Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Earliest Luminous Sources and the Damping Wing of the Gunn-Peterson
  Trough   Recent observations of high-redshift galaxies and quasars indicate that the
hydrogen component of the intergalactic medium (IGM) must have been reionized
at some redshift z>6. Prior to complete reionization, sources of ultraviolet
radiation will be seen behind intervening gas that is still neutral, and their
spectra should show the red damping wing of the Gunn-Peterson trough. While
this characteristic feature may, in principle, totally suppress the
Lyman-alphaa emission line in the spectra of the first generation of objects in
the universe, we show here that the IGM in the vicinity of luminous quasars
will be highly photoionized on several Mpc scales due to the source emission of
Lyman-continuum photons. If the quasar lifetime is shorter than the expansion
and gas recombination timescales, the volume ionized will be proportional to
the total number of photons produced above 13.6 eV: the effect of this local
photoionization is to greatly reduce the scattering opacity between the
redshift of the quasar and the boundary of its HII region. We find that the
transmission on the red side of the Lyman-alpha resonance is always greater
than 50% for sources radiating a total of 1e69.5 ionizing photons into the IGM.
The detection of a strong Lyman-alpha emission line in the spectra of bright
QSOs shining for >1e7 yr cannot then be used, by itself, as a constraint on the
reionization epoch. The first signs of an object radiating prior to the
transition from a neutral to an ionized universe may be best searched for in
the spectra of luminous sources with a small escape fraction of Lyman-continuum
photons into the IGM, or sources with a short duty cycle.

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The categories of this paper are: physics
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: math-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: acc-phys
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ph
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
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The categories of this paper are: q-bio