Searching for star formation outside galaxies: Multiwavelength analysis of the intragroup medium of Hickson Compact Group 100

Abstract

We use multiwavelength data (H I, FUV, NUV, R) to search for evidence of star formation in the intragroup medium of the Hickson Compact Group 100. We find that young star-forming regions are located in the intergalactic H I clouds of the compact group which extend to over 130 kpc away from the main galaxies. A tidal dwarf galaxy (TDG) candidate is located in the densest region of the H I tail, 61 kpc from the brightest group member and its age is estimated to be only 3.3 Myr. Fifteen other intragroup H II regions and TDG candidates are detected in the Galaxy Evolution Explorer (GALEX) FUV image and within a field 10′ × 10′ encompassing the H I tail. They have ages <200 Myr, H I masses of 109.2-10.4 M, 0.001 <0.01 M yr -1, and stellar masses 104.3-106.5 M. The H I clouds to which many of them are associated have column densities about one order of magnitude lower than N(H I) 1021 cm-2. © 2008. The American Astronomical Society. All rights reserved.