ANDROMEDA XXVIII: A DWARF GALAXY MORE THAN 350 kpc FROM ANDROMEDA

We report the discovery of a new dwarf galaxy, Andromeda XXVIII, using data from the recently released Sloan Digital Sky Survey Data Release 8. The galaxy is a likely satellite of Andromeda, and, at a separation of 365(-1)(+17) kpc, would be one of the most distant of Andromeda's satellites. Its heliocentric distance is 650(-80)(+150) kpc, and analysis of its structure and luminosity shows that it has an absolute magnitude of M-V = -8.5(-1.0)(+0.4) and half-light radius of r(h) = 210(-50)(+60) pc, similar to many other faint Local Group dwarfs. With presently available imaging we are unable to determine whether there is ongoing or recent star formation, which prevents us from classifying it as a dwarf spheroidal or a dwarf irregular.