Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Starbursts versus Truncated Star Formation in Nearby Clusters of
  Galaxies   We present long-slit spectroscopy, B and R bandpass imaging, and 21 cm
observations of a sample of early-type galaxies in nearby clusters which are
known to be either in a star-forming phase or to have had star formation which
recently terminated. From the long-slit spectra, obtained with the Blanco 4-m
telescope, we find that emission lines in the star-forming cluster galaxies are
significantly more centrally concentrated than in a sample of field galaxies.
The broadband imaging reveals that two currently star-forming early-type
galaxies in the Pegasus I cluster have blue nuclei, again indicating that
recent star formation has been concentrated. In contrast, the two galaxies for
which star formation has already ended show no central color gradient. The
Pegasus I galaxy with the most evident signs of ongoing star formation
(NGC7648), exhibits signatures of a tidal encounter. Neutral hydrogen
observations of that galaxy with the Arecibo radiotelescope reveal the presence
of ~4 x 10^8 solar masses of HI. Arecibo observations of other current or
recent star-forming early-type galaxies in Pegasus I indicate smaller amounts
of gas in one of them, and only upper limits in others.

19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
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The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs