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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)

   Abstract 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 ( $\log f\left(W_r\right)=m\log \left(W_r\right)+b$) 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 of 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. A Massive H i -absorption-selected Galaxy at z  ≈ 2.356

   https://doi.org/10.3847/2041-8213/adb83d  

   Kaur, B; Kanekar, N; Neeleman, M; Zhu, Y; Prochaska, J X; Rafelski, M; Becker, G (March 2025, The Astrophysical Journal Letters)

   Abstract We use the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array to detect CO(1–0), CO(3–2), and rest-frame 349 GHz continuum emission from an Hi-selected galaxy, DLA1020+2733g, atz ≈ 2.3568 in the field of thez= 2.3553 damped Lyαabsorber (DLA) toward QSO J1020+2733. The VLA CO(1–0) detection yields a molecular gas mass of (2.84 ± 0.42) × 10¹¹ × (α_CO/4.36)M_⊙, the largest ever measured in an Hi-selected galaxy. The DLA metallicity is +0.28 ± 0.16, from the Zniiλ2026 absorption line detected in a Keck Echellette Spectrograph and Imager spectrum. This continues the trend of high-metallicity DLAs being frequently associated with massive galaxies. We obtain a star formation rate (SFR) of ≲400M_⊙yr⁻¹from the rest-frame 349 GHz continuum emission and a relatively long molecular gas depletion timescale of ≳0.6 Gyr. The excitation of theJ= 3 rotational level is subthermal, with $r_{31}\equiv L{\prime }_{\mathrm{CO}(3-2)}/L{\prime }_{\mathrm{CO}(1-0)}=0.513\pm 0.081$, suggesting that DLA1020+2733g has a low SFR surface density. The large velocity spread of the CO lines, ≈500 km s⁻¹, and the long molecular gas depletion timescale suggest that DLA1020+2733g is likely to be a cold rotating-disk galaxy. 

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3. Braving the Storm: Quantifying Disk-wide Ionized Outflows in the Large Magellanic Cloud with ULLYSES

   https://doi.org/10.3847/1538-4357/ad64d2  

   Zheng_郑, Yong_永; Tchernyshyov, Kirill; Olsen, Knut; Choi, Yumi; Bustard, Chad; Roman-Duval, Julia; Zhu, Robert; Di_Teodoro, Enrico_M; Werk, Jessica; Putman, Mary; et al (October 2024, The Astrophysical Journal)

   Abstract The Large Magellanic Cloud (LMC) is home to many Hiiregions, which may lead to significant outflows. We examine the LMC’s multiphase gas (T∼10^4-5K) in Hi, Sii, Siiv, and Civusing 110 stellar sight lines from the Hubble Space Telescope’s Ultraviolet Legacy Library of Young Stars as Essential Standards program. We develop a continuum fitting algorithm based on the concept of Gaussian process regression and identify reliable LMC interstellar absorption overv_helio= 175–375 km s⁻¹. Our analyses show disk-wide ionized outflows in Siivand Civacross the LMC with bulk velocities of ∣v_{out, bulk}∣ ∼ 20–60 km s⁻¹, which indicates that most of the outflowing mass is gravitationally bound. The outflows’ column densities correlate with the LMC’s star formation rate surface densities (Σ_SFR), and the outflows with higher Σ_SFRtend to be more ionized. Considering outflows from both sides of the LMC as traced by Civ, we conservatively estimate a total outflow rate of ${\dot{M}}_{\mathrm{out}}\gtrsim 0.03M_{\odot }{\mathrm{yr}}^{-1}$and a mass-loading factor ofη≳ 0.15. We compare the LMC’s outflows with those detected in starburst galaxies and simulation predictions, and find a universal scaling relation of $\mid v_{\mathrm{out},\mathrm{bulk}}\mid \propto {\mathrm{\Sigma }}_{\mathrm{SFR}}^{0.23}$over a wide range of star-forming conditions (Σ_SFR∼ 10^−4.5–10²M_⊙yr⁻¹kpc⁻²). Lastly, we find that the outflows are corotating with the LMC’s young stellar disk and the velocity field does not seem to be significantly impacted by external forces; we thus speculate on the existence of a bow shock leading the LMC, which may have shielded the outflows from ram pressure as the LMC orbits the Milky Way. 

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4. The Cosmic Ultraviolet Baryon Survey (CUBS). VII. On the Warm-hot Circumgalactic Medium Probed by O vi and Ne viii at 0.4 ≲ z ≲ 0.7

   https://doi.org/10.3847/1538-4357/ad410b  

   Qu, Zhijie; Chen, Hsiao-Wen; Johnson, Sean D; Rudie, Gwen C; Zahedy, Fakhri S; DePalma, David; Schaye, Joop; Boettcher, Erin T; Cantalupo, Sebastiano; Chen, Mandy C; et al (June 2024, The Astrophysical Journal)

   Abstract This paper presents a newly established sample of 103 unique galaxies or galaxy groups at 0.4 ≲z≲ 0.7 from the Cosmic Ultraviolet Baryon Survey (CUBS) for studying the warm-hot circumgalactic medium (CGM) probed by both Oviand Neviiiabsorption. The galaxies and associated neighbors are identified at <1 physical Mpc from the sightlines toward 15 CUBS QSOs atz_QSO≳ 0.8. A total of 30 galaxies or galaxy groups exhibit associated Oviλλ1031, 1037 doublet absorption within a line-of-sight velocity interval of ±250 km s⁻¹, while the rest show no trace of Ovito a detection limit of $\log N_{\mathrm{OVI}}/{\mathrm{cm}}^{-2}\approx 13.7$. Meanwhile, only five galaxies or galaxy groups exhibit the Neviiiλλ770, 780 doublet absorption, down to a limiting column density of $\log N_{\mathrm{NeVIII}}/{\mathrm{cm}}^{-2}\approx 14.0$. These Ovi- and Neviii-bearing halos reside in different galaxy environments with stellar masses ranging from $\log M_{\mathrm{star}}/M_{\odot }\approx 8$to ≈11.5. The warm-hot CGM around galaxies of different stellar masses and star formation rates exhibits different spatial profiles and kinematics. In particular, star-forming galaxies with $\log M_{\mathrm{star}}/M_{\odot }\approx 9–11$show a significant concentration of metal-enriched warm-hot CGM within the virial radius, while massive quiescent galaxies exhibit flatter radial profiles of both column densities and covering fractions. In addition, the velocity dispersion of Oviabsorption is broad withσ_υ> 40 km s⁻¹for galaxies of $\log M_{\mathrm{star}}/M_{\odot }>9$within the virial radius, suggesting a more dynamic warm-hot halo around these galaxies. Finally, the warm-hot CGM probed by Oviand Neviiiis suggested to be the dominant phase in sub-L* galaxies with $\log M_{\mathrm{star}}/M_{\odot }\approx 9–10$based on their high ionization fractions in the CGM. 

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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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