[DUM2012] NGC 2623 1 , the SIMBAD biblio

We present new Gemini spectra of 14 new objects found within the HI tails of Hickson Compact Groups (HCGs) 92 and 100. Nine of them are Galaxy Evolution Explorer (GALEX) far-ultraviolet (FUV) and near-ultraviolet (NUV) sources. The spectra confirm that these objects are members of the compact groups and have metallicities close to solar, with an average value of 12+log(O/H) ∼ 8.5. They have average FUV luminosities 7 x 10⁴⁰erg/s and very young ages (<100Myr), and two of them resemble tidal dwarf galaxy (TDG) candidates. We suggest that they were created within gas clouds that were ejected during galaxy–galaxy interactions into the intergalactic medium, which would explain the high metallicities of the objects, inherited from the parent galaxies from which the gas originated. We conduct a search for similar objects in six interacting systems with extended HI tails: NGC 2623, NGC 3079, NGC 3359, NGC 3627, NGC 3718 and NGC 4656. We found 35 ultraviolet (UV) sources with ages < 100Myr; however, most of them are on average less luminous/massive than the UV sources found around HCG 92 and HCG 100. We speculate that this might be an environmental effect and that compact groups of galaxies are more favourable to TDG formation than other interacting systems.

Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the National Science Foundation (NSF) on behalf of the Gemini partnership: the NSF (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnologia e Innovacion Productiva (Argentina) – Observing run ID: GN-2003A-Q-53 and GN-2007B-Q-87.