Speaker: Daniel Wik (University of Virginia)
The abundance of galaxy clusters as a function of mass and redshift depends sensitively on the background cosmology and can be used as a precision probe of dark energy if these properties can be efficiently extracted from surveys. Upcoming SZ surveys, for example, will provide accurate cluster masses if the state of the intracluster gas is sufficiently relaxed and/or understood. However, merger events between clusters can disrupt this state, and they also reveal a nonthermal, relativistic phase of the gas that may add non-negligible pressure support and thus bias mass-observable scaling relations. In this talk, Professor Wik will show that while major cluster mergers temporarily boost the SZ Comptonization parameter, these boosts will not lead to biased cosmological parameter estimates as long as the SZ signal is integrated over the entire cluster. He will also present Suzaku and Swift searches for inverse Compton emission from clusters, including Coma and Abell 3667, which imply that relativistic components in the ICM may be energetically significant.