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1. Constraints on the z ∼ 5 Star-forming Galaxy Luminosity Function From Hubble Space Telescope Imaging of an Unbiased and Complete Sample of Long Gamma-Ray Burst Host Galaxies

   https://doi.org/10.3847/1538-4357/ad2e93  

   Sears, Huei; Chornock, Ryan; Strader, Jay; Perley, Daniel A; Blanchard, Peter K; Margutti, Raffaella; Tanvir, Nial R (April 2024, The Astrophysical Journal)

   Abstract We present rest-frame UV Hubble Space Telescope imaging of the largest and most complete sample of 23 long-duration gamma-ray burst (GRB) host galaxies between redshifts 4 and 6. Of these 23, we present new WFC3/F110W imaging for 19 of the hosts, which we combine with archival WFC3/F110W and WFC3/F140W imaging for the remaining four. We use the photometry of the host galaxies from this sample to characterize both the rest-frame UV luminosity function (LF) and the size–luminosity relation of the sample. We find that when assuming the standard Schechter-function parameterization for the UV LF, the GRB host sample is best fit with $\alpha =-{1.30}_{-0.25}^{+0.30}$and $M_{*}=-{20.33}_{-0.54}^{+0.44}$mag, which are consistent with results based onz∼ 5 Lyman-break galaxies. We find that ∼68% of our size–luminosity measurements fall within or below the same relation for Lyman-break galaxies atz∼ 4. This study observationally confirms expectations that atz∼ 5 Lyman-break and GRB host galaxies should trace the same population and demonstrates the utility of GRBs as probes of hidden star formation in the high-redshift Universe. Under the assumption that GRBs unbiasedly trace star formation at this redshift, our nondetection fraction of 7/23 is consistent at the 95% confidence level with 13%–53% of star formation at redshiftz∼ 5 occurring in galaxies fainter than our detection limit ofM_1600Å≈ −18.3 mag. 

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2. Short GRB Host Galaxies. II. A Legacy Sample of Redshifts, Stellar Population Properties, and Implications for Their Neutron Star Merger Origins

   https://doi.org/10.3847/1538-4357/ac91d1  

   Nugent, Anya E.; Fong, Wen-Fai; Dong 董, Yuxin 雨欣; Leja, Joel; Berger, Edo; Zevin, Michael; Chornock, Ryan; Cobb, Bethany E.; Kelley, Luke Zoltan; Kilpatrick, Charles D.; et al (November 2022, The Astrophysical Journal)

   Abstract We present the stellar population properties of 69 short gamma-ray burst (GRB) host galaxies, representing the largest uniformly modeled sample to date. Using theProspectorstellar population inference code, we jointly fit photometry and/or spectroscopy of each host galaxy. We find a population median redshift of $z={0.64}_{-0.32}^{+0.83}$(68% confidence), including nine photometric redshifts atz≳ 1. We further find a median mass-weighted age oft_m= ${0.8}_{-0.53}^{+2.71}$Gyr, stellar mass of log(M_*/M_⊙) = ${9.69}_{-0.65}^{+0.75}$, star formation rate of SFR = ${1.44}_{-1.35}^{+9.37}$M_⊙yr⁻¹, stellar metallicity of log(Z_*/Z_⊙) = $-{0.38}_{-0.42}^{+0.44}$, and dust attenuation of $A_V={0.43}_{-0.36}^{+0.85}$mag (68% confidence). Overall, the majority of short GRB hosts are star-forming (≈84%), with small fractions that are either transitioning (≈6%) or quiescent (≈10%); however, we observe a much larger fraction (≈40%) of quiescent and transitioning hosts atz≲ 0.25, commensurate with galaxy evolution. We find that short GRB hosts populate the star-forming main sequence of normal field galaxies, but do not include as many high-mass galaxies as the general galaxy population, implying that their binary neutron star (BNS) merger progenitors are dependent on a combination of host star formation and stellar mass. The distribution of ages and redshifts implies a broad delay-time distribution, with a fast-merging channel atz> 1 and a decreased neutron star binary formation efficiency from high to low redshifts. If short GRB hosts are representative of BNS merger hosts within the horizon of current gravitational wave detectors, these results can inform future searches for electromagnetic counterparts. All of the data and modeling products are available on the Broadband Repository for Investigating Gamma-ray burst Host Traits website. 

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3. The Space Density of Intermediate-redshift, Extremely Compact, Massive Starburst Galaxies

   https://doi.org/10.3847/1538-3881/ac958f  

   Whalen, Kelly E.; Hickox, Ryan C.; Coil, Alison L.; Diamond-Stanic, Aleksandar M.; Geach, James E.; Moustakas, John; Rudnick, Gregory H.; Rupke, David S. N.; Sell, Paul H.; Tremonti, Christy A.; et al (October 2022, The Astronomical Journal)

   Abstract We present a measurement of the intrinsic space density of intermediate-redshift (z∼ 0.5), massive (M_*∼ 10¹¹M_⊙), compact (R_e∼ 100 pc) starburst (Σ_SFR∼ 1000M_⊙yr⁻¹kpc⁻¹) galaxies with tidal features indicative of them having undergone recent major mergers. A subset of them host kiloparsec-scale, > 1000 km s⁻¹outflows and have little indication of AGN activity, suggesting that extreme star formation can be a primary driver of large-scale feedback. The aim for this paper is to calculate their space density so we can place them in a better cosmological context. We do this by empirically modeling the stellar populations of massive, compact starburst galaxies. We determine the average timescale on which galaxies that have recently undergone an extreme nuclear starburst would be targeted and included in our spectroscopically selected sample. We find that massive, compact starburst galaxies targeted by our criteria would be selectable for $\sim {148}_{-24}^{+27}$Myr and have an intrinsic space density $n_{\mathrm{CS}}\sim \left({1.1}_{-0.3}^{+0.5}\right)\times {10}^{-6}{\mathrm{Mpc}}^{-3}$. This space density is broadly consistent with ourz∼ 0.5 compact starbursts being the most extremely compact and star-forming low-redshift analogs of the compact star-forming galaxies in the early universe, as well as them being the progenitors to a fraction of intermediate-redshift, post-starburst, and compact quiescent galaxies. 

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4. ODIN: Clustering Analysis of 14,000 Ly α -emitting Galaxies at z = 2.4, 3.1, and 4.5

   https://doi.org/10.3847/2041-8213/adec82  

   Herrera, Danisbel; Gawiser, Eric; Benda, Barbara; Firestone, Nicole M; Ramakrishnan, Vandana; Moon, Byeongha; Lee, Kyoung-Soo; Park, Changbom; Valdes, Francisco; Yang, Yujin; et al (July 2025, The Astrophysical Journal Letters)

   Abstract Lyαemitters (LAEs) are star-forming galaxies that efficiently probe the spatial distribution of galaxies in the high-redshift Universe. The spatial clustering of LAEs reflects the properties of their individual host dark matter halos, allowing us to study the evolution of the galaxy–halo connection. We analyze the clustering of 5233, 5220, and 3706 LAEs atz= 2.4, 3.1, and 4.5, respectively, in the 9 deg²COSMOS field from the One-hundred-deg²DECam Imaging in Narrowbands survey. After correcting for redshift-space distortions, LAE contamination rates, and the integral constraint, the observed angular correlation functions imply linear galaxy bias factors ofb= $1.72_{-0.27}^{+0.26},2.01_{-0.29}^{+0.26},$and $2.95_{-0.46}^{+0.40}$forz= 2.4, 3.1, and 4.5, respectively. The median dark matter halo masses inferred from these measurements are $\log (M_h/M_{\odot })$= $11.44_{-0.28}^{+0.30},11.13_{-0.26}^{+0.26},\mathrm{and}10.85_{-0.24}^{+0.24}$for the three samples, respectively. The analysis also reveals that LAEs occupy roughly 3%–7% of the halos whose clustering strength matches that of the LAEs. 

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5. Merger Signatures are Common, but not Universal, in Massive, Recently Quenched Galaxies at z ∼ 0.7

   https://doi.org/10.3847/1538-4357/acc38b  

   Verrico, Margaret E.; Setton, David J.; Bezanson, Rachel; Greene, Jenny E.; Suess, Katherine A.; Goulding, Andy D.; Spilker, Justin S.; Kriek, Mariska; Feldmann, Robert; Narayanan, Desika; et al (May 2023, The Astrophysical Journal)

   Abstract We present visual classifications of merger-induced tidal disturbances in 143M_*∼ 10¹¹M_⊙post-starburst galaxies atz∼ 0.7 identified in the $\mathrm{SQuIGG}\vec{L}\mathrm{E}$Sample. This sample spectroscopically selects galaxies from the Sloan Digital Sky Survey that have stopped their primary epoch of star formation within the past ∼500 Myr. Visual classifications are performed on Hyper Suprime-Cam imaging. We compare to a control sample of mass- and redshift-matched star-forming and quiescent galaxies from the Large Early Galaxy Census and find that post-starburst galaxies are more likely to be classified as disturbed than either category. This corresponds to a factor of ${3.6}_{-1.3}^{+2.9}$times the disturbance rate of older quiescent galaxies and ${2.1}_{-.73}^{+1.9}$times the disturbance rate of star-forming galaxies. Assuming tidal features persist for ≲500 Myr, this suggests merging is coincident with quenching in a significant fraction of these post-starbursts. Galaxies with tidal disturbances are younger on average than undisturbed post-starburst galaxies in our sample, suggesting tidal features from a major merger may have faded over time. This may be exacerbated by the fact that, on average, the undisturbed subset is fainter, rendering low-surface-brightness tidal features harder to identify. However, the presence of 10 young (≲150 Myr since quenching) undisturbed galaxies suggests that major mergers are not the only fast physical mechanism that shut down the primary epoch of star formation in massive galaxies at intermediate redshift. 

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