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1. A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): JWST Discovers an Overdensity around a Metal Absorption-selected Galaxy at z ∼ 5.5

   https://doi.org/10.3847/2041-8213/acfee3  

   Wu, Yunjing; Wang, Feige; Cai, Zheng; Fan, Xiaohui; Finlator, Kristian; Yang, Jinyi; Hennawi, Joseph F; Sun, Fengwu; Champagne, Jaclyn B; Lin, Xiaojing; et al (October 2023, The Astrophysical Journal Letters)

   Abstract The launch of JWST opens a new window for studying the connection between metal-line absorbers and galaxies at the end of the Epoch of Reionization. Previous studies have detected absorber–galaxy pairs in limited quantities through ground-based observations. To enhance our understanding of the relationship between absorbers and their host galaxies atz> 5, we utilized the NIRCam wide-field slitless spectroscopy to search for absorber-associated galaxies by detecting their rest-frame optical emission lines (e.g., [OIII] + Hβ). We report the discovery of a Mgii-associated galaxy atz= 5.428 using data from the JWST ASPIRE program. The Mgiiabsorber is detected on the spectrum of quasar J0305–3150 with a rest-frame equivalent width of 0.74 Å. The associated galaxy has an [OIII] luminosity of 10^42.5erg s⁻¹with an impact parameter of 24.9 pkpc. The joint Hubble Space Telescope–JWST spectral energy distribution (SED) implies a stellar mass and star formation rate ofM_*≈ 10^8.8M_⊙, star-formation rate  ≈ 10M_⊙yr⁻¹. Its [OIII] equivalent width and stellar mass are typical of [OIII] emitters at this redshift. Furthermore, connecting the outflow starting time to the SED-derived stellar age, the outflow velocity of this galaxy is ∼300 km s⁻¹, consistent with theoretical expectations. We identified six additional [OIII] emitters with impact parameters of up to ∼300 pkpc at similar redshifts (∣dv∣ < 1000 km s⁻¹). The observed number is consistent with that in cosmological simulations. This pilot study suggests that systematically investigating the absorber–galaxy connection within the ASPIRE program will provide insights into the metal-enrichment history in the early Universe. 

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2. The CGM ² Survey: Circumgalactic O vi from Dwarf to Massive Star-forming Galaxies

   https://doi.org/10.3847/1538-4357/ac450c  

   Tchernyshyov, Kirill; Werk, Jessica K.; Wilde, Matthew C.; Prochaska, J. Xavier; Tripp, Todd M.; Burchett, Joseph N.; Bordoloi, Rongmon; Howk, J. Christopher; Lehner, Nicolas; O’Meara, John M.; et al (March 2022, The Astrophysical Journal)

   Abstract We combine 126 new galaxy-Oviabsorber pairs from the CGM²survey with 123 pairs drawn from the literature to examine the simultaneous dependence of the column density of Oviabsorbers (N_OVI) on galaxy stellar mass, star-formation rate, and impact parameter. The combined sample consists of 249 galaxy-Oviabsorber pairs coveringz= 0–0.6, with host galaxy stellar massesM_*= 10^7.8–10^11.2M_⊙and galaxy-absorber impact parametersR_⊥= 0–400 proper kiloparsecs. In this work, we focus on the variation ofN_OVIwith galaxy mass and impact parameter among the star-forming galaxies in the sample. We find that the averageN_OVIwithin one virial radius of a star-forming galaxy is greatest for star-forming galaxies withM_*= 10^9.2–10¹⁰M_⊙. Star-forming galaxies withM_*between 10⁸and 10^11.2M_⊙can explain most Ovisystems with column densities greater than 10^13.5cm⁻². Sixty percent of the Ovimass associated with a star-forming galaxy is found within one virial radius, and 35% is found between one and two virial radii. In general, we find that some departure from hydrostatic equilibrium in the CGM is necessary to reproduce the observed Oviamount, galaxy mass dependence, and extent. Our measurements serve as a test set for CGM models over a broad range of host galaxy masses. 

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3. The Cosmic Ultraviolet Baryon Survey (CUBS). IX. The Enriched Circumgalactic and Intergalactic Medium Around Star-forming Field Dwarf Galaxies Traced by O vi Absorption

   https://doi.org/10.3847/1538-4357/ad7b0a  

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

   Abstract The shallow potential wells of star-forming dwarf galaxies make their surrounding circumgalactic and intergalactic medium (CGM/IGM) sensitive laboratories for studying the inflows and outflows thought to regulate galaxy evolution. We present new absorption-line measurements in quasar sight lines, probing within projected distances of <300 kpc from 91 star-forming field dwarf galaxies with a median stellar mass of $\log M_{\star }/M_{\odot }\approx 8.3$at 0.077 <z< 0.73, from the Cosmic Ultraviolet Baryon Survey (CUBS). In this redshift range, the CUBS quasar spectra cover a suite of transitions including Hi, low, and intermediate metal ions (e.g., Cii, Siii, Ciii, and Siiii), and highly ionized Ovi. This CUBS-Dwarfs survey enables constraints with samples nine times larger than past dwarf CGM/IGM studies with similar ionic coverage. We find that low and intermediate ionization metal absorption is rare around dwarf galaxies, consistent with previous surveys of local dwarfs. In contrast, highly ionized Oviis commonly observed in sight lines that pass within the virial radius of a dwarf, and Ovidetection rates are nonnegligible at projected distances of 1−2× the virial radius. Based on these measurements, we estimate that the Ovi-bearing phase of the CGM/IGM accounts for a dominant share of the metal budget of dwarf galaxies. The absorption kinematics suggest that a relatively modest fraction of the Ovi-bearing gas is formally unbound. Together, these results imply that low-mass systems atz≲ 1 effectively retain a substantial fraction of their metals within the nearby CGM and IGM. 

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4. MUSE–ALMA Haloes – IX. Morphologies and stellar properties of gas-rich galaxies

   https://doi.org/10.1093/mnras/stad2134  

   Karki, Arjun; Kulkarni, Varsha_P; Weng, Simon; Péroux, Céline; Augustin, Ramona; Hayes, Matthew; Ayromlou, Mohammadreza; Kacprzak, Glenn_G; Howk, J_Christopher; Szakacs, Roland; et al (July 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Understanding how galaxies interact with the circumgalactic medium (CGM) requires determining how galaxies’ morphological and stellar properties correlate with their CGM properties. We report an analysis of 66 well-imaged galaxies detected in Hubble Space Telescope and Very Large Telescope MUSE observations and determined to be within ±500 km s−1 of the redshifts of strong intervening quasar absorbers at 0.2 ≲ z ≲ 1.4 with H i column densities $$N_{\rm H I} \gt 10^{18}\, \rm cm^{-2}$$. We present the geometrical properties (Sérsic indices, effective radii, axis ratios, and position angles) of these galaxies determined using galfit. Using these properties along with star formation rates (SFRs, estimated using the H α or [O ii] luminosity) and stellar masses (M* estimated from spectral energy distribution fits), we examine correlations among various stellar and CGM properties. Our main findings are as follows: (1) SFR correlates well with M*, and most absorption-selected galaxies are consistent with the star formation main sequence of the global population. (2) More massive absorber counterparts are more centrally concentrated and are larger in size. (3) Galaxy sizes and normalized impact parameters correlate negatively with NHI, consistent with higher NHI absorption arising in smaller galaxies, and closer to galaxy centres. (4) Absorption and emission metallicities correlate with M* and specific SFR, implying metal-poor absorbers arise in galaxies with low past star formation and faster current gas consumption rates. (5) SFR surface densities of absorption-selected galaxies are higher than predicted by the Kennicutt–Schmidt relation for local galaxies, suggesting a higher star formation efficiency in the absorption-selected galaxies. 

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5. The Bimodal Absorption System Imaging Campaign (BASIC). I. A Dual Population of Low-metallicity Absorbers at z < 1

   https://doi.org/10.3847/1538-4357/acb047  

   Berg, Michelle_A; Lehner, Nicolas; Howk, J_Christopher; O’Meara, John_M; Schaye, Joop; Straka, Lorrie_A; Cooksey, Kathy_L; Tripp, Todd_M; Prochaska, J_Xavier; Oppenheimer, Benjamin_D; et al (February 2023, The Astrophysical Journal)

   Abstract The bimodal absorption system imaging campaign (BASIC) aims to characterize the galaxy environments of a sample of 36 Hi-selected partial Lyman limit systems (pLLSs) and Lyman limit systems (LLSs) in 23 QSO fields atz≲ 1. These pLLSs/LLSs provide a unique sample of absorbers with unbiased and well-constrained metallicities, allowing us to explore the origins of metal-rich and low-metallicity circumgalactic medium (CGM) atz< 1. Here we present Keck/KCWI and Very Large Telescope/MUSE observations of 11 of these QSO fields (19 pLLSs) that we combine with Hubble Space Telescope/Advanced Camera for Surveys imaging to identify and characterize the absorber-associated galaxies at 0.16 ≲z≲ 0.84. We find 23 unique absorber-associated galaxies, with an average of one associated galaxy per absorber. For seven absorbers, all with <10% solar metallicities, we find no associated galaxies with $\log M_{\star }\gtrsim 9.0$withinρ/R_virand ∣Δv∣/v_esc≤ 1.5 with respect to the absorber. We do not find any strong correlations between the metallicities or Hicolumn densities of the gas and most of the galaxy properties, except for the stellar mass of the galaxies: the low-metallicity ([X/H] ≤ −1.4) systems have a probability of ${0.39}_{-0.15}^{+0.16}$for having a host galaxy with $\log M_{\star }\ge 9.0$withinρ/R_vir≤ 1.5, while the higher metallicity absorbers have a probability of ${0.78}_{-0.13}^{+0.10}$. This implies metal-enriched pLLSs/LLSs atz< 1 are typically associated with the CGM of galaxies with $\log M_{\star }>9.0$, whereas low-metallicity pLLSs/LLSs are found in more diverse locations, with one population arising in the CGM of galaxies and another more broadly distributed in overdense regions of the universe. Using absorbers not associated with galaxies, we estimate the unweighted geometric mean metallicity of the intergalactic medium to be [X/H] ≲ −2.1 atz< 1, which is lower than previously estimated. 

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