MUSEQuBES: the column density, covering fraction, mass, and environmental dependence of cool Hi gas around low-redshift galaxies

Abstract

We investigate cool Hi gas traced by Lyman series absorption around 256 galaxies at z ≈ 0.48 (median stellar mass, log10 (M*/M⊙) = 8.7) using 15 background quasars (median impact parameter, D = 140 pkpc), as part of the MUSE Quasar-fields Blind Emitters Survey (MUSEQuBES). We find that the Hi column density (N(HI)) profile around isolated star-forming galaxies spanning ≈ 3 dex in M* is well described by a power law with slope ≈ -3 when expressed as a function of normalized impact parameter D/Rvir. The HI covering fraction (k) within the virial radius for log10(N(HI)/cm-2) = 14 is significantly lower in high-mass passive galaxies than in isolated star-forming galaxies. The k-profile of isolated star-forming galaxies suggests a characteristic size of the Hi-rich CGM of ≈ 1.5 Rvir across the stellar mass range. The mean Hi mass in the outer CGM (0.3–1 Rvir) increases with M*, ranging from ≈ 105.0 to 106.6 M⊙. The b-parameters of the strongest Hi components correlate and anticorrelate with specific star-formation rate (sSFR) and mass, respectively, with > 2σ significance. Broad Lyα absorbers (BLAs) with b>60 kms-1 are predominantly associated with high-mass galaxies, likely tracing the warm-hot phase of the CGM. The velocity centroids of Hi components indicate that absorbers at D< Rvir are largely consistent with being gravitationally bound to their galaxies, independent of stellar mass. Finally, leveraging ≈ 3000 galaxies from the wide-field Magellan follow-up of six MUSEQuBES fields, we find that non-isolated galaxies exhibit an Hi-rich environment extending roughly three times farther than in isolated counterparts.