A Survey for Low Surface Brightness Galaxies Around M31. II. The Newly Discovered Dwarf Andromeda VI

Abstract

We present B-, V-, and I-band images, as well as an H alpha image, of And VI. This is the second newly identified dwarf spheroidal (dSph) companion to M31 found using a digital filtering technique applied to the second Palomar Sky Survey for which 1550 square degrees now have been surveyed. And VI was confirmed to be a nearby dSph galaxy when it resolved into stars easily with a short 4-m V-band exposure. Sub-arcsec images taken at the Kitt Peak WIYN 3.5-m telescope provided (I,V-I) and (V,B-V) color-magnitude diagrams that yield a distance of 775 +/- 35 kpc using the tip of the red giant branch method, and a mean metallicity of [Fe/H] = -1.58 +/- 0.20 with a dispersion of approximately 0.3 dex. And VI has a galactocentric distance of approximately 271 kpc and an absolute V magnitude of -11.3. All observed properties of And VI are consistent with its classification as a dSph companion to M31. Despite the recent identification of the And V, And VI, and Cas dwarfs, the Local Group luminosity function remains highly deficient in faint galaxies relative both to CDM simulations of its formation, and to the luminosity functions for richer clusters of galaxies.