Shock Structure and Shock Heating in the Galactic Central Molecular Zone
  We present maps of a large number of dense molecular gas tracers across the
Central Molecular Zone of our Galaxy. The data were taken with the CSIRO/CASS
Mopra telescope in Large Projects in the 1.3cm, 7mm, and 3mm wavelength
regimes. Here, we focus on the brightness of the shock tracers SiO and HNCO,
molecules that are liberated from dust grains under strong (SiO) and weak
(HNCO) shocks. The shocks may have occurred when the gas enters the bar regions
and the shock differences could be due to differences in the moving cloud mass.
Based on tracers of ionizing photons, it is unlikely that the morphological
differences are due to selective photo-dissociation of the molecules. We also
observe direct heating of molecular gas in strongly shocked zones, with a high
SiO/HNCO ratios, where temperatures are determined from the transitions of
ammonia. Strong shocks appear to be the most efficient heating source of
molecular gas, apart from high energy emission emitted by the central
supermassive black hole Sgr A* and the processes within the extreme star
formation region Sgr B2.
