A distance limited sample of massive star forming cores from the RMS survey

TL;DR

This study analyzes C$^{18}$O data from a distance-limited sample of 99 massive star-forming cores, revealing Larson-like relationships, consistent core properties across evolutionary stages, and a strong mass-luminosity correlation, indicating similar developmental phases.

Contribution

It provides new insights into the properties and evolutionary stages of massive star-forming cores using a representative, distance-limited sample and molecular line data.

Findings

Larson-like relationships are observed in the cores.

No significant differences between MYSOs and HII regions.

Core masses correlate strongly with luminosities.

Abstract

We analyse C$^{18}$O ($J=3-$2) data from a sample of 99 infrared-bright massive young stellar objects (MYSOs) and compact HII regions that were identified as potential molecular-outflow sources in the Red MSX source (RMS) survey. We extract a distance limited (D $<$ 6 kpc) sample shown to be representative of star formation covering the transition between the source types. At the spatial resolution probed, Larson-like relationships are found for these cores, though the alternative explanation, that Larson's relations arise where surface-density-limited samples are considered, is also consistent with our data. There are no significant differences found between source properties for the MYSOs and HII regions, suggesting that the core properties are established prior to the formation of massive stars, which subsequently have little impact at the later evolutionary stages investigated. There is a strong correlation between dust-continuum and C$^{18}$O-gas masses, supporting the interpretation that both trace the same material in these IR-bright sources. A clear linear relationship is seen between the independently established core masses and luminosities. The position of MYSOs and compact HII regions in the mass-luminosity plane is consistent with the luminosity expected a cluster of protostars when using a $\sim$40 percent star-formation efficiency and indicates that they are at a similar evolutionary stage, near the end of the accretion phase.