Joint Astrophysics Colloquium

Constraining Dark Energy by Counting X-ray Galaxy Clusters

Alexey Vikhlinin

CfA
Harvard University

Observations of the evolving cluster mass function provide a sensitive cosmological test which internally combines the geometric and growth of structure components. If cluster masses can be measured reliably from observables, the statistical power of this test is comparable to that from a similar number of high-z SN Ia. I will present results from a 400 square degrees X-ray cluster survey. Combination of cluster data with other cosmological datasets (WMAP, SNIa, BAO) constrains the equation of state parameter to better than 5%.