Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Origin of a Chemically Enriched lya Absorption System at z=0.167   We present the first detailed analysis of the chemical abundances, ionization
state, and origin of a partial Lyman limit system (N(\hI) ~ 10^{16} \cmjj) at
low redshift (z=0.167 towards PKS0405-1219). Two galaxies at ~ 70 h^{-1} kpc
projected distance to the QSO have been identified at the absorber redshift. We
analyze an echelle spectrum of the QSO obtained with the Space Telescope
Imaging Spectrograph and find that this absorption system exhibits associated
lines produced by C^+, N^+, O^0, Si^+, Si^{++}, Si^{+3}, Fe^+, and Fe^{++}, and
most interestingly, O^{+5} and N^{+4}. The results of our analysis show that
the partial Lyman limit system traced by various ions is likely to be embedded
in a collisionally ionized \ovi gas of larger spatial extent. Furthermore, the
partial Lyman limit system appears to have a metallicity of {\em at least} 1/10
solar and most likely solar or super solar despite the fact that no luminous
galaxies are seen within a projected distance \rho = 60 h^{-1} kpc to the QSO.
Finally, adopting the temperature estimated for the hot gas T ~ 2.5\times 10^5
K and assuming a simple isothermal halo, we estimate that the galaxy or galaxy
group that supports the extended gas may have a total mass ~ 1.5\times 10^{12}
M_\odot and a gas number density \apl 3\times 10^{-5} cm^{-3}.

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The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
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The categories of this paper are: nlin
13
The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc
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The categories of this paper are: adap-org
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The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
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The categories of this paper are: cs
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The categories of this paper are: econ
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat