Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spitzer IRS observations of k+a galaxies: A link between PAH emission
  properties and AGN feedback?   We have performed IRS low resolution 5-12 micron spectroscopy on a sample of
galaxies selected to be at 3 distinct post-starburst evolutionary stages based
on their optical spectral indices. The resulting IRS spectra show distinctive
PAH emission line structures at 6.2, 7.7, 8.6 and 11.3 micron and little
silicate absorption, indicative of ongoing star formation. However the PAH
inter-line ratios, in particular the 11.3/6.2 micron and 7.7/6.2 micron ratio,
show large variations. These variations are found to correlate with both time
since the most recent starburst and AGN activity. We speculate that the
evolution observed in these PAH ratios is related to an increase in AGN
activity with time since star burst.

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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ex
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
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The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin