Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Probing the halo of Centaurus A: a merger dynamical model for the PN
  population   Photometry and kinematics of the giant elliptical galaxy NGC~5128
(Centaurus~A) based on planetary nebulae observations (Hui~\etal 1995) are used
to build dynamical models which allow us to infer the presence of a dark matter
halo. To this end, we apply a Quadratic Programming method. Constant
mass-to-light ratio models fail to reproduce the major axis velocity dispersion
measurements at large radii: the profile of this kind of models falls off too
steeply when compared to the observations, clearly suggesting the necessity of
including a dark component in the halo. By assuming a mass-to-light ratio which
is increasing with radius, the model satisfactorily matches the observations.
The total mass for the best fit model is $\sim4\times10^{11}M_\odot$ of which
about 50\% is dark matter. However, models with different total masses and dark
halos are also consistent with the data; we estimate that the total mass of
Cen~A within 50~kpc may vary between $3\times10^{11}M_\odot$ and
$5\times10^{11}M_\odot$. The best fit model consists of 75\% of stars rotating
around the short axis $z$ and 25\% of stars rotating around the long axis $x$.
Finally, the morphology of the projected velocity field is analyzed using
Statler's classification criteria (Statler 1991). We find that the appearance
of our velocity field is compatible with a type 'Nn' or 'Nd'.

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The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga
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The categories of this paper are: math
13
The categories of this paper are: quant-ph
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The categories of this paper are: funct-an
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The categories of this paper are: eess
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The categories of this paper are: acc-phys
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The categories of this paper are: nlin
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The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
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The categories of this paper are: physics
37
The categories of this paper are: supr-con
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The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-ex
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin