Baryonic Masses and Properties of Gaseous Satellite Galaxies

Abstract We present a sample of 127 gas-bearing dwarf galaxies around 56 late-type host galaxies within 30 Mpc using 21 cm H i data from the WALLABY, MHONGOOSE, and ALFALFA surveys. We characterize the environment of each dwarf galaxy based on its host galaxy halo and derive optical properties using the DESI Legacy Surveys for 110. The gaseous satellites span log ( M H I / M ⊙ ) = 5.8 − 9.7 and log ( M ⋆ / M ⊙ ) = 5.6 − 10.0 , with a median velocity line width of W 50 = 40 km s −1 , comparable to the Local Group gaseous dwarf galaxies. We assess the H i mass sensitivity of the data by injecting model dwarf galaxies and find M H I , lim ≈ 1 0 6.7 M ⊙ for WALLABY and M H I , lim ≈ 1 0 5.4 M ⊙ for MHONGOOSE at 10 Mpc. Our sample has lower average atomic gas fractions ( M H I / M ⋆ ) than previous gaseous dwarf samples in field and satellite environments, although this offset partly reflects differences in H i sensitivity. The abundance of gaseous satellites per host is low and increases with host mass: 0—2 for dwarf centrals and 0—5 to five for Milky Way–mass spiral hosts. These numbers are consistent with the Milky Way, M31, and star-forming satellite abundances from recent deep optical surveys. The inferred quenched fractions and gas-depleted satellites indicate that environmental quenching is effective in Milky Way–mass hosts, likely driven by gas stripping processes.