Clusters of galaxies and gravitational lensing by clusters of galaxies have been used as probes of baryonic and dark matter for several decades, and their use continues to mature. However, their use in constraining cosmological parameters in future surveys is currently limited by large systematics errors. Errors in weak lensing shear measurements need to improve by an order of magnitude, and masses determinations of clusters of galaxies need reliable corrections for non-virialized structures. This project intends to combine observational measurements of weak lensing in galaxy clusters with realistic simulations of weakly lensed images with the goal of gaining sufficient understanding of the above systematic errors to allow weak lensing and cluster mass studies to lead to precise and reliable measurements of cosmological parameters.
Specifically, the investigators plan the following: (1) Building on previous success from the Bullet Cluster study, to use known cluster mergers and search for unknown ones to determine whether gravity at large distances really does follow an inverse square force law. The intent is to rule out models of gravity "mixed" with part classical and part alternative. (2) To use four different techniques on a sample of clusters, chosen to be close to virial equilibrium, to determine clusters masses and determine their consistency. This intent is to provide correction factors and/or statistics to identify any biased or problematic techniques and to identify and eliminate problem clusters from existing catalogues for the entire scientific community. (3) To combine observational measurements with simulations to what precision a point spread function (PSF) can be determined in all parts of an image. This work is intended to be part of larger international simulation program called "STeP" to provide accurate simulations for future surveys.
Educationally, this project provides training for three undergraduate and three graduate students through direct involvement in research and technical training in modern research tools. In addition, this project includes an education and public outreach program with the goal of increasing scientific literacy in the historically underserved Appalachian regions of Ohio, West Virginia, and Kentucky through a combination of public outreach events and the development of a new laboratory component to an introductory astronomy class that makes use of the data obtained in this project.