XMM-Newton discovery of an X-ray filament in coma

XMM-Newton observations of the outskirts of the Coma cluster of galaxies confirm the existence of warm X-ray gas claimed previously and provide a robust estimate of its temperature (similar to 0.2 keV) and oxygen abundance (similar to 0.1 solar). Associating this emission with a 20 Mpc infall region in front of Coma. seen in the skewness of its galaxy velocity distribution, yields an estimate of the density of the warm gas of similar to 50(Pcritical). Our measurements of gas mass associated with the warm emission strongly support its nonvirialized nature, suggesting that we are observing the warm-hot intergalactic medium (WHIM). Our measurements provide a direct estimate of the O, Ne and Fe abundance of the W-MM. Differences with the reported Ne/O ratio for some OVI absorbers hints to different origin of the OVI absorbers and the Coma filament.