SUBARU SCIENCE SEMINAR

Friday 29 May 1998 at 10:30am in the Subaru HQ Seminar Room

Tetsu Kitayama - University of Tokyo

"Number counts of galaxy clusters in X-ray and submm bands"

ABSTRACT:"The number counts (logN-logS relation) of X-ray clusters of galaxies recently obtained from ROSAT surveys (Ebeling et al. 1997; Rosati et al. 1997) are constructed from nearly 300 clusters, the largest samples of clusters to date. In addition, the future projects such as PLANK and LMSA will provide rather independent cluster samples in mm/submm bands via the Sunyaev-Zel'dovich effect. We discussed in detail their implications on cosmology and obtained the following results: 1) the observed X-ray logN-logS is reproduced remarkably well by a certain set of cosmological models, and can be used to constrain the density parameter (Omega_0) and the fluctuation amplitude (sigma_8); 2) if one combine this result with the COBE data, low-density universe is favored; 3) the redshift evolution of cluster population, which will become available from future X-ray/optical observations, can place further constraints on Omega_0; 4) the cluster number counts in multi-bands, X-ray and submm, can be combined to give another way of segregating viable cosmological models."