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Cosmology with velocity dispersion counts: an alternative to measuring cluster halo masses

Caldwell, CE and McCarthy, IG and Baldry, IK and Collins, CA and Schaye, J and Bird, S (2016) Cosmology with velocity dispersion counts: an alternative to measuring cluster halo masses. Monthly Notices of the Royal Astronomical Society, 462 (4). ISSN 0035-8711

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The evolution of galaxy cluster counts is a powerful probe of several fundamental cosmological parameters. A number of recent studies using this probe have claimed tension with the cosmology preferred by the analysis of the Planck primary CMB data, in the sense that there are fewer clusters observed than predicted based on the primary CMB cosmology. One possible resolution to this problem is systematic errors in the absolute halo mass calibration in cluster studies, which is required to convert the standard theoretical prediction (the halo mass function) into counts as a function of the observable (e.g., X-ray luminosity, Sunyaev-Zel'dovich flux, optical richness). Here we propose an alternative strategy, which is to directly compare predicted and observed cluster counts as a function of the one-dimensional velocity dispersion of the cluster galaxies. We argue that the velocity dispersion of groups/clusters can be theoretically predicted as robustly as mass but, unlike mass, it can also be directly observed, thus circumventing the main systematic bias in traditional cluster counts studies. With the aid of the BAHAMAS suite of cosmological hydrodynamical simulations, we demonstrate the potential of the velocity dispersion counts for discriminating even similar lambda CDM models. These predictions can be compared with the results from redshift surveys such as the highly complete Galaxy And Mass Assembly (GAMA) survey.

Item Type: Article
Additional Information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record "Cosmology with velocity dispersion counts: an alternative to measuring cluster halo masses" is available online at:http://dx.doi.org/10.1093/mnras/stw1892
Uncontrolled Keywords: astro-ph.CO; astro-ph.CO
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
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Date Deposited: 01 Aug 2016 09:54
Last Modified: 23 Jan 2017 13:37
URI: http://researchonline.ljmu.ac.uk/id/eprint/3123

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