A case study for a tidal interaction between dwarf galaxies in UGC 6741

TL;DR

This paper presents a detailed case study of tidal interactions between dwarf galaxies UGC 6741 and its companion, revealing star formation, potential globular cluster progenitors, and implications for galaxy evolution.

Contribution

It provides the first evidence of progenitors of UCDs in dwarf galaxy mergers and explores the transformation of BCDs into dEs through such interactions.

Findings

Presence of a 15 kpc stellar bridge connecting the galaxies.

Identification of star-forming knots that may become UCDs.

UGC 6741's properties suggest it could evolve from a BCD to a dE.

Abstract

We present a case study of the tidal interaction between low mass, star-forming, galaxies initially found exploring the Sloan Digital Sky Survey (SDSS) images and further analyzed with SDSS spectroscopy and UV GALEX photometry. With a luminosity of M$_{r}$ = $-$17.7 mag and exhibiting a prominent tidal filament, UGC 6741 appears as a scale down version of massive gas--rich interacting systems and mergers.The stellar disk of the smaller companion, UGC 6741_B, which is three times less massive, has likely been already destroyed. Both galaxies, which are connected by a 15 kpc long stellar bridge, have a similar oxygen abundance of 12+log(O/H)$\sim$8.3. Several knots of star-forming regions are identified along the bridge, some with masses exceeding $\sim$10$^{7}$ M$_{\sun}$. The most compact of them, which are unresolved, may evolve into globular clusters or Ultra Compact Dwarf galaxies (UCDs). This would be the first time progenitors of such objects are detected in mergers involving dwarf galaxies. UGC 6741 has currently the color and star formation properties of Blue Compact Dwarf galaxies (BCDs). However the analysis of its surface photometry suggests that the galaxy lies within the scaling relations defined by early-type dwarf galaxies (dEs). Thus UGC 6741 appears as a promising system to study the possible transformation of BCDs into dEs, through possibly a merger episode. The frequency of such dwarf-dwarf mergers should now be explored.