Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: RXJ0142.0+2131: I. The galaxy content of an X-ray-luminous galaxy
  cluster at z=0.28   We present a photometric and spectroscopic study of stellar populations in
the X-ray-luminous cluster of galaxies RXJ0142.0+2131 at z=0.280. This paper
analyses the results of high signal-to-noise spectroscopy, as well as g'-, r'-,
and i'-band imaging, using the Gemini Multi-Object Spectrograph on Gemini
North. Of 43 spectroscopic targets, we find 30 cluster members over a range in
color. Central velocity dispersions and absorption-line strengths for lines in
the range 3700A < lambda_rest < 5800A are derived for cluster members, and are
compared with a low-redshift sample of cluster galaxies, and single stellar
population (SSP) models. We use a combination of these indicators to estimate
luminosity-weighted mean ages, metallicities ([M/H]), and alpha-element
abundance ratios ([alpha/Fe]).
  RXJ0142.0+2131 is a relatively poor cluster and lacks galaxies with high
central velocity dispersions. Although the red sequence and the Faber-Jackson
relation are consistent with pure passive evolution of the early-type
population with a formation redshift of z_form = 2, the strengths of the 4000A
break and scaling relations between metal line indices and velocity dispersion
reject this model with high significance. By inverting SSP models for the
Hbeta_G, Mgb, and <Fe> line indices, we calculate that, at a given velocity
dispersion and metallicity, galaxies in RXJ0142.0+2131 have luminosity-weighted
mean ages 0.14 +- 0.07 dex older than the low-redshift sample. We also find
that [alpha/Fe] in stellar populations in RXJ0142.0+2131 is 0.14 +- 0.03
greater than at low redshift. All scaling relations are consistent with these
estimated offsets. (abridged)

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The categories of this paper are: eess
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The categories of this paper are: q-alg
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-bio
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: math
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The categories of this paper are: physics
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The categories of this paper are: q-fin
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The categories of this paper are: quant-ph
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The categories of this paper are: math-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ph