Addition of the Local Volume sample of galaxies from the FAST HI survey

Abstract

We report the discovery of 20 new dwarf galaxies in the Local Volume identified as optical counterparts to the Five-hundred-meter Aperture Spherical radio Telescope (FAST) All Sky HI Survey (FASHI) sources. The galaxies have a median stellar mass of 7.8 × 106 M⊙ and a median HI mass of 1.0 × 107 M⊙. Most of them are field galaxies, while three are probable members of the M 101 and M 106 groups. We also found seven FASHI radio sources to be probable dark HI clouds in nearby groups. Together with four other known HI clouds in the local groups, their mean-square radial velocity difference of 49 km s−1 with respect to the host galaxies yields an average total mass of (2.7 ± 1.0)×1011 M⊙ for these groups on the projected scale of 90 kpc.