DETECTION OF EMISSION FROM WARM-HOT GAS IN THE UNIVERSE WITH XMM?

Abstract

Recently, claims have been made of the detection of 'warm-hot' gas in the intergalactic medium. Kaastra et al. (2003) claimed detection of <TEX>${\~} 10^6$</TEX> K material in the Coma Cluster but studies by Arnaud et al. (2001), and our analysis of the Chandra observations of Coma (Vikhlinin et al. 2001), find no evidence for a <TEX>$10^6$</TEX> K gas in the cluster. Finoguenov et al. (2003) claimed the detection of <TEX>$3 {\times} 10^6$</TEX> gas slightly off-center from the Coma Cluster. However, our analysis of ROSAT data from this region shows no excess in this region. We propose an alternative explanation which resolves all these conflicting reports. A number of studies (e.g. Robertson et al., 2001) have shown that the local interstellar medium undergoes charge exchange with the solar wind. The resulting recombination spectrum shows lines of O VII and O VIII (Wargelin et al. 2004). Robertson & Cravens (2003) have .shown that as much as <TEX>$25\%$</TEX> of the Galactic polar flux is heliospheric recombination radiation and that this component is highly variable. Sporadic heliospheric emission could account for all the claims of detections of 'warm-hot' gas and explain the conflicts cited above.