M. Bonamente et al., ROSAT and BeppoSAX evidence of soft X-ray excess emission in the Shapley supercluster: A3571, A3558, A3560, and A3562, ASTROPHYS J, 552(1), 2001, pp. L7-L11
Excess soft X-ray emission in clusters of galaxies has so far been detected
for sources that lie along lines of sight to very low Galactic H I column
density [such as Coma, A1795, A2199, and Virgo; N(H)similar to (0.9-2.0) x
10(20) cm(-2)]. We show that the cluster soft excess emission can be invest
igated even at higher N-H, which provides an opportunity for investigating
soft X-ray emission characteristics among a large number of clusters. The R
OSAT Position Sensitive Proportional Counter analysis of some members of th
e Shapley concentration [A3571, A3558, A3560, and A3562 at N(H)similar to (
4-4.5) x 10(20) cm(-2)] bears evidence for excess emission in the 1/4 keV b
and. We were able to confirm the finding for the case of A3571 by a pointed
BeppoSAX observation. Within the current sample, the soft X-ray flux is ag
ain found to be consistently above the level expected from a hot virialized
plasma. The data quality is, however insufficient to enable a discriminati
on between alternative models of the excess low-energy flux.