Cosmological Tests Using X-ray Observations of Clusters of Galaxies

X-ray emission from massive clusters of galaxies offers two independent and complementary methods for studying cosmology. The first uses measurements of the ratio of gas to total mass in hot, dynamically
relaxed clusters to provide a standard ruler, directly tracing the expansion of the Universe. This procedure produces constraints on dark energy and the mean dark matter density that are competitive with those
from type Ia supernova studies. The second method uses measurements of the distribution and growth of cosmic structure observed through the cluster X-ray luminosity function. These studies place tight constraints
on the amplitude of the density perturbation power spectrum and provide an independent probe of dark energy. The growth of structure is also potentially a powerful probe of modified gravity theories and inflation.
I will review recent results from these experiments and describe the prospects for improvement in the future.

A. Mantz

Stanford University