Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Intrinsic Properties of the <z>=2.7 Lyman Alpha Forest from Keck Spectra
  of QSO HS 1946+7658   We present the highest quality Lyman Alpha forest spectra published to date,
from the QSO HS 1946+7658. The distribution of H I column densities is a power
law of slope -1.5 from Log N = 12.1 - 14. This power law can extend to N = 0,
because lines weaker than Log N = 12.1 do not have a large H I optical depth.
Low column lines with Log N > 9 could account for all observed He II
absorption, but lines with Log N > 12 alone are unlikely to do so. The b
distribution between 20 and 60 km/sec is a Gaussian with a mean of 23 km/sec
(less than reported in past at this z), and a sigma b of 14 km/sec. We report
no evolution in the Lyman alpha forest (except the number of lines), because Lu
et al. (1997) found the same N and b distributions at <z> = 3.7. We see lines
with 14 < b < 20 km/sec and b > 80 km/sec that cannot be accounted for by noise
or blending effects. We discover that the lower cutoff in the b distribution
varies with N, from b = 14 km/sec at Log N = 12.5 to b = 22 km/sec at Log N =
14.0, but otherwise b and N are not correlated. We see no Lyman Alpha line
clustering above 50 \kms, in disagreement with previous results from lower
signal to noise data, but we do see a 3 sigma clustering signal at 25 - 50
km/sec among lines with Log N > 13.6

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The categories of this paper are: cond-mat
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The categories of this paper are: math-ph
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys
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The categories of this paper are: nlin
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The categories of this paper are: plasm-ph
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The categories of this paper are: funct-an
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The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-alg
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The categories of this paper are: physics