Looking for outflow and infall signatures in high mass star forming regions

TL;DR

This study investigates how infall and outflow signatures in high mass star forming regions vary with evolutionary stage, revealing that SiO emission increases with age and infall often coincides with outflow activity.

Contribution

It provides new observational evidence linking outflow and infall signatures to the evolutionary stages of high mass star forming regions using JCMT data.

Findings

SiO detection is surprisingly low in hypercompact HII regions.

SiO line intensity increases with evolutionary stage.

Infall signatures are always accompanied by outflow signatures in ultracompact HII regions.

Abstract

(Context) Many physical parameters change with time in star forming regions. Here we attempt to correlate changes in infall and outflow motions in high mass star forming regions with evolutionary stage using JCMT observations. (Aims) From a sample of 45 high mass star forming regions in three phases of evolution, we investigate the presence of established infall and outflow tracers to determine whether there are any trends attributable to the age of the source. (Methods) We obtained JCMT observations of HCO+/H13CO+ J=4-3 to trace large scale infall, and SiO J=8-7 to trace recent outflow activity. We compare the infall and outflow detections to the evolutionary stage of the host source (high mass protostellar objects, hypercompact HII regions and ultracompact HII regions). We also note that the integrated intensity of SiO varies with the full width at half maximum of the H13CO+. (Results) We find a surprising lack of SiO detections in the middle stage (Hypercompact HII regions), which may be due to an observational bias. When SiO is detected, we find that the integrated intensity of the line increases with evolutionary stage. We also note that all of the sources with infall signatures onto Ultracompact HII regions have corresponding outflow signatures as well.