Thomas J. Armitage
The Cluster-EAGLE project: velocity bias and the velocity dispersion–mass relation of cluster galaxies
Armitage, Thomas J.; Barnes, David J.; Kay, Scott T.; Bahé, Yannick M.; Dalla Vecchia, Claudio; Crain, Robert A.; Theuns, Tom
Authors
David J. Barnes
Scott T. Kay
Yannick M. Bahé
Claudio Dalla Vecchia
Robert A. Crain
Professor Tom Theuns tom.theuns@durham.ac.uk
Professor
Abstract
We use the Cluster-EAGLE simulations to explore the velocity bias introduced when using galaxies, rather than dark matter particles, to estimate the velocity dispersion of a galaxy cluster, a property known to be tightly correlated with cluster mass. The simulations consist of 30 clusters spanning a mass range 14.0 ≤ log10(M200 c/M⊙) ≤ 15.4, with their sophisticated subgrid physics modelling and high numerical resolution (subkpc gravitational softening), making them ideal for this purpose. We find that selecting galaxies by their total mass results in a velocity dispersion that is 5–10 per cent higher than the dark matter particles. However, selecting galaxies by their stellar mass results in an almost unbiased (<5 per cent) estimator of the velocity dispersion. This result holds out to z = 1.5 and is relatively insensitive to the choice of cluster aperture, varying by less than 5 per cent between r500 c and r200 m. We show that the velocity bias is a function of the time spent by a galaxy inside the cluster environment. Selecting galaxies by their total mass results in a larger bias because a larger fraction of objects have only recently entered the cluster and these have a velocity bias above unity. Galaxies that entered more than 4 Gyr ago become progressively colder with time, as expected from dynamical friction. We conclude that velocity bias should not be a major issue when estimating cluster masses from kinematic methods.
Journal Article Type | Article |
---|---|
Acceptance Date | Nov 16, 2017 |
Online Publication Date | Nov 23, 2017 |
Publication Date | Mar 1, 2018 |
Deposit Date | Jan 16, 2018 |
Publicly Available Date | Jan 17, 2018 |
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 | 474 |
Issue | 3 |
Pages | 3746-3759 |
DOI | https://doi.org/10.1093/mnras/stx3020 |
Public URL | https://durham-repository.worktribe.com/output/1341334 |
Related Public URLs | https://arxiv.org/abs/1708.00508 |
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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
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