Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ages and Metallicities in Elliptical Galaxies from the H_beta, <Fe>, and
  Mg2 Diagnostics   Systematic variations in the line strength indices H_beta, Mg2, and <Fe> are
observed across elliptical galaxies and from one object to another. Furthermore
arguments are given for an enhancement of Mg (\alfa in general) with respect to
Fe toward the center of these galaxies. In this study we have investigated the
ability of the H_beta, Mg2 and <Fe> diagnostics to assess the metallicity,
[Mg/Fe] ratios, and ages of elliptical galaxies. To this aim, first we derive
basic calibrations for the variations dH_beta, dMg2 and d<Fe> as a function of
Dlog(t), Dlog(Z/Zo), and D[Mg/Fe]. Second, we analyze how the difference
dH_beta, dMg2, and d<Fe> between the external and central values translates
into D[Mg/Fe], Dlog(Z/Zo), and Dlog(t). Third, we explore the variation from
galaxy to galaxy of the nuclear values of H_beta, Mg2, and <Fe> limited to a
sub-sample of the Gonzales (1993) list. The differences dH_beta, dMg2, and
d<Fe> are converted into the differences Dlog(t), Dlog(Z/Zo), and D[Mg/Fe].
Various correlations among the age, metallicity, and enhancement variations are
explored. In particular we thoroughly examine the relationship Dlog(t)-Mv. It
is found that a sort of age limit is likely to exist in this plane, traced by
galaxies with mild or no sign of rejuvenation. In these objects, the duration
of the star forming activity is likely to have increased at decreasing galactic
mass. The results are discussed in the context of current theories of galaxy
formation and evolution. i.e. merger and isolation. Finally, the suggestion is
advanced that models with time and space dependent IMF might be able to
alleviate some of the difficulties encountered by the standard SN-driven
galactic wind model.

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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys
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The categories of this paper are: math-ph
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The categories of this paper are: physics
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The categories of this paper are: eess
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: cs
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-th
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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: patt-sol
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The categories of this paper are: stat