Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for Three Subpopulations of Globular Clusters in the Early-Type
  Post-Starburst Shell Galaxy AM 0139-655   We present deep HST ACS images of the post-starburt shell galaxy AM 0139-655.
We find evidence for the presence of three distinct globular cluster
subpopulations associated with this galaxy: a centrally concentrated young
population (~ 0.4 Gyr), an intermediate age population (~ 1 Gyr) and an old,
metal-poor population similar to that seen around normal galaxies. The g-I
color distribution of the clusters is bimodal with peaks at 0.85 and 1.35. The
redder peak at g-I=1.35 is consistent with the predicted color for an old
metal-poor population. The clusters associated with the peak at g-I=0.85 are
centrally concentrated and interpreted as a younger and more metal-rich
population. We suggest that these clusters have an age of ~ 0.4 Gyr and solar
metallicity based on a comparison with population synthesis models. The
luminosity function of these "blue" clusters is well represented by a power
law. Interestingly, the brightest shell associated with the galaxy harbors some
of the youngest clusters observed. This seems to indicate that the same merger
event was responsible for the formation of both the shells and the young
clusters. The red part of the color distribution contains several very bright
clusters, which are not expected for an old, metal-poor population.
Furthermore, the luminosity function of the "red" GCs cannot be fit well by
either a single gaussian or a single power law. A composite (gaussian + power
law) fit to the LF of the red clusters yields both a low rms and very plausible
properties for an old population plus an intermediate-age population of GCs.
Hence, we suggest that the red clusters in AM 0139-655 consist of two distinct
GC subpopulations, one being an old, metal-poor population as seen in normal
galaxies and one having formed during a recent dissipative galaxy merger.

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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: physics
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The categories of this paper are: chao-dyn
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The categories of this paper are: plasm-ph
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin
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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: dg-ga
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The categories of this paper are: q-alg
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The categories of this paper are: q-fin
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The categories of this paper are: econ
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The categories of this paper are: q-bio