Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: OVI in Elliptical Galaxies: Indicators of Cooling Flows   Early-type galaxies often contain a hot X-ray emitting interstellar medium
(3-8E6 K) with an apparent radiative cooling time much less than a Hubble time.
If unopposed by a heating mechanism, the gas will radiatively cool to
temperatures <= 10E4 K at a rate proportional to L_X/T_X, typically 0.03-1
M_solar yr^-1. We can test if gas is cooling through the 3E5 K range by
observing the OVI doublet, whose luminosity is proportional to the cooling
rate. Here we report on a study of an unbiased sample of 24 galaxies, obtaining
Far Ultraviolet Spectroscopic Explorer spectra to complement the X-ray data of
ROSAT} and Chandra. The OVI line emission was detected in about 40% of the
galaxies and at a luminosity level similar to the prediction from the cooling
flow model. There is a correlation between Mdot_OVI and Mdot_X, although there
is significant dispersion about the relationship, where the OVI is brighter or
dimmer than expected by a factor of three or more. If the cooling flow picture
is to be retained, this dispersion requires that cooling flows be
time-dependent, as might occur by the activity of an AGN. However, of detected
objects, those with the highest or lowest values of Mdot_OVI/Mdot_X are not
systematically hot or cool, as one might predict from AGN heating.

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The categories of this paper are: nucl-th
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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: hep-th
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The categories of this paper are: cond-mat
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
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The categories of this paper are: plasm-ph
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The categories of this paper are: math
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The categories of this paper are: cs
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The categories of this paper are: econ
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The categories of this paper are: stat
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The categories of this paper are: comp-gas