Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Detection of Warm and Cold Phases of the Neutral ISM in a Damped
  Ly-alpha Absorber   We present a detailed study of the HI 21cm absorption system at z=0.0912
towards the radio quasar B0738+313. The uncommonly narrow main absorption line
and weak secondary line are resolved for the first time. In addition we find it
necessary to add a third, broader shallow component to obtain a good fit to the
spectrum. Although the harmonic mean spin temperature calculated by comparison
of the 21cm lines to the damped Ly-alpha line is T_s = 775 K, the thermal
kinetic temperatures of the two narrow components, calculated from their
widths, are much lower: T_k \leq 297 and \leq 103 K respectively. This is the
first case of a redshifted absorption system for which T_k is measured to be
less than T_s. We discuss this result in the context of a two phase gas model,
in which the damped Ly-alpha gas is sensitive to a significant neutral column
density of warm phase gas as well as the cold phase gas of the narrow 21cm
lines. The third component is interpreted as representing the warm phase gas
with with T_k \leq 5050 K. The combined column density of the three 21cm
components is approximately equal to that derived from fits to the damped
Ly-alpha line.

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The categories of this paper are: cond-mat
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ph
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
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The categories of this paper are: mtrl-th
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The categories of this paper are: supr-con
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The categories of this paper are: acc-phys
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The categories of this paper are: comp-gas
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The categories of this paper are: gr-qc
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The categories of this paper are: chao-dyn
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The categories of this paper are: funct-an
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The categories of this paper are: hep-lat
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The categories of this paper are: eess