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Chemical enrichment and the origin of the colour-magnitude relation of elliptical galaxies in a hierarchical merger model

1998; Oxford University Press; Volume: 294; Issue: 4 Linguagem: Inglês

10.1046/j.1365-8711.1998.01322.x

1365-2966

Guinevere Kauffmann, S. Charlot,

Astronomy and Astrophysical Research

Monthly Notices of the Royal Astronomical SocietyVolume 294, Issue 4 p. 705-717 Chemical enrichment and the origin of the colour–magnitude relation of elliptical galaxies in a hierarchical merger model Guinevere Kauffmann, Guinevere Kauffmann Max-Planck-Institut für Astrophysik, D-85740 Garching, Germany,Search for more papers by this authorStéphane Charlot, Stéphane Charlot Institut d'Astrophysique du CNRS, 98 bis Boulevard Arago, F-75014 Paris, FranceSearch for more papers by this author Guinevere Kauffmann, Guinevere Kauffmann Max-Planck-Institut für Astrophysik, D-85740 Garching, Germany,Search for more papers by this authorStéphane Charlot, Stéphane Charlot Institut d'Astrophysique du CNRS, 98 bis Boulevard Arago, F-75014 Paris, FranceSearch for more papers by this author First published: 04 April 2002 https://doi.org/10.1046/j.1365-8711.1998.01322.xCitations: 93AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract In this paper, we present a model of the formation and chemical enrichment of elliptical galaxies that differs from the conventional picture in two fundamental ways. (i) Ellipticals do not form in a single monolithic collapse and burst of star formation at high redshift. Instead, most of their stars form at modest rates in disc galaxies, which then merge to form the ellipticals. (ii) Galaxies do not undergo 'closed-box' chemical evolution. Instead, metals can be transferred between the stars, cold gas and hot gas haloes of the galaxies. It is assumed that metals are ejected out of disc galaxies during supernova explosions and that these metals enter the hot gas component. The fact that metals are more easily ejected from small galaxies leads to the establishment of a mass–metallicity relation for the disc systems. Large ellipticals are more metal-rich because they are formed from the mergers of larger discs. We use semi-analytic techniques to follow the formation, evolution and chemical enrichment of cluster elliptical galaxies in a merging hierarchy of dark matter haloes. The inclusion of the new metallicity-dependent spectral synthesis models of Bruzual & Charlot enables us to compute the colours, line indices and mass-to-light ratios of these galaxies. We find that with physically realistic parameters and with the assumption that feedback is efficient, even in massive galaxies, we are able to reproduce the slope and scatter of the colour–magnitude and the Mg2–σ relations for cluster ellipticals. Bright field ellipticals have the same metallicities but are younger than their cluster counterparts, and thus exhibit more scatter in the equivalent widths of their Balmer absorption lines. We are not able to match the increase in M/L for bright ellipticals if we assume their mass to measure purely the total quantity of stars in these objects. We also study the evolution of these relations to high redshift. We show that the luminosity–metallicity relation does not change with redshift, but the mean stellar age of the galaxies scales with the age of the Universe. This is why the evolution of cluster ellipticals appears to be well described by simple passive evolution. Finally, we study the enrichment history of the intracluster gas. Our models predict that more than 80 per cent of the metals were ejected by galaxies with circular velocities less than 250 km s−1 at redshifts greater than 1. The metallicity of the intracluster medium is thus predicted to evolve very little out to z>1. Citing Literature Volume294, Issue4March 1998Pages 705-717 RelatedInformation