All Puffed Up: Exploring Ultra-diffuse Galaxy Origins through Galaxy Interactions

TL;DR

This study investigates the origins of ultra-diffuse galaxies (UDGs) with tidal features, suggesting they often result from dwarf galaxies undergoing stripping and tidal heating, with some possibly forming in the field before environmental processing.

Contribution

It provides new observational evidence linking tidal interactions to UDG formation, including detailed imaging and gas analysis of two UDGs with tidal features.

Findings

UDGs have globular cluster counts typical of dwarf galaxies.

One UDG shows active gas stripping, the other does not.

Tidal features suggest diverse origins, including mergers and heating.

Abstract

We present new follow-up observations of two ultra-diffuse galaxies (UDGs) selected for their distorted morphologies and tidal features, suggestive of tidal influence. Using Hubble Space Telescope Advanced Camera for Surveys F555W and F814W imaging, we identify $8\pm2$ globular clusters (GCs) in KUG 0203-Dw1 and $6\pm2$ in KDG 013, abundances typical for normal dwarf galaxies of similar stellar mass. Jansky Very Large Array data reveal a clear HI detection of KUG 0203-Dw1 with a gas mass estimate of $\log{M_{\rm{HI}}/M_{\odot}}\lesssim 7.4$ and evidence of active stripping by the host, while KDG 013 has no clear gas detection. The UDGs likely originated as normal dwarf galaxies that have been subjected to significant stripping and tidal heating, causing them to become more diffuse. These two UDGs complete a sample of five exhibiting tidal features in the full Canada-France-Hawaii Telescope Legacy Survey area (CFHTLS; $\sim150^{2}$ deg). These tidally influenced UDGs exhibit diversse properties; one stands out as a potential result of a dwarf merger, while the remainder suggest tidal heating origins. We also cannot conclusively rule out that these galaxies became UDGs in the field before processing by the group environment, underscoring the need for broader searches of diffuse galaxies to better understand the impact of galaxy interactions.