ANDROMEDA X, A NEW DWARF SPHEROIDAL SATELLITE OF M31: PHOTOMETRY

摘要

We report the discovery of Andromeda X, a new dwarf spheroidal satellite of M31, based on stellar photometry from the Sloan Digital Sky Survey. Using follow-up imaging data we have estimated its distance and other physical properties. We find that Andromeda X has a dereddened central surface brightness ofμ_(v,0) ～ 26.7 mag arcsec~(-2) and a total apparent magnitude of V_(tot) ～ 16.1, which at the derived distance modulus, (m — M)_0 ～ 24.12-24.34, yields an absolute magnitude of M_v～-8.1 ± 0.5; these values are quite comparable to those of Andromeda IX, a previously discovered low-luminosity M31 satellite. The discoveries of Andromeda X and of numerous other extremely faint satellites around M31 and the Milky Way in the past few years suggest that such objects may be plentiful in the Local Group.