The Interstellar Bubbles of G38.9-0.4 and the Impact of Stellar Feedback on Star Formation

TL;DR

This study investigates the star formation activity in the G38.9-0.4 region, finding no evidence of feedback-triggered star formation and highlighting the dominant role of gas density over stellar feedback in star formation processes.

Contribution

The paper provides a detailed multiwavelength analysis of G38.9-0.4, demonstrating that stellar feedback does not significantly trigger star formation in this region, emphasizing the importance of gas density.

Findings

No classical signs of triggered star formation detected.

Strong correlation between YSO mass surface density and gas mass surface density.

Star formation efficiency appears unaffected by stellar feedback.

Abstract

We present a study of the star formation (SF) region G38.9-0.4 using publicly available multiwavelength Galactic Plane surveys from ground- and space-based observatories. This region is composed of four bright mid-IR bubbles and numerous infrared dark clouds. Two bubbles, N 74 and N 75, each host a star cluster anchored by a single O9.5V star. We identified 162 young stellar objects (YSOs) and classify 54 as stage I, 7 stage II, 6 stage III, and 32 ambiguous. We do not detect the classical signposts of triggered SF, i.e., star-forming pillars or YSOs embedded within bubble rims. We conclude that feedback-triggered SF has not occurred in G38.9-0.4. The YSOs are preferentially coincident with infrared dark clouds. This leads to a strong correlation between areal YSO mass surface density and gas mass surface density with a power law slope near 1.3, which closely matches the Schmidt-Kennicutt Law. The correlation is similar inside and outside the bubbles and may mean that the SF efficiency is neither enhanced nor supressed in regions potentially influenced by stellar feedback. This suggests that gas density, regardless of how it is collected, is a more important driver of SF than stellar feedback. Larger studies should be able to quantify the fraction of all SF that is feedback-triggered by determining the fraction SF, feedback-compressed gas surrounding HII regions relative to that already present in molecular clouds.