GSH 91.5+2-114: A large HI shell in the outer part of the Galaxy

TL;DR

This paper studies a large HI shell in the outer Galaxy, analyzing its physical properties and possible origins from stellar winds and supernovae, and explores star formation triggered by its expansion.

Contribution

It provides a detailed analysis of the physical parameters of GSH 91.5+2-114 and investigates its likely origin from combined stellar winds and supernova activity.

Findings

The HI shell is likely formed by stellar winds and supernova explosions.

No obvious stellar counterparts are detected due to high extinction.

Potential star formation regions are identified near the shell's periphery.

Abstract

GSH91.5+2-114 is a large HI shell located in the outer Galaxy at a kinematic distance of about 15 kpc. It was first identified in the Canadian Galactic Plane Survey (CGPS) by Pineault et al. (2002) as being possibly associated with objects possessing infrared colors which indicates strong stellar winds. The HI shell has no obvious continuum counterpart in the CGPS radio images at 408 and 1420 MHz or in the IRAS images. We found no evidence for early-type massive stars, most likely as a result of the large extinction that is expected for this large distance. An analysis of the energetics and of the main physical parameters of the HI shell shows that this shell is likely the result of the combined action of the stellar winds and supernova explosions of many stars. We investigate whether a number of slightly extended regions characterized by a thermal radio continuum and located near the periphery of the HI shell could be the result of star formation triggered by the expanding shell.