The Gas Content and Stripping of Local Group Dwarf Galaxies

The gas content of the complete compilation of Local Group dwarf galaxies (119 within 2 Mpc) is presented using H i survey data. Within the virial radius of the Milky Way (224 kpc here), 53 of 55 dwarf galaxies are devoid of gas to limits of M (H i ) < 10(4) M (circle dot). Within the virial radius of M31 (266 kpc), 27 of 30 dwarf galaxies are devoid of gas (with limits typically M (circle dot)). Beyond the virial radii of the Milky Way and M31, the majority of the dwarf galaxies have detected H i gas and H i masses higher than the limits. When the relationship between gas content and distance is investigated using a Local Group virial radius, more of the nondetected dwarf galaxies are within this radius (85 +/- 1 of the 93 nondetected dwarf galaxies) than within the virial radii of the Milky Way and M31. Using the Gaia proper-motion measurements available for 38 dwarf galaxies, the minimum gas density required to completely strip them of gas is calculated. Halo densities between 10(-5) and 5 x 10(-4) cm(-3) are typically required for instantaneous stripping at perigalacticon. When compared to halo density with radius expectations from simulations and observations, 80% of the dwarf galaxies with proper motions are consistent with being stripped by ram pressure at Milky Way pericenter. The results suggest that a diffuse gaseous galactic halo medium is important in quenching dwarf galaxies, and that a Local Group medium also potentially plays a role.

Automated summary

The study presents the gas content of Local Group dwarf galaxies using H i survey data, revealing that most dwarf galaxies within the virial radii of the Milky Way and M31 lack gas. More of the undetected dwarf galaxies are found within the Local Group virial radius. The results suggest that halo densities play a significant role in stripping dwarf galaxies of gas.