Stellar feedback and triggered star formation in the prototypical bubble RCW 120

TL;DR

This study uses velocity-resolved observations of RCW 120 to show that massive star feedback can rapidly trigger new star formation within 0.15 million years, highlighting the short timescale of positive feedback.

Contribution

It provides the first direct evidence that triggered star formation can occur on very short timescales, less than 0.15 million years, due to feedback from massive stars.

Findings

Gas shell expanding at 15 km/s observed

Molecular gas forms a fragmented ring of star-forming clumps

Triggered star formation occurs on timescales shorter than 0.15 million years

Abstract

Radiative and mechanical feedback of massive stars regulates star formation and galaxy evolution. Positive feedback triggers the creation of new stars by collecting dense shells of gas, while negative feedback disrupts star formation by shredding molecular clouds. Although key to understanding star formation, their relative importance is unknown. Here, we report velocity-resolved observations from the SOFIA (Stratospheric Observatory for Infrared Astronomy) legacy program FEEDBACK of the massive star-forming region RCW 120 in the [CII] 1.9-THz fine-structure line, revealing a gas shell expanding at 15 km/s. Complementary APEX (Atacama Pathfinder Experiment) CO J=3-2 345-GHz observations exhibit a ring structure of molecular gas, fragmented into clumps that are actively forming stars. Our observations demonstrate that triggered star formation can occur on much shorter time scales than hitherto thought (<0.15 million years), suggesting that positive feedback operates on short time periods.