Department of Physics & Astronomy

Fall 2008 Colloquia

 

Steven Allen

Steven Allen

Stanford University
Cosmological Constraints from X-ray Studies of Galaxy Clusters
November 3, 2008, 4PM, Thornton 411

X-ray observations of galaxy clusters provide powerful cosmological constraints via two independent methods. The first uses measurements of the baryonic mass fraction in the largest, dynamically relaxed clusters. This method, like type Ia supernovae studies, measures distance as a function of redshift and traces the acceleration of the Universe directly. It also provides a tight constraint on the mean matter density. The second method observes the evolution of the galaxy cluster mass function. It leads to tight constraints on the amplitude of mass fluctuations in the Universe, and new constraints on dark energy. I will discuss the latest results from both experiments, emphasizing the conservative allowances for systematic uncertainties incorporated into the analyses, and placing the results in context with other, current cosmological data. I will also discuss the prospects for significant near-term improvements in the results.
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