Dr. Hossein Khiabanian

Brown University

"Statistics of Dark Matter Halos via Maximum-Likelihood Weak Lensing Mass Reconstruction"

Gravitational lensing is formed when the light from a distant source is "bent" around a massive object. Recent access to deep, wide field, multi-color optical imaging has established weak gravitational lensing as an effective tool for discovering new clusters of galaxies and measuring the dark matter content of the Universe, so much that it is one of the main tools that will be employed in the future surveys to study the dark energy and its equation of state as well as the evolution of galaxy clustering. Weak gravitational lensing provides a parameter-free reconstruction of the projected mass distribution in clusters of galaxies without the disadvantage of relying on the luminous matter. However, it is otherwise an observationally expensive detection technique. Therefore, it is essential to make use of all the information provided by the data to improve the quality of the lensing analysis. Motivated by the limitations encountered with the commonly used "direct" reconstruction methods, I have developed an "inverse" multi-resolution maximum-likelihood reconstruction technique for producing two dimensional mass maps, which is capable of incorporating in the analysis many of the observables provided by gravitational lensing data sets. I present the method in detail and also the results of its application to the Deep Lens Survey data set. This reconstruction of the F2 field reveals a network of possible filamentary structures. I will discuss the properties of the highest significance peaks associated with these structures and also present the global statistics of peaks in the entire field. Filamentary structures in F2 appear to surround a significant candidate under-density or "void" detected at a S/N ~ 5, however the void interpretation could be complicated by lensing projection effects.

Back to Spring 2008 Astrophysics Seminars

Received May 5, 2008