Discovery of New Dwarf Galaxy near The Isolated Spiral Galaxy NGC 6503
  We report the discovery of a new dwarf galaxy (NGC6503-d1) during the Subaru
extended ultraviolet (XUV) disk survey. It is a likely companion of the spiral
galaxy NGC6503. The resolved images, in B, V, R, i, and Halpha, show an
irregular appearance due to bright stars with underlying, smooth and unresolved
stellar emission. It is classified as the transition type (dIrr/dSph). Its
structural properties are similar to those of the dwarfs in the Local Group,
with a V absolute magnitude ~ -10.5, half-light radius ~400 pc, and central
surface brightness ~25.2. Despite the low stellar surface brightness
environment, one HII region was detected, though its Halpha luminosity is low,
indicating an absence of any appreciable O-stars at the current epoch. The
presence of multiple stellar populations is indicated by the color-magnitude
diagram of ~300 bright resolved stars and the total colors of the dwarf, with
the majority of its total stellar mass ~4x10^6 Msun in an old stellar
population.
