Discovery of 14NH3 (2,2) maser emission in Sgr B2-Main
  We report the discovery of the first 14NH3 (2,2) maser, seen in the Sgr B2
Main star forming region near the center of the Milky Way, using data from the
Very Large Array radio telescope. The maser is seen in both lower resolution
(3" or ~0.1 pc) data from 2012 and higher resolution (0''.1 or ~1000 AU) data
from 2018. In the higher resolution data ammonia (2,2) maser emission is
detected toward 5 independent spots. The maser spots are not spatially or
kinematically coincident with any other masers in this region, or with the
peaks of the radio continuum emission from the numerous ultracompact and
hypercompact \hii\, regions in this area. While the (2,2) maser spots are
spatially unresolved in our highest resolution observations, they have
unusually broad linewidths of several kilometers per second, which suggests
that each of these spots consists of multiple masers tracing unresolved
velocity structure. No other ammonia lines observed in Sgr B2 Main are seen to
be masers, which continues to challenge theories of ammonia, maser emission
that predict simultaneous maser emission in multiple ammonia transitions.
