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Published July 17, 2009 | Published
Journal Article Open

Testing model predictions of the cold dark matter cosmology for the sizes, colours, morphologies and luminosities of galaxies with the SDSS

Abstract

The huge size and uniformity of the Sloan Digital Sky Survey (SDSS) make possible an exacting test of current models of galaxy formation. We compare the predictions of the galform semi-analytical galaxy formation model for the luminosities, morphologies, colours and scalelengths of local galaxies. galform models the luminosity and size of the disc and bulge components of a galaxy, and so we can compute quantities which can be compared directly with SDSS observations, such as the Petrosian magnitude and the Sérsic index. We test the predictions of two published models set in the cold dark matter cosmology: the Baugh et al. model, which assumes a top-heavy initial mass function (IMF) in starbursts and superwind feedback, and the Bower et al. model, which uses active galactic nucleus feedback and a standard IMF. The Bower et al. model better reproduces the overall shape of the luminosity function, the morphology–luminosity relation and the colour bimodality observed in the SDSS data, but gives a poor match to the size–luminosity relation. The Baugh et al. model successfully predicts the size–luminosity relation for late-type galaxies. Both models fail to reproduce the sizes of bright early-type galaxies. These problems highlight the need to understand better both the role of feedback processes in determining galaxy sizes, in particular the treatment of the angular momentum of gas reheated by supernovae, and the sizes of the stellar spheroids formed by galaxy mergers and disc instabilities.

Additional Information

© 2009 The Authors. Journal compilation. Accepted 2009 May 9. Received 2009 March 31; in original form 2008 December 23. We thank Shiyin Shen for kindly providing results in electronic form to include in our figures and the anonymous referee for providing a useful report. This work was supported in part by the European Commission's ALFA-II project through its funding of the Latin American European Network for Astrophysics and Cosmology (LENAC), by a Science and Technology Facilities Council rolling grant and by the Royal Society. JEG acknowledges receipt of a fellowship funded by the European Commission's Framework Programme 6, through the Marie Curie Early Stage Training project MEST-CT-2005-021074. AJB acknowledges the support of the Gordon and Betty Moore Foundation. Funding for the creation and distribution of the SDSS Archive has been provided by the Alfred P. Sloan Foundation, the participating institutions, the National Aeronautics and Space Administration, the National Science Foundation, the US Department of Energy, the Japanese Monbukagakusho and the Max Planck Society. The SDSS web site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the participating institutions. The participating institutions are The University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, Los Alamos National Laboratory, the Max Planck Institute for Astronomy (MPIA), the Max Planck Institute for Astrophysics (MPA), New Mexico State University, Princeton University, the United States Naval Observatory and the University of Washington.

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August 20, 2023
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