M. Roncarelli, N. Cappelluti, S. Borgani, E. Branchini, L. Moscardini
At present, 30-40 per cent of the baryons in the local Universe is still
undetected. According to theoretical predictions, this gas should reside in
filaments filling the large-scale structure (LSS) in the form of a Warm-Hot
Intergalactic Medium (WHIM), at temperatures of 10^5 - 10^7 K, thus emitting in
the soft X-ray energies via free-free interaction and line emission from heavy
elements. In this work we characterize the properties of the X-ray emission of
the WHIM, and the LSS in general, focusing on the influence of different
physical mechanisms, namely galactic winds (GWs), black-hole feedback and
star-formation, and providing estimates of possible observational constraints.
To this purpose we use a set of cosmological hydrodynamical simulations that
include a self-consistent treatment of star-formation and chemical enrichment
of the intergalactic medium, that allows us to follow the evolution of
different metal species. We construct a set of simulated light-cones to make
predictions of the emission in the 0.3-10 keV energy range. We obtain that GWs
increase by a factor of 2 the emission of both galaxy clusters and WHIM. The
amount of oxygen at average temperature and, consequently, the amount of
expected bright Ovii and Oviii lines is increased by a factor of 3 due to GWs
and by 20 per cent when assuming a top-heavy IMF. We compare our results with
current observational constraints and find that the emission from faint groups
and WHIM should account from half to all of the unresolved X-ray background in
the 1-2 keV band.
View original:
http://arxiv.org/abs/1202.4275
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