Mon. Not. R. Astron. Soc., 440, 1690-1711 (2014/May-2)
Dissecting the red sequence: the bulge and disc colours of early-type galaxies in the Coma cluster.
HEAD J.T.C.G., LUCEY J.R., HUDSON M.J. and SMITH R.J.
Abstract (from CDS):
We explore the internal structure of red-sequence galaxies in the Coma cluster across a wide range of luminosities (-17 > Mg > -22) and cluster-centric radii (0 < rcluster < 1.3 r200). We present the 2D bulge-disc decomposition of galaxies in deep Canada-France-Hawaii Telescope u, g, i imaging using galfit. Rigorous filtering is applied to identify an analysis sample of 200 galaxies which are well described by an `archetypal' S0 structure (central bulge + outer disc). We consider internal bulge and/or disc colour gradients by allowing component sizes to vary between bands. Gradients are required for 30 percent of analysis sample galaxies. Bulge half-light radii are found to be uncorrelated with galaxy luminosity (Re ∼ 1kpc, n ∼ 2) for all but the brightest galaxies (Mg < -20.5). The S0 discs are brighter (at fixed size, or smaller at fixed luminosity) than those of star-forming spirals. A similar colour-magnitude relation is found for both bulges and discs. The global red sequence for S0s in Coma hence results from a combination of both component trends. We measure an average bulge - disc colour difference of 0.09±0.01 mag in g - i, and 0.16±0.01 mag in u - g. Using simple stellar population models, bulges are either ∼ 2-3times older, or ∼ 2times more metal rich than discs. The trend towards bluer global S0 colours observed further from Coma's core is driven by a significant correlation in disc colour with cluster-centric radius. An equivalent trend is detected in bulge colours at a marginal significance level. Our results therefore favour environment-mediated mechanisms of disc fading as the dominant factor in S0 formation.
© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2014)
galaxies: clusters: individual: Abell 1656 - galaxies: elliptical and lenticular, cD - galaxies: evolution - galaxies: formation - galaxies: structure
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<Available at CDS (J/MNRAS/440/1690): tabled1.dat tabled3.dat>
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