Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the thermodynamic self-similarity of the nearest, most relaxed, giant
  ellipticals   We present detailed spatially resolved measurements of the thermodynamic
properties of the X-ray emitting gas in the inner regions of the five nearest,
X-ray and optically brightest, and most X-ray morphologically relaxed giant
elliptical galaxies known. Beyond the innermost region at r > 1 kpc, and out to
r ~ 6 kpc, the density, pressure, entropy, and cooling time distributions for
the X-ray emitting gas follow remarkably similar, simple, power-law like
distributions. Notably, the entropy profiles follow a power-law form, with an
index 0.92-1.07. The cumulative hot X-ray emitting gas mass profiles and the
gas-mass to stellar-light ratios of all five galaxies are also similar. Overall
the observed similarity of the thermodynamic profiles in this radial range
argues that, in these systems, relativistic jets heat the gas at a similar rate
averaged over time scales longer than the cooling time of 10^8 yr. These jets
are powered by accretion from the hot gas, or material entrained within it,
onto the central super-massive black hole. This jet heating creates an energy
balance where heating and cooling are in equilibrium, keeping the hot galactic
atmospheres in a `steady-state'. Within r < 1 kpc, this similarity breaks down:
the observed entropy profiles show well resolved flattening and the values
differ from system to system substantially. The accretion rate onto the black
hole and the AGN activity, heating the interstellar medium, must therefore vary
significantly on time scales shorter than the cooling time of 10^7 - 10^8 yr.

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The categories of this paper are: acc-phys
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The categories of this paper are: econ
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: chem-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
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The categories of this paper are: q-bio
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: funct-an
1
The categories of this paper are: cs