A Survey for Low Surface Brightness Galaxies around M31. I. The Newly Discovered Dwarf Andromeda V

Abstract

We present images and a color-magnitude diagram for And V, a new dwarf spheroidal companion to M31 that was found using a digital filtering technique applied to 1550 deg2 of the second Palomar Sky Survey. And V resolves into stars easily in follow-up 4 m V- and I-band images, from which we deduce a distance of 810 ± 45 kpc using the tip of the red giant branch method. Within the uncertainties, this distance is identical to the Population II distances for M31 and, combined with a projected separation of 112 kpc, provides strong support for a physical association between the two galaxies. There is no emission from And V detected in Hα, 1.4 GHz radio continuum, or IRAS bandpasses, and there is no young population seen in the color-magnitude diagram that might suggest that And V is an irregular. Thus, the classification as a new dwarf spheroidal member of the Local Group seems secure. With an extinction-corrected central surface brightness of 25.2 V mag arcsec-2, a mean metal abundance of [Fe/H] ≈ -1.5, and no evidence for upper asymptotic giant branch stars, And V resembles And I and III.