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Morpho-kinematic and photoionization models of the multipolar structures in planetary nebula NGC 6572
We have studied the planetary nebula (PN) NGC 6572 through 3D
morpho-kinematic and photoionization modelling. The 3D morphology is
reconstructed from the Hubble Space Telescope images in different narrow band
filters and position-velocity spectra. The PN have a multipolar morphology
consisting of highly collimated outflows. The nebular image show signatures of
multiple lobes within a spiral-ring-like structure. The multipolar structure is
modelled with two bipolar shells (axes ratios 5.5:1 and 3:1), having closed and
opened lobes, respectively. A toroidal structure (radius:height = 1:3)
surrounds the shells at the waist. The toroidal axis aligns with the major axes
of the bipolar shells. Our study reveals the nebula to have a history of
collimated polar outflow perpendicular to a higher density equatorial wind with
the outflow seemingly have episodes of changing direction of ejection. We
construct a photoionization model of NGC 6572 using the deep optical spectra
obtained at the 2 m Himalayan Chandra Telescope. For the photoionization model,
we configure the input shell geometry in form of a highly bipolar nebular shell
with reference to the 3D morphology. Our photoionization model satisfactorily
reproduces the observables. We estimate the nebular elemental abundances, and
important characteristic parameters of the central star (e.g., effective
temperature, luminosity, gravity, mass, etc.) and the nebula (e.g., hydrogen
density profiles, radii, etc.). We compare the resolved H, [O III], and
[N II] profiles in the 4.2 m William Herschel Telescope with that from the
photoionization model and find a good characteristic match.Comment: 14 pages, 10 figures, 6 table
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