Lasse Albæk's MSc thesis defense
Lasse Albæk MSc thesis defense
Title: Dark Matter Dynamics in Galaxy Clusters
Date: Thurs., July 7 2016
Place: DARK Lounge
Supervisor: Steen H. Hansen
Censor: Steen Hannestad, Aarhus U.
Dark matter is the main matter component of the universe, yet next to nothing is known about the particles of which it consists. One of the dynamical properties that is expected to be sensitive to the dark matter self-interaction cross section is the velocity anisotropy, β, in dark matter haloes. Previously, the ability to measure β has been limited by the resolution and signal-to-noise ratio in X-ray spectroscopy. Also, testing and calibrating a method for estimating β has been hindered by the inability of simulations to produce realistic ICM properties. Now, observations and simulations have advanced to a point where it should be possible to estimate β(r) in the nearest galaxy clusters. In this thesis a new method for estimating β(r) beyond r200 is tested on clusters from 2 hydrodynamic cosmological simu- lations, and is found to give fairly accurate results inside 1.3 r200. The method is then used to estimate β(r) in the Perseus cluster out to 1.1 r200, where it is found to be positive and slightly increasing as a function of radius. In both cases the method is found to contain a large degree of uncertainty, but this is shown to mainly be the result of uncertainties in the hydrodynamic mass profile estimates. The results therefore indicate that it is possible to measure β(r) in clusters using the developed method, if the cluster mass profile can be accurately estimated.