Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Self-Absorption of Ionizing Radiation and Extended Lyman Alpha Emission
  in High- Redshift QSOs   We calculate the neutral hydrogen column density of self-absorption in QSOs
predicted in a model where the QSOs are located in the same halos that contain
the gas in damped Lya absorption systems. The model is parameterized by the
probability P_0 that any halo has an active QSO. We assume that the QSOs ionize
the gas, but do not expel or heat it. The derived HI column densities produce
negligible Lyman limit absorption, even in the lowest luminosity QSOs, with an
optical depth of only ~ 10% for luminosity L=0.01 L_*, when P_0=10^{-2}. We
also compute the HeII Lyman limit self-absorption, which is slightly higher but
still negligible. The self-absorption can be higher if the gas is highly
clumped; only in this case the overall emissivity from QSOs could be
significantly reduced due to absorption by the known damped Lya systems, to
affect the predicted intensity of the ionizing background or the epoch of HeII
reionization. The presence of the gas associated with damped absorption systems
around QSOs could also be detected from the narrow Lya emission line, which
should have and angular extent of 0.1 to 1'' in typical high-redshift QSOs.

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The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: q-bio
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The categories of this paper are: hep-th
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: adap-org
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The categories of this paper are: funct-an
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The categories of this paper are: nlin
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The categories of this paper are: bayes-an
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The categories of this paper are: math-ph