@article{21341,
  abstract     = {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.},
  author       = {Kotiwale, Gauri and Matthee, Jorryt J and Kashino, Daichi and Vijayan, Aswin P. and Torralba Torregrosa, Alberto and Di Cesare, Claudia and Iani, Edoardo and Bordoloi, Rongmon and Leja, Joel and Maseda, Michael V. and Tacchella, Sandro and Shivaei, Irene and Heintz, Kasper E. and Danhaive, A. Lola and Mascia, Sara and Kramarenko, Ivan and Navarrete, Benjamín and Mackenzie, Ruari and Naidu, Rohan P. and Sobral, David},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  publisher    = {EDP Sciences},
  title        = {{Rapid, out-of-equilibrium metal enrichment indicated by a flat mass-metallicity relation at z ∼ 6 from NIRCam grism spectroscopy}},
  doi          = {10.1051/0004-6361/202556597},
  volume       = {706},
  year         = {2026},
}

@article{21451,
  abstract     = {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.},
  author       = {Torralba Torregrosa, Alberto and Matthee, Jorryt J and Pezzulli, Gabriele and Naidu, Rohan P. and Ishikawa, Yuzo and Brammer, Gabriel B. and Chang, Seok Jun and Chisholm, John and De Graaff, Anna and D’Eugenio, Francesco and Di Cesare, Claudia and Eilers, Anna Christina and Greene, Jenny E. and Gronke, Max and Iani, Edoardo and Kokorev, Vasily and Kotiwale, Gauri and Kramarenko, Ivan and Ma, Yilun and Mascia, Sara and Navarrete, Benjamín and Nelson, Erica and Oesch, Pascal and Simcoe, Robert A. and Wuyts, Stijn},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  publisher    = {EDP Sciences},
  title        = {{The warm outer layer of a little red dot as the source of [Fe ii] and collisional Balmer lines with scattering wings}},
  doi          = {10.1051/0004-6361/202557537},
  volume       = {707},
  year         = {2026},
}

@article{21452,
  abstract     = {Galaxies exhibit a tight correlation between their star formation rate (SFR) and stellar mass over a wide redshift range known as the star-forming main sequence (SFMS). With JWST, the SFMS can now be investigated at high redshifts down to masses of ∼106 M⊙, using sensitive star formation rate tracers such as the Hα emission, which allow us to probe the variability in the star formation histories. We present inferences of the SFMS based on 316 Hα-selected galaxies at z ∼ 4 − 5 with log(M★/M⊙) = 6.4 − 10.6. These galaxies were identified behind the Abell 2744 lensing cluster with NIRCam grism spectroscopy from the survey All the Little Things (ALT). At face value, our data suggest a shallow slope in the SFMS (SFR ∝ M★α, with α = 0.45). After we corrected this for the Hα-flux limited nature of our survey using a Bayesian framework, the slope steepened to α = 0.59+0.10−0.09, whereas current data on their own are inconclusive on the mass dependence of the scatter. These slopes differ significantly from the slope of ∼1 that is expected from the observed evolution of the galaxy stellar mass function and from simulations. When we fixed the slope to α = 1, we found evidence for a decreasing intrinsic scatter with stellar mass (from ∼0.5 dex at M★ = 108 M⊙ to 0.4 dex at M★ = 1010 M⊙). This difference might be explained by a (combination of) luminosity-dependent SFR(Hα) calibration, a population of (mini)-quenched low-mass galaxies, or underestimated dust attenuation in high-mass galaxies. Future deep observations with different facilities can quantify these processes, which will enable us to achieve better insights into the variability of the star formation histories.},
  author       = {Di Cesare, Claudia and Matthee, Jorryt J and Naidu, Rohan P. and Torralba, Alberto and Kotiwale, Gauri and Kramarenko, Ivan and Blaizot, Jeremy and Rosdahl, Joakim and Leja, Joel and Iani, Edoardo and Adamo, Angela and Covelo-Paz, Alba and Furtak, Lukas J. and Heintz, Kasper E. and Mascia, Sara and Navarrete, Benjamín and Oesch, Pascal A. and Romano, Michael and Shivaei, Irene and Tacchella, Sandro},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  publisher    = {EDP Sciences},
  title        = {{The slope and scatter of the star-forming main sequence at z ∼ 5: Reconciling observations with simulations}},
  doi          = {10.1051/0004-6361/202557790},
  volume       = {707},
  year         = {2026},
}

@article{21045,
  abstract     = {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.},
  author       = {Torralba Torregrosa, Alberto and Matthee, Jorryt J and Pezzulli, Gabriele and Urrutia, Tanya and Gronke, Max and Mascia, Sara and D’Eugenio, Francesco and Di Cesare, Claudia and Eilers, Anna Christina and Greene, Jenny E. and Iani, Edoardo and Ishikawa, Yuzo and Mackenzie, Ruari and Naidu, Rohan P. and Navarrete, Benjamín and Kotiwale, Gauri},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  publisher    = {EDP Sciences},
  title        = {{A weak Ly α halo for an extremely bright little red dot. Indications of enshrouded supermassive black hole growth}},
  doi          = {10.1051/0004-6361/202555596},
  volume       = {705},
  year         = {2026},
}

@article{21727,
  abstract     = {We present a comprehensive analysis of the MIRI Extremely Red Object Virgil, a Lyα emitter at zspec = 6.6379 ± 0.0035 with the photometric properties of a Little Red Dot. Leveraging new JWST/MIRI imaging from the MIDIS and PAHSPECS programs, we confirm Virgil’s extraordinary nature among galaxies in JADES/GOODS-South, exhibiting a strikingly red NIRCam-to-MIRI color (F444W–F1500W = 2.84 ± 0.04 mag). Deep NIRSpec/PRISM spectroscopy from the OASIS program offers key insights into the host galaxy, revealing properties of an average star-forming galaxy during Cosmic Reionization, such as a subsolar metallicity, low-to-moderate dust content, and a relatively high ionization parameter and electron temperature. By estimating the star formation rate of Virgil from UV and Hα, we find evidence that the galaxy is either entering or fading out of a bursty episode. Although line-ratio diagnostics employed at high z would classify Virgil as an active galactic nucleus (AGN), this classification becomes ambiguous once redshift evolution is considered. Nonetheless, Virgil occupies the same parameter space as recently confirmed AGNs at similar redshifts. The new deep MIRI data at 15 μm reinforce the AGN nature of Virgil, as inferred from multiple spectral energy distribution (SED) fitting codes. Virgil’s rising infrared SED and UV excess resemble those of Dust-Obscured Galaxies (DOGs) studied with Spitzer at Cosmic Noon, particularly blue-excess HotDOGs. Our results highlight the need for a multiwavelength approach incorporating MIRI to uncover such extreme sources at z ≳ 6 and to shed light on the interplay between galaxy evolution and early black hole growth during Cosmic Reionization.},
  author       = {Rinaldi, Pierluigi and Pérez-González, Pablo G. and Rieke, George H. and Lyu, Jianwei and D’Eugenio, Francesco and Wu, Zihao and Carniani, Stefano and Looser, Tobias J. and Shivaei, Irene and Boogaard, Leindert A. and Diaz-Santos, Tanio and Colina, Luis and Östlin, Göran and Alberts, Stacey and Álvarez-Márquez, Javier and Annuziatella, Marianna and Aravena, Manuel and Bhatawdekar, Rachana and Bunker, Andrew J. and Caputi, Karina I. and Charlot, Stéphane and Crespo Gómez, Alejandro and Curti, Mirko and Eckart, Andreas and Gillman, Steven and Hainline, Kevin and Kumari, Nimisha and Hjorth, Jens and Iani, Edoardo and Inami, Hanae and Ji, Zhiyuan and Johnson, Benjamin D. and Jones, Gareth C. and Labiano, Álvaro and Maiolino, Roberto and Melinder, Jens and Moutard, Thibaud and Peissker, Florian and Rieke, Marcia and Robertson, Brant and Scholtz, Jan and Tacchella, Sandro and Van Der Werf, Paul P. and Walter, Fabian and Williams, Christina C. and Willott, Chris and Witstok, Joris and Übler, Hannah and Zhu, Yongda},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {1},
  publisher    = {IOP Publishing},
  title        = {{Deciphering the nature of Virgil: An obscured active galactic nucleus lurking within an apparently normal Lyα emitter during cosmic reionization}},
  doi          = {10.3847/1538-4357/ae089c},
  volume       = {994},
  year         = {2025},
}

@article{19845,
  abstract     = {Context. The recently launched James Webb Space Telescope (JWST) is opening new observing windows on the distant Universe. Among JWST’s instruments, the Mid Infrared Instrument (MIRI) offers the unique capability of imaging observations at wavelengths of λ > 5 μm. This enables unique access to the rest frame near-infrared (NIR, λ ≥ 1 μm) emission from galaxies at redshifts of z > 4 and the visual (λ ≳ 5000 Å) rest frame for z > 9. We report here on the guaranteed time observations (GTO), from the MIRI European Consortium, of the Hubble Ultra Deep Field (HUDF), forming the MIRI Deep Imaging Survey (MIDIS), consisting of an on source integration time of ∼41 hours in the MIRI/F560W (5.6 μm) filter. The F560W filter was selected since it would produce the deepest data in terms of AB magnitudes in a given time. To our knowledge, this constitutes the longest single filter exposure obtained with JWST of an extragalactic field as of yet.
Aims. The HUDF is one of the most observed extragalactic fields, with extensive multi-wavelength coverage, where (before JWST) galaxies up to z ∼ 7 have been confirmed, and at z > 10 suggested, from HST photometry. We aim to characterise the galaxy population in HUDF at 5.6 μm, enabling studies such as: the rest frame NIR morphologies for galaxies at z ≲ 4.6, probing mature stellar populations and emission lines in z > 6 sources, intrinsically red and dusty galaxies, and active galactic nuclei (AGNs) and their host galaxies at intermediate redshifts.

Methods. We reduced the MIRI data using the official JWST pipeline, augmented by in-house custom scripts. We measured the noise characteristics of the resulting image. Galaxy photometry was obtained, and photometric redshifts were estimated for sources with available multi-wavelength photometry (and compared to spectroscopic redshifts when available).

Results. Over the deepest part of our image, the 5σ point source limit is 28.65 mag AB (12.6 nJy), ∼0.35 mag better than predicted by the JWST exposure time calculator. We find ∼2500 sources, the overwhelming majority of which are distant galaxies, but we note that spurious sources likely remain at faint magnitudes due to imperfect cosmic ray rejection in the JWST pipeline. More than 500 galaxies with available spectroscopic redshifts, up to z ≈ 11, have been identified, the majority of which are at z < 6. More than 1000 galaxies have reliable photometric redshift estimates, of which ∼25 are at 6 < z < 12. The point spread function in the F560W filter has a full width at half maximum (FWHM) of ≈0.2″ (corresponding to 1.4 kpc at z = 4), allowing the NIR rest frame morphologies and stellar mass distributions to be resolved for z < 4.5. Moreover, > 100 objects with very red NIRCam vs MIRI (3.6–5.6 μm > 1 mag) colours have been found, suggestive of dusty or old stellar populations at high redshifts.

Conclusions. We conclude that MIDIS surpasses preflight expectations and that deep MIRI imaging has great potential to characterise the galaxy population from cosmic noon to dawn.},
  author       = {Östlin, Göran and Pérez-González, Pablo G. and Melinder, Jens and Gillman, Steven and Iani, Edoardo and Costantin, Luca and Boogaard, Leindert A. and Rinaldi, Pierluigi and Colina, Luis and Nørgaard-Nielsen, Hans Ulrik and Dicken, Daniel and Greve, Thomas R. and Wright, Gillian and Alonso-Herrero, Almudena and Álvarez-Márquez, Javier and Annunziatella, Marianna and Bik, Arjan and Bosman, Sarah E.I. and Caputi, Karina I. and Gomez, Alejandro Crespo and Eckart, Andreas and Garcia-Marin, Macarena and Hjorth, Jens and Ilbert, Olivier and Jermann, Iris and Kendrew, Sarah and Labiano, Alvaro and Langeroodi, Danial and Le Fevre, Olivier and Libralato, Mattia and Meyer, Romain A. and Moutard, Thibaud and Peissker, Florian and Pye, John P. and Tikkanen, Tuomo V. and Topinka, Martin and Walter, Fabian and Ward, Martin and Van Der Werf, Paul and Van Dishoeck, Ewine F. and Güdel, Manuel and Henning, Thomas and Lagage, Pierre Olivier and Ray, Tom P. and Vandenbussche, Bart},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  publisher    = {EDP Sciences},
  title        = {{MIRI Deep Imaging Survey (MIDIS) of the Hubble Ultra Deep Field: Survey description and early results for the galaxy population detected at 5.6 µm}},
  doi          = {10.1051/0004-6361/202451723},
  volume       = {696},
  year         = {2025},
}

@article{20217,
  abstract     = {We present Virgil, a Mid-Infrared Instrument (MIRI) extremely red object detected with the F1000W filter as part of the MIRI Deep Imaging Survey observations of the Hubble Ultra Deep Field. Virgil is an Lyα emitter (LAE) at zspec = 6.6312 ± 0.0019 (from the Very Large Telescope/MUSE) with a rest-frame UV-to-optical spectral energy distribution (SED) typical of LAEs at similar redshifts. However, MIRI observations reveal an unexpected extremely red color at rest-frame near-infrared (NIR) wavelengths, F444W − F1000W = 2.33 ± 0.06. Such a steep
rise in the NIR, completely missed without MIRI imaging, is poorly reproduced by models including only stellar populations and hints toward the presence of an active galactic nucleus, although alternative explanations such as extreme dust obscuration and strong nebular continuum and emission lines contribution due to young stellar ages cannot be completely ruled out. According to the shape of its overall SED, Virgil belongs to the recently discovered
population of little red dots but displays an extended rest-frame UV-optical wavelength morphology following a 2DSérsic profile with an average index of n = 0.93+0.85_0.31 and re = 0.49+0.05_0.11  pkpc. Only at MIRI wavelengths, Virgil is unresolved due to the coarser point-spread function. This discovery demonstrates the crucial importance of deep MIRI surveys to reveal the true nature and properties of high-z galaxies that otherwise would be misinterpreted and raises the question of how common Virgil-like objects could be in the early Universe.},
  author       = {Iani, Edoardo and Rinaldi, Pierluigi and Caputi, Karina I. and Annunziatella, Marianna and Langeroodi, Danial and Melinder, Jens and Pérez-González, Pablo G. and Álvarez-Márquez, Javier and Boogaard, Leindert A. and Bosman, Sarah E.I. and Costantin, Luca and Moutard, Thibaud and Colina, Luis and Östlin, Göran and Greve, Thomas R. and Wright, Gillian and Alonso-Herrero, Almudena and Bik, Arjan and Gillman, Steven and Crespo Gómez, Alejandro and Hjorth, Jens and Kendrew, Sarah and Labiano, Alvaro and Pye, John P. and Tikkanen, Tuomo V. and Walter, Fabian and Güdel, Manuel and Henning, Thomas and Van Der Werf, Paul P.},
  issn         = {1538-4357},
  journal      = {The Astrophysical Journal},
  number       = {2},
  publisher    = {IOP Publishing},
  title        = {{MIDIS: MIRI uncovers Virgil, the first Little Red Dot with clear detection of its host galaxy at z ≃ 6.6}},
  doi          = {10.3847/1538-4357/ade5a6},
  volume       = {989},
  year         = {2025},
}

@article{20589,
  abstract     = {Context. This paper investigates the star formation histories (SFHs) of a sample of massive galaxies (M⋆ ≥ 1010 M⊙) in the redshift range 1 < z < 4.5.
Methods. We analyzed spectro-photometric data, combining broadband photometry from HST and JWST with low-resolution grism spectroscopy from JWST/NIRISS, obtained as part of the MIRI Deep Imaging Survey program. SFHs were derived through spectral energy distribution fitting using two independent codes, BAGPIPES and synthesizer, under various SFH assumptions. This approach enables a comprehensive assessment of the biases introduced by different modeling choices.
Results. The inclusion of NIRISS spectroscopy, even with its low resolution, significantly improves constraints on key physical parameters, such as the mass-weighted stellar age (tM) and formation redshift (zform), by narrowing their posterior distributions. The massive galaxies in our sample exhibit rapid stellar mass assembly, forming 50% of their mass between 3 ≤ z ≤ 9. The highest inferred formation redshifts are compatible with elevated star formation efficiencies (ϵ) at early epochs. Nonparametric SFHs generally imply an earlier and slower mass assembly compared to parametric forms, highlighting the sensitivity of inferred formation timescales to the chosen SFH model–particularly for galaxies at z < 2. We find that quiescent galaxies are, on average, older (tM ∼ 1.1 Gyr) and assembled more rapidly at earlier times than their star-forming counterparts. These findings support the “downsizing” scenario, in which more massive and passive systems form earlier and more efficiently.},
  author       = {Annunziatella, M. and P’Erez-Gonz’Alez, P. G. and Álvarez-Márquez, J. and Costantin, L. and Iani, Edoardo and Labiano, Unknown and Rinaldi, P. and Boogaard, L. and Meyer, R. A. and Östlin, G. and Colina, L. and Melinder, J. and Jermann, I. and Gillman, S. and Langeroodi, D. and Hjorth, J. and Alonso-Herrero, A. and Eckart, A. and Walter, F. and Van Der Werf, P. P. and Bik, A. and Peißker, F. and Caputi, K. I. and García-Marín, M. and Wright, G. and Greve, T. R.},
  issn         = {1432-0746},
  journal      = {Astronomy & Astrophysics},
  publisher    = {EDP Sciences},
  title        = {{MIDIS: Unveiling the star formation history in massive galaxies at 1 < z < 4.5 with spectro-photometric analysis}},
  doi          = {10.1051/0004-6361/202453298},
  volume       = {702},
  year         = {2025},
}