[{"publication_status":"published","type":"journal_article","quality_controlled":"1","doi":"10.1051/0004-6361/202556597","oa":1,"publisher":"EDP Sciences","date_published":"2026-02-01T00:00:00Z","article_processing_charge":"No","citation":{"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 &#38; Astrophysics. 706, A165.","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 &#38; Astrophysics 706 (2026).","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.” <i>Astronomy &#38; Astrophysics</i>. EDP Sciences, 2026. <a href=\"https://doi.org/10.1051/0004-6361/202556597\">https://doi.org/10.1051/0004-6361/202556597</a>.","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. <i>Astronomy &#38; Astrophysics</i>. EDP Sciences. <a href=\"https://doi.org/10.1051/0004-6361/202556597\">https://doi.org/10.1051/0004-6361/202556597</a>","ieee":"G. Kotiwale <i>et al.</i>, “Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy,” <i>Astronomy &#38; Astrophysics</i>, vol. 706. EDP Sciences, 2026.","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.” <i>Astronomy &#38; Astrophysics</i>, vol. 706, A165, EDP Sciences, 2026, doi:<a href=\"https://doi.org/10.1051/0004-6361/202556597\">10.1051/0004-6361/202556597</a>.","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. <i>Astronomy &#38; Astrophysics</i>. 2026;706. doi:<a href=\"https://doi.org/10.1051/0004-6361/202556597\">10.1051/0004-6361/202556597</a>"},"article_type":"original","file_date_updated":"2026-02-24T07:46:47Z","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."}],"_id":"21341","author":[{"id":"1438afc8-1ff6-11ee-9fa6-cd4a75d66875","full_name":"Kotiwale, Gauri","last_name":"Kotiwale","first_name":"Gauri"},{"orcid":"0000-0003-2871-127X","last_name":"Matthee","first_name":"Jorryt J","full_name":"Matthee, Jorryt J","id":"7439a258-f3c0-11ec-9501-9df22fe06720"},{"full_name":"Kashino, Daichi","first_name":"Daichi","last_name":"Kashino"},{"full_name":"Vijayan, Aswin P.","first_name":"Aswin P.","last_name":"Vijayan"},{"last_name":"Torralba Torregrosa","first_name":"Alberto","orcid":"0000-0001-5586-6950","id":"018f0249-0e87-11f0-b167-cbce08fbd541","full_name":"Torralba Torregrosa, Alberto"},{"full_name":"Di Cesare, Claudia","id":"2d002343-372f-11ef-98ec-a164d20427cb","last_name":"Di Cesare","first_name":"Claudia"},{"full_name":"Iani, Edoardo","id":"4053390a-6b68-11ef-9828-a3b8adef8d0a","orcid":"0000-0001-8386-3546","first_name":"Edoardo","last_name":"Iani"},{"last_name":"Bordoloi","first_name":"Rongmon","full_name":"Bordoloi, Rongmon"},{"full_name":"Leja, Joel","last_name":"Leja","first_name":"Joel"},{"first_name":"Michael V.","last_name":"Maseda","full_name":"Maseda, Michael V."},{"first_name":"Sandro","last_name":"Tacchella","full_name":"Tacchella, Sandro"},{"full_name":"Shivaei, Irene","first_name":"Irene","last_name":"Shivaei"},{"full_name":"Heintz, Kasper E.","first_name":"Kasper E.","last_name":"Heintz"},{"first_name":"A. Lola","last_name":"Danhaive","full_name":"Danhaive, A. Lola"},{"full_name":"Mascia, Sara","id":"edaf889c-c7cd-11ef-ab1b-bb28c431bd29","first_name":"Sara","last_name":"Mascia"},{"first_name":"Ivan","last_name":"Kramarenko","orcid":"0000-0001-5346-6048","id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4","full_name":"Kramarenko, Ivan"},{"full_name":"Navarrete, Benjamín","id":"aa14a535-50c9-11ef-b52e-e0c373d10148","last_name":"Navarrete","first_name":"Benjamín"},{"full_name":"Mackenzie, Ruari","first_name":"Ruari","last_name":"Mackenzie"},{"first_name":"Rohan P.","last_name":"Naidu","full_name":"Naidu, Rohan P."},{"full_name":"Sobral, David","first_name":"David","last_name":"Sobral"}],"date_created":"2026-02-22T23:01:35Z","project":[{"name":"Young galaxies as tracers and agents of cosmic reionization","_id":"bd9b2118-d553-11ed-ba76-db24564edfea","grant_number":"101076224"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","file":[{"date_created":"2026-02-24T07:46:47Z","relation":"main_file","file_id":"21355","date_updated":"2026-02-24T07:46:47Z","access_level":"open_access","file_name":"2026_AstronomyAstrophysics_Kotiwale.pdf","file_size":6531719,"content_type":"application/pdf","creator":"dernst","checksum":"6f5849d29ad43bee32f90152f6fc0294","success":1}],"OA_type":"diamond","OA_place":"publisher","title":"Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy","ddc":["520"],"article_number":"A165","external_id":{"arxiv":["2510.19959"]},"intvolume":"       706","department":[{"_id":"JoMa"},{"_id":"GradSch"}],"has_accepted_license":"1","publication":"Astronomy & Astrophysics","oa_version":"Published Version","scopus_import":"1","language":[{"iso":"eng"}],"corr_author":"1","publication_identifier":{"eissn":["1432-0746"],"issn":["0004-6361"]},"DOAJ_listed":"1","day":"01","year":"2026","volume":706,"date_updated":"2026-02-24T07:49:42Z","tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"arxiv":1,"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).","PlanS_conform":"1","status":"public","month":"02"},{"tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"date_updated":"2026-03-02T15:10:27Z","volume":706,"month":"02","status":"public","acknowledgement":"We thank the referee for several helpful suggestions. AGA, MGO and IM acknowledge financial support from the Severo Ochoa grant CEX2021-001131-S, funded by MICIU/AEI/10.13039/501100011033. AGA also acknowledges FPI support under grant code CEX2021-001131-S20-7. Both AGA and MGO acknowledge support from the research grant\r\nPID2022-136598NB-C32 (“Estallidos8”). MGO also acknowledges the support by the project ref. AST22_00001_Subp_11 funded from the EU – NextGenerationEU. RA acknowledges support from PID2023-147386NB-I00 funded by MICIU/AEI/10.13039/501100011033 and ERDF/EU. IM acknowledges support from PID2022-140871NB-C21 funded by MICIU/AEI/10.13039/501100011033 and FEDER/UE. RGD acknowledge financial support from the project PID2022-141755NB-I00, and the Severo Ochoa grant CEX2021-001131-S funded\r\nby MICIU/AEI/ 10.13039/501100011033. JAFO and AE acknowledge support from the Spanish Ministry of Science and Innovation and the EU–NextGenerationEU through the RRF project ICTS-MRR-2021-03-CEFCA. AHC and ALC acknowledge support from MCIN/AEI/10.13039/501100011033, “ERDF A way of making Europe”, and “EU NextGenerationEU/PRTR” through PID2021-124918NB-C44 and CNS2023-145339, as well as from the RRF project ICTS-MRR-2021-03-CEFCA ALC and RPT acknowledge the financial\r\nsupport from the European Union – NextGenerationEU through the RRF program Planes Complementarios con las CCAA de Astrofísica y Física de Altas Energías – LA4. I.B. acknowledges support from the EU Horizon 2020 programme (Marie Sklodowska-Curie Grant 101059532) and the Franziska Seidl Funding Program, University of Vienna. This paper has gone through internal‘ review by the J-PAS collaboration. Based on observations made with the\r\nJST/T250 telescope and JPCam at the Observatorio Astrofísico de Javalambre (OAJ), in Teruel, owned, managed, and operated by the Centro de Estudios de Física del Cosmos de Aragón (CEFCA). We acknowledge the OAJ Data Processing and Archiving Unit (UPAD) for reducing and calibrating the OAJ data used in this work. Funding for the J-PAS Project has been provided by the Governments of Spain and Aragón through the Fondo de Inversiones de Teruel; the Aragonese Government through the Research Groups E96, E103, E16_17R, E16_20R, and E16_23R; the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033 y FEDER, Una manera de hacer Europa) with grants PID2021-124918NB-C41, PID2021-124918NB-C42, PID2021-124918NA-C43, and PID2021-124918NB-C44; the Spanish Ministry\r\nof Science, Innovation and Universities (MCIU/AEI/FEDER, UE) with grants\r\nPGC2018-097585-B-C21 and PGC2018-097585-B-C22; the Spanish Ministry of Economy and Competitiveness (MINECO) under AYA2015-66211-C2-1-P, AYA2015-66211-C2-2, and AYA2012-30789; and European FEDER funding (FCDD10-4E-867, FCDD13-4E-2685).","arxiv":1,"language":[{"iso":"eng"}],"scopus_import":"1","publication":"Astronomy & Astrophysics","oa_version":"Published Version","year":"2026","day":"01","DOAJ_listed":"1","publication_identifier":{"eissn":["1432-0746"],"issn":["0004-6361"]},"OA_type":"diamond","OA_place":"publisher","title":"J-PAS: First identification, physical properties, and ionization efficiency of extreme emission line galaxies","file":[{"creator":"dernst","content_type":"application/pdf","file_size":1813456,"checksum":"cd25a05386ab5638ae5baf8add0ecbee","success":1,"file_name":"2026_AstronomyAstrophysics_GimenezAlcazar.pdf","date_updated":"2026-03-02T14:51:57Z","access_level":"open_access","date_created":"2026-03-02T14:51:57Z","file_id":"21391","relation":"main_file"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","date_created":"2026-03-02T10:06:10Z","author":[{"last_name":"Giménez-Alcázar","first_name":"A.","full_name":"Giménez-Alcázar, A."},{"first_name":"R.","last_name":"Amorín","full_name":"Amorín, R."},{"last_name":"Vílchez","first_name":"J. M.","full_name":"Vílchez, J. M."},{"full_name":"Hernán-Caballero, A.","last_name":"Hernán-Caballero","first_name":"A."},{"first_name":"M.","last_name":"González-Otero","full_name":"González-Otero, M."},{"first_name":"A.","last_name":"Arroyo-Polonio","full_name":"Arroyo-Polonio, A."},{"full_name":"Iglesias-Páramo, J.","last_name":"Iglesias-Páramo","first_name":"J."},{"first_name":"A.","last_name":"Lumbreras-Calle","full_name":"Lumbreras-Calle, A."},{"last_name":"Fernández-Ontiveros","first_name":"J. A.","full_name":"Fernández-Ontiveros, J. A."},{"first_name":"C.","last_name":"López-Sanjuan","full_name":"López-Sanjuan, C."},{"full_name":"Bonatto, L.","first_name":"L.","last_name":"Bonatto"},{"full_name":"González Delgado, R. M.","last_name":"González Delgado","first_name":"R. M."},{"first_name":"C.","last_name":"Kehrig","full_name":"Kehrig, C."},{"id":"018f0249-0e87-11f0-b167-cbce08fbd541","full_name":"Torralba Torregrosa, Alberto","first_name":"Alberto","last_name":"Torralba Torregrosa","orcid":"0000-0001-5586-6950"},{"last_name":"Rahna","first_name":"P. T.","full_name":"Rahna, P. T."},{"full_name":"Jiménez-Teja, Y.","last_name":"Jiménez-Teja","first_name":"Y."},{"full_name":"Márquez, I.","first_name":"I.","last_name":"Márquez"},{"last_name":"Breda","first_name":"I.","full_name":"Breda, I."},{"full_name":"Álvarez-Candal, A.","last_name":"Álvarez-Candal","first_name":"A."},{"last_name":"Abramo","first_name":"R.","full_name":"Abramo, R."},{"full_name":"Alcaniz, J.","first_name":"J.","last_name":"Alcaniz"},{"full_name":"Benitez, N.","first_name":"N.","last_name":"Benitez"},{"full_name":"Bonoli, S.","last_name":"Bonoli","first_name":"S."},{"last_name":"Carneiro","first_name":"S.","full_name":"Carneiro, S."},{"last_name":"Cenarro","first_name":"J.","full_name":"Cenarro, J."},{"full_name":"Cristóbal-Hornillos, D.","first_name":"D.","last_name":"Cristóbal-Hornillos"},{"full_name":"Dupke, R.","first_name":"R.","last_name":"Dupke"},{"first_name":"A.","last_name":"Ederoclite","full_name":"Ederoclite, A."},{"first_name":"C.","last_name":"Hernández-Monteagudo","full_name":"Hernández-Monteagudo, C."},{"full_name":"Marín-Franch, A.","first_name":"A.","last_name":"Marín-Franch"},{"full_name":"Mendes de Oliveira, C.","first_name":"C.","last_name":"Mendes de Oliveira"},{"first_name":"M.","last_name":"Moles","full_name":"Moles, M."},{"first_name":"L.","last_name":"Sodré","full_name":"Sodré, L."},{"first_name":"K.","last_name":"Taylor","full_name":"Taylor, K."},{"first_name":"J.","last_name":"Varela","full_name":"Varela, J."},{"full_name":"Vázquez Ramió, H.","first_name":"H.","last_name":"Vázquez Ramió"}],"has_accepted_license":"1","department":[{"_id":"JoMa"}],"intvolume":"       706","external_id":{"arxiv":["2512.08484"]},"article_number":"A261","ddc":["520"],"oa":1,"publisher":"EDP Sciences","doi":"10.1051/0004-6361/202557358","quality_controlled":"1","type":"journal_article","publication_status":"published","_id":"21380","file_date_updated":"2026-03-02T14:51:57Z","abstract":[{"lang":"eng","text":"Context. Extreme emission line galaxies (EELGs) are believed to significantly contribute to the star formation activity and mass assembly in galaxies. EELGs likely also play a leading role in the cosmic re-ionization as their interstellar medium may allow a significant fraction of their ionizing photons to escape (> 5%). Finding low-redshift analogues of these high-z galaxies is therefore essential to characterizing the physical conditions in the interstellar medium of these galaxies and understanding the processes that re-ionized the Universe.\r\n\r\nAims. We aimed to develop a robust and efficient method for the photometric identification of EELGs using the J-PAS survey. J-PAS will cover approximately 8500 deg2 of the sky with 54 narrow-band filters in the optical range plus i-SDSS, enabling detailed studies of the physical properties of these galaxies. In this work we focused on an initial subset of the survey: a 30 square degree area with complete observations in all bands.\r\n\r\nMethods. We combine equivalent width (EW) measurements from J-PAS narrow-band photometry with artificial intelligence techniques to identify galaxies with emission lines exceeding 300 Å. We validated our selection using spectroscopic data from DESI DR1 and characterized the selected sample through spectral energy distribution fitting with CIGALE.\r\n\r\nResults. We identify 917 EELGs up to z = 0.8 over 30 deg2, achieving a purity of 95% and a completeness of 96% for i-SDSS < 22.5 mag. Importantly, active galactic nucleus contamination was carefully considered and is estimated to be around 5%. Furthermore, a cross-match with DESI yielded 79 counterparts; their redshifts are in excellent agreement with our photometric estimates, thereby confirming the reliability of our redshift determination. In addition, the derived emission line fluxes are in good agreement with spectroscopic measurements. Moreover, the selected sample reveals strong correlations between the ionizing photon production efficiency (ξion) and EW(Hβ), which are consistent with previous observational studies at low and high redshifts and theoretical expectations. Finally, most of the sources surpass the ionizing efficiency threshold required for re-ionization, highlighting their relevance as local analogues of early-Universe galaxies."}],"citation":{"chicago":"Giménez-Alcázar, A., R. Amorín, J. M. Vílchez, A. Hernán-Caballero, M. González-Otero, A. Arroyo-Polonio, J. Iglesias-Páramo, et al. “J-PAS: First Identification, Physical Properties, and Ionization Efficiency of Extreme Emission Line Galaxies.” <i>Astronomy &#38; Astrophysics</i>. EDP Sciences, 2026. <a href=\"https://doi.org/10.1051/0004-6361/202557358\">https://doi.org/10.1051/0004-6361/202557358</a>.","apa":"Giménez-Alcázar, A., Amorín, R., Vílchez, J. M., Hernán-Caballero, A., González-Otero, M., Arroyo-Polonio, A., … Vázquez Ramió, H. (2026). J-PAS: First identification, physical properties, and ionization efficiency of extreme emission line galaxies. <i>Astronomy &#38; Astrophysics</i>. EDP Sciences. <a href=\"https://doi.org/10.1051/0004-6361/202557358\">https://doi.org/10.1051/0004-6361/202557358</a>","ista":"Giménez-Alcázar A, Amorín R, Vílchez JM, Hernán-Caballero A, González-Otero M, Arroyo-Polonio A, Iglesias-Páramo J, Lumbreras-Calle A, Fernández-Ontiveros JA, López-Sanjuan C, Bonatto L, González Delgado RM, Kehrig C, Torralba Torregrosa A, Rahna PT, Jiménez-Teja Y, Márquez I, Breda I, Álvarez-Candal A, Abramo R, Alcaniz J, Benitez N, Bonoli S, Carneiro S, Cenarro J, Cristóbal-Hornillos D, Dupke R, Ederoclite A, Hernández-Monteagudo C, Marín-Franch A, Mendes de Oliveira C, Moles M, Sodré L, Taylor K, Varela J, Vázquez Ramió H. 2026. J-PAS: First identification, physical properties, and ionization efficiency of extreme emission line galaxies. Astronomy &#38; Astrophysics. 706, A261.","short":"A. Giménez-Alcázar, R. Amorín, J.M. Vílchez, A. Hernán-Caballero, M. González-Otero, A. Arroyo-Polonio, J. Iglesias-Páramo, A. Lumbreras-Calle, J.A. Fernández-Ontiveros, C. López-Sanjuan, L. Bonatto, R.M. González Delgado, C. Kehrig, A. Torralba Torregrosa, P.T. Rahna, Y. Jiménez-Teja, I. Márquez, I. Breda, A. Álvarez-Candal, R. Abramo, J. Alcaniz, N. Benitez, S. Bonoli, S. Carneiro, J. Cenarro, D. Cristóbal-Hornillos, R. Dupke, A. Ederoclite, C. Hernández-Monteagudo, A. Marín-Franch, C. Mendes de Oliveira, M. Moles, L. Sodré, K. Taylor, J. Varela, H. Vázquez Ramió, Astronomy &#38; Astrophysics 706 (2026).","mla":"Giménez-Alcázar, A., et al. “J-PAS: First Identification, Physical Properties, and Ionization Efficiency of Extreme Emission Line Galaxies.” <i>Astronomy &#38; Astrophysics</i>, vol. 706, A261, EDP Sciences, 2026, doi:<a href=\"https://doi.org/10.1051/0004-6361/202557358\">10.1051/0004-6361/202557358</a>.","ama":"Giménez-Alcázar A, Amorín R, Vílchez JM, et al. J-PAS: First identification, physical properties, and ionization efficiency of extreme emission line galaxies. <i>Astronomy &#38; Astrophysics</i>. 2026;706. doi:<a href=\"https://doi.org/10.1051/0004-6361/202557358\">10.1051/0004-6361/202557358</a>","ieee":"A. Giménez-Alcázar <i>et al.</i>, “J-PAS: First identification, physical properties, and ionization efficiency of extreme emission line galaxies,” <i>Astronomy &#38; Astrophysics</i>, vol. 706. EDP Sciences, 2026."},"article_type":"original","article_processing_charge":"No","date_published":"2026-02-01T00:00:00Z"},{"publication_status":"published","type":"journal_article","publisher":"EDP Sciences","oa":1,"doi":"10.1051/0004-6361/202557537","quality_controlled":"1","citation":{"ieee":"A. Torralba Torregrosa <i>et al.</i>, “The warm outer layer of a little red dot as the source of [Fe ii] and collisional Balmer lines with scattering wings,” <i>Astronomy &#38; Astrophysics</i>, vol. 707. EDP Sciences, 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. <i>Astronomy &#38; Astrophysics</i>. 2026;707. doi:<a href=\"https://doi.org/10.1051/0004-6361/202557537\">10.1051/0004-6361/202557537</a>","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.” <i>Astronomy &#38; Astrophysics</i>, vol. 707, A75, EDP Sciences, 2026, doi:<a href=\"https://doi.org/10.1051/0004-6361/202557537\">10.1051/0004-6361/202557537</a>.","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 &#38; Astrophysics 707 (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 &#38; Astrophysics. 707, A75.","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.” <i>Astronomy &#38; Astrophysics</i>. EDP Sciences, 2026. <a href=\"https://doi.org/10.1051/0004-6361/202557537\">https://doi.org/10.1051/0004-6361/202557537</a>.","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. <i>Astronomy &#38; Astrophysics</i>. EDP Sciences. <a href=\"https://doi.org/10.1051/0004-6361/202557537\">https://doi.org/10.1051/0004-6361/202557537</a>"},"article_type":"original","date_published":"2026-03-01T00:00:00Z","article_processing_charge":"No","_id":"21451","abstract":[{"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.","lang":"eng"}],"file_date_updated":"2026-03-16T10:57:49Z","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","project":[{"grant_number":"101076224","_id":"bd9b2118-d553-11ed-ba76-db24564edfea","name":"Young galaxies as tracers and agents of cosmic reionization"}],"date_created":"2026-03-15T23:01:36Z","author":[{"full_name":"Torralba Torregrosa, Alberto","id":"018f0249-0e87-11f0-b167-cbce08fbd541","orcid":"0000-0001-5586-6950","first_name":"Alberto","last_name":"Torralba Torregrosa"},{"orcid":"0000-0003-2871-127X","last_name":"Matthee","first_name":"Jorryt J","full_name":"Matthee, Jorryt J","id":"7439a258-f3c0-11ec-9501-9df22fe06720"},{"first_name":"Gabriele","last_name":"Pezzulli","full_name":"Pezzulli, Gabriele"},{"first_name":"Rohan P.","last_name":"Naidu","full_name":"Naidu, Rohan P."},{"full_name":"Ishikawa, Yuzo","last_name":"Ishikawa","first_name":"Yuzo"},{"full_name":"Brammer, Gabriel B.","first_name":"Gabriel B.","last_name":"Brammer"},{"full_name":"Chang, Seok Jun","first_name":"Seok Jun","last_name":"Chang"},{"first_name":"John","last_name":"Chisholm","full_name":"Chisholm, John"},{"first_name":"Anna","last_name":"De Graaff","full_name":"De Graaff, Anna"},{"last_name":"D’Eugenio","first_name":"Francesco","full_name":"D’Eugenio, Francesco"},{"last_name":"Di Cesare","first_name":"Claudia","full_name":"Di Cesare, Claudia","id":"2d002343-372f-11ef-98ec-a164d20427cb"},{"full_name":"Eilers, Anna Christina","last_name":"Eilers","first_name":"Anna Christina"},{"first_name":"Jenny E.","last_name":"Greene","full_name":"Greene, Jenny E."},{"first_name":"Max","last_name":"Gronke","full_name":"Gronke, Max"},{"full_name":"Iani, Edoardo","id":"4053390a-6b68-11ef-9828-a3b8adef8d0a","orcid":"0000-0001-8386-3546","first_name":"Edoardo","last_name":"Iani"},{"full_name":"Kokorev, Vasily","last_name":"Kokorev","first_name":"Vasily"},{"id":"1438afc8-1ff6-11ee-9fa6-cd4a75d66875","full_name":"Kotiwale, Gauri","first_name":"Gauri","last_name":"Kotiwale"},{"first_name":"Ivan","last_name":"Kramarenko","orcid":"0000-0001-5346-6048","id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4","full_name":"Kramarenko, Ivan"},{"last_name":"Ma","first_name":"Yilun","full_name":"Ma, Yilun"},{"id":"edaf889c-c7cd-11ef-ab1b-bb28c431bd29","full_name":"Mascia, Sara","last_name":"Mascia","first_name":"Sara"},{"id":"aa14a535-50c9-11ef-b52e-e0c373d10148","full_name":"Navarrete, Benjamín","first_name":"Benjamín","last_name":"Navarrete"},{"last_name":"Nelson","first_name":"Erica","full_name":"Nelson, Erica"},{"full_name":"Oesch, Pascal","last_name":"Oesch","first_name":"Pascal"},{"full_name":"Simcoe, Robert A.","first_name":"Robert A.","last_name":"Simcoe"},{"full_name":"Wuyts, Stijn","first_name":"Stijn","last_name":"Wuyts"}],"OA_place":"publisher","title":"The warm outer layer of a little red dot as the source of [Fe ii] and collisional Balmer lines with scattering wings","OA_type":"diamond","file":[{"file_id":"21460","relation":"main_file","date_created":"2026-03-16T10:57:49Z","date_updated":"2026-03-16T10:57:49Z","access_level":"open_access","file_name":"2026_AstronomyAstrophysics_Torralba2.pdf","creator":"dernst","file_size":2510157,"content_type":"application/pdf","checksum":"fcab9cb3dcf1d68612e1fdc8191643c1","success":1}],"intvolume":"       707","external_id":{"arxiv":["2510.00103"]},"article_number":"A75","ddc":["520"],"has_accepted_license":"1","department":[{"_id":"JoMa"}],"scopus_import":"1","oa_version":"Published Version","publication":"Astronomy & Astrophysics","corr_author":"1","language":[{"iso":"eng"}],"day":"01","DOAJ_listed":"1","publication_identifier":{"eissn":["1432-0746"],"issn":["0004-6361"]},"year":"2026","tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"volume":707,"date_updated":"2026-03-16T10:59:16Z","arxiv":1,"month":"03","status":"public","PlanS_conform":"1","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."},{"type":"journal_article","publication_status":"published","doi":"10.3847/2041-8213/ae58a5","publisher":"IOP Publishing","oa":1,"quality_controlled":"1","article_type":"original","citation":{"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.” <i>The Astrophysical Journal Letters</i>, vol. 1002, no. 1, L4, IOP Publishing, 2026, doi:<a href=\"https://doi.org/10.3847/2041-8213/ae58a5\">10.3847/2041-8213/ae58a5</a>.","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. <i>The Astrophysical Journal Letters</i>. 2026;1002(1). doi:<a href=\"https://doi.org/10.3847/2041-8213/ae58a5\">10.3847/2041-8213/ae58a5</a>","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,” <i>The Astrophysical Journal Letters</i>, vol. 1002, no. 1. IOP Publishing, 2026.","apa":"Baggen, J. F. W., Scoggins, M. T., Van Dokkum, P., Haiman, Z., Torralba Torregrosa, A., &#38; Matthee, J. J. (2026). Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner sources enabling direct-collapse Black Hole formation. <i>The Astrophysical Journal Letters</i>. IOP Publishing. <a href=\"https://doi.org/10.3847/2041-8213/ae58a5\">https://doi.org/10.3847/2041-8213/ae58a5</a>","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.” <i>The Astrophysical Journal Letters</i>. IOP Publishing, 2026. <a href=\"https://doi.org/10.3847/2041-8213/ae58a5\">https://doi.org/10.3847/2041-8213/ae58a5</a>.","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.","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)."},"date_published":"2026-04-10T00:00:00Z","article_processing_charge":"Yes","_id":"21846","file_date_updated":"2026-05-11T06:44:37Z","abstract":[{"lang":"eng","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."}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","date_created":"2026-05-10T22:02:15Z","project":[{"name":"Young galaxies as tracers and agents of cosmic reionization","_id":"bd9b2118-d553-11ed-ba76-db24564edfea","grant_number":"101076224"}],"author":[{"full_name":"Baggen, Josephine F.W.","last_name":"Baggen","first_name":"Josephine F.W."},{"first_name":"Matthew T.","last_name":"Scoggins","full_name":"Scoggins, Matthew T."},{"last_name":"Van Dokkum","first_name":"Pieter","full_name":"Van Dokkum, Pieter"},{"last_name":"Haiman","first_name":"Zoltán","orcid":"0000-0003-3633-5403","id":"7c006e8c-cc0d-11ee-8322-cb904ef76f36","full_name":"Haiman, Zoltán"},{"id":"018f0249-0e87-11f0-b167-cbce08fbd541","full_name":"Torralba Torregrosa, Alberto","last_name":"Torralba Torregrosa","first_name":"Alberto","orcid":"0000-0001-5586-6950"},{"orcid":"0000-0003-2871-127X","last_name":"Matthee","first_name":"Jorryt J","full_name":"Matthee, Jorryt J","id":"7439a258-f3c0-11ec-9501-9df22fe06720"}],"issue":"1","title":"Connecting the dots: UV-bright companions of Little Red Dots as Lyman–Werner sources enabling direct-collapse Black Hole formation","OA_type":"gold","OA_place":"publisher","file":[{"date_updated":"2026-05-11T06:44:37Z","access_level":"open_access","relation":"main_file","date_created":"2026-05-11T06:44:37Z","file_id":"21851","content_type":"application/pdf","creator":"dernst","file_size":13359642,"success":1,"checksum":"8c31d8603cd6ad39c772a72d136dc3f8","file_name":"2026_AstrophysicalJourLetters_Baggen.pdf"}],"intvolume":"      1002","external_id":{"arxiv":["2602.02702"]},"article_number":"L4","ddc":["520"],"has_accepted_license":"1","department":[{"_id":"ZoHa"},{"_id":"JoMa"}],"scopus_import":"1","oa_version":"Published Version","publication":"The Astrophysical Journal Letters","language":[{"iso":"eng"}],"day":"10","DOAJ_listed":"1","publication_identifier":{"eissn":["2041-8213"],"issn":["2041-8205"]},"year":"2026","tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"volume":1002,"date_updated":"2026-05-11T06:48:33Z","arxiv":1,"month":"04","PlanS_conform":"1","status":"public","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)."},{"date_created":"2026-06-07T22:01:36Z","project":[{"name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224","_id":"bd9b2118-d553-11ed-ba76-db24564edfea"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","author":[{"last_name":"Sun","first_name":"Wendy Q.","full_name":"Sun, Wendy Q."},{"first_name":"Rohan P.","last_name":"Naidu","full_name":"Naidu, Rohan P."},{"first_name":"Jorryt J","last_name":"Matthee","orcid":"0000-0003-2871-127X","id":"7439a258-f3c0-11ec-9501-9df22fe06720","full_name":"Matthee, Jorryt J"},{"first_name":"Anna","last_name":"De Graaff","full_name":"De Graaff, Anna"},{"full_name":"Chisholm, John","last_name":"Chisholm","first_name":"John"},{"full_name":"Greene, Jenny E.","first_name":"Jenny E.","last_name":"Greene"},{"first_name":"Pascal A.","last_name":"Oesch","full_name":"Oesch, Pascal A."},{"id":"018f0249-0e87-11f0-b167-cbce08fbd541","full_name":"Torralba Torregrosa, Alberto","first_name":"Alberto","last_name":"Torralba Torregrosa","orcid":"0000-0001-5586-6950"},{"full_name":"Hviding, Raphael E.","first_name":"Raphael E.","last_name":"Hviding"},{"full_name":"Brammer, Gabriel","first_name":"Gabriel","last_name":"Brammer"},{"first_name":"Robert A.","last_name":"Simcoe","full_name":"Simcoe, Robert A."},{"first_name":"Sownak","last_name":"Bose","full_name":"Bose, Sownak"},{"full_name":"Bouwens, Rychard","last_name":"Bouwens","first_name":"Rychard"},{"full_name":"Dayal, Pratika","first_name":"Pratika","last_name":"Dayal"},{"full_name":"Eilers, Anna Christina","last_name":"Eilers","first_name":"Anna Christina"},{"full_name":"Fei, Qinyue","last_name":"Fei","first_name":"Qinyue"},{"full_name":"Furtak, Lukas J.","first_name":"Lukas J.","last_name":"Furtak"},{"full_name":"Gottumukkala, Rashmi","last_name":"Gottumukkala","first_name":"Rashmi"},{"full_name":"Goulding, Andy","first_name":"Andy","last_name":"Goulding"},{"full_name":"Heintz, Kasper E.","first_name":"Kasper E.","last_name":"Heintz"},{"last_name":"Hirschmann","first_name":"Michaela","full_name":"Hirschmann, Michaela"},{"first_name":"Vasily","last_name":"Kokorev","full_name":"Kokorev, Vasily"},{"first_name":"Joel","last_name":"Leja","full_name":"Leja, Joel"},{"full_name":"Liu, Zhaoran","first_name":"Zhaoran","last_name":"Liu"},{"full_name":"Natarajan, Priyamvada","first_name":"Priyamvada","last_name":"Natarajan"},{"last_name":"Santarelli","first_name":"Andrew D.","full_name":"Santarelli, Andrew D."},{"last_name":"Setton","first_name":"David J.","full_name":"Setton, David J."},{"full_name":"Smith, Aaron","last_name":"Smith","first_name":"Aaron"},{"full_name":"Tacchella, Sandro","first_name":"Sandro","last_name":"Tacchella"},{"full_name":"Volonteri, Marta","first_name":"Marta","last_name":"Volonteri"},{"last_name":"Walter","first_name":"Fabian","full_name":"Walter, Fabian"},{"first_name":"Andrea","last_name":"Weibel","full_name":"Weibel, Andrea"},{"last_name":"Williams","first_name":"Christina C.","full_name":"Williams, Christina C."}],"OA_place":"publisher","title":"Little Red Dot - Host Galaxy = Black Hole Star: A gas-enshrouded heart at the center of every Little Red Dot","OA_type":"diamond","file":[{"file_size":7591188,"creator":"dernst","content_type":"application/pdf","checksum":"33c4a444f7c37b3f47ecbd53eb187c1b","success":1,"file_name":"2026_OpenJourAstrophysics_Sun.pdf","date_updated":"2026-06-08T08:23:37Z","access_level":"open_access","date_created":"2026-06-08T08:23:37Z","file_id":"21952","relation":"main_file"}],"external_id":{"arxiv":["2601.20929"]},"intvolume":"         9","ddc":["520"],"has_accepted_license":"1","department":[{"_id":"JoMa"}],"publication_status":"published","type":"journal_article","doi":"10.33232/001c.162505","publisher":"Maynooth Academic Publishing","oa":1,"quality_controlled":"1","article_processing_charge":"No","date_published":"2026-05-25T00:00:00Z","article_type":"original","citation":{"ieee":"W. Q. Sun <i>et al.</i>, “Little Red Dot - Host Galaxy = Black Hole Star: A gas-enshrouded heart at the center of every Little Red Dot,” <i>The Open Journal of Astrophysics</i>, 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. <i>The Open Journal of Astrophysics</i>. 2026;9. doi:<a href=\"https://doi.org/10.33232/001c.162505\">10.33232/001c.162505</a>","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.” <i>The Open Journal of Astrophysics</i>, vol. 9, Maynooth Academic Publishing, 2026, doi:<a href=\"https://doi.org/10.33232/001c.162505\">10.33232/001c.162505</a>.","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).","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.","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.” <i>The Open Journal of Astrophysics</i>. Maynooth Academic Publishing, 2026. <a href=\"https://doi.org/10.33232/001c.162505\">https://doi.org/10.33232/001c.162505</a>.","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. <i>The Open Journal of Astrophysics</i>. Maynooth Academic Publishing. <a href=\"https://doi.org/10.33232/001c.162505\">https://doi.org/10.33232/001c.162505</a>"},"abstract":[{"lang":"eng","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"}],"file_date_updated":"2026-06-08T08:23:37Z","_id":"21951","tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"date_updated":"2026-06-08T08:25:40Z","volume":9,"arxiv":1,"month":"05","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).","PlanS_conform":"1","status":"public","scopus_import":"1","publication":"The Open Journal of Astrophysics","oa_version":"Published Version","language":[{"iso":"eng"}],"publication_identifier":{"eissn":["2565-6120"]},"DOAJ_listed":"1","day":"25","year":"2026"},{"tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"date_updated":"2026-07-08T06:38:23Z","volume":705,"das_tickbox":"1","month":"01","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.","status":"public","PlanS_conform":"1","arxiv":1,"corr_author":"1","language":[{"iso":"eng"}],"scopus_import":"1","oa_version":"Published Version","publication":"Astronomy & Astrophysics","year":"2026","publication_identifier":{"issn":["0004-6361"],"eissn":["1432-0746"]},"day":"14","OA_type":"diamond","title":"A weak Ly α halo for an extremely bright little red dot. Indications of enshrouded supermassive black hole growth","OA_place":"publisher","file":[{"file_name":"2026_AstronomyAstrophysics_Torralba.pdf","file_size":2259914,"content_type":"application/pdf","creator":"dernst","success":1,"checksum":"3782e03bc0843438aae8487f6af779c5","date_created":"2026-02-16T07:35:03Z","relation":"main_file","file_id":"21224","date_updated":"2026-02-16T07:35:03Z","access_level":"open_access"}],"project":[{"_id":"bd9b2118-d553-11ed-ba76-db24564edfea","grant_number":"101076224","name":"Young galaxies as tracers and agents of cosmic reionization"}],"date_created":"2026-01-25T23:01:41Z","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","author":[{"id":"018f0249-0e87-11f0-b167-cbce08fbd541","full_name":"Torralba Torregrosa, Alberto","last_name":"Torralba Torregrosa","first_name":"Alberto","orcid":"0000-0001-5586-6950"},{"full_name":"Matthee, Jorryt J","id":"7439a258-f3c0-11ec-9501-9df22fe06720","orcid":"0000-0003-2871-127X","last_name":"Matthee","first_name":"Jorryt J"},{"full_name":"Pezzulli, Gabriele","last_name":"Pezzulli","first_name":"Gabriele"},{"full_name":"Urrutia, Tanya","first_name":"Tanya","last_name":"Urrutia"},{"last_name":"Gronke","first_name":"Max","full_name":"Gronke, Max"},{"id":"edaf889c-c7cd-11ef-ab1b-bb28c431bd29","full_name":"Mascia, Sara","first_name":"Sara","last_name":"Mascia"},{"first_name":"Francesco","last_name":"D’Eugenio","full_name":"D’Eugenio, Francesco"},{"first_name":"Claudia","last_name":"Di Cesare","id":"2d002343-372f-11ef-98ec-a164d20427cb","full_name":"Di Cesare, Claudia"},{"last_name":"Eilers","first_name":"Anna Christina","full_name":"Eilers, Anna Christina"},{"full_name":"Greene, Jenny E.","first_name":"Jenny E.","last_name":"Greene"},{"orcid":"0000-0001-8386-3546","first_name":"Edoardo","last_name":"Iani","full_name":"Iani, Edoardo","id":"4053390a-6b68-11ef-9828-a3b8adef8d0a"},{"full_name":"Ishikawa, Yuzo","first_name":"Yuzo","last_name":"Ishikawa"},{"full_name":"Mackenzie, Ruari","first_name":"Ruari","last_name":"Mackenzie"},{"first_name":"Rohan P.","last_name":"Naidu","full_name":"Naidu, Rohan P."},{"first_name":"Benjamín","last_name":"Navarrete","full_name":"Navarrete, Benjamín","id":"aa14a535-50c9-11ef-b52e-e0c373d10148"},{"last_name":"Kotiwale","first_name":"Gauri","full_name":"Kotiwale, Gauri","id":"1438afc8-1ff6-11ee-9fa6-cd4a75d66875"}],"has_accepted_license":"1","department":[{"_id":"JoMa"},{"_id":"GradSch"}],"external_id":{"arxiv":["2505.09542"]},"intvolume":"       705","ddc":["520"],"article_number":"A147","publisher":"EDP Sciences","doi":"10.1051/0004-6361/202555596","oa":1,"quality_controlled":"1","type":"journal_article","publication_status":"published","file_date_updated":"2026-02-16T07:35:03Z","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."}],"_id":"21045","date_published":"2026-01-14T00:00:00Z","article_processing_charge":"No","citation":{"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.” <i>Astronomy &#38; Astrophysics</i>. EDP Sciences, 2026. <a href=\"https://doi.org/10.1051/0004-6361/202555596\">https://doi.org/10.1051/0004-6361/202555596</a>.","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. <i>Astronomy &#38; Astrophysics</i>. EDP Sciences. <a href=\"https://doi.org/10.1051/0004-6361/202555596\">https://doi.org/10.1051/0004-6361/202555596</a>","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 &#38; Astrophysics 705 (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 &#38; Astrophysics. 705, A147.","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. <i>Astronomy &#38; Astrophysics</i>. 2026;705. doi:<a href=\"https://doi.org/10.1051/0004-6361/202555596\">10.1051/0004-6361/202555596</a>","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.” <i>Astronomy &#38; Astrophysics</i>, vol. 705, A147, EDP Sciences, 2026, doi:<a href=\"https://doi.org/10.1051/0004-6361/202555596\">10.1051/0004-6361/202555596</a>.","ieee":"A. Torralba Torregrosa <i>et al.</i>, “A weak Ly α halo for an extremely bright little red dot. Indications of enshrouded supermassive black hole growth,” <i>Astronomy &#38; Astrophysics</i>, vol. 705. EDP Sciences, 2026."},"article_type":"original"},{"month":"07","status":"public","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).","arxiv":1,"tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"supplementarymaterial":"yes","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).","date_updated":"2026-07-13T08:08:41Z","volume":1005,"das_tickbox":"1","year":"2026","researchdata_availability":"yes","DOAJ_listed":"1","day":"10","publication_identifier":{"eissn":["2041-8213"],"issn":["2041-8205"]},"corr_author":"1","language":[{"iso":"eng"}],"scopus_import":"1","oa_version":"Published Version","publication":"The Astrophysical Journal Letters","has_accepted_license":"1","department":[{"_id":"JoMa"},{"_id":"IlCa"},{"_id":"GradSch"}],"intvolume":"      1005","external_id":{"arxiv":["2603.28335"]},"article_number":"L37","ddc":["520"],"OA_place":"publisher","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","OA_type":"gold","file":[{"date_created":"2026-07-13T07:46:22Z","file_id":"22274","relation":"main_file","date_updated":"2026-07-13T07:46:22Z","access_level":"open_access","file_name":"2026_AstrophysicalJourLetters_Torralba.pdf","content_type":"application/pdf","creator":"dernst","file_size":5419071,"success":1,"checksum":"7600db260d799ddea45cf3bd01effe41"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","project":[{"name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224","_id":"bd9b2118-d553-11ed-ba76-db24564edfea"}],"date_created":"2026-07-12T22:02:17Z","author":[{"id":"018f0249-0e87-11f0-b167-cbce08fbd541","full_name":"Torralba Torregrosa, Alberto","last_name":"Torralba Torregrosa","first_name":"Alberto","orcid":"0000-0001-5586-6950"},{"orcid":"0000-0003-2871-127X","last_name":"Matthee","first_name":"Jorryt J","full_name":"Matthee, Jorryt J","id":"7439a258-f3c0-11ec-9501-9df22fe06720"},{"full_name":"Weibel, Andrea","last_name":"Weibel","first_name":"Andrea"},{"last_name":"Naidu","first_name":"Rohan P.","full_name":"Naidu, Rohan P."},{"last_name":"Ma","first_name":"Yilun","full_name":"Ma, Yilun"},{"last_name":"Cloonan","first_name":"Aidan P.","full_name":"Cloonan, Aidan P."},{"full_name":"Desai, Aayush A","id":"502cfd30-32c1-11ee-a9a4-d8dad5c6739e","last_name":"Desai","first_name":"Aayush A"},{"first_name":"Anna","last_name":"De Graaff","full_name":"De Graaff, Anna"},{"full_name":"Greene, Jenny E.","first_name":"Jenny E.","last_name":"Greene"},{"full_name":"Jespersen, Christian Kragh","last_name":"Jespersen","first_name":"Christian Kragh"},{"full_name":"Kramarenko, Ivan","id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4","orcid":"0000-0001-5346-6048","first_name":"Ivan","last_name":"Kramarenko"},{"last_name":"Mascia","first_name":"Sara","id":"edaf889c-c7cd-11ef-ab1b-bb28c431bd29","full_name":"Mascia, Sara"},{"last_name":"Oesch","first_name":"Pascal A.","full_name":"Oesch, Pascal A."},{"full_name":"Sun, Wendy Q.","last_name":"Sun","first_name":"Wendy Q."},{"full_name":"Williams, Christina C.","last_name":"Williams","first_name":"Christina C."}],"issue":"2","_id":"22263","abstract":[{"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.","lang":"eng"}],"file_date_updated":"2026-07-13T07:46:22Z","citation":{"ieee":"A. Torralba Torregrosa <i>et al.</i>, “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,” <i>The Astrophysical Journal Letters</i>, vol. 1005, no. 2. IOP Publishing, 2026.","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.” <i>The Astrophysical Journal Letters</i>, vol. 1005, no. 2, L37, IOP Publishing, 2026, doi:<a href=\"https://doi.org/10.3847/2041-8213/ae7bfd\">10.3847/2041-8213/ae7bfd</a>.","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. <i>The Astrophysical Journal Letters</i>. 2026;1005(2). doi:<a href=\"https://doi.org/10.3847/2041-8213/ae7bfd\">10.3847/2041-8213/ae7bfd</a>","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.","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).","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. <i>The Astrophysical Journal Letters</i>. IOP Publishing. <a href=\"https://doi.org/10.3847/2041-8213/ae7bfd\">https://doi.org/10.3847/2041-8213/ae7bfd</a>","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.” <i>The Astrophysical Journal Letters</i>. IOP Publishing, 2026. <a href=\"https://doi.org/10.3847/2041-8213/ae7bfd\">https://doi.org/10.3847/2041-8213/ae7bfd</a>."},"article_type":"original","article_processing_charge":"Yes","date_published":"2026-07-10T00:00:00Z","publisher":"IOP Publishing","oa":1,"doi":"10.3847/2041-8213/ae7bfd","quality_controlled":"1","publication_status":"published","type":"journal_article"},{"publication_identifier":{"eissn":["1538-4357"],"issn":["0004-637X"]},"day":"29","DOAJ_listed":"1","year":"2025","scopus_import":"1","publication":"The Astrophysical Journal","oa_version":"Published Version","corr_author":"1","language":[{"iso":"eng"}],"arxiv":1,"month":"07","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).","PlanS_conform":"1","status":"public","tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"volume":988,"date_updated":"2026-02-09T08:22:01Z","article_processing_charge":"Yes","date_published":"2025-07-29T00:00:00Z","citation":{"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).","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.","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. <i>The Astrophysical Journal</i>. IOP Publishing. <a href=\"https://doi.org/10.3847/1538-4357/ade886\">https://doi.org/10.3847/1538-4357/ade886</a>","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.” <i>The Astrophysical Journal</i>. IOP Publishing, 2025. <a href=\"https://doi.org/10.3847/1538-4357/ade886\">https://doi.org/10.3847/1538-4357/ade886</a>.","ieee":"J. J. Matthee <i>et al.</i>, “Environmental evidence for overly massive Black Holes in low-mass galaxies and a Black Hole–Halo mass relation at z ∼ 5,” <i>The Astrophysical Journal</i>, vol. 988, no. 2. IOP Publishing, 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. <i>The Astrophysical Journal</i>. 2025;988(2). doi:<a href=\"https://doi.org/10.3847/1538-4357/ade886\">10.3847/1538-4357/ade886</a>","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.” <i>The Astrophysical Journal</i>, vol. 988, no. 2, 246, IOP Publishing, 2025, doi:<a href=\"https://doi.org/10.3847/1538-4357/ade886\">10.3847/1538-4357/ade886</a>."},"article_type":"original","file_date_updated":"2026-02-09T08:20:14Z","abstract":[{"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.","lang":"eng"}],"_id":"21062","publication_status":"published","type":"journal_article","publisher":"IOP Publishing","doi":"10.3847/1538-4357/ade886","oa":1,"quality_controlled":"1","intvolume":"       988","external_id":{"arxiv":["2412.02846"]},"ddc":["520"],"article_number":"246","has_accepted_license":"1","department":[{"_id":"JoMa"}],"project":[{"name":"Young galaxies as tracers and agents of cosmic reionization","grant_number":"101076224","_id":"bd9b2118-d553-11ed-ba76-db24564edfea"}],"date_created":"2026-01-28T15:25:42Z","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","issue":"2","author":[{"last_name":"Matthee","first_name":"Jorryt J","orcid":"0000-0003-2871-127X","id":"7439a258-f3c0-11ec-9501-9df22fe06720","full_name":"Matthee, Jorryt J"},{"full_name":"Naidu, Rohan P.","first_name":"Rohan P.","last_name":"Naidu"},{"id":"1438afc8-1ff6-11ee-9fa6-cd4a75d66875","full_name":"Kotiwale, Gauri","last_name":"Kotiwale","first_name":"Gauri"},{"last_name":"Furtak","first_name":"Lukas J.","full_name":"Furtak, Lukas J."},{"id":"9a9394cb-3200-11ee-973b-f5ba2a8b16e4","full_name":"Kramarenko, Ivan","last_name":"Kramarenko","first_name":"Ivan","orcid":"0000-0001-5346-6048"},{"full_name":"Mackenzie, Ruari","first_name":"Ruari","last_name":"Mackenzie"},{"full_name":"Greene, Jenny","last_name":"Greene","first_name":"Jenny"},{"full_name":"Adamo, Angela","last_name":"Adamo","first_name":"Angela"},{"last_name":"Bouwens","first_name":"Rychard J.","full_name":"Bouwens, Rychard J."},{"first_name":"Claudia","last_name":"Di Cesare","id":"2d002343-372f-11ef-98ec-a164d20427cb","full_name":"Di Cesare, Claudia"},{"first_name":"Anna-Christina","last_name":"Eilers","full_name":"Eilers, Anna-Christina"},{"last_name":"de Graaff","first_name":"Anna","full_name":"de Graaff, Anna"},{"last_name":"Heintz","first_name":"Kasper E.","full_name":"Heintz, Kasper E."},{"full_name":"Kashino, Daichi","last_name":"Kashino","first_name":"Daichi"},{"full_name":"Maseda, Michael V.","last_name":"Maseda","first_name":"Michael V."},{"full_name":"Tacchella, Sandro","first_name":"Sandro","last_name":"Tacchella"},{"orcid":"0000-0001-5586-6950","last_name":"Torralba Torregrosa","first_name":"Alberto","full_name":"Torralba Torregrosa, Alberto","id":"018f0249-0e87-11f0-b167-cbce08fbd541"}],"OA_place":"publisher","title":"Environmental evidence for overly massive Black Holes in low-mass galaxies and a Black Hole–Halo mass relation at z ∼ 5","OA_type":"gold","file":[{"creator":"dernst","file_size":6237415,"content_type":"application/pdf","success":1,"checksum":"a49fbed72f2ff9c0b13129acb6f44f9d","file_name":"2025_AstrophysicalJournal_Matthee.pdf","date_updated":"2026-02-09T08:20:14Z","access_level":"open_access","date_created":"2026-02-09T08:20:14Z","file_id":"21168","relation":"main_file"}]},{"oa":1,"doi":"10.1051/0004-6361/202453547","publisher":"EDP Sciences","quality_controlled":"1","type":"journal_article","publication_status":"published","_id":"19929","file_date_updated":"2025-06-30T08:28:40Z","abstract":[{"text":"Context. The observed Lyman-alpha (Lyα) line profile is a convolution of the complex Lyα radiative transfer taking place in the interstellar, circumgalactic, and intergalactic media (ISM, CGM, and IGM, respectively). Discerning the different components of the Lyα line is crucial in order to use it as a probe of galaxy formation or the evolution of the IGM.\r\n\r\nAims. We aim to present the second version of zELDA (redshift Estimator for Line profiles of Distant Lyman-Alpha emitters), an open-source Python module focused on modelling and fitting observed Lyα line profiles. This new version of zELDA focuses on disentangling the galactic from the IGM effects.\r\n\r\nMethods. We built realistic Lyα line profiles that include the ISM and IGM contributions by combining the Monte Carlo radiative-transfer simulations for the so-called shell model (ISM) and IGM transmission curves generated from TNG100. We used these mock line profiles to train different artificial neural networks. These use the observed spectrum as input and the outflow parameters of the best fitting ‘shell model’ as output along with the redshift and Lyα emission IGM escape fraction of the source.\r\n\r\nResults. We measured the accuracy of zELDA on mock Lyα line profiles. We find that zELDA is capable of reconstructing the ISM emerging Lyα line profile with high levels of accuracy (Kolmogórov-Smirnov<0.1) for 95% of the cases for HST/COS-like observations and 80% for MUSE-WIDE-like observations. zELDA is able to measure the IGM transmission with typical uncertainties below 10% for HST/COS and MUSE-WIDE data.\r\n\r\nConclusions. This work represents a step forward in the high-precision reconstruction of IGM-attenuated Lyα line profiles. zELDA allows the disentanglement of the galactic and IGM contribution shaping the Lyα line shape and thus allows us to use Lyα as a tool to study galaxy and ISM evolution.","lang":"eng"}],"citation":{"chicago":"Gurung-López, Siddhartha, Chris Byrohl, Max Gronke, Daniele Spinoso, Alberto Torralba Torregrosa, Alberto Fernández-Soto, Pablo Arnalte-Mur, and Vicent J. Martínez. “ZELDA II: Reconstruction of Galactic Lyman-Alpha Spectra Attenuated by the Intergalactic Medium Using Neural Networks.” <i>Astronomy &#38; Astrophysics</i>. EDP Sciences, 2025. <a href=\"https://doi.org/10.1051/0004-6361/202453547\">https://doi.org/10.1051/0004-6361/202453547</a>.","apa":"Gurung-López, S., Byrohl, C., Gronke, M., Spinoso, D., Torralba Torregrosa, A., Fernández-Soto, A., … Martínez, V. J. (2025). zELDA II: Reconstruction of galactic Lyman-alpha spectra attenuated by the intergalactic medium using neural networks. <i>Astronomy &#38; Astrophysics</i>. EDP Sciences. <a href=\"https://doi.org/10.1051/0004-6361/202453547\">https://doi.org/10.1051/0004-6361/202453547</a>","short":"S. Gurung-López, C. Byrohl, M. Gronke, D. Spinoso, A. Torralba Torregrosa, A. Fernández-Soto, P. Arnalte-Mur, V.J. Martínez, Astronomy &#38; Astrophysics 698 (2025).","ista":"Gurung-López S, Byrohl C, Gronke M, Spinoso D, Torralba Torregrosa A, Fernández-Soto A, Arnalte-Mur P, Martínez VJ. 2025. zELDA II: Reconstruction of galactic Lyman-alpha spectra attenuated by the intergalactic medium using neural networks. Astronomy &#38; Astrophysics. 698, A139.","ama":"Gurung-López S, Byrohl C, Gronke M, et al. zELDA II: Reconstruction of galactic Lyman-alpha spectra attenuated by the intergalactic medium using neural networks. <i>Astronomy &#38; Astrophysics</i>. 2025;698. doi:<a href=\"https://doi.org/10.1051/0004-6361/202453547\">10.1051/0004-6361/202453547</a>","mla":"Gurung-López, Siddhartha, et al. “ZELDA II: Reconstruction of Galactic Lyman-Alpha Spectra Attenuated by the Intergalactic Medium Using Neural Networks.” <i>Astronomy &#38; Astrophysics</i>, vol. 698, A139, EDP Sciences, 2025, doi:<a href=\"https://doi.org/10.1051/0004-6361/202453547\">10.1051/0004-6361/202453547</a>.","ieee":"S. Gurung-López <i>et al.</i>, “zELDA II: Reconstruction of galactic Lyman-alpha spectra attenuated by the intergalactic medium using neural networks,” <i>Astronomy &#38; Astrophysics</i>, vol. 698. EDP Sciences, 2025."},"article_type":"original","date_published":"2025-06-01T00:00:00Z","article_processing_charge":"No","title":"zELDA II: Reconstruction of galactic Lyman-alpha spectra attenuated by the intergalactic medium using neural networks","OA_place":"publisher","OA_type":"diamond","file":[{"file_name":"2025_AstronomyAstrophysics_GurungLopez.pdf","file_size":5758102,"content_type":"application/pdf","creator":"dernst","success":1,"checksum":"a50a817b72f03534c6a867035b51e433","date_created":"2025-06-30T08:28:40Z","file_id":"19933","relation":"main_file","date_updated":"2025-06-30T08:28:40Z","access_level":"open_access"}],"isi":1,"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","date_created":"2025-06-29T22:01:15Z","author":[{"full_name":"Gurung-López, Siddhartha","last_name":"Gurung-López","first_name":"Siddhartha"},{"full_name":"Byrohl, Chris","last_name":"Byrohl","first_name":"Chris"},{"last_name":"Gronke","first_name":"Max","full_name":"Gronke, Max"},{"full_name":"Spinoso, Daniele","first_name":"Daniele","last_name":"Spinoso"},{"orcid":"0000-0001-5586-6950","first_name":"Alberto","last_name":"Torralba Torregrosa","full_name":"Torralba Torregrosa, Alberto","id":"018f0249-0e87-11f0-b167-cbce08fbd541"},{"last_name":"Fernández-Soto","first_name":"Alberto","full_name":"Fernández-Soto, Alberto"},{"last_name":"Arnalte-Mur","first_name":"Pablo","full_name":"Arnalte-Mur, Pablo"},{"full_name":"Martínez, Vicent J.","last_name":"Martínez","first_name":"Vicent J."}],"has_accepted_license":"1","department":[{"_id":"JoMa"}],"intvolume":"       698","external_id":{"arxiv":["2501.04077"],"isi":["001507317300003"]},"article_number":"A139","ddc":["520"],"language":[{"iso":"eng"}],"scopus_import":"1","publication":"Astronomy & Astrophysics","oa_version":"Published Version","year":"2025","day":"01","publication_identifier":{"eissn":["1432-0746"],"issn":["0004-6361"]},"tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"date_updated":"2026-02-16T12:11:56Z","volume":698,"month":"06","status":"public","acknowledgement":"The authors acknowledge the financial support from the MICIU with funding from the European Union NextGenerationEU and Generalitat Valenciana in the call Programa de Planes Complementarios de I+D+i (PRTR 2022) Project (VAL-JPAS), reference ASFAE/2022/025. This work is part of the research Project PID2023-149420NB-I00 funded by MICIU/AEI/10.13039/501100011033 and by ERDF/EU. This work is also supported by the project of excellence PROMETEO CIPROM/2023/21 of the Conselleria de Educación, Universidades y Empleo (Generalitat Valenciana). MG thanks the Max Planck Society for support through the Max Planck Research Group. DS acknowledges the support by the Tsinghua Shui Mu Scholarship, funding of the National Key R&D Program of China (grant no. 2023YFA1605600), the science research grants from the China Manned Space Project with no. CMS-CSST2021-A05, and the Tsinghua University Initiative Scientific Research Program (no. 20223080023). This research made use of matplotlib, a Python library for publication quality graphics (Hunter 2007), NumPy (Harris et al. 2020) and SciPy (Virtanen et al. 2020).","arxiv":1}]