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Clusters and cosmic onions: a description of galaxy dynamics in the quasi-linear regime

Hall, Emily Anne; (2018) Clusters and cosmic onions: a description of galaxy dynamics in the quasi-linear regime. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

This thesis investigates the dynamics of galaxies around clusters in the quasi-linear regime, with the ultimate aim of providing cluster mass constraints which can be combined with weak lensing measurements in order to perform tests of General Relativity. Dark matter simulations are populated with galaxies using a halo occupation distribution, and used to develop and test models which describe di↵erent aspects of galaxy dynamics around clusters. A heuristic analytical model is presented describing the infall profile of galaxies onto a cluster of given mass, which is shown to fit the simulations remarkably well on quasilinear scales. The velocity dispersion of galaxies in the simulations is also examined, and a model developed which describes how this e↵ect varies as a function of position relative to the cluster centre. These models of galaxy infall and velocity dispersion are combined to provide predictions of the cluster-galaxy redshift space correlation function, or cosmic onion, which show a relatively good agreement with the simulations. The cosmic onion model is used to obtain cluster mass constraints from redshift space distortions observed in the simulations, in order to demonstrate the robustness of this method. In this work the uncertainty on cluster mass was estimated with all other halo parameters fixed, and was found to be approximately 2% at the 2 confidence level for a halo mass of ⇠ 1013 Msolarh1. However in practice the accuracy of these constraints depends on how many free parameters are considered in the halo occupation distribution, as some are degenerate with the cluster mass. The techniques developed here can be applied to observational data from the upcoming generation of spectroscopic galaxy surveys, potentially improving constraints on the dynamic mass of clusters measured from redshift space distortions.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Clusters and cosmic onions: a description of galaxy dynamics in the quasi-linear regime
Event: UCL
Open access status: An open access version is available from UCL Discovery
Language: English
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10057210
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