EXC-Halo Lensing Profiles and Merging Histories

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

AST 0205935 Cohn In modern cosmology, the basic building block of all cosmic structure is a halo, i.e., a condensed clump of matter. The Universe is constantly evolving, with these halos falling towards each other and merging under the influence of gravity. This theoretical project will study two aspects of these basic building blocks: The first part of the project involves haloes of individual galaxies. Numerical calculations will be used to model the patterns formed when distant light sources (such as distant galaxies) have their light bent by gravity when it passes close to a second galaxy which lies between the earth and the more distant one (gravitational lensing). The halo around the intervening galaxy can be studied using this method. Since the constant merging of halos implies that haloes of nearby galaxies will contain clumps and sub-clumps, these structures can be mapped-out using gravitational lensing. The numerical calculations will identify what lensing as a tool can discern about the shape of a galaxy halo. This knowledge will then be applied to the wealth of new observational data that is available and used to determine the actual structure of nearby galaxy haloes. The second part of this project focuses on major mergers of larger halos, which are associated with clusters of galaxies. Major mergers produce a severely disrupted halo. They can both create new observational signals and contaminate measurements which rely on models which assume undisturbed, idealized properties for the cluster haloes. Numerical calculations will be used to determine how often these mergers occur, how closely in space they are expected to occur and how these results depend upon the many different observational and numerical parameters which characterize a cluster halo. These numerical results will then be used to interpret observations of galaxy cluster halo lensing. ***