Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Metal Absorption Systems in Spectra of Pairs of QSOs   We present the first large sample of absorption systems in paired QSOs
consisting of 691 absorption systems in the spectra of 310 QSOs including 170
pairings. All these absorption systems have metal lines, usually C IV or Mg II.
We see 17 cases of absorption in one line-of-sight within 200 km/s (1 Mpc) of
absorption in the paired line-of-sight with the probability at least approx 50%
at 100kpc, declining rapidly to 23% at 100 - 200 kpc. We detect clustering on
0.5Mpc scales and see a hint of the "fingers of God" redshift-space distortion.
The distribution matches absorbers arising in galaxies at z=2 with a normal
correlation function and systematic infall velocities but unusually low random
pair-wise velocity differences. Absorption in gas flowing out from galaxies at
a mean velocity of 250 km/s would produce vastly more elongation than we see.
The UV absorption from fast winds that Adelberger et al. 2005 see in spectra of
LBGs is not representative of the absorption that we see. Either the winds are
confined to LBGs, or they can not extend to 40 kpc with large velocities, while
continuing to make UV absorption we see, implying most metals were in place in
the IGM long before z=2. Separately, when we examine the absorption seen when a
sight line passes a second QSO, we see 19 absorbers within 400 km/s of the
partner QSO. The probability of seeing absorption is approximately constant for
impact parameters 0.1 - 1.5 Mpc. Perhaps we do not see a rapid rise in the
probability at small impact parameters because the UV from QSOs destroys some
absorbers near to the QSOs. The 3D distribution of 64 absorbers around 313 QSOs
is to first order isotropic, with just a hint of the anisotropy expected if the
QSO UV emission is beamed, or alternatively QSOs might emit UV isotropically
but for a surprisingly short time of only 0.3Myr.

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The categories of this paper are: chao-dyn
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The categories of this paper are: cond-mat
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The categories of this paper are: stat
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The categories of this paper are: econ
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The categories of this paper are: hep-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: gr-qc
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The categories of this paper are: math-ph
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The categories of this paper are: eess
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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: solv-int
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The categories of this paper are: q-bio
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The categories of this paper are: hep-lat
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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas