# SG1120-1202: Mass-Quenching as Tracked by UV Emission in the Group Environment at z=0.37

## TL;DR

This study uses Hubble imaging to analyze UV emission in a galaxy group at z=0.37, revealing mass-quenching as the main factor extinguishing star formation, with environmental effects influencing galaxy morphology and UV properties.

## Contribution

It demonstrates that mass-quenching dominates UV emission suppression in group galaxies, and identifies jellyfish-like UV morphologies in a group environment for the first time.

## Key findings

- UV emission decreases with proximity to group center
- Mass is the primary predictor of UV emission
- Jellyfish-like UV morphologies are observed in the group environment

## Abstract

We use the Hubble Space Telescope to obtain WFC3/F390W imaging of the supergroup SG1120-1202 at z=0.37, mapping the UV emission of 138 spectroscopically confirmed members. We measure total (F390W-F814W) colors and visually classify the UV morphology of individual galaxies as "clumpy" or "smooth." Approximately 30% of the members have pockets of UV emission (clumpy) and we identify for the first time in the group environment galaxies with UV morphologies similar to the jellyfish galaxies observed in massive clusters. We stack the clumpy UV members and measure a shallow internal color gradient, which indicates unobscured star formation is occurring throughout these galaxies. We also stack the four galaxy groups and measure a strong trend of decreasing UV emission with decreasing projected group distance ($R_{proj}$). We find that the strong correlation between decreasing UV emission and increasing stellar mass can fully account for the observed trend in (F390W-F814W) - $R_{proj}$, i.e., mass-quenching is the dominant mechanism for extinguishing UV emission in group galaxies. Our extensive multi-wavelength analysis of SG1120-1202 indicates that stellar mass is the primary predictor of UV emission, but that the increasing fraction of massive (red/smooth) galaxies at $R_{proj}$ < 2$R_{200}$ and existence of jellyfish candidates is due to the group environment.