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, filamentary gas, which has yet to be detected. In this paper, we use numerical simulations 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 noise, the extragalactic source distribution, and vignetting. A number of cosmological models are examined as well as a range of very simple prescriptions to account for the effect of supernovae feedback (preheating). We show that XMM has a good chance of observing emission from strong filaments at z similar to 0.1. This becomes much more difficult by z similar to 0.5. The primary difficulties lie in detecting such a large, diffuse object and in selecting an appropriate field. We also describe the range of group sizes that XMM should be sensitive to (both for detection and spectral analysis), although this is more dependent on the unknown nature of the feedback. Such observations will greatly improve our understanding of feedback and should also provide stronger cosmological constraints.