Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray Absorption by the Low-redshift Intergalactic Medium: A Numerical
  Study of the Lambda CDM model   Using a hydrodynamic simulation of a LCDM universe, we investigate the "X-ray
forest" absorption imprinted on the spectra of background quasars by the
intervening intergalactic medium (IGM). In agreement with previous studies, we
find that OVII and OVIII produce the strongest absorption features. The strong
oxygen absorbers that might be detectable with Chandra or XMM-Newton arise in
gas with T ~ 10^6 K and overdensities delta >~ 100 that are characteristic of
galaxy groups. Future X-ray missions could detect weaker oxygen absorption
produced by gas with a wider range of temperatures and the lower densities of
unvirialized structures; they could also detect X-ray forest absorption by C,
N, Ne, Fe, and possibly Si. If the IGM metallicity is 0.1 solar, then the
predicted number of systems strong enough for a ~5\sigma detection with Chandra
or XMM-Newton is extremely low, though scatter in metallicity would increase
the number of strong absorbers even if the mean metallicity remained the same.
Our simulation reproduces the high observed incidence of OVI absorbers (in the
UV), and the most promising strategy for finding the X-ray forest is to search
at the redshifts of known OVI systems, thus reducing the signal-to-noise
threshold required for a significant detection. However, while many OVI
absorbers have associated OVII or OVIII absorption, the OVI systems trace only
the low temperature phases of the X-ray forest, and a full accounting of the
strong OVII and OVIII systems will require a mission with the anticipated
capabilities of Constellation-X. The large effective area of the XEUS satellite
would make it an extremely powerful instrument for studying the IGM, measuring
X-ray forest absorption by a variety of elements and revealing the shock-heated
filaments that may be an important reservoir of cosmic baryons.

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The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
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The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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The categories of this paper are: dg-ga
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The categories of this paper are: gr-qc