8th HEAD Meeting, 8-11 September, 2004
Session 3 Surveys and the Cosmic X-ray Background
Poster, Wednesday, September 8, 2004, 9:00am-10:00pm

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[3.06] Expected X-ray emission from the Warm Hot Intergalactic Medium (WHIM)

M. Galeazzi, E. Ursino (University of Miami), W. T. Sanders (University of Wisconsin)

The number of detected baryons in the Universe at z<0.5 is much smaller than predicted by standard big bang nucleosynthesis and by the detailed observation of the Lyman alpha forest at red-shift z=2. Hydrodynamical simulations indicate that a large fraction of the baryons today is expected to be in a ''warm-hot'' (105~V 107 K) filamentary gas, distributed in the intergalactic medium (WHIM). It is currently believed that a significant fraction of the diffuse x-ray background in the energy band 0.5-1 keV is due to thermal emission from this intergalactic medium. The signature of the WHIM can be observed in red-shifted (z < 1) strong soft x-ray and UV emission lines from highly ionized elements.

Using the prediction of the hydrodynamic models we simulated the expected x-ray emission due to the WHIM and compared it with local and high red-shift components. We then investigated the effect of the X-ray emission due to the WHIM on future missions as Astro-E2 and Constellation-X.

Our results show that as much as 20% of the diffuse x-ray background (DXB) in the energy range 0.37-0.925 keV could be due to x-ray emission from the WHIM, 70% of which comes from gas at red-shift z between 0.1 and 0.6. Simulations done using a FOV of 3~R, comparable with that of Astro-E2 and Constellation-X, also show that in more than 40% of the observations we expect the WHIM emission to contribute to more than 20% of the DXB. These simulations also show that in more than 20% of all the observations the WHIM emission is due to a single bright filament in the FOV that accounts, alone, for more than 20% of the DXB emission. Red-shifted oxygen lines should be clearly visible in these observations.

The author(s) of this abstract have provided an email address for comments about the abstract: galeazzi@physics.miami.edu

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© 2004. The American Astronomical Soceity.