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IMAGES IV: strong evolution of the oxygen abundance in gaseous phases of intermediate mass galaxies from z ~ 0.8
Stockholm University, Faculty of Science, Department of Astronomy.
2008 (Swedish)In: Astronomy and Astrophysics, Vol. 492Article in journal (Other (popular science, discussion, etc.)) Published
Abstract [sv]

Context: Intermediate mass galaxies (> 1010 M_ȯ) 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 S/N allowing us to remove biases coming from interstellar absorption lines and extinction, to establish robust values of R23 = ([OII]λ3727 + [OIII]λλ4959, 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 z = 1 to z = 0 and after comparing with other studies, from z = 3 to z = 0. 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.

Place, publisher, year, edition, pages
2008. Vol. 492
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:su:diva-17924OAI: diva2:184445
Available from: 2009-01-22 Created: 2009-01-22 Last updated: 2011-01-10Bibliographically approved

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Östlin, Göran
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Department of Astronomy
Astronomy, Astrophysics and Cosmology

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