Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Poststarburst Models of LINERs   Since the discovery of low-ionization nuclear emission-line regions in many
galaxies (LINERs), it has been recognized that they constitute a class of
active galactic nuclei (AGNs) which are thought to be powered by gas accretion
onto a central, supermassive black hole. LINERs are observed in approximately
one third of galaxies in the local universe and it has been often thought that
they harbor an AGN-like central engine with moderate activity. However, some
LINERs show no direct evidence for AGNs such as broad emission lines, radio
jets, hard X-ray emission, spectral energy distributions which are inconsistent
with starlight, and so on. For such LINERs (a subset of type 2 LINERs), we
present new poststarburst models which explain some of their most important
optical narrow emission-line ratios. In these models, the ionization sources
are planetary nebula nuclei (PNNs) with temperature of ~ 10^5 K which appear in
the late-phase evolution of intermediate-mass stars with mass between ~ 3
M_solar and ~ 6 M_solar. Such PNNs left in a typical starburst nucleus can
produce an Halpha luminosity of L(Halpha) ~ 10^38 ergs s^-1 for typical
poststarburst LINERs and ~ 10^39 ergs s^-1 only in exceptionally bright cases.
The PNN phase lasts until the death of the lowest-mass stars formed in the
starburst, which is ~ 5 x 10^8 yr for an assumed lower limit of the initial
mass function of 3 M_solar. This long duration appears consistent with the
observed higher frequency of occurrence of LINERs if every galaxy could
experience the starburst activity several times in its life. We therefore
propose that some LINERs which show no direct evidence for AGNs may be
poststarburst nuclei powered by a cluster of PNNs.

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The categories of this paper are: gr-qc
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ph
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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn
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The categories of this paper are: econ
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The categories of this paper are: supr-con
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The categories of this paper are: eess
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The categories of this paper are: math-ph
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The categories of this paper are: hep-lat
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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: mtrl-th
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The categories of this paper are: stat
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The categories of this paper are: cs
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The categories of this paper are: acc-phys