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1. Spatially Resolved Galactic Winds at Cosmic Noon: Outflow Kinematics and Mass Loading in a Lensed Star-forming Galaxy at z = 1.87

   https://doi.org/10.3847/1538-4357/ada95b  

   G_C, Keerthi Vasan; Jones, Tucker; Shajib, Anowar J; Rhoades, Sunny; Chen, Yuguang; Sanders, Ryan L; Stark, Daniel P; Ellis, Richard S; Leethochawalit, Nicha; Kacprzak, Glenn G; et al (March 2025, The Astrophysical Journal)

   We study the spatially resolved outflow properties of CSWA13, an intermediate-mass (M_* = 10⁹M_⊙), gravitationally lensed star-forming galaxy atz= 1.87. We use Keck/KCWI to map outflows in multiple rest-frame UV interstellar medium (ISM) absorption lines, along with fluorescent Siii* emission, and nebular emission from Ciii] tracing the local systemic velocity. The spatial structure of the outflow velocity mirrors that of the nebular kinematics, which we interpret to be a signature of a young galactic wind that is pressurizing the ISM of the galaxy but is yet to burst out. From the radial extent of Siii* emission, we estimate that the outflow is largely encapsulated within 3.5 kpc. We explore the geometry (e.g., patchiness) of the outflow by measuring the covering fraction at different velocities, finding that the maximum covering fraction is at velocitiesv ≃ −150 km s⁻¹. Using the outflow velocity (v_out), radius (R), column density (N), and solid angle (Ω) based on the covering fraction, we measure the mass-loss rate $\log {\dot{m}}_{\mathrm{out}}/\left(M_{\odot }{\text{yr}}^{-1}\right)=1.73\pm 0.23$and mass loading factor $\log \eta =0.04\pm 0.34$for the low-ionization outflowing gas in this galaxy. These values are relatively large and the bulk of the outflowing gas is moving with speeds less than the escape velocity of the galaxy halo, suggesting that the majority of the outflowing mass will remain in the circumgalactic medium and/or recycle back into the galaxy. The results support a picture of high outflow rates transporting mass and metals into the inner circumgalactic medium, providing the gas reservoir for future star formation. 

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2. 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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3. On the Metallicities and Kinematics of the Circumgalactic Media of Damped Lyα Systems at z ∼ 2.5*

   https://doi.org/10.3847/1538-4357/acd34a  

   Urbano_Stawinski, Stephanie_M; Rubin, Kate_H_R; Prochaska, J_Xavier; Hennawi, Joseph_F; Tejos, Nicolas; Fumagalli, Michele; Rafelski, Marc; Kirby, Evan_N; Lusso, Elisabeta; Hafen, Zachary (July 2023, The Astrophysical Journal)

   Abstract We use medium- and high-resolution spectroscopy of close pairs of quasars to analyze the circumgalactic medium (CGM) surrounding 32 damped Lyαabsorption systems (DLAs). The primary quasar sightline in each pair probes an intervening DLA in the redshift range 1.6 <z_abs< 3.5, such that the secondary sightline probes absorption from Lyαand a large suite of metal-line transitions (including Oi, Cii, Civ, Siii, and Siiv) in the DLA host galaxy’s CGM at transverse distances 24 kpc ≤R_⊥≤ 284 kpc. Analysis of Lyαin the CGM sightlines shows an anticorrelation betweenR_⊥and Hicolumn density (N_HI) with 99.8% confidence, similar to that observed around luminous galaxies. The incidences of Ciiand SiiiwithN> 10¹³cm⁻²within 100 kpc of DLAs are larger by 2σthan those measured in the CGM of Lyman break galaxies (C_f(N_CII) > 0.89 and ${\mathrm{C}}_f\left(N_{\mathrm{Si}\mathrm{II}}\right)={0.75}_{-0.17}^{+0.12}$). Metallicity constraints derived from ionic ratios for nine CGM systems with negligible ionization corrections andN_HI> 10^18.5cm⁻²show a significant degree of scatter (with metallicities/limits across the range $-2.06\lesssim \log Z/Z_{\odot }\lesssim -0.75$), suggesting inhomogeneity in the metal distribution in these environments. Velocity widths of Civλ1548 and low-ionization metal species in the DLA versus CGM sightlines are strongly (>2σ) correlated, suggesting that they trace the potential well of the host halo overR_⊥≲ 300 kpc scales. At the same time, velocity centroids for Civλ1548 differ in DLA versus CGM sightlines by >100 km s⁻¹for ∼50% of velocity components, but few components have velocities that would exceed the escape velocity assuming dark matter host halos of ≥10¹²M_⊙. 

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4. Asymmetries and Circumstellar Interaction in the Type II SN 2024bch

   https://doi.org/10.3847/1538-4357/ada555  

   Andrews, Jennifer E; Shrestha, Manisha; Bostroem, K Azalee; Dong_董, Yize 一泽; Pearson, Jeniveve; Fausnaugh, M M; Sand, David J; Valenti, S; Ravi, Aravind P; Hoang, Emily; et al (February 2025, The Astrophysical Journal)

   Abstract We present a comprehensive multi-epoch photometric and spectroscopic study of SN 2024bch, a nearby (19.9 Mpc) Type II supernova (SN) with prominent early high-ionization emission lines. Optical spectra from 2.8 days after the estimated explosion reveal narrow lines of H i, He ii, C iv, and N ivthat disappear by day 6. High-cadence photometry from the ground and Transiting Exoplanet Survey Satellite show that the SN brightened quickly and reached a peakM_V ~ −17.8 mag within a week of explosion, and late-time photometry suggests a⁵⁶Ni mass of 0.050M_⊙. High-resolution spectra from days 7.9 and 43 trace the unshocked circumstellar medium (CSM) and indicate a wind velocity of 30–40 km s⁻¹, a value consistent with a red supergiant (RSG) progenitor. Comparisons between models and the early spectra suggest a pre-SN mass-loss rate of $\dot{M}~10^{-3}–10^{-2}{M}_{\odot }{\mathrm{yr}}^{-1}$, which is too high to be explained by quiescent mass loss from RSGs, but is consistent with some recent measurements of similar SNe. Persistent blueshifted H iand [O i] emission lines seen in the optical and near-IR spectra could be produced by asymmetries in the SN ejecta, while the multicomponent Hαmay indicate continued interaction with an asymmetric CSM well into the nebular phase. SN 2024bch provides another clue to the complex environments and mass-loss histories around massive stars. 

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5. The RESOLVE and ECO G3 Initiative: Drivers of H i Content and X-Ray Emission in Galaxy Groups

   https://doi.org/10.3847/1538-4357/adc395  

   Hutchens, Zackary L; Kannappan, Sheila J; Hess, Kelley M; Baker, Andrew J; Sun, Ming; Carr, Derrick S; Eckert, Kathleen D; Stark, David V (May 2025, The Astrophysical Journal)

   Abstract Adding to the RESOLVE and ECO Gas in Galaxy Groups (G3) initiative, we examine possible drivers of group-integrated Hi-to-halo mass ratios (M_HI,grp/M_halo) and group X-ray emission, including group halo mass (M_halo), virialization as probed by crossing time (t_cross), presence of active galactic nuclei (AGN), and group-integrated fractional stellar mass growth rate (FSMGR_grp). G3 groups spanM_halo= 10¹¹−10^14.5M_⊙with comprehensive Higas and AGN information, which we combine with X-ray stacking of ROSAT All-Sky data. We detect hot gas emission exceeding AGN and X-ray binary backgrounds confidently forM_halo= 10^12.6−10¹⁴M_⊙and unambiguously forM_halo> 10¹⁴M_⊙, reflecting an inverse dependence ofM_HI,grp/M_haloand hot gas emission on halo mass. At fixed halo mass,M_HI,grp/M_halotransitions to greater spread belowt_cross∼ 2 Gyr. Dividing groups across this transition, lower-t_crossgroups show elevated X-ray emission compared to higher-t_crossgroups forM_halo> 10^13.3M_⊙, but this trend reverses forM_halo= 10^12.6−10^13.3M_⊙. Additionally, AGN-hosting halos belowM_halo∼ 10^12.1M_⊙exhibit a broad, ∼0.25 dex deep valley inM_HI,grp/M_halocompared to non-AGN-hosting halos with correspondingly reduced FSMGR_grp. When diluted by non-AGN-hosting halos, this valley becomes shallower and narrower, falling roughly between $M_{\mathrm{halo}}={10}^{11.5}{M}_{\odot }$and $M_{\mathrm{halo}}={10}^{12.1}{M}_{\odot }$in the overallM_HI,grp/M_halovs.M_halorelation. We may also detect a second, less easily interpreted valley atM_halo∼ 10¹³M_⊙. Neither valley matches theoretical predictions of a deeper valley located at or above $M_{\mathrm{halo}}={10}^{12.1}{M}_{\odot }$. 

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