Abstract
Suzaku performed observations of 3 regions in and around the Shapley supercluster: a region located between A3558 and A3556, at similar to 0.9 times the virial radii of both clusters, and two other regions at 1 degrees and 4 degrees away from the first pointing. The 4 degrees-offset observation was used to evaluate the Galactic foreground emission. We did not detect significant redshifted Oxygen emission lines (O-VII and O-VIII) in the spectra of all three pointings, after subtracting the contribution of foreground and background emission. An upper limit for the redshifted O-VIII K alpha line intensity of the warm-hot intergalactic medium (WHIM) is 1.5 x 10(-7) photons s(-1) cm(-2) arcmin(-2), which corresponds to an overdensity of similar to 380 (Z/0.1 Z(circle dot))(-1/2)(L/3 Mpc)(-1/2), assuming T = 3 x 10(6) K. We found excess continuum emission in the 1 degrees-offset and on-filament regions, represented by thermal models with kT similar to 1 keV and similar to 2 keV, respectively. The redshifts of both 0 and that of the supercluster (0.048) are consistent with the observed spectra. The similar to 1 keV emission can be also fitted with Ne-rich Galactic (zero redshift) thin thermal emission. Radial intensity profile of 2 keV component suggests contribution from nearby clusters A3558 and A3556, but with significant steepening of the intensity slope in the outer region of A3558.
