MSc defense by William Gruffyd Perry – University of Copenhagen

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MSc defense by William Gruffyd Perry

Title:  Analysing the Mass Structure of Small Gravitational Lens Galaxies in Galaxy Clusters

Supervisors: Claudio Grillo and Lise Christensen

Abstract: This thesis focuses on the estimate of the total mass of early-type galaxies, using strong gravitational lensing models, and the measurement of the luminous mass of these galaxies, using SED fitting techniques. These analyses require good photometric and spectroscopic data with which it becomes possible to explore the distribution of matter, luminous and dark, in lens galaxies. A gravitational lens works similarly to a normal optical lens, where in the former the deflection is due to the gravitational potential of the lens. Strong lensing systems are characterised by the presence of multiple images of a single background source. The images typically surround the central main lens. The system studied in this thesis is composed of 4 multiple images of a source at z = 2.387 created by two lens galaxies residing in a galaxy cluster at z = 0.352. The available observations were taken as part of the Cluster Lensing and Supernova survey with Hubble, CLASH, and its spectroscopic follow-up programme at the Very Large Telescope, CLASH-VLT.

The thesis will follow the following structure. Chapter 1 will introduce gravitational lensing and discuss, in detail, strong lensing theory, with focus being directed towards the description of lenses which are elliptical galaxies. In chapter 2 there will be a discussion of the general properties of elliptical galaxies and the laws which govern their structure and dynamics. An introduction of the lensing system that will be studied is done in chapter 3, followed by an estimate of the luminous masses of the two lenses found in that system and the redshifts of the lenses and the source. Chapter 4 will use strong lensing models to estimate the total mass contribution from the two lenses and attempt to disentangle their individual contributions. Chapter 5 will discuss the obtained results and estimate the luminous over total mass fraction of the main lensing galaxy and finally, chapter 6 will compare the results with other studies of this kind and discuss how this work can be expanded upon.

Thesis here >>