Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Infall Region of Abell 576: Independent Mass and Light Profiles   We describe observations of the nearby cluster of galaxies A576 beyond the
virial radius and into the infall region. Using 1057 redshifts, we use the
infall pattern in redshift space to determine the mass profile of A576 to a
radius of ~4 Mpc/h. This mass estimation technique makes no assumptions about
the equilibrium state of the cluster. Within 1 Mpc/h, the mass profile we
derive exceeds that determined from X-ray observations by a factor of 2.5. At
\~2.5 Mpc/h, however, the mass profile agrees with virial mass estimates. Our
mass profile is consistent with a NFW or Hernquist profile, but it is
inconsistent with an isothermal sphere. R-band images of a $3^\circ x 3^\circ$
region centered on the cluster allow an independent determination of the
cluster light profile. We calculate the integrated mass-to-light ratio as a
function of cluster radius; it decreases smoothly from the core to ~4 Mpc/h.
The differential dM/dL_R profile decreases more steeply; we find M/L_R ~100 h
at ~4 Mpc/h, in good agreement with the mass-to-light ratios of individual
galaxies. This value implies $\Omega_m \lesssim 0.4$ at 95% confidence. For a
Hernquist model, the best-fit mass profiles differ from the observed surface
number density of galaxies; the galaxies have a larger scale radius than the
mass. This result is consistent with the centrally peaked $M/L_R$ profile.
Similarly, the scale radius of the light profile is larger than that of the
mass profile. We discuss some potential systematic effects; none can easily
reconcile our results with a constant mass-to-light ratio. (abstract edited)

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The categories of this paper are: physics
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: cs
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: math
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The categories of this paper are: chem-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: hep-lat
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The categories of this paper are: acc-phys