Star-forming regions in the intragroup medium of compact groups of galaxies

TL;DR

This study investigates star formation in the intragroup medium of seven compact galaxy groups using multiwavelength data, revealing that evolved groups with HI clouds host young objects and a tidal dwarf galaxy candidate.

Contribution

It provides new evidence linking group evolutionary stage and intragroup HI clouds to star formation activity in the intragroup medium.

Findings

Evolved groups contain young objects in the intragroup medium.

Less evolved groups lack intragroup young objects.

Discovery of a tidal dwarf galaxy candidate in NGC 92's tail.

Abstract

We present the results of a multiwavelength campaign searching for young objects in the intragroup medium of seven compact groups of galaxies: HCG 2, 7, 22, 23, 92, 100 and NGC 92. We used Fabry-Perot velocity fields and rotation curves together with GALEX NUV and FUV images, optical R-band and HI maps to evaluate the stage of interaction of each group. We conclude that groups (i) HCG 7 and HCG 23 are in an early stage of interaction, (ii) HCG 2 and HCG 22 are mildly interacting, and (iii) HCG 92, HCG 100 and NGC 92 are in a late stage of evolution. Evolved groups have a population of young objects in their intragroup medium while no such population is found within the less evolved groups. We also report the discovery of a tidal dwarf galaxy candidate in the tail of NGC 92. These three groups, besides containing galaxies which have peculiar velocity fields, also show extended HI tails. Our results indicate that the advanced stage of evolution of a group together with the presence of intragroup HI clouds may lead to star formation in the intragroup medium.