The G305 star forming complex: Wide-Area molecular mapping of NH3 and H2O masers

TL;DR

This study maps the G305 star forming complex using NH3 and H2O masers to identify dense gas reservoirs, physical conditions, and active star formation regions, revealing significant molecular mass and correlations with star formation tracers.

Contribution

It provides the first wide-area NH3 and H2O maser mapping of G305, detailing dense gas structures, physical parameters, and their relation to star formation activity.

Findings

Identified 15 NH3 (1,1), 12 NH3 (2,2), 6 NH3 (3,3) clumps.

Total molecular mass of G305 is approximately 6x10^5 solar masses.

Detected 16 H2O masers correlating with NH3 clumps and star formation tracers.

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 YSOs and ultra compact HII 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 \sim 1.5\circ x 1\circ region with \sim 2' angular resolution and a sensitivity of \sim 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 HII 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 > 10^4 M\odot and find the total molecular mass of the complex to be \sim 6x10^5 M\odot. 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, find they correlate with the detected ammonia clumps and in general are found closer to the NH3 clump cores than star formation tracers of later evolutionary stages.