Spirals, Bridges, and Tails: A GALEX UV Atlas of Interacting Galaxies

TL;DR

This study uses GALEX UV imaging combined with optical data to analyze star formation and morphological features in 42 nearby interacting galaxy pairs, revealing enhanced star formation in tidal features and identifying new candidate tidal dwarf galaxies.

Contribution

It provides a detailed UV-optical analysis of tidal features in interacting galaxies, highlighting star formation patterns and discovering new tidal dwarf galaxy candidates.

Findings

Tidal features are bluer in UV, indicating enhanced star formation.

Some tidal dwarf galaxy candidates were identified.

UV imaging reveals features not seen in HI maps.

Abstract

We have used the GALEX ultraviolet telescope to study stellar populations and star formation morphology in a well-defined sample of 42 nearby optically-selected pre-merger interacting galaxy pairs. Galaxy interactions were likely far more common in the early Universe than in the present, thus our study provides a nearby well-resolved comparison sample for high redshift studies. We have combined the GALEX NUV and FUV images with broadband optical maps from the Sloan Digitized Sky Survey to investigate the ages and extinctions of the tidal features and the disks. The distributions of the UV/optical colors of the tidal features and the main disks of the galaxies are similar, however, the tidal features are bluer on average in NUV - g when compared with their own parent disks, thus tails and bridges are often more prominent relative to the disks in UV images compared to optical maps. This effect is likely due to enhanced star formation in the tidal features compared to the disks rather than reduced extinction, however, lower metallicities may also play a role. We have identified a few new candidate tidal dwarf galaxies in this sample. Other interesting morphologies such as accretion tails and `beads on a string' are also seen in these images. We also identify a possible `Taffy' galaxy in our sample, which may have been produced by a head-on collision between two galaxies. In only a few cases are strong tidal features seen in HI maps but not in GALEX.