An XMM pre-view of the cosmic network: galaxy groups and filaments

A large fraction of the baryons today are predicted to be in hot, filamenta ry gas, which has yet to be detected. In this paper, we use numerical simul ations of dark matter and gas to determine if these filaments and groups of galaxy will be observable by XMM. The simulated maps include free-free and line emission, galactic absorption, the XMM response function, photon nois e, the extragalactic source distribution, and vignetting. A number of cosmo logical models are examined as well as a range of very simple prescriptions to account for the effect of supernovae feedback (preheating). We show tha t XMM has a good chance of observing emission from strong filaments at z si milar to 0.1. This becomes much more difficult by z similar to 0.5. The pri mary difficulties lie in detecting such a large, diffuse object and in sele cting an appropriate field. We also describe the range of group sizes that XMM should be sensitive to (both for detection and spectral analysis), alth ough this is more dependent on the unknown nature of the feedback. Such obs ervations will greatly improve our understanding of feedback and should als o provide stronger cosmological constraints.