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How typical is the Coma cluster?

Pimbblet, Kevin A.; Penny, Samantha J.; Davies, Roger L.


Samantha J. Penny

Roger L. Davies


Coma is frequently used as the archetype z ∼ 0 galaxy cluster to compare higher redshift work against. It is not clear, however, how representative the Coma cluster is for galaxy clusters of its mass or X-ray luminosity, and significantly, recent works have suggested that the galaxy population of Coma may be in some ways anomalous. In this work, we present a comparison of Coma to an X-ray-selected control sample of clusters. We show that although Coma is typical against the control sample in terms of its internal kinematics (sub-structure and velocity dispersion profile), it has a significantly high (∼3σ) X-ray temperature set against clusters of comparable mass. By de-redshifting our control sample cluster galaxies star formation rates using a fit to the galaxy main-sequence evolution at z < 0.1, we determine that the typical star formation rate of Coma galaxies as a function of mass is higher than for galaxies in our control sample at a confidence level of >99 per cent. One way to alleviate this discrepancy and bring Coma in line with the control sample would be to have the distance to Coma to be slightly lower, perhaps through a non-negligible peculiar velocity with respect to the Hubble expansion, but we do not regard this as likely given precision measurements using a variety of approaches. Therefore, in summary, we urge caution in using Coma as a z ∼ 0 baseline cluster in galaxy evolution studies.


Pimbblet, K. A., Penny, S. J., & Davies, R. L. (2014). How typical is the Coma cluster?. Monthly notices of the Royal Astronomical Society, 438(4), 3049-3057.

Journal Article Type Article
Acceptance Date Dec 12, 2013
Online Publication Date Jan 9, 2014
Publication Date Mar 1, 2014
Deposit Date Jun 5, 2015
Publicly Available Date Jun 5, 2015
Journal Monthly notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 438
Issue 4
Pages 3049-3057
Keywords Galaxies -- clusters -- general; Galaxies -- clusters -- individual -- Coma cluster; Galaxies -- evolution; X-rays -- galaxies -- clusters
Public URL
Publisher URL
Additional Information 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.


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Copyright Statement
© 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society

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