KIM 3: AN ULTRA-FAINT STAR CLUSTER IN THE CONSTELLATION OF CENTAURUS
Dongwon Kim, Helmut Jerjen, Dougal Mackey, Gary S. Da Costa, Antonino P. Milone
We report the discovery of an ultra-faint star cluster in the constellation of Centaurus. This new stellar system, Kim 3, features a half light radius of r_h=2.29^+1.28_-0.52 pc and a total luminosity of M_V=+0.7±0.3. Approximately 26 stars are identified as candidate member stars down to four magnitudes below the main-sequence turn-off, which makes Kim 3 the least luminous star cluster known to date. The compact physical size and extreme low luminosity place it close to faint star clusters in
... he size-luminosity plane. The stellar population of Kim 3 appears to be relatively young (9.5^+3.0_-1.7 Gyr) and metal-poor ([Fe/H]=-1.6^+0.45_-0.30) at a heliocentric distance of 15.14^+1.00_-0.28 kpc. The cluster lacks a well-defined center and a small but prominent group of stars consistent with the Kim 3 isochrone is present approximately 9.7 pc in projection south of the cluster center. Both are signs of the cluster being in the final stage of tidal disruption.