ar X iv : a st ro - p h / 04 09 66 1 v 1 27 S ep 2 00 4 WHIM emission and the cluster soft excess : a model comparison

The confirmation of the cluster soft excess (CSE) by XMM-Newton has rekindled interest as to its origin. The recent detections of CSE emission at large cluster radii together with reports of O VII line emission associated with the CSE has led many authors to conjecture that the CSE is, in fact, a signature of the warm-hot intergalactic medium (WHIM). In this paper we test the scenario by comparing the observed properties of the CSE with predictions based on models of the WHIM. We find that emission from the WHIM in current models is 3 to 4 orders of magnitude too faint to explain the CSE. We discuss different possibilities for this discrepancy including issues of simulation resolution and scale, and the role of small density enhancements or galaxy groups. Our final conclusion is that the WHIM alone is unlikely to be able to accout for the observed flux of the CSE. Subject headings: diffuse radiation – intergalactic medium – large-scale structure of universe – X-rays:galaxies:clusters