Journal Article

The 6dF Galaxy Survey: stellar population trends across and through the Fundamental Plane

Christopher M. Springob, Christina Magoulas, Rob Proctor, Matthew Colless, D. Heath Jones, Chiaki Kobayashi, Lachlan Campbell, John Lucey and Jeremy Mould

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 420, issue 4, pages 2773-2784
Published in print March 2012 | ISSN: 0035-8711
Published online March 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19900.x
The 6dF Galaxy Survey: stellar population trends across and through the Fundamental Plane

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We present results from an analysis of stellar population parameters for 7132 galaxies in the 6dF Galaxy Survey Fundamental Plane (FP) sample. We bin the galaxies along the axes, v1, v2 and v3, of the tri-variate Gaussian to which we have fitted the galaxy distribution in effective radius, surface brightness and central velocity dispersion (FP space), and compute median values of stellar age, [Fe/H], [Z/H] and [α/Fe]. We determine the directions of the vectors in FP space along which each of the binned stellar population parameters vary most strongly. In contrast to previous work, we find stellar population trends not just with velocity dispersion and FP residual, but with radius and surface brightness as well. The most remarkable finding is that the stellar population parameters vary through the plane (v1 direction) and across the plane (v3 direction), but show no variation at all along the plane (v2 direction). The v2 direction in FP space roughly corresponds to ‘luminosity density’. We interpret a galaxy’s position along this vector as being closely tied to its merger history, such that early-type galaxies with lower luminosity density are more likely to have undergone major mergers. This conclusion is reinforced by an examination of the simulations of Kobayashi, which show clear trends of merger history with v2.

Keywords: galaxies: elliptical and lenticular, cD; galaxies: evolution; galaxies: fundamental parameters; galaxies: structure

Journal Article.  9590 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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