AstroSat-UVIT observations of a possibly interacting pair of galaxies in HCG 77

TL;DR

This study uses high-resolution UVIT observations to analyze star-forming regions and physical properties of a possibly interacting galaxy pair in HCG 77, revealing tidal features and a candidate tidal dwarf galaxy.

Contribution

First high-resolution FUV imaging of the galaxy pair in HCG 77, identifying star-forming regions and a candidate tidal dwarf galaxy, and analyzing their physical properties.

Findings

Identification of multiple star-forming regions

Detection of a candidate tidal dwarf galaxy

Physical property analysis of the galaxies

Abstract

We aim to study star-forming regions and the spectral energy distribution of two possibly interacting galaxies, PGC 56121 and PGC 56125, in the Hickson Compact Group 77. We utilized the far-ultraviolet (FUV) channel of the Ultra Violet Imaging Telescope (UVIT) on board AstroSat to observe and produce FUV images of the galaxies. Our FUV images are at a much higher resolution in comparison to those obtained from previous galaxy surveys by GALEX in the near-UV and those from PS-1, DSS. We have identified several star-forming regions in the two possibly interacting galaxies, PGC 56121 and PGC 56125. These two galaxies form a pair widely separated in redshift and are seen in projection. We also report the presence of a candidate tidal dwarf galaxy at the end of one of the tidal tails located to the east of the pair, and we identified three major star-forming regions in the tidal dwarf. The spectral energy distribution of three galaxies in the system is presented and analyzed to investigate the key physical properties, such as stellar mass, dust mass, total luminosity, and star formation history, of the three galaxies. Based on these observations and on a comparison with observations in radio, these three galaxies are probably part of a small group of interacting galaxies.