IRAS 01202+6133 : A Possible Case of Protostellar Collapse Triggered by a Small HII Region

TL;DR

This study analyzes molecular line observations of IRAS 01202+6133, suggesting it is a young protostar likely formed due to the expansion of nearby HII region KR 120, indicating triggered star formation.

Contribution

It introduces modified radiative transfer models to fit complex line profiles and provides evidence for triggered protostellar collapse near an HII region.

Findings

IRAS 01202+6133 is a young Class I YSO with infall and outflow motions.

Line profile analysis supports a collapse scenario influenced by the HII region.

The formation of IRAS 01202+6133 was likely triggered by KR 120 expansion.

Abstract

We present an analysis of HCO+ (J=3-2) and H13CO+ (J=3-2) observations of the massive (M ~ 20 Msun) submm/IR source IRAS 01202+6133 located on the periphery of the HII region KR 120 (Sh 2-187). The HCO+ line profile has a classic blue-asymmetric shape with the optically thin H13CO+ line peaking at the position expected if the HCO+ line arises from a combination of self-absorption and infall motion. We have modified existing analytic radiative transfer models to allow for the fitting of submm/mm line profiles that have both self-absorption features and optically thin wings and applied these models to our HCO+ spectrum of IRAS 01202+6133. We conclude that it is a young Class I YSO with a substantial envelope undergoing slow infall and having some outflow motions. The young age of the HII region rules out a "collect and collapse" scenario. While we cannot eliminate the possibility that IRAS 01202+6133 formed spontaneously at its current location, considering its early evolutionary state and its proximity to the HII region we think that the formation of IRAS 01202+6133 was triggered by the expansion of KR 120 (Sh 2-187).