Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Lyman-alpha Forest at z~4: Keck HIRES Observations of Q 0000-26   This paper describes a study of the Lyman-alpha forest absorption clouds
along the quasar sightline Q0000-26 (zem=4.1). The spectrum was obtained with
the High Resolution Spectrometer on the 10m Keck telescope. We derive accurate
H I column density and Doppler width distributions for the clouds from Voigt
profile fitting. We also analyze simulated Lyman-alpha forest spectra of
matching characteristics in order to gauge the effects of line
blending/blanketing and noise in the data. The results are compared with
similar studies at lower redshifts in order to study any possible evolution in
the clouds' properties. We also estimate the mean intensity of the UV
background at z=4 from an analysis of the proximity effect.

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The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
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The categories of this paper are: nlin
7
The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
2
The categories of this paper are: math
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The categories of this paper are: acc-phys
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The categories of this paper are: stat
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph