GS305+04-26:Revisiting the ISM around the CenOB1 stellar association

TL;DR

This study investigates a large HI shell, GS305+04-26, associated with the CenOB1 stellar association, revealing its properties and suggesting it was formed by the energy output of massive stars in the association.

Contribution

It provides a detailed multi-wavelength analysis of the HI shell and links its formation to the stellar winds and energy from CenOB1 stars, offering new insights into ISM modification by massive stars.

Findings

The HI shell GS305+04-26 is centered at (l,b)=(305°, +4°) with a velocity of -26 km/s.

The shell has an estimated distance of 2.5 ± 0.9 kpc and dimensions of 440 x 270 pc.

The shell's expansion velocity is approximately 8 km/s, with a mass of about 2.4 x 10^5 solar masses.

Abstract

Massive stars deeply modify their surrounding ISM via their high throughput of ionizing photons and their strong stellar winds. In this way they may create large expanding structures of neutral gas. We study a new large HI shell, labelled GS305+04-26, and its relationship with the OB association CenOB1. To carry out this study we have used a multi-wavelenght approach. We analyze neutral hydrogen (HI) line data retrieved from the Leiden-Argentina-Bonn (LAB) survey, new spectroscopic optical observations obtained at CASLEO, and make use of proper motion databases available via Internet. The analysis of the HI data reveals a large expanding structure GS305+04-26 centered at (l,b)=(305$^{\degr}$, +4$^{\degr}$) in the velocity range from -33 to -17 km/s. Based on its central velocity, -26 km/s, and using standard galactic rotation models, a distance of 2.5(+-)0.9 kpc is inferred. This structure, elliptical in shape, has major and minor axis of 440 and 270 pc, respectively. Its expansion velocity, total gaseous mass, and kinetic energy are ~8 km/s, (2.4(+-)0.5)x10^5 Mo, and (1.6(+-)0.4)x10^{50} erg, respectively. Several stars of the OB-association CenOB1 are seen projected onto, and within, the boundaries of GS305+04-26. Based on an analysis of proper motions, new members of CenOB1 are identified. The mechanical energy injected by these stars could have been the origin of this HI structure.