Multi-generation massive star-formation in NGC3576
  Recent 1.2-mm continuum observations have shown the giant HII region NGC3576
to be embedded in the centre of an extended filamentary dust-cloud. The bulk of
the filament away from the HII region contains a number of clumps seen only at
(sub-)millimetre wavelengths and which may host massive protostellar objects at
a very early stage of evolution. We have used the Australia Telescope Compact
Array (ATCA) to image the cloud for the NH3(1,1), (2,2) and (4,4) transitions,
22 GHz water masers, and 23 GHz continuum emission. We also utilised the 22-m
Mopra antenna to map the region for the molecular lines 13CO (1-0), C18O (1-0),
HCO+ (1-0), H13CO+ (1-0), CS (1-0) and N2H+ (1-0).The HII region is observed to
be expanding into the molecular cloud, sweeping up a clumpy shell of gas, while
the central star cluster is dispersing the molecular gas to the east.
Temperatures are highest adjacent to the central HII region, indicating that
the embedded cluster of young stars there is heating the gas. Six new water
masers were detected in the arms of the filament, all associated with NH3
emission peaks, confirming that star-formation has begun within these cores.
Core masses range from 5 to 516 solar masses and most appear to be
gravitationally bound. Complementary results by Andr\'e et al. (2008) imply
that seven cores will go on to form massive stars between 15 and 50 solar
masses. The large scale velocity structure of the filament is smooth, but at
least one clump shows the signature of inward gas motions via asymmetries in
the NH3 (1,1) line profiles. The same clump exhibits an enhanced abundance of
N2H+, which coupled with an absence of CO indicates depletion onto the dust
grain surface. The HII region at the heart of NGC3576 is potentially triggering
the formation of massive stars in the bulk of the associated cloud.
