Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evolved Galaxies at z > 1.5 from the Gemini Deep Deep Survey: The
  Formation Epoch of Massive Stellar Systems   We present spectroscopic evidence from the Gemini Deep Deep Survey (GDDS) for
a significant population of color-selected red galaxies at 1.3 < z < 2.2 whose
integrated light is dominated by evolved stars. Unlike radio-selected objects,
the z > 1.5 old galaxies have a sky density > 0.1 per sq. arcmin. Conservative
age estimates for 20 galaxies with z > 1.3; <z> = 1.49, give a median age of
1.2 Gyr and <z_f> = 2.4. One quarter of the galaxies have inferred z_f > 4.
Models restricted to abundances less than or equal to solar give median ages
and z_f of 2.3 Gyr and 3.3, respectively. These galaxies are among the most
massive and contribute approximately 50% of the stellar mass density at 1 < z <
2. The derived ages and most probable star formation histories suggest a high
star-formation-rate (300-500 solar masses per year) phase in the progenitor
population. We argue that most of the red galaxies are not descendants of the
typical z=3 Lyman break galaxies. Galaxies associated with luminous sub-mm
sources have the requisite star formation rates to be the progenitor
population. Our results point toward early and rapid formation for a
significant fraction of present day massive galaxies.

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The categories of this paper are: nlin
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The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
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The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
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The categories of this paper are: atom-ph
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The categories of this paper are: physics
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math