Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: From Globular Clusters to Tidal Dwarfs: Structure Formation in the Tidal
  Tails of Merging Galaxies   Using V and I images obtained with WFPC2/HST, we investigate compact stellar
structures within tidal tails. Six regions of tidal debris in the four classic
``Toomre Sequence'' mergers: NGC 4038/39 (``Antennae''), NGC 3256, NGC 3921,
and NGC 7252 (``Atoms for Peace'') have been studied in order to explore how
the star formation depends upon the local and global physical conditions. These
mergers sample a range of stages in the evolutionary sequence and tails with
and without embedded tidal dwarf galaxies. The six tails are found to contain a
variety of stellar structures, with sizes ranging from those of globular
clusters up to those of dwarf galaxies. From V and I WFPC2 images, we measure
the luminosities and colors of the star clusters. NGC 3256 is found to have a
large population of blue clusters (0.2 < V-I < 0.9), particularly in its
Western tail, similar to those found in the inner region of the merger. In
contrast, NGC 4038/39 has no clusters in the observed region of the tail, only
less luminous point sources likely to be individual stars. A significant
cluster population is clearly associated with the prominent tidal dwarf
candidates in the eastern and western tails of NGC 7252. The cluster-rich
Western tail of NGC 3256 is not distinguished from the others by its dynamical
age or by its total HI mass. However, the mergers that have few clusters in the
tail all have tidal dwarf galaxies, while NGC 3256 does not have prominent
tidal dwarfs. We speculate that star formation in tidal tails may manifest
itself either in small structures like clusters along the tail or in large
structures such as dwarf galaxies, but not in both. Also, NGC 3256 has the
highest star formation rate of the four mergers studied, which may contribute
to the high number of star clusters in its tidal tails.

17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
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The categories of this paper are: stat
9
The categories of this paper are: nlin
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The categories of this paper are: econ
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The categories of this paper are: eess
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: dg-ga