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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.; Smith, R.J.

Dissecting the red sequence: the bulge and disc colours of early-type galaxies in the Coma cluster Thumbnail


Authors

J.T.C.G. Head

M.J. Hudson



Abstract

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 per cent of analysis sample galaxies. Bulge half-light radii are found to be uncorrelated with galaxy luminosity (Re ∼ 1 kpc, 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 ∼2–3  times older, or ∼ 2  times 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.

Citation

Head, J., Lucey, J., Hudson, M., & Smith, R. (2014). Dissecting the red sequence: the bulge and disc colours of early-type galaxies in the Coma cluster. Monthly Notices of the Royal Astronomical Society, 440(2), 1690-1711. https://doi.org/10.1093/mnras/stu325

Journal Article Type Article
Acceptance Date Feb 14, 2014
Online Publication Date Mar 26, 2014
Publication Date May 11, 2014
Deposit Date Apr 4, 2014
Publicly Available Date Apr 7, 2014
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 440
Issue 2
Pages 1690-1711
DOI https://doi.org/10.1093/mnras/stu325
Keywords Galaxies, Clusters, Abell 1656, Elliptical and lenticular, CD, Evolution, Formation, Structure.

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Copyright Statement
Advance online version This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2014 The Authors
Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.


Published Journal Article (Final published version) (4.6 Mb)
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Copyright Statement
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