# Outflow and Infall in a Sample of Massive Star Forming Regions

## TL;DR

This study investigates molecular outflows and infall in 23 massive star-forming regions using specific molecular line observations, revealing insights into the evolutionary stages and accretion processes of massive protostars.

## Contribution

It provides new observational evidence linking SiO outflows and HCO$^+$ infall signatures, suggesting both ionized and halted accretion models are relevant in massive star formation.

## Key findings

- SiO detected in 14 sources, indicating active outflows.
- HCO$^+$ traces infall in 9 sources, with estimated mass infall rates.
- Correlation between SiO and H$^{13}$CO$^+$ abundances.

## Abstract

We present single pointing observations of SiO, HCO$^+$ and H$^{13}$CO$^+$ from the James Clerk Maxwell Telescope towards 23 massive star forming regions previously known to contain molecular outflows and ultracompact HII regions. We detected SiO towards 14 sources and suggest that the non-detections in the other nine sources could be due to those outflows being older and without ongoing shocks to replenish the SiO. We serendipitously detected SO$_2$ towards 17 sources in the same tuning as HCO$^+$. We detected HCO$^+$ towards all sources, and suggest that it is tracing infall in nine cases. For seven infall candidates, we estimate mass infall rates between 1$\times10^{-2}$ and 2$\times10^{-5}$ M$_{\odot}$ yr$^{-1}$. Seven sources show both SiO detections (young outflows) and HCO$^+$ infall signatures. We also find that the abundance of H$^{13}$CO$^+$ tends to increase along with the abundance of SiO in sources for which we could determine abundances. We discuss these results with respect to current theories of massive star formation via accretion. From this survey, we suggest that perhaps both models of ionized accretion and halted accretion may be important in describing the evolution of a massive protostar (or protostars) beyond the formation of an HII region.