Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Limits on the Gunn-Peterson Effect at z = 5   We report new limits on the Gunn-Peterson effect at a redshift near 5 using
spectroscopic observations of the z = 5 Sloan Digital Sky Survey quasar,
J033829.31+002156.3, made with the LRIS and HIRES spectrographs on the Keck
telescopes. Lower resolution spectrophotometrically calibrated observations
made with LRIS over the wavelength region 4500-9600 angstroms were used to
obtain a continuum shape and to flux calibrate much higher resolution (R =
36,000) observations made with HIRES. The LRIS data show an Oke D_A index of
0.75. Portions of the HIRES spectrum return to near the extrapolated continuum
level. Including both statistical and systematic errors we place an upper limit
of tau = 0.1 on the regions of minimum opacity. We argue that, even if this
opacity arises in underdense regions of the intergalactic gas, we require a
high value of the metagalactic ionizing flux at these redshifts ($J_{\nu} \gg 4
\times 10^{-23}~{\rm ergs cm^{-2} s^{-1} Hz^{-1} sr^{-1}}$ at $z\sim4.72$) to
produce a solution which is consistent with even minimum nucleosynthesis
estimates of the baryon density. We also report the presence of a Mg II
absorption system of extremely high equivalent width
($W_{\lambda,rest}(2796)=1.73$ \AA) at z=2.304.

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The categories of this paper are: patt-sol
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: math-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: econ
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The categories of this paper are: math
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The categories of this paper are: stat
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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: adap-org
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The categories of this paper are: supr-con
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The categories of this paper are: hep-ph