Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Under the Shadow of the Magellanic Bridge: A Measurement of the
  Extragalactic Background at $\sim 0.7$~keV   We measured the extragalactic 0.7 keV X-ray background by observing the X-ray
shadow of a neutral gas cloud in the Magellanic Bridge region. Two \rosat PSPC
observations of total 104~ks were complemented by a detailed H I mapping of the
cloud with both the Parkes 64~m telescope and the Australia Telescope Compact
Array. From the detected anti-correlation between the observed background
intensity and the \ion{H}{1} column density of the cloud, we derived the
unabsorbed extragalactic background intensity as 28 keV s^{-1} cm^{-2} keV^{-1}
sr^{-1} at 0.7~keV. The 95% confidence lower limit 18 keV s^{-1} cm^{-2} keV^
{-1} sr^{-1}} is greater than the expected point-like source contribution < 14
keV s^{-1} cm^{-2} keV^{-1} sr^{-1}, constrained by the mean source spectrum
together with the total background intensity in the 1-2 keV band. A significant
fraction of the 0.7 keV background likely arises in a diffuse hot intergalactic
medium of a few million degrees, as has been predicted in hydrodynamic
simulations of cosmological structure formation.

18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
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The categories of this paper are: eess
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The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
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The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
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The categories of this paper are: solv-int