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1. Constraining the Size of the Circumgalactic Medium Using the Transverse Autocorrelation Function of C iv Absorbers in Paired Quasar Spectra

   https://doi.org/10.3847/1538-3881/ac764d  

   Mintz, Abby ; Rafelski, Marc ; Jorgenson, Regina A. ; Fumagalli, Michele ; Dutta, Rajeshwari ; Martin, Crystal L. ; Lusso, Elisabeta ; Rubin, Kate H. R. ; O’Meara, John M. ( July 2022 , The Astronomical Journal)

   The circumgalactic medium (CGM) plays a vital role in the formation and evolution of galaxies, acting as a lifeline between galaxies and the surrounding intergalactic medium. In this study, we leverage a unique sample of quasar pairs to investigate the properties of the CGM with absorption line tomography. We present a new sample of medium-resolution Keck/ESI, Magellan/MagE, and VLT/XSHOOTER spectra of 29 quasar pairs at redshift 2 <z< 3. We supplement the sample with additional spectra of 32 pairs from the literature, creating a catalog of 61 quasar pairs with angular separations between 1.″7 and 132.″9 and projected physical separations (r_⊥) between 14 kpc and 887 kpc. We construct a catalog of 906 metal-line absorption doublets of Civ(λλ1548, 1550) with equivalent widths ranging from 6 m Å ≤W_r,1550≤ 2053 m Å. The best-fit linear model to the log-space equivalent width frequency distribution ($\log f(W_r)=m\log (W_r)+b$) of the sample yields coefficients ofm= −1.44 ± 0.16 andb= −0.43 ± 0.16. To constrain the projected extent of Civ, we calculate the transverse autocorrelation function. The flattening of the autocorrelation function at lowr_⊥provides a lower limit for the coherence length of the metal enriched CGM—on the order ofmore »200h⁻¹comoving kpc. This physical size constraint allows us to refine our understanding of the metals in the CGM, where the extent of Civin the CGM depends on gas flows, feedback, timescale of metal injection and mixing, and the mass of the host galaxies.

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2. Discovery of a Damped Lyα Absorber Originating in a Spectacular Interacting Dwarf Galaxy Pair at z = 0.026

   https://doi.org/10.3847/2041-8213/ac5250  

   Boettcher, Erin ; Gupta, Neeraj ; Chen, Hsiao-Wen ; Chen, Mandy C. ; Józsa, Gyula I. G. ; Rudie, Gwen C. ; Cantalupo, Sebastiano ; Johnson, Sean D. ; Balashev, S. A. ; Combes, Françoise ; et al ( February 2022 , The Astrophysical Journal Letters)

   We present the discovery of neutral gas detected in both damped Lyαabsorption (DLA) and Hi21 cm emission outside of the stellar body of a galaxy, the first such detection in the literature. A joint analysis between the Cosmic Ultraviolet Baryon Survey and the MeerKAT Absorption Line Survey reveals an Hibridge connecting two interacting dwarf galaxies (log (M_star/M_⊙) = 8.5 ± 0.2) that host az= 0.026 DLA with log[N(Hi)/cm⁻²] = 20.60 ± 0.05 toward the QSO J2339−5523 (z_QSO= 1.35). At impact parameters ofd= 6 and 33 kpc, the dwarf galaxies have no companions more luminous than ≈0.05L_*within at least Δv= ±300 km s⁻¹andd≈ 350 kpc. The Hi21 cm emission is spatially coincident with the DLA at the 2σ–3σlevel per spectral channel over several adjacent beams. However, Hi21 cm absorption is not detected against the radio-bright QSO; if the background UV and radio sources are spatially aligned, the gas is either warm or clumpy (with a spin temperature to covering factor ratioT_s/f_c> 1880 K). Observations with VLT-MUSE demonstrate that theα-element abundance of the ionized interstellar medium (ISM) is consistent with the DLA (≈10% solar), suggesting that the neutral gas envelope is perturbed ISM gas. This study showcases the impact of dwarf–dwarfmore »interactions on the physical and chemical state of neutral gas outside of star-forming regions. In the SKA era, joint UV and Hi21 cm analyses will be critical for connecting the cosmic neutral gas content to galaxy environments.

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3. Multiphase ISM in the z = 5.7 Hyperluminous Starburst SPT 0346–52

   https://doi.org/10.3847/1538-4357/ac58f9  

   Litke, Katrina C. ; Marrone, Daniel P. ; Aravena, Manuel ; Béthermin, Matthieu ; Chapman, Scott C. ; Dong, Chenxing ; Hayward, Christopher C. ; Hill, Ryley ; Jarugula, Sreevani ; Malkan, Matthew A. ; et al ( April 2022 , The Astrophysical Journal)

   With Σ_SFR∼ 4200M_⊙yr⁻¹kpc⁻², SPT 0346–52 (z= 5.7) is the most intensely star-forming galaxy discovered by the South Pole Telescope. In this paper, we expand on previous spatially resolved studies, using ALMA observations of dust continuum, [Nii] 205μm, [Cii] 158μm, [Oi] 146μm, and undetected [Nii] 122μm and [Oi] 63μm emission to study the multiphase interstellar medium (ISM) in SPT 0346–52. We use pixelated, visibility-based lens modeling to reconstruct the source-plane emission. We also model the source-plane emission using the photoionization codecloudyand find a supersolar metallicity system. We calculateT_dust= 48.3 K andλ_peak= 80μm and see line deficits in all five lines. The ionized gas is less dense than comparable galaxies, withn_e< 32 cm⁻³, while ∼20% of the [Cii] 158μm emission originates from the ionized phase of the ISM. We also calculate the masses of several phases of the ISM. We find that molecular gas dominates the mass of the ISM in SPT 0346–52, with the molecular gas mass ∼4× higher than the neutral atomic gas mass and ∼100× higher than the ionized gas mass.
4. Physical Properties of Massive Compact Starburst Galaxies with Extreme Outflows

   https://doi.org/10.3847/1538-4357/ac2fa4  

   Perrotta, Serena ; George, Erin R. ; Coil, Alison L. ; Tremonti, Christy A. ; Rupke, David S. N. ; Davis, Julie D. ; Diamond-Stanic, Aleksandar M. ; Geach, James E. ; Hickox, Ryan C. ; Moustakas, John ; et al ( December 2021 , The Astrophysical Journal)

   We present results on the nature of extreme ejective feedback episodes and the physical conditions of a population of massive (M_*∼ 10¹¹M_⊙), compact starburst galaxies atz= 0.4–0.7. We use data from Keck/NIRSPEC, SDSS, Gemini/GMOS, MMT, and Magellan/MagE to measure rest-frame optical and near-IR spectra of 14 starburst galaxies with extremely high star formation rate surface densities (mean Σ_SFR∼ 2000M_⊙yr⁻¹kpc⁻²) and powerful galactic outflows (maximum speedsv₉₈∼ 1000–3000 km s⁻¹). Our unique data set includes an ensemble of both emission ([Oii]λλ3726,3729, Hβ, [Oiii]λλ4959,5007, Hα, [Nii]λλ6549,6585, and [Sii]λλ6716,6731) and absorption (Mgiiλλ2796,2803, and Feiiλ2586) lines that allow us to investigate the kinematics of the cool gas phase (T∼ 10⁴K) in the outflows. Employing a suite of line ratio diagnostic diagrams, we find that the central starbursts are characterized by high electron densities (mediann_e∼ 530 cm⁻³), and high metallicity (solar or supersolar). We show that the outflows are most likely driven by stellar feedback emerging from the extreme central starburst, rather than by an AGN. We also present multiple intriguing observational signatures suggesting that these galaxies may have substantial Lyman continuum (LyC) photon leakage, including weak [Sii]nebular emission lines. Our results imply that these galaxies may be captured in a short-lived phase of extrememore »star formation and feedback where much of their gas is violently blown out by powerful outflows that open up channels for LyC photons to escape.

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5. ALMA Reveals Extended Cool Gas and Hot Ionized Outflows in a Typical Star-forming Galaxy at Z = 7.13

   https://doi.org/10.3847/1538-4357/ac795b  

   Akins, Hollis B. ; Fujimoto, Seiji ; Finlator, Kristian ; Watson, Darach ; Knudsen, Kirsten K. ; Richard, Johan ; C. Bakx, Tom J. L. ; Hashimoto, Takuya ; Inoue, Akio K. ; Matsuo, Hiroshi ; et al ( July 2022 , The Astrophysical Journal)

   We present spatially resolved morphological properties of [CII] 158μm, [OIII] 88μm, dust, and rest-frame ultraviolet (UV) continuum emission for A1689-zD1, a strongly lensed, sub-L* galaxy atz= 7.13, by utilizing deep Atacama Large Millimeter/submillimeter Array (ALMA) and Hubble Space Telescope (HST) observations. While the [OIII] line and UV continuum are compact, the [CII] line is extended up to a radius ofr∼ 12 kpc. Using multi-band rest-frame far-infrared continuum data ranging from 52 to 400μm, we find an average dust temperature and emissivity index of$T_{\mathrm{dust}}={41}_{-14}^{+17}$K and$\beta ={1.7}_{-0.7}^{+1.1}$, respectively, across the galaxy. We find slight differences in the dust continuum profiles at different wavelengths, which may indicate that the dust temperature decreases with distance. We map the star formation rate (SFR) via IR and UV luminosities and determine a total SFR of 37 ± 1M_⊙yr⁻¹with an obscured fraction of 87%. While the [OIII] line is a good tracer of the SFR, the [CII] line shows deviation from the localL_[CII]-SFR relations in the outskirts of the galaxy. Finally, we observe a clear difference in the line profile between [CII] and [OIII], with significant residuals (∼5σ) in the [OIII] line spectrum after subtracting a single Gaussian model. This suggestsmore »a possible origin of the extended [CII] structure from the cooling of hot ionized outflows. The extended [CII] and high-velocity [OIII] emission may both contribute in part to the highL_[OIII]/L_[CII]ratios recently reported inz> 6 galaxies.

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