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1. The MOSFIRE Deep Evolution Field Survey: Implications of the Lack of Evolution in the Dust Attenuation–Mass Relation to z ∼ 2*

   https://doi.org/10.3847/1538-4357/ac4742  

   Shapley, Alice E. ; Sanders, Ryan L. ; Salim, Samir ; Reddy, Naveen A. ; Kriek, Mariska ; Mobasher, Bahram ; Coil, Alison L. ; Siana, Brian ; Price, Sedona H. ; Shivaei, Irene ; et al ( February 2022 , The Astrophysical Journal)

   We investigate the relationship between dust attenuation and stellar mass (M_*) in star-forming galaxies over cosmic time. For this analysis, we compare measurements from the MOSFIRE Deep Evolution Field survey atz∼ 2.3 and the Sloan Digital Sky Survey (SDSS) atz∼ 0, augmenting the latter optical data set with both UV Galaxy Evolution Explorer (GALEX) and mid-infrared Wide-field Infrared Survey Explorer (WISE) photometry from the GALEX-SDSS-WISE Catalog. We quantify dust attenuation using both spectroscopic measurements of Hαand Hβemission lines, and photometric measurements of the rest-UV stellar continuum. The Hα/Hβratio is used to determine the magnitude of attenuation at the wavelength of Hα,A_Hα. Rest-UV colors and spectral energy distribution fitting are used to estimateA₁₆₀₀, the magnitude of attenuation at a rest wavelength of 1600 Å. As in previous work, we find a lack of significant evolution in the relation between dust attenuation andM_*over the redshift rangez∼ 0 toz∼ 2.3. Folding in the latest estimates of the evolution ofM_dust, (M_dust/M_gas), and gas surface density at fixedM_*, we find that the expectedM_dustand dust mass surface density are both significantly higher atz∼ 2.3 than atz∼ 0. These differences appear at odds with the lack of evolution in dust attenuation. To explain the striking constancymore »in attenuation versusM_*, it is essential to determine the relationship between metallicity and (M_dust/M_gas), the dust mass absorption coefficient and dust geometry, and the evolution of these relations and quantities fromz∼ 0 toz∼ 2.3.

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2. Now You See It, Now You Don’t: Star Formation Truncation Precedes the Loss of Molecular Gas by ∼100 Myr in Massive Poststarburst Galaxies at z ∼ 0.6

   https://doi.org/10.3847/1538-4357/ac3dfa  

   Bezanson, Rachel ; Spilker, Justin S. ; Suess, Katherine A. ; Setton, David J. ; Feldmann, Robert ; Greene, Jenny E. ; Kriek, Mariska ; Narayanan, Desika ; Verrico, Margaret ( February 2022 , The Astrophysical Journal)

   We use ALMA observations of CO(2–1) in 13 massive (M_*≳ 10¹¹M_⊙) poststarburst galaxies atz∼ 0.6 to constrain the molecular gas content in galaxies shortly after they quench their major star-forming episode. The poststarburst galaxies in this study are selected from the Sloan Digital Sky Survey spectroscopic samples (Data Release 14) based on their spectral shapes, as part of the Studying QUenching at Intermediate-z Galaxies: Gas, angu$$\overrightarrow{L}\mathrm{ar}$$momentum, and Evolution ($\mathit{SQuIGG}\vec{L}E$) program. Early results showed that two poststarburst galaxies host large H₂reservoirs despite their low inferred star formation rates (SFRs). Here we expand this analysis to a larger statistical sample of 13 galaxies. Six of the primary targets (45%) are detected, with$M_{{\mathrm{H}}_2}\gtrsim {10}^9$M_⊙. Given their high stellar masses, this mass limit corresponds to an average gas fraction of$〈f_{{\mathrm{H}}_2}\equiv M_{{\mathrm{H}}_2}/M_{*}〉\sim 7\%$or ∼14% using lower stellar masses estimates derived from analytic, exponentially declining star formation histories. The gas fraction correlates with theD_n4000 spectral index, suggesting that the cold gas reservoirs decrease with time since burst, as found in local K+A galaxies. Star formation histories derived from flexible stellar population synthesis modeling support thismore »empirical finding: galaxies that quenched ≲150 Myr prior to observation host detectable CO(2–1) emission, while older poststarburst galaxies are undetected. The large H₂reservoirs and low SFRs in the sample imply that the quenching of star formation precedes the disappearance of the cold gas reservoirs. However, within the following 100–200 Myr, the$\mathit{SQuIGG}\vec{L}E$galaxies require the additional and efficient heating or removal of cold gas to bring their low SFRs in line with standard H₂scaling relations.

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3. First Census of Gas-phase Metallicity Gradients of Star-forming Galaxies in Overdense Environments at Cosmic Noon

   https://doi.org/10.3847/2041-8213/ac626f  

   Li, Zihao ; Wang, Xin ; Cai, Zheng ; Shi, Dong Dong ; Fan, Xiaohui ; Zheng, Xian Zhong ; Malkan, Matthew A. ; Teplitz, Harry I. ; Henry, Alaina L. ; Bian, Fuyan ; et al ( April 2022 , The Astrophysical Journal Letters)

   Abstract We report the first spatially resolved measurements of gas-phase metallicity radial gradients in star-forming galaxies in overdense environments at z ≳ 2. The spectroscopic data are acquired by the MAMMOTH-Grism survey, a Hubble Space Telescope (HST) cycle 28 medium program. This program is obtaining 45 orbits of WFC3/IR grism spectroscopy in the density peak regions of three massive galaxy protoclusters (BOSS 1244, BOSS 1542, and BOSS 1441) at z = 2–3. Our sample in the BOSS 1244 field consists of 20 galaxies with stellar mass ranging from 10 9.0 to 10 10.3 M ⊙ , star formation rate (SFR) from 10 to 240 M ⊙ yr −1 , and global gas-phase metallicity ( 12 + log ( O / H ) ) from 8.2 to 8.6. At 1 σ confidence level, 2/20 galaxies in our sample show positive (inverted) gradients—the relative abundance of oxygen increasing with galactocentric radius, opposite the usual trend. Furthermore, 1/20 shows negative gradients, and 17/20 are consistent with flat gradients. This high fraction of flat/inverted gradients is uncommon in simulations and previous observations conducted in blank fields at similar redshifts. To understand this, we investigate the correlations among various observed properties of our sample galaxies.more »We find an anticorrelation between metallicity gradient and global metallicity of our galaxies residing in extreme overdensities, and a marked deficiency of metallicity in our massive galaxies as compared to their coeval field counterparts. We conclude that the cold-mode gas accretion plays an active role in shaping the chemical evolution of galaxies in the protocluster environments, diluting their central chemical abundance, and flattening/inverting their metallicity gradients.« less
4. A Massive, Dusty, Hi Absorption–Selected Galaxy at z ≈ 2.46 Identified in a CO Emission Survey

   https://doi.org/10.3847/1538-4357/ac7b2c  

   Kaur, B. ; Kanekar, N. ; Revalski, M. ; Rafelski, M. ; Neeleman, M. ; Prochaska, J. X. ; Walter, F. ( July 2022 , The Astrophysical Journal)

   We report a NOrthern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter/submillimeter Array search for redshifted CO emission from the galaxies associated with seven high-metallicity ([M/H] ≥ −1.03) damped Lyαabsorbers (DLAs) atz≈ 1.64–2.51. Our observations yielded one new detection of CO(3–2) emission from a galaxy atz= 2.4604 using NOEMA, associated with thez= 2.4628 DLA toward QSO B0201+365. Including previous searches, our search results in detection rates of CO emission of$\approx {56}_{-24}^{+38}$% and$\approx {11}_{-9}^{+26}$%, respectively, in the fields of DLAs with [M/H] > −0.3 and [M/H] < −0.3. Further, the Hi–selected galaxies associated with five DLAs with [M/H] > −0.3 all have high molecular gas masses, ≳5 × 10¹⁰M_⊙. This indicates that the highest-metallicity DLAs atz≈ 2 are associated with the most massive galaxies. The newly identifiedz≈ 2.4604 Hi–selected galaxy, DLA0201+365g, has an impact parameter of ≈7 kpc to the QSO sightline, and an implied molecular gas mass of (5.04 ± 0.78) × 10¹⁰× (α_CO/4.36) × (r₃₁/0.55)M_⊙. Archival Hubble Space Telescope Wide Field and Planetary Camera 2 imaging covering the rest-frame near-ultraviolet (NUV) and far-ultraviolet (FUV) emission from this galaxy yield nondetections of rest-frame NUV and FUV emission, and a 5σupper limit of 2.3M_⊙yr⁻¹on the unobscuredmore »star formation rate (SFR). The low NUV-based SFR estimate, despite the very high molecular gas mass, indicates that DLA0201+365g either is a very dusty galaxy, or has a molecular gas depletion time that is around 2 orders of magnitude larger than that of star-forming galaxies at similar redshifts.

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5. CLEAR: The Evolution of Spatially Resolved Star Formation in Galaxies between 0.5 ≲ z ≲ 1.7 Using Hα Emission Line Maps

   https://doi.org/10.3847/1538-4357/ac8471  

   Matharu, Jasleen ; Papovich, Casey ; Simons, Raymond C. ; Momcheva, Ivelina ; Brammer, Gabriel ; Ji, Zhiyuan ; Backhaus, Bren E. ; Cleri, Nikko J. ; Estrada-Carpenter, Vicente ; Finkelstein, Steven L. ; et al ( September 2022 , The Astrophysical Journal)

   Using spatially resolved Hαemission line maps of star-forming galaxies, we study the spatial distribution of star formation over a wide range in redshift (0.5 ≲z≲ 1.7). Ourz∼ 0.5 measurements come from deep Hubble Space Telescope (HST) Wide Field Camera 3 G102 grism spectroscopy obtained as part of the CANDELS LyαEmission at Reionization Experiment. For star-forming galaxies with log(M_*/M_⊙) ≥ 8.96, the mean Hαeffective radius is 1.2 ± 0.1 times larger than that of the stellar continuum, implying inside-out growth via star formation. This measurement agrees within 1σwith those measured atz∼ 1 andz∼ 1.7 from the 3D-HST and KMOS^3Dsurveys, respectively, implying no redshift evolution. However, we observe redshift evolution in the stellar mass surface density within 1 kpc (Σ_1kpc). Star-forming galaxies atz∼ 0.5 with a stellar mass of log(M_*/M_⊙) = 9.5 have a ratio of Σ_1kpcin Hαrelative to their stellar continuum that is lower by (19 ± 2)% compared toz∼ 1 galaxies. Σ_1kpc,Hα/Σ_1kpc,Contdecreases toward higher stellar masses. The majority of the redshift evolution in Σ_1kpc,Hα/Σ_1kpc,Contversus stellar mass stems from the fact that log(Σ_1kpc,Hα) declines twice as much as log(Σ_1kpc,Cont) fromz∼ 1 to 0.5 (at a fixed stellar mass of log(M_*/M_⊙) = 9.5). By comparing our results to the TNG50 cosmologicalmore »magneto-hydrodynamical simulation, we rule out dust as the driver of this evolution. Our results are consistent with inside-out quenching following in the wake of inside-out growth, the former of which drives the significant drop in Σ_1kpc,Hαfromz∼ 1 toz∼ 0.5.

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