Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: alpha-Enhanced Integrated Lick/IDS Spectral Indices and Milky Way and
  M31 Globular Clusters and Early-type Galaxies   All 25 Lick/IDS spectral indices have been computed for the integrated light
of simple stellar populations over broad ranges of age and metallicity and with
effects from horizontal-branch stars fully implemented. For Balmer indices a
significant response was noted for Hgamma and Hdelta when a-elements are
enhanced, but Hbeta is rather a-insensitive. We also find that our 5 Gyr and 12
Gyr models of Hgamma and Hdelta overlap in the metal-poor regime because of
changing populations of blue horizontal-branch stars. Furthermore, for
populations younger than 1 Gyr, Balmer lines become weaker in the metal-poor
regime because the main-sequence turnoff is hotter than 10,000 K. We present
models at fixed [Fe/H] (rather than fixed heavy element mass fraction Z), and
compare to Milky Way globular clusters that have independently estimated mean
[Fe/H] and [a/Fe]. Comparison of our models with observations of Milky Way and
M31 globular clusters in index-index space are favorable, tracing the
observations at a model age of 12 Gyr without any zero-point shifts that are
needed by some other models. Contrary to the literature values, the Milky Way
globular cluster NGC 6553 appears more metal-rich than NGC 6528 from metal
indices. We present Hdelta and Hgamma Lick/IDS indices for the Lick/IDS sample
of galaxies. We confirm the well-known enhancement of Mg and Na relative to Fe
and Ca among early-type galaxies, and its increase with increasing velocity
dispersion. There are distinct differences between globular clusters and
galaxies in diagrams involving CN1 and CN2, hinting that the globular cluster
environment may be a special one in terms of the amount of N incorporated into
stars. (abridged)

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The categories of this paper are: mtrl-th
2
The categories of this paper are: math
19
The categories of this paper are: eess
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The categories of this paper are: econ
11
The categories of this paper are: hep-lat
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The categories of this paper are: hep-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas
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The categories of this paper are: math-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: ao-sci
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The categories of this paper are: bayes-an
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The categories of this paper are: physics
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The categories of this paper are: cs
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The categories of this paper are: q-fin