Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: PAIRWISE VELOCITIES OF GALAXIES IN THE CFA AND SSRS2 REDSHIFT SURVEYS   (compressed version) We combine the CfA Redshift Survey (CfA2) and the
Southern Sky Redshift Survey (SSRS2) to estimate the pairwise velocity
dispersion of galaxies $\sig12$ on a scale of $\sim 1 \hmpc$. Both surveys are
complete to an apparent magnitude limit $B(0)=15.5$. Our sample includes 12,812
galaxies distributed in a volume $1.8 \times 10^6 \hmpc3$. We conclude: 1) The
pairwise velocity dispersion of galaxies in the combined CfA2+SSRS2 redshift
survey is $\sig12=540 \kms \pm 180 \kms$. Both the estimate and the variance of
$\sig12$ significantly exceed the canonical values $\sig12=340 \pm40$ measured
by Davis \& Peebles (1983) using CfA1. 2) We derive the uncertainty in $\sig12$
from the variation among subsamples with volumes on the order of $7 \times
10^5$ \hmpc3. This variation is nearly an order of magnitude larger than the
formal error, 36 $\kms$, derived using least-squares fits to the CfA2+SSRS2
correlation function. This variation among samples is consistent with the
conclusions of Mo \etal (1993) for a number of smaller surveys and with the
analysis of CfA1 by Zurek \etal (1994). 3) When we remove Abell clusters with
$R\ge1$ from our sample, the pairwise velocity dispersion of the remaining
galaxies drops to $295 \pm 99 \kms$. Thus the dominant source of variance in
$\sig12$ is the shot noise contributed by dense virialized systems. 4) The
distribution of pairwise velocities is consistent with an isotropic exponential
with velocity dispersion independent of scale.

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The categories of this paper are: cs
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The categories of this paper are: hep-th
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The categories of this paper are: cond-mat
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The categories of this paper are: math
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: bayes-an
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The categories of this paper are: stat
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The categories of this paper are: cmp-lg
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The categories of this paper are: solv-int
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The categories of this paper are: eess
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn