Cometary shaped sources at the Galactic Center - Evidence for a wind
  from the central 0.2 pc
  In 2007 we reported two cometary shaped sources in the vicinity of Sgr A*
(0.8" and 3.4" projected distance), named X7 and X3. The symmetry axes of the
two sources are aligned to within 5 degrees in the plane of the sky and the
tips of their bow-shocks point towards Sgr A*. Our measurements show that the
proper motion vectors of both features are pointing in directions more than 45
deg away from the line that connects them with Sgr A*. This misalignment of the
bow-shock symmetry axes and their proper motion vectors, combined with the high
proper motion velocities of several 100 km/s, suggest that the bow-shocks must
be produced by an interaction with some external fast wind, possibly coming
from Sgr A*, or stars in its vicinity. We have developed a bow-shock model to
fit the observed morphology and constrain the source of the external wind. The
result of our modeling allows us to estimate the velocity of the external wind,
making sure that all likely stellar types of the bow-shock stars are
considered. We show that neither of the two bow-shocks (one of which is clearly
associated with a stellar source) can be produced by influence of a stellar
wind of a single mass-losing star in the central parsec. Instead, an outflow
carrying a momentum comparable to the one contributed by the ensemble of the
massive young stars, can drive shock velocities capable of producing the
observed cometary features. We argue that a collimated outflow arising
perpendicular to the plane of the clockwise rotating stars (CWS), can easily
account for the two features and the mini-cavity. However, the collective wind
from the CWS has a scale of >10''. The presence of a strong, mass-loaded
outbound wind at projected distances from Sgr A* of <1'' is in fact in
agreement with models that predict a highly inefficient accretion onto the
central black hole due to a strongly radius dependent accretion flow.
