Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: To Be or Not To Be: Very Young Globular Clusters in M31   We present observations made with the newly commissioned Keck laser-guide
star adaptive optics system of 6 objects in M31 that are alleged in multiple
recent studies to be young globular clusters (GCs); all are supposed to have
ages less than 5 Gyr. The resulting FWHM of the PSF core in our images is ~70
mas. The four youngest of these objects are asterisms; they are with certainty
not young GCs in M31. Based on their morphology, the two oldest are GCs in M31.
While the M31 GCs with ages 5 -- 8 Gyr appear to be mostly genuine, it appears
that many of the alleged very young GCs in M31 are spurious identifications.
This problem will be even more severe in studies of the GC systems of more
distant spiral galaxies now underway, for which imaging at the spatial
resolution of our observations in M31 may not be adequate to detect sample
contamination by asterisms.

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The categories of this paper are: atom-ph
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The categories of this paper are: nlin
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ex
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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: math-ph
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The categories of this paper are: eess
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The categories of this paper are: ao-sci
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The categories of this paper are: q-bio
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The categories of this paper are: comp-gas
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The categories of this paper are: cond-mat
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The categories of this paper are: physics
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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ph