Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gravo-thermodynamics of the Intracluster Medium: negative heat capacity
  and dilation of cooling time scales   The time scale for cooling of the gravitationally bound gaseous intracluster
medium (ICM) is not determined by radiative processes alone. If the ICM is in
quasi-hydrostatic equilibrium in the fixed gravitational field of the dark
matter halo then energy losses incurred by the gravitational potential energy
of the gas should also be taken into account. This "gravitational heating" has
been known for a while using explicit solutions to the equations of motion.
Here, we re-visit this effect by applying the virial theorem to gas in
quasi-hydrostatic equilibrium in an external gravitational field, neglecting
the gravity of the gas. For a standard NFW form of halo profiles and for a
finite gas density, the response of the gas temperature to changes in the total
energy is significantly delayed. The effective cooling time could be prolonged
by more than an order of magnitude inside the scale radius ($\rs$) of the halo.
Gas lying at a distance twice the scale radius, has negative heat capacity so
that the temperature increases as a result of energy losses. Although external
heating (e.g. by AGN activity) is still required to explain the lack of cool
ICM near the center, the analysis here may circumvent the need for heating in
farther out regions where the effective cooling time could be prolonged to
become larger than the cluster age and also explains the increase of
temperature with radius in these regions.

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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: atom-ph
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
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The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
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The categories of this paper are: chem-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: nlin
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg