Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: High-Resolution Near-Infrared Imaging and Polarimetry of Four
  Proto-Planetary Nebulae   High-resolution near-infrared HST NICMOS (F160W, F222M) images and
polarization (2 um) observations were made of four bipolar proto-planetary
nebulae (PPNs): IRAS 17150-3224, IRAS 17441-2411, IRAS 17245-3951, and IRAS
16594-4656. The first three of these are viewed nearly edge-on, and for the
first time the central stars in them are seen. Color maps reveal a reddened
torus between the bipolar lobes in the edge-on cases, with bluer lobes. The
polarization values are high, with maximum values ranging from 40 to 80%. The
polarization patterns are basically centrosymmetric, with some deviations in
the low polarization equatorial regions. For IRAS 17150-3224, circumstellar
arcs are seen at 1.6 um, along with a newly-discovered loop in the equatorial
region. Bright caps are seen at the end of the lobes, indicating that they are
not open-ended. A distinct point-symmetric pattern is seen in the strengths of
the polarization vectors, especially in IRAS 17150-3224. HST NICMOS
observations provide a valuable complement to the WFPC2 visible images in
deriving the basic structure of bipolar PPNs.

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The categories of this paper are: nucl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga
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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: cs
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The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom