Constraints on Cosmological Parameters from Future Galaxy Cluster Surveys

Abstract

We study the expected redshift evolution of galaxy cluster abundance between\n0 < z < 3 in different cosmologies, including the effects of the cosmic\nequation of state parameter w=p/rho. Using the halo mass function obtained in\nrecent large scale numerical simulations, we model the expected cluster yields\nin a 12 deg^2 Sunyaev-Zeldovich Effect (SZE) survey and a deep 10^4 deg^2 X-ray\nsurvey over a wide range of cosmological parameters. We quantify the\nstatistical differences among cosmologies using both the total number and\nredshift distribution of clusters. Provided that the local cluster abundance is\nknown to a few percent accuracy, we find only mild degeneracies between w and\neither Omega_m or h. As a result, both surveys will provide improved\nconstraints on Omega_m and w. The Omega_m-w degeneracy from both surveys is\ncomplementary to those found either in studies of CMB anisotropies or of\nhigh-redshift Supernovae (SNe). As a result, combining these surveys together\nwith either CMB or SNe studies can reduce the statistical uncertainty on both w\nand Omega_m to levels below what could be obtained by combining only the latter\ntwo data sets. Our results indicate a formal statistical uncertainty of about\n3% (68% confidence) on both Omega_m and w when the SZE survey is combined with\neither the CMB or SN data; the large number of clusters in the X-ray survey\nfurther suppresses the degeneracy between w and both Omega_m and h. Systematics\nand internal evolution of cluster structure at the present pose uncertainties\nabove these levels. We briefly discuss and quantify the relevant systematic\nerrors. By focusing on clusters with measured temperatures in the X-ray survey,\nwe reduce our sensitivity to systematics such as non-standard evolution of\ninternal cluster structure.\n