Allen

Cosmological Constraints from X-ray Studies of Galaxy Clusters
Steven Allen (KIPAC (Stanford/SLAC))

X-ray observations of galaxy clusters provide one of our most powerful tools to investigate dark energy. I will discuss the latest results from two independent techniques based on X-ray cluster studies. 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 experiment uses observations of the growth of cosmic structure, as manifested in the evolution of the X-ray luminosity function of galaxy clusters. It leads to tight constraints on the amplitude of mass fluctuations in the Universe, and new constraints on dark energy. I will emphasize the allowances for systematic uncertainties incorporated into these experiments and place the results in the context of other current cosmological data. I also will comment on the prospects for improving these results over the next few years.