More Like this

1. 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 cosmological 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.

    

   more » « less
2. The MOSDEF survey: the dependence of H α-to-UV SFR ratios on SFR and size at z ∼ 2

   https://doi.org/10.1093/mnras/stab2570  

   Fetherolf, Tara ; Reddy, Naveen A ; Shapley, Alice E ; Kriek, Mariska ; Siana, Brian ; Coil, Alison L ; Mobasher, Bahram ; Freeman, William R ; Sanders, Ryan L ; Price, Sedona H ; et al ( October 2021 , Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We perform an aperture-matched analysis of dust-corrected H α and UV star formation rates (SFRs) using 303 star-forming galaxies with spectroscopic redshifts 1.36 < zspec < 2.66 from the MOSFIRE Deep Evolution Field survey. By combining H α and H β emission line measurements with multiwaveband resolved Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey/3D-HST imaging, we directly compare dust-corrected H α and UV SFRs, inferred assuming a fixed attenuation curve shape and constant SFHs, within the spectroscopic aperture. Previous studies have found that H α and UV SFRs inferred with these assumptions generally agree for typical star-forming galaxies, but become increasingly discrepant for galaxies with higher SFRs (≳100 M⊙ yr−1), with H α-to-UV SFR ratios being larger for these galaxies. Our analysis shows that this trend persists even after carefully accounting for the apertures over which H α and UV-based SFRs (and the nebular and stellar continuum reddening) are derived. Furthermore, our results imply that H α SFRs may be higher in the centres of large galaxies (i.e. where there is coverage by the spectroscopic aperture) compared to their outskirts, which could be indicative of inside-out galaxy growth. Overall, we suggest that the persistent difference between nebular and stellar continuum reddening and high H α-to-UV SFR ratios at the centres of large galaxies may be indicative of a patchier distribution of dust in galaxies with high SFRs. 

   more » « less
3. Lyα Escape from Low-mass, Compact, High-redshift Galaxies

   https://doi.org/10.3847/1538-3881/ac83a9  

   Pucha, Ragadeepika ; Reddy, Naveen A. ; Dey, Arjun ; Juneau, Stéphanie ; Lee, Kyoung-Soo ; Prescott, Moire K. ; Shivaei, Irene ; Hong, Sungryong ( September 2022 , The Astronomical Journal)

   We investigate the effects of stellar populations and sizes on Lyαescape in 27 spectroscopically confirmed and 35 photometric Lyαemitters (LAEs) atz≈ 2.65 in seven fields of the Boötes region of the NOAO Deep Wide-Field Survey. We use deep HST/WFC3 imaging to supplement ground-based observations and infer key galaxy properties. Compared to typical star-forming galaxies (SFGs) at similar redshifts, the LAEs are less massive (M_⋆≈ 10⁷–10⁹M_⊙), younger (ages ≲1 Gyr), smaller (r_e< 1 kpc), and less dust-attenuated (E(B−V) ≤ 0.26 mag) but have comparable star formation rates (SFRs ≈ 1–100M_⊙yr⁻¹). Some of the LAEs in the sample may be very young galaxies having low nebular metallicities (Z_neb≲ 0.2Z_⊙) and/or high ionization parameters ($\log (\mathrm{U})\gtrsim -2.4$). Motivated by previous studies, we examine the effects of the concentration of star formation and gravitational potential on Lyαescape by computing SFR surface density, Σ_SFR, and specific SFR surface density, Σ_sSFR. For a given Σ_SFR, the Lyαescape fraction is higher for LAEs with lower stellar masses. The LAEs have a higher Σ_sSFR, on average, compared to SFGs. Our results suggest that compact star formation in a low gravitational potential yields conditions amenable to the escape of Lyαphotons. These results have important implications for the physics of Lyαradiative transfer and for the type of galaxies that may contribute significantly to cosmic reionization.

    

   more » « less
4. Radiative Transfer in Lyα Nebulae. I. Modeling a Continuous or Clumpy Spherical Halo with a Central Source

   https://doi.org/10.3847/1538-4357/acac98  

   Chang, Seok-Jun ; Yang, Yujin ; Seon, Kwang-Il ; Zabludoff, Ann ; Lee, Hee-Won ( March 2023 , The Astrophysical Journal)

   To understand the mechanism behind high-zLyαnebulae, we simulate the scattering of Lyαin a Hihalo about a central Lyαsource. For the first time, we consider both smooth and clumpy distributions of halo gas, as well as a range of outflow speeds, total Hicolumn densities, Hispatial concentrations, and central source galaxies (e.g., with Lyαline widths corresponding to those typical of active galactic nucleus or star-forming galaxies). We compute the spatial-frequency diffusion and the polarization of the Lyαphotons scattered by atomic hydrogen. Our scattering-only model reproduces the typical size of Lyαnebulae (∼100 kpc) at total column densitiesN_{H I}≥ 10²⁰cm⁻²and predicts a range of positive, flat, and negative polarization radial gradients. We also find two general classes of Lyαnebula morphologies: with and without bright cores. Cores are seen whenN_{H I}is low, i.e., when the central source is directly visible, and are associated with a polarization jump, a steep increase in the polarization radial profile just outside the halo center. Of all the parameters tested in our smooth or clumpy medium model,N_{H I}dominates the trends. The radial behaviors of the Lyαsurface brightness, spectral line shape, and polarization in the clumpy model with covering factorf_c≳ 5 approach those of the smooth model at the sameN_{H I}. A clumpy medium with highN_{H I}and lowf_c≲ 2 generates Lyαfeatures via scattering that the smooth model cannot: a bright core, symmetric line profile, and polarization jump.

    

   more » « less
5. 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 unobscured 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.

    

   more » « less