GeminiFocus December 2012 | Page 22

ter the nature of these “baby galaxies.” From Gemini spectroscopy, we were able to detect the chemical elements already present in these galaxies and determined they are more metalrich than typical dwarf galaxies (de Mello et al., 2012). Figure 1. GALEX NUV image measuring 10’ × 10’ with H I contours. Four HCG 100 members are marked as ”a, b, c, and d“. Intragroup objects are circled (radius = 8 arcseconds) and numbered. VLA NH I contours are 0.6, 1.2, 2.1, 3.6, 4.4, 5.1, 5.9, 6.6, and 7.4 ×1020 cm−2 (Verdes Montenegro et al. 2006). North is up and east is to the left. Objects 3 and 4 from de Mello et al. (2008) are the “Baby Galaxies” identified in the NUV image and for the first time seen in the optical r-Band with Gemini. In 2008 we started a pilot project with Gemini to explore the nature of a dozen UV sources found in the H I tidal tail of a group of galaxies known as Hickson Compact Group 100 (HCG 100). Located 249 million light-years away, this group is formed by a bright central spiral galaxy (HCG 100a), an irregular galaxy with an optical tidal tail (HCG 100b), a late-type barred spiral (HCG 100c), a late-type edge-on spiral (HCG 100d), and a really long H I tidal tail extending more than 424,000 light-years from the interacting galaxies. In de Mello et al. (2008), we present GALEX images of this group, where we identified a dozen UV sources located in the vicinity of the H I tail. When we compared their UV light to the ones of stellar populations from theoretical models, we estimated that they are only a few million years old. Gemini Baby Galaxies With the Gemini Multi-Object Spectrograph (GMOS), we confirmed that two of the largest UV sources lie at the same distance as the Hickson group and therefore they may belong to this interacting system. With Gemini optical (r) images, we discovered the knotty morphology of these objects (Figure 1), just like one would expect from young galaxies. But GMOS data provided us with one more piece of information that helped us understand bet- 22 GeminiFocus Therefore, due to their morphology and chemical composition, we suggested