The RMS Survey: The Bolometric Fluxes and Luminosity Distributions of Young Massive Stars

TL;DR

This study derives bolometric fluxes and luminosity distributions for a large sample of young massive stars using spectral energy distribution fitting and kinematic distances, revealing differences between young stellar objects and ultra-compact HII regions.

Contribution

It provides a comprehensive set of bolometric fluxes and luminosities for over a thousand young massive stars, improving accuracy over previous methods and analyzing their luminosity distributions.

Findings

Bolometric fluxes obtained for 1173 sources, with 1069 having reliable distances.

Luminosity distributions differ between young stellar objects and HII regions.

Few massive young stellar objects exceed luminosities of 10^5 solar luminosities.

Abstract

Context: The Red MSX Source (RMS) survey is returning a large sample of massive young stellar objects (MYSOs) and ultra-compact (UC) \HII{} regions using follow-up observations of colour-selected candidates from the MSX point source catalogue. Aims: To obtain the bolometric fluxes and, using kinematic distance information, the luminosities for young RMS sources with far-infrared fluxes. Methods: We use a model spectral energy distribution (SED) fitter to obtain the bolometric flux for our sources, given flux data from our work and the literature. The inputs to the model fitter were optimised by a series of investigations designed to reveal the effect varying these inputs had on the resulting bolometric flux. Kinematic distances derived from molecular line observations were then used to calculate the luminosity of each source. Results: Bolometric fluxes are obtained for 1173 young RMS sources, of which 1069 have uniquely constrained kinematic distances and good SED fits. A comparison of the bolometric fluxes obtained using SED fitting with trapezium rule integration and two component greybody fits was also undertaken, and showed that both produce considerable scatter compared to the method used here. Conclusions: The bolometric flux results allowed us to obtain the luminosity distributions of YSOs and UC\HII{} regions in the RMS sample, which we find to be different. We also find that there are few MYSOs with L $\geq$ 10$^{5}$\lsol{}, despite finding many MYSOs with 10$^{4}$\lsol{} $\geq$ L $\geq$ 10$^{5}$\lsol{}.