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1. 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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2. Efficient Ionizers with Low H β + [O iii ] Equivalent Widths: JADES Spectroscopy of a Peculiar High-redshift Population

   https://doi.org/10.3847/1538-4357/adddb5  

   Laseter, Isaac H; Maseda, Michael V; Simmonds, Charlotte; Endsley, Ryan; Stark, Daniel; Bunker, Andrew J; Bhatawdekar, Rachana; Boyett, Kristan; Cameron, Alex J; Carniani, Stefano; et al (July 2025, The Astrophysical Journal)

   Abstract Early JWST photometric studies discovered a population of UV-faint ( $<{\mathit{L}}_{\mathrm{UV}}^{*}$ )z ∼ 6.5–8 Lyman break galaxies with spectral energy distributions implying young ages (∼10 Myr) yet relatively weak Hβ+ [Oiii] equivalent widths (EW_{Hβ+ [Oiii]} ≈ 400 Å). These galaxies seemingly contradict the implicit understanding that young star-forming galaxies are ubiquitously strong Hβ+ [Oiii] emitters, i.e., extreme emission line galaxies (EW ≳750 Å). Low metallicities, high Lyman continuum escape fractions, and rapidly declining star formation histories have been proposed as primary drivers behind low Hβ+ [Oiii] EWs, but the blend of Hβ+ [Oiii] in photometric studies makes proving one of these scenarios difficult. We aim to characterize this peculiar population with deep spectroscopy from the JWST Advanced Deep Extragalactic Survey. We find that a significant subset of these galaxies atz ≳ 2 with modest Hβ+ [Oiii] EWs (≈300–600 Å) have high ionization efficiencies ( $\log {\xi }_{\mathrm{ion}}\gtrsim 25.5\mathrm{Hz}{\mathrm{erg}}^{-1}$ ). Suppressed [Oiii] EW values yet elevated Hαand HβEW values imply that the level of chemical enrichment is the primary culprit, supported by spectroscopic measurements of metallicities below 12 + log(O/H) ≈ 7.70 (0.1Z_⊙). We demonstrate that integrated Hβ+ [Oiii] selections (e.g., Hβ+ [Oiii] EW > 700 Å) exclude the most metal-poor efficient ionizers and favor (1) more chemically enriched systems with comparable extreme radiation fields and (2) older starbursting systems. In contrast, metallicity degeneracies are reduced in Hαspace, enabling the identification of these metal-poor efficient ionizers by their specific star formation rate. 

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3. ASPIRE: The Environments and Dark Matter Halos of Luminous Quasars in the Epoch of Reionization

   https://doi.org/10.3847/1538-4357/ae7bfa  

   Wang, Feige; Champagne, Jaclyn B; Huang, Jiamu; Yang, Jinyi; Hennawi, Joseph F; Fan, Xiaohui; Zhang, Haowen; Costa, Tiago; Decarli, Roberto; Habouzit, Melanie; et al (July 2026, The Astrophysical Journal)

   Abstract We present a systematic study of the environments of 25 luminous quasars atz > 6.5 from the ASPIRE program. Using JWST/NIRCam wide-field slitless spectroscopy data, we identified 487 galaxies at 5.3 ≲ z ≲ 7.0 exhibiting [Oiii] emission. Among these, 122 [Oiii] emitters lie within ∣Δv_los∣ < 1000 km s⁻¹of the quasars, corresponding to a ∼9.4-fold enhancement relative to the average galaxy density at other redshifts. Furthermore, we identified 16 [Cii]-emitting galaxies at the quasar redshifts from Atacama Large Millimeter/submillimeter Array (ALMA) mosaic observations. A cross-correlation function analysis between quasars and [Oiii]+[Cii] emitters yields a cross-correlation length of $r_0^{\mathrm{QG}}=8.68_{-0.55}^{+0.51}{h}^{-1}\mathrm{cMpc}$ and an autocorrelation of $r_0^{\mathrm{QQ}}=15.76_{-2.70}^{+2.48}{h}^{-1}\mathrm{cMpc}$ , indicating thatz ∼ 7 quasars reside in dark matter halos with $M_{\mathrm{halo}}=10^{12.27_{-0.26}^{+0.21}}{M}_{\odot }$ and have a quasar lifetime of $t_Q=10^{{7.05}_{-1.01}^{+0.95}}\mathrm{yr}$ . Notably, the number of [Oiii]-emitting galaxies at quasar redshifts varies significantly from field to field, ranging from 0 to 20, highlighting a diverse quasar environment. Remarkably, seven quasars trace significant galaxy overdensities (i.e., protoclusters), withδ_gal > 5 within a volume ofV ∼ 500 cMpc³. We also find that ∣Δv_los∣ increases rapidly toward smaller galaxy–quasar separations in protocluster fields, consistent with galaxy kinematics around extremely massive halos in cosmological simulations. By combining JWST and ALMA data, we reveal the complex and diverse environments of these early quasars, providing robust evidence that the earliest luminous quasars are effective tracers of galaxy overdensities, albeit with substantial field-to-field variation. 

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4. EELG1002: A Record-breaking [O iii ]+H β EW ∼ 3700 Å Galaxy at z  ∼ 0.8—Analog of Early Galaxies?

   https://doi.org/10.3847/1538-4357/ae0330  

   Khostovan, Ali Ahmad; Kartaltepe, Jeyhan S; Brinch, Malte; Casey, Caitlin; Faisst, Andreas; Harish, Santosh; Gozaliasl, Ghassem; Onodera, Masato; Yabe, Kiyoto (November 2025, The Astrophysical Journal)

   Abstract Extreme emission line galaxies (EELGs) are powerful low-zanalogs of high-zgalaxies that can provide us valuable insights of early Universe conditions. We present a detailed analysis of EELG1002: az= 0.8275 EELG identified within archival Gemini/GMOS spectroscopy as part of the ongoing COSMOS Spectroscopic Archive. We find EELG1002 is a low-mass (∼10⁸M_⊙), compact (∼530 pc), bursty star-forming galaxy with a ∼15–35 Myr mass doubling timescale. EELG1002 has record-breaking rest-frame [Oiii]+HβEW ∼3100–3700 Å; ∼32–36× higher than typicalz ∼ 0.8 [Oiii] emitters with similar stellar mass; and higher than typicalz > 5 galaxies. We find no clear evidence of an active galactic nucleus suggesting the emission lines are star formation driven. EELG1002 is chemically unevolved (directT_e; $12+{\log }_{10}\left(\mathrm{O/H}\right)\sim 7.52$ consistent withz > 5 galaxies at fixed stellar mass) and may be undergoing a first intense, bursty star formation phase analogous to conditions expected of galaxies in the early Universe. We find evidence for a highly energetic interstellar medium ([Oiii]/[Oii] ∼ 9) and hard ionizing radiation field (elevated [Neiii]/[Oii] at fixed [Oiii]/[Oii]). Coupled with its compact, metal-poor, and actively star-forming nature, EELG1002 is found to efficiently produce ionizing photons (ξ_ion ∼ 10^25.74erg⁻¹Hz) and may have ∼10%–20% Lyman Continuum (LyC) escape suggesting such sources may be important analogs of galaxies responsible for reionization. We find a dynamical mass of ∼10⁹M_⊙suggesting copious amounts of gas to support intense star formation as also suggested by identified Illustris-TNG analogs. EELG1002 may be an ideal low-zlaboratory of galaxies in the early Universe and demonstrates how archival data sets can support high-zscience and next-generation surveys planned with Euclid and Roman. 

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5. A [C ii ] 158 μ m Survey of Damped Lyα Absorber Galaxies at z  ∼ 4: Observations of Dense and Metal-enriched Neutral Gas within the Circumgalactic Medium of Star-forming Galaxies

   https://doi.org/10.3847/1538-4357/adbbd1  

   Neeleman, Marcel; Kanekar, Nissim; Prochaska, J Xavier; Rafelski, Marc A; Kahinga, Lordrick A (April 2025, The Astrophysical Journal)

   Abstract We present a survey undertaken with the Atacama Large Millimeter/submillimeter Array (ALMA) to study the galaxies associated with a representative sample of 16 damped Lyαabsorbers (DLAs) atz ≈ 4.1–4.5, using the [Cii] 158μm ([Cii]) line. We detect seven [Cii]-emitting galaxies in the fields of five DLAs, all of which have absorption metallicity [M/H] > −1.5. We find that the detectability of these Hi-selected galaxies with ALMA is a strong function of DLA metallicity, with a detection rate of $71_{-20}^{+11}$ % for DLAs with [M/H] > −1.5 and 0⁺¹⁸% for DLAs with [M/H] < −1.5. The identified DLA galaxies have far-IR properties similar to those of typical star-forming galaxies atz ∼ 4, with estimated obscured star formation rates ranging from ≲6M_⊙yr⁻¹to 110M_⊙yr⁻¹. High-metallicity DLAs therefore provide an efficient way to identify and study samples of high-redshift, star-forming galaxies, without preselecting the galaxies by their emission properties. The agreement between the velocities of the metal absorption lines of the DLA and the [Cii] emission line of the DLA galaxy indicates that the metals within the DLA originated in the galaxy. With observed impact parameters between 14 and 59 kpc, this indicates that star-forming galaxies atz ∼ 4 have a substantial reservoir of dense, cold, neutral gas within their circumgalactic medium that has been enriched with metals from the galaxy. 

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