Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The 3D velocity structure of the planetary nebula NGC 7009   In search for deviations from homologous expansion in planetary nebulae we
present a 3D morphokinematical model of NGC 7009. The model has been
constructed with {\em Shape} based on PV diagrams from the literature and HST
images. We find that the data are consistent with a radial velocity field with
increased gradient at high latitudes compared to the equatorial region (Model
1). In a second model we assume a linearly increasing radial velocity component
with an added poloidal component of order 10 km/s at latitudes around
$70^\circ$. The true velocity field is likely to be in between these two
limiting cases. We also find that the expansion of the ansae is non-radial with
reference to the central star. Their velocity field is focused near the
apparent exit points from the main shell. We predict the proper motion pattern
for the model with a non-zero poloidal velocity component.

18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess