulation data, and Norbert Pirzkal for helpful advice on our NIRCam observing program.\r\n\r\nThis work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations were taken under GTO program No. 1243. The specific observations analyzed can be accessed via doi:10.17909/6grb-j154.\r\n\r\nThe participation of S.J.L. as an Interdisciplinary Scientist in the JWST Flight Science Working Group 2002-2022 has been supported by the European Space Agency. His earlier involvement in the development of the JWST 1996–2001 was supported by the Canadian Space Agency.\r\n\r\nThis work is partially based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 084.A-0360(A), 084.A-0390(A), 086.A-0162(A), 086.A-0574(A), 087.A-0607(A), 089.A-0814(A), 093.A-0707(A), 098.B-0537(A), and 286.A-5025(A). Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c)3 nonprofit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.\r\n\r\nThis work has been supported by JSPS KAKENHI grant No. JP21K13956 (D.K.). J.M. is supported by the European Union (ERC, AGENTS, 101076224).\r\n\r\nFacilities: JWST - James Webb Space Telescope (NIRCam), VLT:Kueyen - Very Large Telescope (Kueyen) (X-Shooter), Magellan:Baade - Magellan I Walter Baade Telescope (FIRE), Keck:I - KECK I Telescope (MOSFIRE), Keck:II - KECK II Telescope (ESI).\r\n\r\nSoftware: Python, numpy (C. R. Harris et al. 2020), scipy (P. Virtanen et al. 2020), Astropy (Astropy Collaboration et al. 2013), Matplotlib (J. D. Hunter 2007), PypeIt (J. X. Prochaska et al. 2019).","date_updated":"2026-10-14T08:12:05Z","ddc":["520"],"publisher":"IOP Publishing","_id":"23117","title":"EIGER. VII. The evolving relationship between galaxies and the intergalactic medium in the final stages of reionization","oa_version":"Published Version","scopus_import":"1","language":[{"iso":"eng"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","month":"01","project":[{"_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224"}],"article_number":"280"},{"volume":66,"quality_controlled":"1","article_type":"original","OA_type":"green","day":"04","author":[{"last_name":"Matthee","id":"7439a258-f3c0-11ec-9501-9df22fe06720","orcid":"0000-0003-2871-127X","first_name":"Jorryt J","full_name":"Matthee, Jorryt J"}],"page":"116-151","OA_place":"repository","date_published":"2025-12-04T00:00:00Z","oa":1,"date_created":"2025-12-29T12:05:25Z","type":"journal_article","issue":"1-4","status":"public","year":"2025","intvolume":" 66","publication":"Contemporary Physics","fulldoi":"https://doi.org/10.1080/00107514.2025.2586370","publication_status":"published","arxiv":1,"project":[{"name":"Young galaxies as tracers and agents of cosmic reionization","_id":"bd9b2118-d553-11ed-ba76-db24564edfea","grant_number":"101076224"}],"scopus_import":"1","month":"12","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","language":[{"iso":"eng"}],"oa_version":"Preprint","main_file_link":[{"url":"https://doi.org/10.48550/arXiv.2511.04843","open_access":"1"}],"title":"JWST provides a new view of cosmic dawn: Latest developments in studies of early galaxies","external_id":{"arxiv":["2511.04843"]},"acknowledgement":"I thank Claudia Di Cesare, Edoardo Iani, Gauri Kotiwale and Wendy Sun for proofreading, Daichi Kashino, Gauri Kotiwale, Sara Mascia, Benjamín Navarette and Joris Witstok for their assistance in preparing some of the Figures, and Richard Ellis and Stephen Blundell for constructive comments. Funded by the European Union (ERC, AGENTS, 101076224).","date_updated":"2026-04-07T08:44:00Z","_id":"20864","publisher":"Taylor & Francis","department":[{"_id":"JoMa"}],"corr_author":"1","abstract":[{"text":"Studies of the distant Universe are providing key insights into our understanding of the formation of galaxies. The advent of the James Webb Space Telescope (JWST) has significantly enhanced our observational capabilities, leading to an expanded redshift frontier, providing unprecedented detail in the characterisation of early galaxies and enabling the discovery of new populations of accreting black holes. This review aims to provide an introduction to the basic processes and components that shape the observed spectra of galaxies, with a focus on their relevance to techniques with which high-redshift galaxies are selected. The review further introduces specific topics that have attracted significant attention in recent literature, including the discovery of highly efficient galaxy formation in the early Universe, the relation between galaxies and the process of reionization, new insights into the formation of the first stars and the enrichment of interstellar gas with heavy elements, and breakthroughs in our understanding of the origins of supermassive black holes.","lang":"eng"}],"publication_identifier":{"issn":["0010-7514"],"eissn":["1366-5812"]},"citation":{"ama":"Matthee JJ. JWST provides a new view of cosmic dawn: Latest developments in studies of early galaxies. Contemporary Physics. 2025;66(1-4):116-151. doi:10.1080/00107514.2025.2586370","short":"J.J. Matthee, Contemporary Physics 66 (2025) 116–151.","chicago":"Matthee, Jorryt J. “JWST Provides a New View of Cosmic Dawn: Latest Developments in Studies of Early Galaxies.” Contemporary Physics. Taylor & Francis, 2025. https://doi.org/10.1080/00107514.2025.2586370.","ista":"Matthee JJ. 2025. JWST provides a new view of cosmic dawn: Latest developments in studies of early galaxies. Contemporary Physics. 66(1–4), 116–151.","ieee":"J. J. Matthee, “JWST provides a new view of cosmic dawn: Latest developments in studies of early galaxies,” Contemporary Physics, vol. 66, no. 1–4. Taylor & Francis, pp. 116–151, 2025.","apa":"Matthee, J. J. (2025). JWST provides a new view of cosmic dawn: Latest developments in studies of early galaxies. Contemporary Physics. Taylor & Francis. https://doi.org/10.1080/00107514.2025.2586370","mla":"Matthee, Jorryt J. “JWST Provides a New View of Cosmic Dawn: Latest Developments in Studies of Early Galaxies.” Contemporary Physics, vol. 66, no. 1–4, Taylor & Francis, 2025, pp. 116–51, doi:10.1080/00107514.2025.2586370."},"doi":"10.1080/00107514.2025.2586370","article_processing_charge":"No"},{"volume":701,"quality_controlled":"1","file":[{"file_size":9994234,"creator":"dernst","file_id":"21166","content_type":"application/pdf","success":1,"checksum":"990e384ca19e14b35296712d3b9e2919","relation":"main_file","date_updated":"2026-02-09T07:28:08Z","access_level":"open_access","date_created":"2026-02-09T07:28:08Z","file_name":"2025_AstronomyAstrophysics_Mascia.pdf"}],"OA_type":"diamond","article_type":"original","day":"01","author":[{"last_name":"Mascia","id":"edaf889c-c7cd-11ef-ab1b-bb28c431bd29","first_name":"Sara","full_name":"Mascia, Sara"},{"last_name":"Pentericci","first_name":"L.","full_name":"Pentericci, L."},{"full_name":"Llerena, M.","first_name":"M.","last_name":"Llerena"},{"last_name":"Calabrò","first_name":"A.","full_name":"Calabrò, A."},{"last_name":"Matthee","id":"7439a258-f3c0-11ec-9501-9df22fe06720","orcid":"0000-0003-2871-127X","first_name":"Jorryt J","full_name":"Matthee, Jorryt J"},{"last_name":"Flury","first_name":"S.","full_name":"Flury, S."},{"last_name":"Pacucci","full_name":"Pacucci, F.","first_name":"F."},{"last_name":"Jaskot","first_name":"A.","full_name":"Jaskot, A."},{"last_name":"Amorín","first_name":"R. O.","full_name":"Amorín, R. O."},{"last_name":"Bhatawdekar","first_name":"R.","full_name":"Bhatawdekar, R."},{"full_name":"Castellano, M.","first_name":"M.","last_name":"Castellano"},{"last_name":"Cleri","full_name":"Cleri, N.","first_name":"N."},{"last_name":"Costantin","first_name":"L.","full_name":"Costantin, L."},{"last_name":"Davis","first_name":"K.","full_name":"Davis, K."},{"id":"2d002343-372f-11ef-98ec-a164d20427cb","last_name":"Di Cesare","first_name":"Claudia","full_name":"Di Cesare, Claudia"},{"first_name":"M.","full_name":"Dickinson, M.","last_name":"Dickinson"},{"full_name":"Fontana, A.","first_name":"A.","last_name":"Fontana"},{"last_name":"Guo","full_name":"Guo, Y.","first_name":"Y."},{"last_name":"Giavalisco","first_name":"M.","full_name":"Giavalisco, M."},{"last_name":"Holwerda","first_name":"B. W.","full_name":"Holwerda, B. W."},{"last_name":"Hu","first_name":"W.","full_name":"Hu, W."},{"last_name":"Huertas-Company","full_name":"Huertas-Company, M.","first_name":"M."},{"first_name":"Intae","full_name":"Jung, Intae","last_name":"Jung"},{"first_name":"J.","full_name":"Kartaltepe, J.","last_name":"Kartaltepe"},{"full_name":"Kashino, D.","first_name":"D.","last_name":"Kashino"},{"full_name":"Koekemoer, A. M.","first_name":"A. M.","last_name":"Koekemoer"},{"full_name":"Lucas, R. A.","first_name":"R. A.","last_name":"Lucas"},{"full_name":"Lotz, J.","first_name":"J.","last_name":"Lotz"},{"last_name":"Napolitano","first_name":"L.","full_name":"Napolitano, L."},{"full_name":"Jogee, S.","first_name":"S.","last_name":"Jogee"},{"first_name":"S.","full_name":"Wilkins, S.","last_name":"Wilkins"}],"OA_place":"publisher","oa":1,"date_published":"2025-09-01T00:00:00Z","date_created":"2026-01-28T15:24:24Z","type":"journal_article","intvolume":" 701","year":"2025","status":"public","PlanS_conform":"1","publication":"Astronomy & Astrophysics","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"arxiv":1,"publication_status":"published","fulldoi":"https://doi.org/10.1051/0004-6361/202553760","article_number":"A122","project":[{"name":"Young galaxies as tracers and agents of cosmic reionization","_id":"bd9b2118-d553-11ed-ba76-db24564edfea","grant_number":"101076224"}],"scopus_import":"1","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","month":"09","language":[{"iso":"eng"}],"oa_version":"Published Version","title":"Little impact of mergers and galaxy morphology on the production and escape of ionizing photons in the early Universe","acknowledgement":"This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with programs GTO 1243, ERS 1345, DDT 2750, and GTO 1180, 1181, 3215, 1210, 1286. Funded by the European Union (ERC, AGENTS, 101076224). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. We acknowledge support from the INAF Large Grant 2022 “Extragalactic Surveys with JWST” (PI Pentericci). We acknowledge support from INAF Mini-grant “Reionization and Fundamental Cosmology with High-Redshift Galaxies” and from PRIN 2022 MUR project 2022CB3PJ3 - First Light And Galaxy aSsembly (FLAGS) funded by the European Union – Next Generation EU. RA acknowledges support of Grant PID2023-147386NB-I00 funded by MICIU/AEI/10.13039/501100011033 and by ERDF/EU, and the Severo Ochoa grant CEX2021-001131-S funded by MCIN/AEI/10.13039/50110001103. The project that gave rise to these results received the support of a fellowship from the “la Caixa” Foundation (ID 100010434). The fellowship code is LCF/BQ/PR24/12050015. LC acknowledges support from grants PID2022-139567NB-I00 and PIB2021-127718NB-I00 funded by the Spanish Ministry of Science and Innovation/State Agency of Research MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”.","external_id":{"arxiv":["2501.08268"]},"_id":"21060","publisher":"EDP Sciences","date_updated":"2026-02-09T07:33:46Z","ddc":["520"],"has_accepted_license":"1","department":[{"_id":"JoMa"}],"corr_author":"1","doi":"10.1051/0004-6361/202553760","citation":{"mla":"Mascia, Sara, et al. “Little Impact of Mergers and Galaxy Morphology on the Production and Escape of Ionizing Photons in the Early Universe.” Astronomy & Astrophysics, vol. 701, A122, EDP Sciences, 2025, doi:10.1051/0004-6361/202553760.","apa":"Mascia, S., Pentericci, L., Llerena, M., Calabrò, A., Matthee, J. J., Flury, S., … Wilkins, S. (2025). Little impact of mergers and galaxy morphology on the production and escape of ionizing photons in the early Universe. Astronomy & Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202553760","ieee":"S. Mascia et al., “Little impact of mergers and galaxy morphology on the production and escape of ionizing photons in the early Universe,” Astronomy & Astrophysics, vol. 701. EDP Sciences, 2025.","ista":"Mascia S, Pentericci L, Llerena M, Calabrò A, Matthee JJ, Flury S, Pacucci F, Jaskot A, Amorín RO, Bhatawdekar R, Castellano M, Cleri N, Costantin L, Davis K, Di Cesare C, Dickinson M, Fontana A, Guo Y, Giavalisco M, Holwerda BW, Hu W, Huertas-Company M, Jung I, Kartaltepe J, Kashino D, Koekemoer AM, Lucas RA, Lotz J, Napolitano L, Jogee S, Wilkins S. 2025. Little impact of mergers and galaxy morphology on the production and escape of ionizing photons in the early Universe. Astronomy & Astrophysics. 701, A122.","chicago":"Mascia, Sara, L. Pentericci, M. Llerena, A. Calabrò, Jorryt J Matthee, S. Flury, F. Pacucci, et al. “Little Impact of Mergers and Galaxy Morphology on the Production and Escape of Ionizing Photons in the Early Universe.” Astronomy & Astrophysics. EDP Sciences, 2025. https://doi.org/10.1051/0004-6361/202553760.","short":"S. Mascia, L. Pentericci, M. Llerena, A. Calabrò, J.J. Matthee, S. Flury, F. Pacucci, A. Jaskot, R.O. Amorín, R. Bhatawdekar, M. Castellano, N. Cleri, L. Costantin, K. Davis, C. Di Cesare, M. Dickinson, A. Fontana, Y. Guo, M. Giavalisco, B.W. Holwerda, W. Hu, M. Huertas-Company, I. Jung, J. Kartaltepe, D. Kashino, A.M. Koekemoer, R.A. Lucas, J. Lotz, L. Napolitano, S. Jogee, S. Wilkins, Astronomy & Astrophysics 701 (2025).","ama":"Mascia S, Pentericci L, Llerena M, et al. Little impact of mergers and galaxy morphology on the production and escape of ionizing photons in the early Universe. Astronomy & Astrophysics. 2025;701. doi:10.1051/0004-6361/202553760"},"file_date_updated":"2026-02-09T07:28:08Z","abstract":[{"text":"Compact, star-forming galaxies with high star formation rate surface densities (ΣSFR) are often efficient Lyman continuum (LyC) emitters at z ≤ 4.5, likely because intense stellar feedback creates low-density channels that allow photons to escape. Irregular or disturbed morphologies, such as those resulting from mergers, can also facilitate LyC escape by creating anisotropic gas distributions. We investigated the influence of galaxy morphology on LyC production and escape at redshifts 5 ≤ z ≤ 7 using observations from various James Webb Space Telescope (JWST) surveys. Our sample consists of 436 sources, which are predominantly low-mass (∼10^8.15 M\f), star-forming galaxies with ionizing photon efficiency (ξion) values consistent with canonical expectations. Since direct measurements of fesc are not possible during the Epoch of Reionization (EoR), we predicted fesc for high-redshift galaxies by applying survival analysis to a subsample of LyC emitters from the Low-Redshift Lyman Continuum Survey (LzLCS), selected to be direct analogs of reionization-era galaxies. We find that these galaxies exhibit, on average, modest predicted escape fractions (∼0.04). In addition, we evaluated the correlation between morphological features and LyC emission. Our findings indicate that neither ξion nor the predicted fesc values show a significant correlation with the presence of merger signatures. This suggests that in low-mass galaxies at z ≥ 5, strong morphological disturbances are not the primary mechanism driving LyC emission and leakage. Instead, compactness and star formation activity likely play a more pivotal role in regulating LyC escape. ","lang":"eng"}],"publication_identifier":{"issn":["0004-6361"],"eissn":["1432-0746"]},"article_processing_charge":"No","DOAJ_listed":"1"},{"arxiv":1,"publication_status":"published","fulldoi":"https://doi.org/10.3847/1538-4357/ade886","publication":"The Astrophysical Journal","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"date_created":"2026-01-28T15:25:42Z","oa":1,"date_published":"2025-07-29T00:00:00Z","intvolume":" 988","year":"2025","PlanS_conform":"1","status":"public","issue":"2","type":"journal_article","author":[{"last_name":"Matthee","id":"7439a258-f3c0-11ec-9501-9df22fe06720","orcid":"0000-0003-2871-127X","full_name":"Matthee, Jorryt J","first_name":"Jorryt J"},{"first_name":"Rohan P.","full_name":"Naidu, Rohan P.","last_name":"Naidu"},{"last_name":"Kotiwale","id":"1438afc8-1ff6-11ee-9fa6-cd4a75d66875","first_name":"Gauri","full_name":"Kotiwale, Gauri"},{"full_name":"Furtak, Lukas J.","first_name":"Lukas J.","last_name":"Furtak"},{"first_name":"Ivan","full_name":"Kramarenko, Ivan","id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4","orcid":"0000-0001-5346-6048","last_name":"Kramarenko"},{"last_name":"Mackenzie","first_name":"Ruari","full_name":"Mackenzie, Ruari"},{"last_name":"Greene","full_name":"Greene, Jenny","first_name":"Jenny"},{"last_name":"Adamo","first_name":"Angela","full_name":"Adamo, Angela"},{"first_name":"Rychard J.","full_name":"Bouwens, Rychard J.","last_name":"Bouwens"},{"id":"2d002343-372f-11ef-98ec-a164d20427cb","last_name":"Di Cesare","full_name":"Di Cesare, Claudia","first_name":"Claudia"},{"first_name":"Anna-Christina","full_name":"Eilers, Anna-Christina","last_name":"Eilers"},{"last_name":"de Graaff","first_name":"Anna","full_name":"de Graaff, Anna"},{"full_name":"Heintz, Kasper E.","first_name":"Kasper E.","last_name":"Heintz"},{"last_name":"Kashino","full_name":"Kashino, Daichi","first_name":"Daichi"},{"full_name":"Maseda, Michael V.","first_name":"Michael V.","last_name":"Maseda"},{"last_name":"Tacchella","full_name":"Tacchella, Sandro","first_name":"Sandro"},{"id":"018f0249-0e87-11f0-b167-cbce08fbd541","orcid":"0000-0001-5586-6950","last_name":"Torralba Torregrosa","first_name":"Alberto","full_name":"Torralba Torregrosa, Alberto"}],"day":"29","OA_place":"publisher","volume":988,"OA_type":"gold","article_type":"original","quality_controlled":"1","file":[{"file_size":6237415,"creator":"dernst","content_type":"application/pdf","file_id":"21168","success":1,"date_updated":"2026-02-09T08:20:14Z","relation":"main_file","checksum":"a49fbed72f2ff9c0b13129acb6f44f9d","date_created":"2026-02-09T08:20:14Z","access_level":"open_access","file_name":"2025_AstrophysicalJournal_Matthee.pdf"}],"corr_author":"1","has_accepted_license":"1","department":[{"_id":"JoMa"}],"DOAJ_listed":"1","article_processing_charge":"Yes","citation":{"mla":"Matthee, Jorryt J., et al. “Environmental Evidence for Overly Massive Black Holes in Low-Mass Galaxies and a Black Hole–Halo Mass Relation at z ∼ 5.” The Astrophysical Journal, vol. 988, no. 2, 246, IOP Publishing, 2025, doi:10.3847/1538-4357/ade886.","apa":"Matthee, J. J., Naidu, R. P., Kotiwale, G., Furtak, L. J., Kramarenko, I., Mackenzie, R., … Torralba Torregrosa, A. (2025). Environmental evidence for overly massive Black Holes in low-mass galaxies and a Black Hole–Halo mass relation at z ∼ 5. The Astrophysical Journal. IOP Publishing. https://doi.org/10.3847/1538-4357/ade886","ieee":"J. J. Matthee et al., “Environmental evidence for overly massive Black Holes in low-mass galaxies and a Black Hole–Halo mass relation at z ∼ 5,” The Astrophysical Journal, vol. 988, no. 2. IOP Publishing, 2025.","ista":"Matthee JJ, Naidu RP, Kotiwale G, Furtak LJ, Kramarenko I, Mackenzie R, Greene J, Adamo A, Bouwens RJ, Di Cesare C, Eilers A-C, de Graaff A, Heintz KE, Kashino D, Maseda MV, Tacchella S, Torralba Torregrosa A. 2025. Environmental evidence for overly massive Black Holes in low-mass galaxies and a Black Hole–Halo mass relation at z ∼ 5. The Astrophysical Journal. 988(2), 246.","chicago":"Matthee, Jorryt J, Rohan P. Naidu, Gauri Kotiwale, Lukas J. Furtak, Ivan Kramarenko, Ruari Mackenzie, Jenny Greene, et al. “Environmental Evidence for Overly Massive Black Holes in Low-Mass Galaxies and a Black Hole–Halo Mass Relation at z ∼ 5.” The Astrophysical Journal. IOP Publishing, 2025. https://doi.org/10.3847/1538-4357/ade886.","short":"J.J. Matthee, R.P. Naidu, G. Kotiwale, L.J. Furtak, I. Kramarenko, R. Mackenzie, J. Greene, A. Adamo, R.J. Bouwens, C. Di Cesare, A.-C. Eilers, A. de Graaff, K.E. Heintz, D. Kashino, M.V. Maseda, S. Tacchella, A. Torralba Torregrosa, The Astrophysical Journal 988 (2025).","ama":"Matthee JJ, Naidu RP, Kotiwale G, et al. Environmental evidence for overly massive Black Holes in low-mass galaxies and a Black Hole–Halo mass relation at z ∼ 5. The Astrophysical Journal. 2025;988(2). doi:10.3847/1538-4357/ade886"},"doi":"10.3847/1538-4357/ade886","file_date_updated":"2026-02-09T08:20:14Z","abstract":[{"lang":"eng","text":"JWST observations have unveiled faint active galactic nuclei (AGNs) at high redshift that provide insights into the formation of supermassive black holes (SMBHs). However, disentangling their stellar from AGN light is challenging. Here, we use an empirical approach to infer the average stellar mass of five faint broad-line (BL) Hα emitters at z = 4–5 with BH masses ≈6 × 10^6 M⊙, with a method independent of their spectral energy distribution (SED). We use the deep JWST/NIRcam grism survey “All the Little Things” to measure the overdensities around BL-Hα emitters and around a spectroscopic reference sample of ∼300 galaxies. In our reference sample, we find that megaparsec-scale overdensity correlates with stellar mass. Their large-scale environments suggest that BL-Hα emitters are hosted by galaxies with stellar masses ≈5 × 10^7 M⊙, ≈40 times lower than those inferred from galaxy-only SED fits. Adding measurements around more luminous z ≈ 6 AGNs, we find tentative correlations between line width, BH mass, and the overdensity, suggestive of a steep BH to halo mass relation. The main implications are (1) when BH masses are taken at face value, we confirm extremely high BH to stellar mass ratios of ≈10%, (2) the galaxies of low stellar mass that host growing SMBHs are in tension with typical hydrodynamical simulations, except those without feedback, (3) a 1% duty cycle implied by the host mass hints at super-Eddington accretion, (4) the masses are at odds with an interpretation of the line broadening in terms of high stellar density, (5) our results imply a luminosity-dependent diversity of galaxy masses, environments, and SEDs among AGN samples."}],"publication_identifier":{"issn":["0004-637X"],"eissn":["1538-4357"]},"title":"Environmental evidence for overly massive Black Holes in low-mass galaxies and a Black Hole–Halo mass relation at z ∼ 5","_id":"21062","publisher":"IOP Publishing","date_updated":"2026-02-09T08:22:01Z","ddc":["520"],"acknowledgement":"We thank the referee for their constructive comments that helped to improve the paper. We thank Junyao Li for sharing model output shown in Figure 13, Rob Crain for sharing results from the ONLYAGN EAGLE model shown in Figure 15, and Adi Zitrin for comments. This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with programs # 3516. Funded by the European Union (ERC, AGENTS, 101076224). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. We acknowledge funding from JWST program GO-3516. Support for this work was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51515.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS 5-26555. A.A. acknowledges support by the Swedish research council Vetenskapsrådet (2021-05559).","external_id":{"arxiv":["2412.02846"]},"month":"07","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","language":[{"iso":"eng"}],"scopus_import":"1","oa_version":"Published Version","article_number":"246","project":[{"grant_number":"101076224","name":"Young galaxies as tracers and agents of cosmic reionization","_id":"bd9b2118-d553-11ed-ba76-db24564edfea"}]},{"OA_place":"publisher","page":"2535-2558","isi":1,"author":[{"full_name":"Claeyssens, Adélaïde","first_name":"Adélaïde","last_name":"Claeyssens"},{"first_name":"Angela","full_name":"Adamo, Angela","last_name":"Adamo"},{"first_name":"Matteo","full_name":"Messa, Matteo","last_name":"Messa"},{"first_name":"Miroslava","full_name":"Dessauges-Zavadsky, Miroslava","last_name":"Dessauges-Zavadsky"},{"first_name":"Johan","full_name":"Richard, Johan","last_name":"Richard"},{"full_name":"Kramarenko, Ivan","first_name":"Ivan","orcid":"0000-0001-5346-6048","last_name":"Kramarenko","id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4"},{"full_name":"Matthee, Jorryt J","first_name":"Jorryt J","last_name":"Matthee","id":"7439a258-f3c0-11ec-9501-9df22fe06720","orcid":"0000-0003-2871-127X"},{"last_name":"Naidu","full_name":"Naidu, Rohan P.","first_name":"Rohan P."}],"day":"01","article_type":"original","OA_type":"gold","file":[{"file_size":35099276,"creator":"dernst","file_id":"19084","content_type":"application/pdf","success":1,"checksum":"431aef05755e6b5472f5e9b4c326cf84","relation":"main_file","date_updated":"2025-02-25T06:38:43Z","access_level":"open_access","date_created":"2025-02-25T06:38:43Z","file_name":"2025_MonthlyNoticesRAS_Claeyssens.pdf"}],"quality_controlled":"1","volume":537,"fulldoi":"https://doi.org/10.1093/mnras/staf058","arxiv":1,"publication_status":"published","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication":"Monthly Notices of the Royal Astronomical Society","year":"2025","status":"public","intvolume":" 537","type":"journal_article","issue":"3","date_created":"2025-02-23T23:01:55Z","date_published":"2025-03-01T00:00:00Z","oa":1,"oa_version":"Published Version","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","language":[{"iso":"eng"}],"month":"03","scopus_import":"1","project":[{"_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224"}],"DOAJ_listed":"1","article_processing_charge":"No","abstract":[{"lang":"eng","text":"We present a sample of 1956 individual stellar clumps at redshift 0.7 < z < 10, detected with JWST/NIRCam in 476 galaxies lensed by the galaxy cluster Abell2744. The lensed clumps present magnifications ranging between μ = 1.8 and μ = 300. We perform simultaneous size-photometry estimates in 20 JWST/NIRCam median and broad-band filters from 0.7 to 5 μm.\r\nSpectral energy distribution (SED) fitting analyses enable us to recover the physical properties of the clumps. The majority of the clumps are spatially resolved and have effective radii in the range Reff = 10–700 pc. We restrict this first study to the 1751 post-reionization era clumps with redshift < 5.5. We find a significant evolution of the average clump ages, star formation rates (SFRs), SFR surface densities, and metallicity with increasing redshift, while median stellar mass and stellar mass surface densities are similar in the probed redshift range. We observe a strong correlation between the clump properties and the properties of their host galaxies, with more massive galaxies hosting more massive and older clumps. We find that clumps closer to their host galactic centre are on average more massive, while their ages do not show clear sign of migration. We find that clumps at cosmic noon sample the upper-mass end of the mass function to higher masses than at z > 3, reflecting the rapid increase towards the peak of the cosmic star formation history. We conclude that the results achieved over the studied redshift range are in agreement with expectation of in situ clump formation scenario from large-scale disc fragmentation. "}],"publication_identifier":{"issn":["0035-8711"],"eissn":["1365-2966"]},"doi":"10.1093/mnras/staf058","citation":{"ista":"Claeyssens A, Adamo A, Messa M, Dessauges-Zavadsky M, Richard J, Kramarenko I, Matthee JJ, Naidu RP. 2025. Tracing star formation across cosmic time at tens of parsec-scales in the lensing cluster field Abell 2744. Monthly Notices of the Royal Astronomical Society. 537(3), 2535–2558.","ieee":"A. Claeyssens et al., “Tracing star formation across cosmic time at tens of parsec-scales in the lensing cluster field Abell 2744,” Monthly Notices of the Royal Astronomical Society, vol. 537, no. 3. Oxford University Press, pp. 2535–2558, 2025.","ama":"Claeyssens A, Adamo A, Messa M, et al. Tracing star formation across cosmic time at tens of parsec-scales in the lensing cluster field Abell 2744. Monthly Notices of the Royal Astronomical Society. 2025;537(3):2535-2558. doi:10.1093/mnras/staf058","chicago":"Claeyssens, Adélaïde, Angela Adamo, Matteo Messa, Miroslava Dessauges-Zavadsky, Johan Richard, Ivan Kramarenko, Jorryt J Matthee, and Rohan P. Naidu. “Tracing Star Formation across Cosmic Time at Tens of Parsec-Scales in the Lensing Cluster Field Abell 2744.” Monthly Notices of the Royal Astronomical Society. Oxford University Press, 2025. https://doi.org/10.1093/mnras/staf058.","short":"A. Claeyssens, A. Adamo, M. Messa, M. Dessauges-Zavadsky, J. Richard, I. Kramarenko, J.J. Matthee, R.P. Naidu, Monthly Notices of the Royal Astronomical Society 537 (2025) 2535–2558.","apa":"Claeyssens, A., Adamo, A., Messa, M., Dessauges-Zavadsky, M., Richard, J., Kramarenko, I., … Naidu, R. P. (2025). Tracing star formation across cosmic time at tens of parsec-scales in the lensing cluster field Abell 2744. Monthly Notices of the Royal Astronomical Society. Oxford University Press. https://doi.org/10.1093/mnras/staf058","mla":"Claeyssens, Adélaïde, et al. “Tracing Star Formation across Cosmic Time at Tens of Parsec-Scales in the Lensing Cluster Field Abell 2744.” Monthly Notices of the Royal Astronomical Society, vol. 537, no. 3, Oxford University Press, 2025, pp. 2535–58, doi:10.1093/mnras/staf058."},"file_date_updated":"2025-02-25T06:38:43Z","department":[{"_id":"JoMa"},{"_id":"GradSch"}],"has_accepted_license":"1","date_updated":"2026-02-16T11:51:48Z","ddc":["520"],"_id":"19066","publisher":"Oxford University Press","external_id":{"arxiv":["2410.10974"],"isi":["001420026000001"]},"acknowledgement":"The authors thank the International Space Science Institute for sponsoring the ISSI team: ‘Star Formation within rapidly evolving galaxies’ where many ideas discussed in this article have been brainstormed. AA and AC acknowledge support by the Swedish research council Vetenskapsrådet (2021-05559). MM acknowledges the financial support through grant PRIN-MIUR 2020SKSTHZ. JM and IK acknowledge support by the European Union (ERC, AGENTS, 101076224). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. RPN acknowledges funding from JWST programme GO-3516. Support for this work was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51515.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.","title":"Tracing star formation across cosmic time at tens of parsec-scales in the lensing cluster field Abell 2744"},{"article_number":"L40","project":[{"_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224"}],"scopus_import":"1","month":"09","language":[{"iso":"eng"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","oa_version":"Published Version","title":"The light echo of a high-redshift quasar mapped with Lyα tomography","external_id":{"arxiv":["2509.05417"],"isi":["001581023000001"]},"acknowledgement":"This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with programs #1243 and #4713.\r\n\r\nAll of the data presented in this Letter were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations analyzed can be accessed via doi:10.17909/w7hm-qb39.\r\nJ.M. is supported by the European Union (ERC, AGENTS, 101076224).","ddc":["520"],"date_updated":"2026-02-16T12:44:42Z","publisher":"IOP Publishing","_id":"20425","department":[{"_id":"JoMa"},{"_id":"GradSch"}],"has_accepted_license":"1","abstract":[{"text":"Ultraviolet (UV) radiation from accreting black holes ionizes the intergalactic gas around early quasars, carving out highly ionized bubbles in their surroundings. Any changes in a quasar’s luminosity are therefore predicted to produce outward-propagating ionization gradients, affecting the Lyα absorption opacity near the quasar’s systemic redshift. This “proximity effect” is well-documented in rest-UV quasar spectra but only provides a one-dimensional probe along our line of sight. Here we present deep spectroscopic observations with the James Webb Space Telescope (JWST) of galaxies in the background of a superluminous quasar at zQSO ≈ 6.3, which reveal the quasar’s “light echo” with Lyα tomography in the transverse direction. This transverse proximity effect is detected for the first time toward multiple galaxy sightlines, allowing us to map the extent and geometry of the quasar’s ionization cone. We obtain constraints on the orientation and inclination of the cone, as well as an upper limit on the obscured solid angle fraction of fobsc < 91%. Additionally, we find a timescale of the quasar’s UV radiation of tqso = 10^5.6+0.1-0.3 yr, which is significantly shorter than would be required to build up the central supermassive black hole (SMBH) with conventional growth models, but is consistent with independent measurements of the quasars’ duty cycle. Our inferred obscured fraction disfavors a scenario where short quasar lifetimes can be explained exclusively by geometric obscuration, and instead supports the idea that radiatively inefficient accretion or growth in initially heavily enshrouded cocoons plays a pivotal role in early SMBH growth. Our results pave the way for novel studies of quasars’ ionizing geometries and radiative histories at early cosmic times.","lang":"eng"}],"publication_identifier":{"eissn":["2041-8213"],"issn":["2041-8205"]},"citation":{"chicago":"Eilers, Anna Christina, Minghao Yue, Jorryt J Matthee, Joseph F. Hennawi, Frederick B. Davies, Robert A. Simcoe, Richard Teague, et al. “The Light Echo of a High-Redshift Quasar Mapped with Lyα Tomography.” The Astrophysical Journal Letters. IOP Publishing, 2025. https://doi.org/10.3847/2041-8213/ae057a.","short":"A.C. Eilers, M. Yue, J.J. Matthee, J.F. Hennawi, F.B. Davies, R.A. Simcoe, R. Teague, R. Bordoloi, G. Brammer, Y. Kang, D. Kashino, R. Mackenzie, R.P. Naidu, B. Navarrete, The Astrophysical Journal Letters 991 (2025).","ama":"Eilers AC, Yue M, Matthee JJ, et al. The light echo of a high-redshift quasar mapped with Lyα tomography. The Astrophysical Journal Letters. 2025;991(2). doi:10.3847/2041-8213/ae057a","ieee":"A. C. Eilers et al., “The light echo of a high-redshift quasar mapped with Lyα tomography,” The Astrophysical Journal Letters, vol. 991, no. 2. IOP Publishing, 2025.","ista":"Eilers AC, Yue M, Matthee JJ, Hennawi JF, Davies FB, Simcoe RA, Teague R, Bordoloi R, Brammer G, Kang Y, Kashino D, Mackenzie R, Naidu RP, Navarrete B. 2025. The light echo of a high-redshift quasar mapped with Lyα tomography. The Astrophysical Journal Letters. 991(2), L40.","mla":"Eilers, Anna Christina, et al. “The Light Echo of a High-Redshift Quasar Mapped with Lyα Tomography.” The Astrophysical Journal Letters, vol. 991, no. 2, L40, IOP Publishing, 2025, doi:10.3847/2041-8213/ae057a.","apa":"Eilers, A. C., Yue, M., Matthee, J. J., Hennawi, J. F., Davies, F. B., Simcoe, R. A., … Navarrete, B. (2025). The light echo of a high-redshift quasar mapped with Lyα tomography. The Astrophysical Journal Letters. IOP Publishing. https://doi.org/10.3847/2041-8213/ae057a"},"file_date_updated":"2025-10-13T09:25:12Z","doi":"10.3847/2041-8213/ae057a","article_processing_charge":"Yes","DOAJ_listed":"1","volume":991,"file":[{"creator":"dernst","file_size":23585591,"success":1,"file_id":"20461","content_type":"application/pdf","relation":"main_file","date_updated":"2025-10-13T09:25:12Z","checksum":"3cb8099b9a915755164e5675b33f8a03","file_name":"2025_AstrophysicalJour_Eilers.pdf","date_created":"2025-10-13T09:25:12Z","access_level":"open_access"}],"quality_controlled":"1","article_type":"original","OA_type":"gold","day":"25","isi":1,"author":[{"full_name":"Eilers, Anna Christina","first_name":"Anna Christina","last_name":"Eilers"},{"last_name":"Yue","first_name":"Minghao","full_name":"Yue, Minghao"},{"id":"7439a258-f3c0-11ec-9501-9df22fe06720","orcid":"0000-0003-2871-127X","last_name":"Matthee","first_name":"Jorryt J","full_name":"Matthee, Jorryt J"},{"last_name":"Hennawi","first_name":"Joseph F.","full_name":"Hennawi, Joseph F."},{"full_name":"Davies, Frederick B.","first_name":"Frederick B.","last_name":"Davies"},{"last_name":"Simcoe","full_name":"Simcoe, Robert A.","first_name":"Robert A."},{"full_name":"Teague, Richard","first_name":"Richard","last_name":"Teague"},{"last_name":"Bordoloi","first_name":"Rongmon","full_name":"Bordoloi, Rongmon"},{"first_name":"Gabriel","full_name":"Brammer, Gabriel","last_name":"Brammer"},{"last_name":"Kang","full_name":"Kang, Yi","first_name":"Yi"},{"full_name":"Kashino, Daichi","first_name":"Daichi","last_name":"Kashino"},{"full_name":"Mackenzie, Ruari","first_name":"Ruari","last_name":"Mackenzie"},{"last_name":"Naidu","first_name":"Rohan P.","full_name":"Naidu, Rohan P."},{"full_name":"Navarrete, Benjamín","first_name":"Benjamín","last_name":"Navarrete","id":"aa14a535-50c9-11ef-b52e-e0c373d10148"}],"OA_place":"publisher","date_published":"2025-09-25T00:00:00Z","oa":1,"date_created":"2025-10-05T22:01:35Z","type":"journal_article","issue":"2","PlanS_conform":"1","year":"2025","status":"public","intvolume":" 991","tmp":{"image":"/images/cc_by.png","short":"CC BY (4.0)","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode"},"publication":"The Astrophysical Journal Letters","fulldoi":"https://doi.org/10.3847/2041-8213/ae057a","publication_status":"published","arxiv":1}]