Distances to 18 Dwarf Galaxies from the Arecibo Survey

Abstract

Based on archival Hubble Space Telescope images, we have performed stellar photometry for 18 dwarf galaxies. Branches of young and old stars are seen on the constructed Hertzsprung–Russell diagrams. Using the photometry of red giants and applying the TRGB method, we have determined accurate distances for all 18 galaxies for the first time. The galaxies AGC 238890 and AGC 747826 have minimum (D = 5.1 Mpc) and maximum (D = 12.0 Mpc) distances, respectively. The distances to the remaining galaxies lie within this range. Low-metallicity galaxies have been identified by measuring the color indices of the red giant branch: AGC 102728, AGC 198691, AGC 205590, AGC 223231, AGC 731921, and AGC 747826. We have determined the distance to AGC 198691 with a record low metallicity. Since AGC 223254, AGC 229053, AGC 229379, AGC 238890, AGC 731921, and AGC 742601 are projected onto the Virgo cluster of galaxies, the distances estimated by us together with the velocities of these galaxies measured previously at Arecibo can be used to refine the effect of galaxy infall to the Virgo cluster.