Y. Tawara, M. Kawada and K. Koyama

Abstract

We carried out scanning observations with the Ginga satellite of the near-by Coma-A1367 supercluster and the void regions. We discovered 4 new sources within these regions with a detection limit of 5 x 10-12 erg/s/sq cm (2-10 keV). This rate corresponds to about 102 sources/sr, and lies on the extrapolated log N-log S line determined by Piccinotti et al. (1982, AAA 142.012). We also compiled blank-sky data in order to determine the surface brightness of the cosmic X-ray background (CXB), mostly taken as background observations of extragalactic sources. By comparing diffuse emission from these two data sets, we found no significant difference between their mean fluxes and distributions. No significant correlation between the surface brightness and the galaxy number density for the region was found, except for the clusters, themselves. We also compared the X-ray flux between the supercluster and void regions, and set a 3 sigma upper-limit for the excess emission of the supercluster region to be 9.5 x 10-13 erg/sq cm/s/sq arcdeg.