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 stateparameter w within the context of the still uncertain redshift evolution ofgalaxy cluster structure. We show that for a particular X-ray survey (SZEsurvey) the constraints on w degrade by roughly a factor of 3 (factor of 2)when one accounts for the possibility of non--standard cluster evolution. Withfollowup measurements of a cosmology independent, mass--like quantity it ispossible to measure cluster evolution, improving constraints on cosmologicalparameters (like w Omega_M). We examine scenarios where 1%, 10% and 100% ofdetected clusters are followed up, showing that even a modest followup programcan enhance the final cosmological constraints. For the case of followupmeasurements on 1% of the cluster sample with an uncertainty of 30% onindividual cluster mass--like quantities, constraints on w are improved by afactor of 2 to 3. For the best case scenario of a zero curvature universe,these particular X-ray and SZE surveys can deliver uncertainties on w of ~4% to6%.Comment: Latex 8 pages, 4 figures, submitted to ApJ June 1