Program: GN-2007B-Q-87

Compact groups are great laboratories for the study of galaxy interaction and contain important clues regarding galaxy formation and evolution. One of the most interesting effects of galaxy interaction concerns the neutral gas, HI, which is often stripped from the galaxies halos. We have started a program searching for evidence of star-formation within these HI clouds using multiwavelength data (FUV/NUV from GALEX, optical, HI) of groups of galaxies. In this proposal we will be probing the intragroup medium (IGM) of a dynamically evolved group, HCG100 (Plana et al. 2003). HI is seen not only around the four members halo but also in a tail elongated more than 100 kpc towards the southern region where no obvious optical source is located. Although relatively empty at first glance, a total of 16 objects are detected in FUV, NUV, and R within an area of 78 arcmin^2. Nine of these objects are within the HI tail. They are blue in colors, small in sizes, and young in ages (1-200 Myr) (de Mello, Torres Flores, Mendes de Oliveira 2007). Our multiwavelength data suggest that the intragroup medium of HCG100 is an active place where stars are formed within HII regions inside HI clouds. One of the most interesting objects is centered in the densest HI cloud in the intragroup medium where we are witnessing a small galaxy in formation with stellar population reaching only 3 Myr. We are asking for GMOS time to obtain spectra of these 14 objects (2 GMOS pointings) in order to (i) confirm whether they are members of the group, (ii) obtain their masses, (iii) estimate their metallicities, (iv) evaluate their role in enriching the intragroup medium, and (v) set constraints on gas properties required for star formation.