Expanded Very Large Array Detection of 44.1 GHz Class I Methanol Masers
  in Sagittarius A
  We report on the detection of 44 GHz Class I methanol (CH3OH) maser emission
in the SgrA complex with the Expanded Very Large Array (EVLA). These EVLA
observations show that the SgrA complex harbors at least four different tracers
of shocked regions in the radio regime. The 44 GHz masers correlate with the
positions and velocities of previously detected 36 GHz CH3OH masers, but less
with 1720 MHz OH masers. Our detections agree with theoretical predictions that
the densities and temperatures conducive for 1720 MHz OH masers may also
produce 36 and 44 GHz CH3OH maser emission. However, many 44 GHz masers do not
overlap with 36 GHz methanol masers, suggesting that 44 GHz masers also arise
in regions too hot and too dense for 36 GHz masers to form. This agrees with
the non-detection of 1720 MHz OH masers in the same area, which are thought to
be excited under even cooler and less dense conditions. We speculate that the
geometry of the 36 GHz masers outlines the current location of a shock front.
