Cosmological Parameter Measurements from Galaxy Cluster Observations
 
Laura Grego 

Harvard-Smithsonian Center for Astrophysics & Union of Concerned Scientists
 
Abstract: 
Galaxy clusters are the largest relaxed structures we know about and are 
distributed widely over space.  As such, they are an ideal laboratory for 
making measurements of cosmological parameters.  
From observations of a cluster's Sunyaev-Zel'dovich effect (SZE), a 
small spectral distortion of the cosmic microwave background radiation by 
the cluster's hot atmosphere, and the X-ray emission from this atmosphere, 
one can measure the cluster's gas mass fraction and its angular diameter 
distance.  From these quantities, one can constrain the universal baryonic 
mass fraction and the Hubble parameter, respectively, along with other 
cosmological parameters of interest.  
 
I will discuss our experiment to measure these quantities using the SZE 
and X-rays, and the results, as well as some insights gained into the 
physics of galaxy clusters through this work.