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

摘要

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 MV = -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.