Physical characterisation of southern massive star-forming regions using Parkes NH$_3$ observations

TL;DR

This study uses Parkes NH3 spectral line observations to characterize the physical properties of southern massive star-forming regions, providing insights into their early stages and differences between star-forming and quiescent clumps.

Contribution

It offers new ammonia spectral data and analysis for a large sample of southern massive star-forming regions, enhancing understanding of their physical conditions and early evolution stages.

Findings

Ammonia observations reveal temperature, density, and turbulence differences among regions.

MM-only clumps are smaller, less turbulent, and likely represent earlier evolutionary stages.

Combining ammonia and continuum data improves physical parameter constraints.

Abstract

We have undertaken a Parkes ammonia spectral line study, in the lowest two inversion transitions, of southern massive star formation regions, including young massive candidate protostars, with the aim of characterising the earliest stages of massive star formation. 138 sources from the submillimetre continuum emission studies of Hill et al., were found to have robust (1,1) detections, including two sources with two velocity components, and 102 in the (2,2) transition. We determine the ammonia line properties of the sources: linewidth, flux density, kinetic temperature, NH$_3$ column density and opacity, and revisit our SED modelling procedure to derive the mass for 52 of the sources. By combining the continuum emission information with ammonia observations we substantially constrain the physical properties of the high-mass clumps. There is clear complementarity between ammonia and continuum observations for derivations of physical parameters. The MM-only class, identified in the continuum studies of Hill et al., display smaller sizes, mass and velocity dispersion and/or turbulence than star-forming clumps, suggesting a quiescent prestellar stage and/or the formation of less massive stars.