ATCA Survey of Ammonia in the Galactic Center: The Temperatures of Dense
  Gas Clumps between SgrA* and SgrB2
  We present a large-scale, interferometric survey of ammonia (1,1) and (2,2)
toward the Galactic Center observed with the Australia Telescope Compact Array
(ATCA). The survey covers Delta l ~1degree (~150pc) at an assumed distance of
8.5 kpc) and Delta b ~0.2degree (~30pc) which spans the region between the
supermassive black hole SgrA* and the massive star forming region SgrB2. The
resolution is ~20'' (~0.8pc) and emission at scales >~2' (>~3.2pc) is filtered
out due to missing interferometric short spacings. Consequently, the data
represent the denser, compact clouds and disregards the large scale, diffuse
gas. Many of the clumps align with the 100 pc dust ring and mostly
anti-correlate with 1.2cm continuum emission. We present a kinetic temperature
map of the dense gas. The temperature distribution peaks at ~38K with a width
at half maximum between 18K and 61K (measurements sensitive within
Tkin~10-80K). Larger clumps are on average warmer than smaller clumps which
suggests internal heating sources. Our observations indicate that the
circumnuclear disk ~1.5 pc around SgrA* is supplied with gas by the 20km/s
molecular cloud. This gas is substantially cooler than gas ~3-15pc away from
SgrA*. We find a strong temperature gradient across SgrB2. Ammonia column
densities correlate well with SCUBA 850um fluxes, but the relation is shifted
from the origin, which may indicate a requirement for a minimum amount of dust
to form and shield ammonia. Around the Arches and Quintuplet clusters we find
shell morphologies with UV-influenced gas in their centers, followed by ammonia
and radio continuum layers.
