Illuminating the dark universe with galaxy clusters

• Main Author: Mulroy, Sarah Louise
• Published: University of Birmingham 2017
• Subjects: 523.1; QC Physics
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.715710

Structure in the Universe formed from tiny density perturbations that grew into the complex cosmic web we see today. At the nodes of this web we find galaxy clusters - the largest gravitationally bound objects ever observed. Their abundance and their properties provide an insight into the evolution of the Universe, so they are important probes of cosmology. Knowledge of their mass is critical for cosmology, but as most of this mass is in the form of dark matter it is a complex measurement, motivating interest in scaling relations between other observables and mass. In this thesis I use a sample of galaxy clusters with high quality multiwavelength observations to investigate these cluster observables and their scaling relations with mass. I find that the easily measured near-infrared and optical cluster luminosities tightly scale with mass, making them promising tools for cosmology with future wide field surveys. I also parameterise scaling relations of observables across a wide range of the electromagnetic spectrum, finding the results to be consistent with self-similarity, in which clusters are formed from a single spherical collapse driven by gravity, and with a closed box picture, in which clusters maintain their baryon budget.