A Hero's Little Horse: Discovery of a Dissolving Star Cluster in Pegasus
  We report the discovery of an ultra-faint stellar system in the constellation
of Pegasus. This concentration of stars was detected by applying our
overdensity detection algorithm to the SDSS-DR10 and confirmed with deeper
photometry from the Dark Energy Camera at the 4-m Blanco telescope. The
best-fitting model isochrone indicates that this stellar system, Kim 1,
features an old (12 Gyr) and metal-poor ([Fe/H]$\sim-1.7$) stellar population
at a heliocentric distance of $19.8\pm0.9$ kpc. We measure a half-light radius
of $6.9\pm0.6$ pc using a Plummer profile. The small physical size and the
extremely low luminosity are comparable to the faintest known star clusters
Segue 3, Koposov 1 & 2, and Mu\~noz 1. However, Kim 1 exhibits a lower star
concentration and is lacking a well defined center. It also has an unusually
high ellipticity and irregular outer isophotes, which suggests that we are
seeing an intermediate mass star cluster being stripped by the Galactic tidal
field. An extended search for evidence of an associated stellar stream within
the 3 sqr deg DECam field remains inconclusive. The finding of Kim 1 is
consistent with current overdensity detection limits and supports the
hypothesis that there are still a substantial number of extreme low luminosity
star clusters undetected in the wider Milky Way halo.
