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Chemical abundances in a UV-selected sample of galaxies
Authors:ThierryContini  Marie ATreyer  MarkSullivan  Richard SEllis
Institution:1Observatoire Astronomique de Strasbourg, 11 rue de l'Université, F-67000 Strasbourg, France; 2Observatoire Midi-Pyrénées, Laboratoire d'Astrophysique (UMR 5572), 14 avenue E. Belin, F-31400 Toulouse, France; 3Laboratoire d'Astrophysique de Marseille, Traverse du Siphon, F-13376 Marseille, France; 4Institute of Astronomy, Madingley Road, Cambridge CB3 0HA; 5California Institute of Technology, Pasadena, CA 91125, USA
Abstract:We discuss the chemical properties of a sample of UV-selected intermediate-redshift  (0≲z≲0.4)  galaxies in the context of their physical nature and star-formation history. This work represents an extension of our previous studies of the rest-frame UV-luminosity function (Treyer et al.) and the star-formation properties of the same sample (Sullivan et al.) . We revisit the optical spectra of these galaxies and perform further emission-line measurements restricting the analysis to those spectra with the full set of emission lines required to derive chemical abundances. Our final sample consists of 68 galaxies with heavy-element abundance ratios and both UV and CCD B -band photometry. Diagnostics based on emission-line ratios show that all but one of the galaxies in our sample are powered by hot, young stars rather than by an AGN. Oxygen-to-hydrogen (O/H) and nitrogen-to-oxygen (N/O) abundance ratios are compared with those of various local and intermediate-redshift samples. Our UV-selected galaxies span a wide range of oxygen abundances, from ∼0.1 to 1 Z, intermediate between low-mass H  ii galaxies and massive starburst nuclei. For a given oxygen abundance, most have strikingly low N/O values. Moreover, UV-selected and H  ii galaxies systematically deviate from the usual metallicity–luminosity relation in the sense of being more luminous by  2–3 mag  . Adopting the 'delayed-release' chemical evolution model, we propose our UV-selected sources are observed at a special stage in their evolution, following a powerful starburst that enriched their ISM in oxygen and temporarily lowered their mass-to-light ratios. We discuss briefly the implications of our conclusions on the nature of similarly selected high-redshift galaxies.
Keywords:galaxies: abundances  galaxies: evolution  galaxies: starburst  ultraviolet: galaxies
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