Bibcode
Armitage, T. J.; Barnes, David J.; Kay, Scott T.; Bahé, Yannick M.; Dalla Vecchia, C.; Crain, Robert A.; Theuns, Tom
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 474, Issue 3, p.3746-3759
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3
2018
Citations
39
Refereed citations
35
Description
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.
Related projects
Numerical Astrophysics: Galaxy Formation and Evolution
How galaxies formed and evolved through cosmic time is one of the key questions of modern astronomy and astrophysics. Cosmological time- and length-scales are so large that the evolution of individual galaxies cannot be directly observed. Only through numerical simulations can one follow the emergence of cosmic structures within the current
Claudio
Dalla Vecchia