Importance of cluster structural evolution in using X-ray and Sunyaev-Zeldovich effect galaxy cluster surveys to study dark energy

We examine the prospects for measuring the dark energy equation-of-state parameter w within the context of the still uncertain redshift evolution of galaxy cluster structure. We show that for a particular X-ray survey ( Sunyaev-Zeldovich effect [SZE] survey), the constraints on w degrade by roughly a factor of 3 ( factor of 2) when one accounts for the possibility of nonstandard cluster evolution. With follow-up measurements of a cosmology-independent, masslike quantity it is possible to measure cluster evolution, improving constraints on cosmological parameters (such as w and Omega(M)). We examine scenarios in which 1%, 10%, and 100% of detected clusters are followed up, showing that even a modest follow-up program can enhance the final cosmological constraints. For the case of follow-up measurements on 1% of the cluster sample with an uncertainty of 30% on individual cluster masslike quantities, constraints on w are improved by a factor of 2 3. For the best-case scenario of a zero-curvature universe, these particular X-ray and SZE surveys can deliver uncertainties on w of similar to4%-6%.