Pericenter passage of the gas cloud G2 in the Galactic Center
  We have further followed the evolution of the orbital and physical properties
of G2, the object currently falling toward the massive black hole in the
Galactic Center on a near-radial orbit. New, very sensitive data were taken in
April 2013 with NACO and SINFONI at the ESO VLT . The 'head' of G2 continues to
be stretched ever further along the orbit in position-velocity space. A
fraction of its emission appears to be already emerging on the blue-shifted
side of the orbit, past pericenter approach. Ionized gas in the head is now
stretched over more than 15,000 Schwarzschild radii RS around the pericenter of
the orbit, at ~ 2000 RS ~ 20 light hours from the black hole. The pericenter
passage of G2 will be a process stretching over a period of at least one year.
The Brackett-{\gamma} luminosity of the head has been constant over the past 9
years, to within +- 25%, as have the line ratios Brackett-{\gamma} /
Paschen-{\alpha} and Brackett-{\gamma} / Helium-I. We do not see any
significant evidence for deviations of G2's dynamical evolution, due to
hydrodynamical interactions with the hot gas around the black hole, from a
ballistic orbit of an initially compact cloud with moderate velocity
dispersion. The constant luminosity and the increasingly stretched appearance
of the head of G2 in the position-velocity plane, without a central peak, is
not consistent with several proposed models with continuous gas release from an
initially bound zone around a faint star on the same orbit as G2.
