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1. A GLIMPSE into the very faint end of the H β +[O III] λλ 4960,5008 luminosity function at z ∼ 7 – 9 behind Abell S1063

   https://doi.org/10.1051/0004-6361/202556868  

   Korber, Damien; Chemerynska, Iryna; Furtak, Lukas J; Atek, Hakim; Endsley, Ryan; Schaerer, Daniel; Chisholm, John; Kokorev, Vasily; Saldana-Lopez, Alberto; Adamo, Angela; et al (April 2026, Astronomy & Astrophysics)

   We used the ultra-deep GLIMPSE JWST/NIRCam survey to constrain the faint end of the [O III]+Hβluminosity function (LF) down to 10³⁹erg s⁻¹atz ∼ 7 − 9 behind the lensed Hubble Frontier Field galaxy cluster Abell S1063. We applied a spectral energy distribution fitting on a Lyman-break galaxy selected sample of 164 lensed galaxies and measured their combined Hβ+[O III]λλ4960, 5008 flux to build the emission line LF. We found a [O III]+HβLF with a faint-end slope (α= −1.78^+0.06_−0.06forz = 7 − 8 andα= −1.55^+0.11_−0.11forz = 8 − 9), which is flatter than the UV LF at similar redshifts (α ≤ −2) and suggests a lower number density of weak [O III]+Hβemitting galaxies at fixedM_UV. We analysed several possible explanations: (i) a decrease in the [O III]+Hβ-to-UV ratio due to bursty star formation histories (SFHs), (ii) the effect of metallicity on the [O III]-to-Hβratio, or (iii) signs of a faint-end turnover in the UV LF. Under the assumption of an evolving [O III]-to-Hβratio, we separated the contribution of [O III]λ5008 and Hβand obtained a flatter [O III]λ5008 LF (α= −1.66^+0.05_−0.05forz = 7 − 8 andα= −1.45^+0.09_−0.10forz = 8 − 9) but steeper HβLF ($$ \alpha=-1.95_{-0.08}^{+0.08} $$ forz = 7 − 8 andα= −1.68^+0.13_−0.14forz = 8 − 9). The combination of a decreasing metallicity and bursty SFH can reconcile the observed differences between the UV and [O III]+HβLF. By converting this LF into the ionising photon-production rateṄ_ion, we show that galaxies withL_Hα ≥ 10³⁹erg s⁻¹, that is, with a star formation rate (SFR) (Hα)  ≥  5 × 10⁻³M_⊙yr⁻¹) cause 31%−90% and 46%−156% of the ionising photon budget (at 7 < z < 8 and 8 < z < 9), when we assume a constant escape fraction of Lyman-continuum photon (f_esc = 0.14). The shape of the LF further shows the negligible contribution of faint galaxies to theṄ_ion. Additionally, we derived the cosmic star formation rate density (SFRD), finding results consistent with previous estimates. However, the sensitivity of GLIMPSE to lower SFRs reinforces the conclusion that very faint galaxies contribute very little toṄ_ionand the SFRD. Our results suggests that GLIMPSE has detected the bulk of the total [O III]+Hβemission from star-forming galaxies, and that galaxies below our detection limits are likely minor contributors to cosmic re-ionisation. 

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2. [CII] luminosity models and large-scale image cubes based on COSMOS 2020 and ALPINE-ALMA [CII] data back to the epoch of reionisation

   https://doi.org/10.1051/0004-6361/202450300  

   Clarke, J; Karoumpis, C; Riechers, D; Magnelli, B; Okada, Y; Dev, A; Nikola, T; Bertoldi, F (September 2024, Astronomy & Astrophysics)

   Aims.We have implemented a novel method to create simulated [CII] emission line intensity mapping (LIM) data cubes using COSMOS 2020 galaxy catalogue data. It allows us to provide solid lower limits for previous simulation-based model predictions and the expected signal strength of upcoming surveys. Methods.We applied [CII]158 μm luminosity models to COSMOS 2020 to create LIM cubes covering a 1.2 × 1.2deg²sky area. These models were derived using galaxy bulk property data from the ALPINE-ALMA survey over the redshift range of 4.4 < z < 5.9, while additional models were taken from the literature. The LIM cubes cover 3.42 < z < 3.87, 4.14 < z < 4.76, 5.34 < z < 6.31, and 6.75 < z < 8.27, matched to planned observations from the EoR-Spec module of the Prime-Cam instrument in the Fred Young Submillimeter Telescope (FYST). We also created predictions including additional galaxies below current detection limits by ‘extrapolating’ from the faint end of the COSMOS 2020 luminosity function, comparing these to predictions from the literature. In addition, we computed the signal-to-noise (S/N) ratios for the power spectra, using parameters from the planned FYST survey with predicted instrumental noise levels. Results.We find lower limits for the expected power spectrum using the likely incomplete empirical data: when normalised by 2π², the amplitudes atk = 1 Mpc⁻¹are 3.06 × 10⁷, 1.43 × 10⁷, 9.80 × 10⁵, 2.77 × 10⁵ (Jy sr⁻¹)²for the aforementioned redshift ranges. For the extrapolated sample, the power spectra are consistent with prior predictions, indicating that extrapolation is a viable method for creating mock LIM cubes. In this case, we expect a result of S/N> 1 when using FYST parameters. However, our high-redshift results remain inconclusive because of the poor completeness of COSMOS 2020 atz > 6.3. These predictions will be improved on the basis of future JWST data. 

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3. Bridging Quasars and Little Red Dots: Insights into Broad-line Active Galactic Nuclei at z = 5–8 from the First JWST COSMOS-3D Dataset

   https://doi.org/10.3847/1538-4357/ae1b9b  

   Lin, Xiaojing; Fan, Xiaohui; Wang, Feige; Sun, Fengwu; Champagne, Jaclyn B; Egami, Eiichi; Kakiichi, Koki; Lyu, Jianwei; Tee, Wei Leong; Yang, Jinyi; et al (December 2025, The Astrophysical Journal)

   Abstract We report the discovery of 13 broad-line active galactic nuclei (AGNs) atz= 5–8 from the first 10% of JWST Cycle 3 Treasury Program COSMOS-3D. These AGNs are identified by their broad Hαor Hβemission lines through NIRCam grism slitless spectroscopy. One object atz= 7.646 with broad Hβemission has an F444W magnitude of 23.6 mag, making it one of the brightestz> 7.5 broad-line AGNs yet known. Among the 13 AGNs, 10 objects exhibit reddened optical continua with slopesβ_opt> 0. The remaining three resemble UV-luminous quasars at similar redshift but withβ_optless blue than those of typical unobscured quasars. We also obtain MIRI photometry (7.7–18μm) for two AGNs and place strong constraints on their rest-frame near-IR spectral energy distribution. We find no significant variability in the rest-frame UV by comparing the COSMOS-3D and COSMOS-Web F115W images taken apart by 60 days in the rest-frame. We compute the Hαluminosity function (LF) atz≈ 5–6 and find potential redshift evolution compared toz≈ 4–5. We also derive the HβLF atz∼ 8 by combining our sample with those from the literature. The broad Hβemitters in this work suggest a number density 2 orders of magnitude higher than that predicted by the quasar LF based on rest-frame UV-selected samples. As a preview, our work showcases the ability of the COSMOS-3D grism survey to provide a complete view of the properties, growth, and evolution of bright broad-line AGNs atz> 5. 

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4. ODIN: Improved Narrowband Lyα Emitter Selection Techniques for z = 2.4, 3.1, and 4.5

   https://doi.org/10.3847/1538-4357/ad71c9  

   Firestone, Nicole M; Gawiser, Eric; Ramakrishnan, Vandana; Lee, Kyoung-Soo; Valdes, Francisco; Park, Changbom; Yang, Yujin; Ciardullo, Robin; Artale, María Celeste; Benda, Barbara; et al (October 2024, The Astrophysical Journal)

   Abstract Lyman-alpha-emitting galaxies (LAEs) are typically young, low-mass, star-forming galaxies with little extinction from interstellar dust. Their low dust attenuation allows their Lyαemission to shine brightly in spectroscopic and photometric observations, providing an observational window into the high-redshift Universe. Narrowband surveys reveal large, uniform samples of LAEs at specific redshifts that probe large-scale structure and the temporal evolution of galaxy properties. The One-hundred-deg²DECam Imaging in Narrowbands (ODIN) utilizes three custom-made narrowband filters on the Dark Energy Camera (DECam) to discover LAEs at three equally spaced periods in cosmological history. In this paper, we introduce the hybrid-weighted double-broadband continuum estimation technique, which yields improved estimation of Lyαequivalent widths. Using this method, we discover 6032, 5691, and 4066 LAE candidates atz= 2.4, 3.1, and 4.5 in the extended COSMOS field (∼9 deg²). We find that [Oii] emitters are a minimal contaminant in our LAE samples, but that interloping Green Pea–like [Oiii] emitters are important for our redshift 4.5 sample. We introduce an innovative method for identifying [Oii] and [Oiii] emitters via a combination of narrowband excess and galaxy colors, enabling their study as separate classes of objects. We present scaled median stacked spectral energy distributions for each galaxy sample, revealing the overall success of our selection methods. We also calculate rest-frame Lyαequivalent widths for our LAE samples and find that the EW distributions are best fit by exponential functions with scale lengths ofw₀= 53 ± 1, 65 ± 1, and 59 ± 1 Å, respectively. 

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5. A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): Spectroscopically Complete Census of Obscured Cosmic Star Formation Rate Density at z  = 4–6

   https://doi.org/10.3847/1538-4357/ad9d0e  

   Sun, Fengwu; Wang, Feige; Yang, Jinyi; Champagne, Jaclyn B; Decarli, Roberto; Fan, Xiaohui; Bañados, Eduardo; Cai, Zheng; Colina, Luis; Egami, Eiichi; et al (January 2025, The Astrophysical Journal)

   Abstract We present a stringent measurement of the dust-obscured star formation rate density (SFRD) atz= 4–6 from the ASPIRE JWST Cycle-1 medium and ALMA Cycle-9 large program. We obtained JWST/NIRCam grism spectroscopy and ALMA 1.2 mm continuum map along 25 independent quasar sightlines, covering a total survey area of  ∼35 arcmin²where we search for dusty star-forming galaxies (DSFGs) atz= 0–7. We identify eight DSFGs in seven fields atz= 4–6 through the detection of Hαor [O iii]λ5008 lines, including fainter lines such as Hβ, [O iii]λ4960, [N ii]λ6585, and [S ii]λλ6718,6733 for six sources. With this spectroscopically complete DSFG sample atz= 4–6 and negligible impact from cosmic variance (shot noise), we measure the infrared luminosity function (IRLF) down toL_IR ∼ 2 × 10¹¹L_⊙. We find flattening of IRLF atz= 4–6 towards the faint end (power-law slope $\alpha =0.59_{-0.45}^{+0.39}$ ). We determine the dust-obscured cosmic SFRD at this epoch to be $\log [{\rho }_{\mathrm{SFR},\mathrm{IR}}/(M_{\odot }{\mathrm{yr}}^{-1}{\mathrm{Mpc}}^{-3}\left)\right]=-1.52_{-0.13}^{+0.14}$ . This is significantly higher than previous determinations using ALMA data in the Hubble Ultra Deep Field, which is void of DSFGs atz= 4–6 because of strong cosmic variance (shot noise). We conclude that the majority (66% ± 7%) of cosmic star formation atz ∼ 5 is still obscured by dust. We also discuss the uncertainty of SFRD propagated from far-IR spectral energy distribution and IRLF at the bright end, which will need to be resolved with future ALMA and JWST observations. 

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