Clusters of Galaxies: Mass Determination Methods, Biases, And Precision Cosmology

Abstract

The mass-function of galaxy clusters in the Universe reveals information about the formation, evolution, and processes behind celestial objects. Previous attempts to probe masses of clusters have depended on various methods, including kinematics and dynamics, X-ray observations, and gravitational lensing. When studies use X-ray observations to derive cluster masses, they assume that the gas within the cluster is in hydrostatic equilibrium (HSE). The problem with this assumption is that clusters are not necessarily in HSE. As such, HSE mass measurements are often compared with more reliable lensing masses in order to reveal the systematic bias of the HSE assumption. In this work, we investigate the uncertainties in the bias of mass determination for a sample of 25 galaxy clusters using precision cosmology. This will enable the use of clusters -- the most massive virialized systems in the universe -- as accurate tools in determining cosmological parameters including the dark-matter and dark-energy density of the universe. In this work, we measure a mean mass bias of $0.9\pm0.09$ -- consistent with the current literature.