Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A dam around the Water Fountain Nebula? The dust shell of IRAS16342-3814
  spatially resolved with VISIR/VLT   Either by collimating a fast stellar wind or by driving a jet via accretion
in the central system, dusty torii or stable disks may be crucial ingredients
for the shaping of PNe. We study the dust distribution in the very young
Proto-Planetary Nebule (PPN) IRAS16342-3814, also known as the Water Fountain
Nebula, which is known to show strong bipolar characteristics in the shape of
two reflection lobes, and high-velocity collimated molecular outlfows. We use
the new Mid-IR (MIR) instrument VISIR on the Very Large Telescope (VLT) both in
imaging and spectroscopy mode at wavelengths from 8 to 13 micron. We present
the first spatially resolved MIR observations of a dusty evolved star obtained
with VISIR and find that the improved spatial resolution contradicts previous
claims of an elliptical brightness distribution at the heart of IRAS16342: we
find the waist region to be dark even in the MIR. We show that the filling
angle of the obscuring dust lane, which is made mostly of amorphous silicates,
is very large, possibly even close to a spherically symmetric superwind as seen
in OH/IR stars. We conclude that, in contrast to the multitude of recent
dusty-disk detections in Post-AGB stars and PNe, IRAS16342 does not show this
extreme equatorial density enhancement, at least not on the scale of the dusty
environment which lends the object its IR appearance. Rather, it appears that
the observed precessing jets are shaping the bipolar nature in the remains of a
spherically symmetric AGB superwind.

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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
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The categories of this paper are: stat
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The categories of this paper are: econ
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The categories of this paper are: cond-mat
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The categories of this paper are: cmp-lg
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
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The categories of this paper are: mtrl-th
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The categories of this paper are: math
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The categories of this paper are: gr-qc