IMAGES IV: strong evolution of the oxygen abundance in gaseous phases of intermediate mass galaxies from z ~ 0.8*
GEPI , Observatoire de Paris, CNRS, University Paris Diderot, 5 place Jules Janssen, 92195 Meudon, France e-mail: email@example.com
2 CENTRA, Instituto Superior Tecnico, Av. Rovisco Pais 1049-001 Lisboa, Portugal
3 ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
4 National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, PR China
5 Laboratoire d'Astrophysique de Marseille, Observatoire Astronomique de Marseille-Provence, 2 place Le Verrier, 13248 Marseille, France
6 MPIA, Königstuhl 17, 69117 Heidelberg, Germany
7 IFARHU-SENACYT, Technological University of Panama, 0819-07289 Panama, Rep. of Panama
8 Centre de Recherche Astronomique de Lyon, 9 Avenue Charles André, 69561 Saint-Genis-Laval Cedex, France
9 Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007, India
10 Stockholm Observatory, AlbaNova University Center, Stockholms Center for Physics, Astronomy and Biotechnology, Roslagstullsbacken 21, 10691 Stockholm, Sweden
11 INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
12 Department of Physics, University of Calicut, Kerala 673635, India
13 INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Florence, Italy
14 IASF-INAF - via Bassini 15, 20133 Milano, Italy
Accepted: 21 September 2008
Context. Intermediate mass galaxies (> 1010 ) at z ~ 0.6 are the likeliest progenitors of the present-day, numerous population of spirals. There is growing evidence that they have evolved rapidly in the last 6 to 8 Gyr, and likely already have formed a significant fraction of their stellar mass, often showing perturbed morphologies and kinematics.
Aims. We have gathered a representative sample of 88 such galaxies and have provided robust estimates of their gas phase metallicity.
Methods. We used moderate spectral resolution spectroscopy at VLT/FORS2 with an unprecedentedly high allowing us to remove biases coming from interstellar absorption lines and extinction, to establish robust values of R23 = ([OII]λ3727 + [OIII]4959, 5007)/Hβ.
Results. We definitively confirm that the predominant population of z ~ 0.6 starbursts and luminous IR galaxies (LIRGs) are on average two times less metal rich than the local galaxies at a given stellar mass. We do find that the metal abundance of the gaseous phase of galaxies evolves linearly with time, from to and after comparing with other studies, from to . Combining our results with the reported evolution of the Tully Fisher relation, we find that such an evolution requires that ~30% of the stellar mass of local galaxies have been formed through an external supply of gas, thus excluding the closed box model. Distant starbursts & LIRGs have properties (metal abundance, star formation efficiency & morphologies) similar to those of local LIRGs. Their underlying physics is likely dominated by gas infall, probably through merging or interactions.
Conclusions. Our study further supports the rapid evolution of z ~ 0.4–1 galaxies. Gas exchange between galaxies is likely the main cause of this evolution.
Key words: galaxies: evolution / galaxies: ISM / galaxies: spiral / galaxies: starburst / infrared: galaxies
© ESO, 2008