IRS 16 SW: A new comoving group of young stars in the central parsec of the Milky Way

One of the most perplexing problems associated with the supermassive black hole at the center of our Galaxy is the origin of the young stars in its close vicinity. Using proper-motion measurements and stellar number density counts based on 9 years of diffraction-limited K-band (2.2 mu m) speckle imaging at the 10 m Keck I Telescope, we have identified a new comoving group of stars, which we call the IRS 16 SW comoving group, located 1."9 (0.08 pc, in projection) from the central black hole. Four of the five members of this comoving group have been spectroscopically identified as massive young stars, specifically, He I emission-line stars and OBN stars. This is the second young comoving group within the central parsec of the Milky Way to be recognized and is the closest, by a factor of 2, in projection to the central black hole. These comoving groups may be the surviving cores of massive infalling star clusters that are undergoing disruption in the strong tidal field of the central supermassive black hole.