The G305 star-forming complex : wide-area molecular mapping of NH3 and H2O masers

Abstract

We present wide-area radio (12 mm) Mopra telescope observations of the complex and rich massive star-forming region G305. Our goals are to determine the reservoir for star formation within G305 using NH3 to trace the dense molecular content, and thus the gas available to form stars; estimate physical parameters of detected NH3 clumps (temperature, column density, mass, etc.); locate current areas of active star formation via the presence of H2O and methanol masers and the distribution of young stellar objects (YSOs) and ultra-compact H ii regions associated with this region. This paper details the NH3 (J, K), (1,1), (2,2) and (3,3) inversion transition and 22 GHz H2O maser observations. We observed a ~ 1.5 x 1 degreedegree region with ~2 ' angular resolution and a sensitivity of ~60 mK per 0.4 km s−1 channel. We identify 15 NH3 (1,1), 12 NH3 (2,2) and 6 NH3 (3,3) clumps surrounding the central H ii region. The sizes of the clumps vary between <2.6 and 10.1 pc; the average kinetic temperature of the gas is 25 K. We calculate clump masses of and find the total molecular mass of the complex to be . We note the positions of 56 star formation tracers, and discover a high degree of correlation with detected NH3 clumps. We have detected 16 H2O masers and find they correlate with the detected ammonia clumps. In general, they are found closer to the NH3 clump cores than star formation tracers of later evolutionary stages.