Near-infrared proper motions and spectroscopy of infrared excess sources
  at the Galactic Center
  There are a number of faint compact infrared excess sources in the central
stellar cluster of the Milky Way. Their nature and origin is unclear. In
addition to several isolated objects of this kind we find a small but dense
cluster of co-moving sources (IRS13N) about 3" west of SgrA* just 0.5" north of
the bright IRS13E cluster of WR and O-type stars. Based on their color and
brightness, there are two main possibilities: (1) they may be dust embedded
stars older than few Myr, or (2) extremely young, dusty stars with ages less
than 1Myr. We present fist H- and Ks-band identifications or proper motions of
the IRS13N members, the high velocity dusty S-cluster object (DSO), and other
infrared excess sources in the central field. We also present results of NIR H-
and Ks-band ESO-SINFONI integral field spectroscopy of ISR13N. We show that
within the uncertainties, the proper motions of the IRS13N sources in Ks- and
L'-band are identical. This indicates that the bright L'-band IRS13N sources
are indeed dust enshrouded stars rather than core-less dust clouds. The proper
motions show that the IRS13N sources are not strongly gravitationally bound to
each other implying that they have been formed recently. We also present a
first H- and Ks-band identification as well as proper motions and HKsL'-colors
of a fast moving DSO which was recently found in the cluster of high speed
S-stars that surround the super-massive black hole Sagittarius A* (SgrA*). Most
of the compact L'-band excess emission sources have a compact H- or Ks-band
counterpart and therefore are likely stars with dust shells or disks. Our new
results and orbital analysis from our previous work favor the hypothesis that
the infrared excess IRS13N members and other dusty sources close to SgrA* are
very young dusty stars and that star formation at the GC is a continuously
ongoing process.
