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 in the vicinity of 256 galaxies (median stellar mass, log10(M*/Msun) = 8.7 and median redshift, z = 0.48) using 15 background quasars (median impact parameter, D ~ 140 physical kpc (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, which span ~ 3 dex in stellar mass, is well described by a power law with a slope of ~ -2.3 when expressed as a function of the normalized impact parameter, D/Rvir. The HI covering fraction (k) within the virial radius, for a threshold of log10(N(HI)/cm^{-2}) = 14, is significantly lower for high-mass passive galaxies compared to their isolated, star-forming counterparts. The k-profile of isolated, star-forming galaxies suggests a characteristic size of the HI-rich CGM of ~ 1.5 Rvir, consistently across the stellar mass range. The mean HI mass in the outer CGM (0.3-1 Rvir ) increases with stellar mass, ranging from ~ 10^{5} to 10^{6.6} Msun. The b-parameters of the strongest HI components correlate and anti-correlate with specific star-formation rate (sSFR) and mass, respectively, with > 2 sigma significance. Broad Lya absorbers (BLAs) with b > 60 km s^{-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 the absorbers at D < Rvir are predominantly consistent with being gravitationally bound to their associated galaxy, regardless of stellar mass. Finally, leveraging ~3000 galaxies with spectroscopic redshifts from the wide-field Magellan follow-up of six MUSEQuBES fields, we find that non-isolated galaxies exhibit an HI-rich environment that extends approximately three times further than for their isolated counterparts.