Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A new, cleaner colour-magnitude diagram for the metal-rich globular
  cluster NGC 6528 - Velocity dispersion in the Bulge, age and proper motion of
  NGC 6528   Using two epochs of HST/WFPC2 images of the metal-rich globular cluster NGC
6528 we derive the proper motions of the stars and use them to separate the
stars belonging to NGC 6528 from those of the Galactic bulge. The stellar
sequences in theresulting colour-magnitude diagram for the cluster are
significantly better determined than in previously published data. From
comparison of the colour-magnitude diagram with the fiducial line for NGC 6553
from Zoccali et al. (2001) we conclude that the two globular clusters have the
same age. Further, using alpha-enhanced stellar isochrones, NGC 6528 is found
to have an age of 11+-2 Gyr. This fitting of isochrones also give that the
cluster is 7.2 kpc away from us. From the measured velocities both the proper
motion of the cluster and the velocity dispersion in the Galactic bulge are
found. NGC 6528 is found to have a proper motion relative to the Galactic bulge
of mu_l=0.006 and mu_b=0.044 arcsec per century. Using stars with 14<V_555<19
(i.e. the red giant branch and horizontal branch) we find, for the Galactic
bulge, sigma_l= 0.33+-0.03 and sigma_{b}= 0.25+-0.02 arcsec per century. This
give sigma_l/sigma_b=1.32+-0.16, consistent both with previous proper motion
studies of K giants in the Galactic bulge as well as with predictions by models
of the kinematics of bulge stars.

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The categories of this paper are: chem-ph
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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: atom-ph
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The categories of this paper are: funct-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: ao-sci
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
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The categories of this paper are: adap-org
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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th