Infall and Outflow Motions towards a Sample of Massive Star Forming Regions from the RMS Survey

TL;DR

This study investigates outflow and infall motions in 31 massive star-forming regions, revealing that SiO emission correlates with younger, more embedded regions and higher outflow velocities, but infall signatures are less evident.

Contribution

It provides new insights into the relationship between outflow activity, SiO emission, and evolutionary stages in massive star-forming regions using multi-molecular line observations.

Findings

SiO detected in 46% of sources, more prevalent in younger regions.

SiO luminosity correlates with flux ratio indicating embeddedness.

Higher outflow velocities linked to SiO presence.

Abstract

We present the results of an outflow and infall survey towards a distance limited sample of 31 massive star forming regions drawn from the RMS survey. The presence of young, active outflows is identified from SiO (8-7) emission and the infall dynamics are explored using HCO$^+$/H$^{13}$CO$^+$ (4-3) emission. We investigate if the infall and outflow parameters vary with source properties, exploring whether regions hosting potentially young active outflows show similarities or differences with regions harbouring more evolved, possibly momentum driven, "fossil" outflows. SiO emission is detected towards approximately 46% of the sources. When considering sources with and without an SiO detection (i.e. potentially active and fossil outflows respectively), only the $^{12}$CO outflow velocity shows a significant difference between samples, indicating SiO is more prevalent towards sources with higher outflow velocities. Furthermore, we find the SiO luminosity increases as a function of the Herschel 70$\mu$m to WISE 22$\mu$m flux ratio, suggesting the production of SiO is prevalent in younger, more embedded regions. Similarly, we find tentative evidence that sources with an SiO detection have a smaller bolometric luminosity-to-mass ratio, indicating SiO (8-7) emission is associated with potentially younger regions. We do not find a prevalence towards sources displaying signatures of infall in our sample. However, the higher energy HCO$^+$ transitions may not be the best suited tracer of infall at this spatial resolution in these regions.