Journal Article

Optical and infrared imaging and spectroscopy of the multiple-shell planetary nebula NGC 6369

G. Ramos-Larios, M. A. Guerrero, R. Vázquez and J. P. Phillips

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 420, issue 3, pages 1977-1989
Published in print March 2012 | ISSN: 0035-8711
Published online February 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.20075.x
Optical and infrared imaging and spectroscopy of the multiple-shell planetary nebula NGC 6369

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NGC 6369 is a double-shell planetary nebula consisting of a bright annular inner shell with faint bipolar extensions and a filamentary envelope. We have used ground- and space-based narrow-band optical and near-infrared (near-IR) images, broad-band mid-IR images, optical long-slit echelle spectra and mid-IR spectra to investigate its physical structure. These observations indicate that the inner shell of NGC 6369 can be described as a barrel-like structure shape with polar bubble-like protrusions, and reveal evidence for H2 and strong polycyclic aromatic hydrocarbons emission from a photodissociative region (PDR) with molecular inclusions located outside the bright inner shell. High-resolution Hubble Space Telescope narrow-band images reveal an intricate excitation structure of the inner shell and a system of ‘cometary’ knots. The knotty appearance of the envelope, the lack of kinematical evidence for shell expansion and the apparent presence of emission from ionized material outside the PDR make us suggest that the envelope of NGC 6369 is not a real shell, but a flattened structure at its equatorial regions. We report the discovery of irregular knots and blobs of diffuse emission in low-excitation and molecular line emission that are located up to 80 arcsec from the central star, well outside the main nebular shells. We also show that the filaments associated to the polar protrusions have spatial extents consistent with post-shock cooling regimes, and likely represent regions of interaction of these structures with surrounding material.

Keywords: ISM: jets and outflows; ISM: lines and bands; planetary nebulae: individual: NGC 6369; infrared: ISM

Journal Article.  7796 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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