A feedback-driven bubble G24.136+00.436: a possible site of triggered star formation

TL;DR

This study investigates the IR bubble G24.136+00.436, revealing molecular gas, dense cores, and young stellar objects, suggesting that the bubble's expansion may have triggered star formation through the collect and collapse process.

Contribution

It provides a detailed multi-wavelength analysis of the bubble, identifying dense cores and YSOs, and proposes a triggered star formation scenario driven by the bubble's expansion.

Findings

Molecular gas forms a shell with a mass of ~2x10^4 M_sun.

Dense cores within the shell are potential high-mass star formation sites.

Active star formation is indicated by YSOs and compact HII regions in the shell.

Abstract

We present a multi-wavelength study of the IR bubble G24.136+00.436. The J=1-0 observations of $^{12}$CO, $^{13}$CO and C$^{18}$O were carried out with the Purple Mountain Observatory 13.7 m telescope. Molecular gas with a velocity of 94.8 km s$^{-1}$ is found prominently in the southeast of the bubble, shaping as a shell with a total mass of $\sim2\times10^{4}$ $M_{\odot}$. It is likely assembled during the expansion of the bubble. The expanding shell consists of six dense cores. Their dense (a few of $10^{3}$ cm$^{-3}$) and massive (a few of $10^{3}$ $M_{\odot}$) characteristics coupled with the broad linewidths ($>$ 2.5 km s$^{-1}$) suggest they are promising sites of forming high-mass stars or clusters. This could be further consolidated by the detection of compact HII regions in Cores A and E. We tentatively identified and classified 63 candidate YSOs based on the \emph{Spitzer} and UKIDSS data. They are found to be dominantly distributed in regions with strong emission of molecular gas, indicative of active star formation especially in the shell. The HII region inside the bubble is mainly ionized by a $\sim$O8V star(s), of the dynamical age $\sim$1.6 Myr. The enhanced number of candidate YSOs and secondary star formation in the shell as well as time scales involved, indicate a possible scenario of triggering star formation, signified by the "collect and collapse" process.