Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Keck Spectroscopy of Two Young Globular Clusters in the Merger Remnant
  NGC 3921   Low-resolution UV-to-visual spectra of two candidate globular clusters in the
merger remnant NGC 3921 are presented. These two clusters of apparent magnitude
V = 22.2 (Mv = -12.5) lie at projected distances of ~5 kpc from the center and
move with halo-type radial velocities relative to the local galaxy background.
Their spectra show strong Balmer absorption lines indicative of main-sequence
turnoffs dominated by A-type stars. Comparisons with model-cluster spectra
computed by Bruzual & Charlot and others yield cluster ages in the range of
200-530 Myr, and metallicities about solar to within a factor of three. Given
their small half-light radii (Reff < 5 pc) and ages corresponding to ~100 core-
crossing times, these clusters are gravitationally bound and, hence, indeed
young globulars. Assuming that they had Chabrier-type initial mass functions,
their estimated current masses are 2.3(+-0.1)x10^6 Msun and 1.5(+-0.1)x10^6
Msun, respectively, or roughly half the mass of omegaCen. Since NGC 3921 itself
shows many signs of being a 0.7(+-0.3) Gyr old protoelliptical, these two young
globulars of roughly solar metallicity and their many counterparts observed
with the Hubble Space Telescope provide supporting evidence that, in the
process of forming elliptical-like remnants, major mergers of gas-rich disks
can also increase the number of metal-rich globular clusters. (Abridged)

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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg
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The categories of this paper are: cmp-lg
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The categories of this paper are: math
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The categories of this paper are: chem-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: cond-mat
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The categories of this paper are: adap-org
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: quant-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: stat
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The categories of this paper are: q-bio
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The categories of this paper are: funct-an