Two New Milky Way Companions

Abstract

We discuss the detection limits and current status of a uniform survey of SDSS I for ultra-faint Milky Way dwarf galaxies. We present the properties of two new, low surface brightness Milky Way companions discovered as a result of this survey. One of these companions is the Ursa Major dwarf, the newest dwarf spheroidal companion to the Milky Way and the lowest luminosity galaxy yet known. Ursa Major is about 100 kpc away and is similar to Sextans, but with roughly an order of magnitude fewer stars. The other companion, SDSSJ1049+5103, lies $\sim$ 50 kpc away. Its stellar distribution suggests that it may be undergoing tidal stripping. This companion is extremely faint (M$_V$ $\sim$ -3) but has a large half-light size for its luminosity. It is therefore unclear whether it is a globular cluster or a dwarf galaxy.

10 pages. Proceedings of "Resolved Stellar Populations". Held in Cancun, Mexico, 18-22 Apr 2005, ASP Conference Series eds D. Valls-Gabaud & M. Chavez