COSMOS-Web: The Role of Galaxy Interactions and Disk Instabilities in Producing Starbursts at z<4

TL;DR

This study investigates how galaxy interactions and disk instabilities contribute to starburst activity in galaxies up to redshift 4, revealing that both processes significantly influence star formation efficiency and galaxy growth.

Contribution

It provides observational evidence that both galaxy interactions and disk instabilities play key roles in triggering starbursts, with disk instabilities maintaining high star formation efficiency over long periods.

Findings

Interacting galaxies are more common in starburst regimes up to z=4.

Isolated disk galaxies with clumpy structures also show increased star formation efficiency.

Disk instabilities contribute significantly to the majority of starburst galaxies.

Abstract

We study of the role of galaxy-galaxy interactions and disk instabilities in producing starburst activity in galaxies out to z = 4. For this, we use a sample of 387 galaxies with robust total star formation rate measurements from Herschel, gas masses from ALMA, stellar masses and redshifts from multi-band photometry, and JWST/NIRCam rest-frame optical imaging. Using mass-controlled samples, we find an increased fraction of interacting galaxies in the starburst regime at all redshifts out to z = 4. This increase correlates with star formation efficiency (SFE), but not with gas fraction. However, the correlation is weak (and only significant out to z = 2), which could be explained by the short duration of SFE increase during interaction. In addition, we find that isolated disk galaxies make up a significant fraction of the starburst population. The fraction of such galaxies with star-forming clumps ("clumpy disks") is significantly increased compared to the main-sequence disk population. Furthermore, this fraction directly correlates with SFE. This is direct observational evidence for a long-term increase of SFE maintained due to disk instabilities, contributing to the majority of starburst galaxies in our sample and hence to substantial mass growth in these systems. This result could also be of importance for explaining the growth of the most massive galaxies at z > 6.