Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Large scale simulations of H and He reionization and heating driven by
  stars and more energetic sources   We present simulations of cosmic reionization and reheating from $z=18$ to
$z=5$, investigating the role of stars (emitting soft UV-photons), nuclear
black holes (BHs, with power-law spectra), X-ray binaries (XRBs, with hard
X-ray dominated spectra), and the supernova-associated thermal bremsstrahlung
of the diffuse interstellar medium (ISM, with soft X-ray spectra). We
post-process the hydrodynamical simulation Massive-Black II (MBII) with
multifrequency ionizing radiative transfer. The source properties are directly
derived from the physical environment of MBII, and our only real free parameter
is the ionizing escape fraction $f_{\rm esc}$. We find that, among the models
explored here, the one with an escape fraction that decreases with decreasing
redshift yields results most in line with observations, such as of the neutral
hydrogen fraction and the Thomson scattering optical depth. Stars are the main
driver of hydrogen reionization and consequently of the thermal history of the
intergalactic medium (IGM). We obtain $\langle x_{\rm HII} \rangle = 0.99998$
at $z=6$ for all source types, with volume averaged temperatures $\langle T
\rangle \sim 20,000~{\rm K}$. BHs are rare and negligible to hydrogen
reionization, but conversely they are the only sources which can fully ionize
helium, increasing local temperatures by $\sim 10^4~{\rm K}$. The thermal and
ionization state of the neutral and lowly ionized hydrogen differs
significantly with different source combinations, with ISM and (to a lesser
extent) XRBs, playing a significant role and, as a consequence, determining the
transition from absorption to emission of the 21 cm signal from neutral
hydrogen.

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The categories of this paper are: eess
30
The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: quant-ph
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The categories of this paper are: physics
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The categories of this paper are: ao-sci
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The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: supr-con
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th