MUSEQuBES: The Column Density, Covering Fraction, Mass, and Environmental Dependence of Cool HI Gas Around Low-Redshift Galaxies

Sayak Dutta, Sowgat Muzahid, Joop Schaye, Sean Johnson, Nicolas F. Bouche, Ramona Augustin, Sebastiano Cantalupo, Hsiao-Wen Chen, Martin Wendt

arXiv7/29/2025·DOI·Read paper

Abstract

We investigate cool HI gas traced by Lyman series absorption around 256 galaxies at z ~ 0.48 (median stellar mass, log10(M*/Msun) = 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 stellar mass 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 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 are predominantly associated with high-mass galaxies, likely tracing the warm-hot phase of the CGM. The velocity centroids of H i 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.

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