Strong gravitational lensing : blueprints for galaxy-cluster core reconstruction

• Main Author: Newbury, Peter Robert
• Format: Others
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/8568

When rays of light pass by a massive object they are very slightly deflected towards the centre-of- mass of the object. If two or more diverging beams of light re-converge onto an serendipitous observer, this observer may see multiple, magnified images of the source of light. This process is known as gravitational lensing, and has been observed in several dozen spectacular cases. Based on the appearance of the lensed arcs of light, we attempt to "invert" the lens to find the distribution of mass that will produce just such a configuration of lensed objects. In this thesis, we propose a two-stage inversion scheme. First, the distribution of mass on the deflector plane and the geometry of the source-deflector-observer optical system are established. This is done by numerically simulating the lensing of light past a parametric mass model, and interactively adjusting the handful of model parameters to match the positions of the simulated and observed lensed arcs. At the same time, this determines the magnification of the background source induced by the lensing process. The predicted magnification is then removed from the data to reveal the intrinsic, though still distorted, background distribution of light. After tracing each lensed ray back to the source plane, the data are recombined to produce a surface brightness distribution of the source. This two-stage inversion scheme produces a parametric model of the deflector and a pixelised rendering of the background source which together mimic the observed gravitationally lensed features. We test the viability of scheme itself on a well-studied collection of lensed objects in the galaxy-cluster MS 2137. Confident in the algorithm, we apply it second time to predict the distribution of mass in the galaxy-cluster MS 1455 responsible for an observed triplet of lensed arcs. Our predictions about the lens in MS 1455 make it particularly interesting, for a single background source is responsible for both tangential arcs and a radial arc. === Science, Faculty of === Mathematics, Department of === Graduate