The IMACS Cluster Building Survey: V. Further Evidence for Starburst Recycling from Quantitative Galaxy Morphologies

TL;DR

This study uses galaxy imaging to analyze morphologies and supports the idea that starbursts are mainly triggered by minor mergers and are part of a recycling process between starforming and quiescent galaxies, with environment playing a limited role.

Contribution

It provides quantitative morphological evidence supporting the recycling model of starbursts and poststarbursts across different environments at intermediate redshifts.

Findings

Starburst and starforming galaxies show structural similarities outside cluster cores.

Poststarburst and passive galaxies are structurally linked, supporting evolutionary connections.

Most starbursts are triggered by minor mergers, not major disruptive events.

Abstract

Using $J$ and $K_s$ band imaging obtained as part of the IMACS Cluster Building Survey (ICBS) we measure S\'ersic indices for 2160 field and cluster galaxies at $0.31 < z < 0.54$. Using both mass- and magnitude-limited samples, we compare the distributions for spectroscopically determined passive, continuously starforming, starburst, and poststarburst systems and show that previously established spatial and statistical connections between these types extend to their gross morphologies. Outside of cluster cores, we find close structural ties between starburst and continuously starforming, as well as poststarburst and passive types, but not between starbursts and poststarbursts. These results independently support two conclusions presented in Paper II of this ICBS series (Dressler et al.): 1) most starbursts are the product of a non-disruptive triggering mechanism that is insensitive to global environment, such as minor-mergers; 2) starbursts and poststarbursts generally represent transient phases in the lives of "normal" starforming and quiescent galaxies, respectively, originating from and returning to these systems in closed "recycling" loops. In this picture, spectroscopically identified poststarbursts constitute a minority of all recently terminated starbursts, largely ruling-out the typical starburst as a quenching event in all but the densest environments.