Bibcode
DOI
Guerrero, Martín A.; Chu, You-Hua; Manchado, A.; Kwitter, Karen B.
Bibliographical reference
The Astronomical Journal, Volume 125, Issue 6, pp. 3213-3221.
Advertised on:
6
2003
Citations
26
Refereed citations
23
Description
The Owl Nebula is a triple-shell planetary nebula with the outermost
shell being a faint bow-shaped halo. We have obtained deep narrowband
images and high-dispersion echelle spectra in the Hα, [O III], and
[N II] emission lines to determine the physical structure of each shell
in the nebula. These spatiokinematic data allow us to rule out
hydrodynamic models that can reproduce only the nebular morphology. Our
analysis shows that the inner shell of the main nebula is slightly
elongated with a bipolar cavity along its major axis, the outer nebula
is a filled envelope coexpanding with the inner shell at 40 km
s-1, and the halo has been braked by the interstellar medium
as the Owl Nebula moves through it. To explain the morphology and
kinematics of the Owl Nebula, we suggest the following scenario for its
formation and evolution. The early mass loss at the TP-AGB phase forms
the halo, and the superwind at the end of the AGB phase forms the main
nebula. The subsequent fast stellar wind compressed the superwind to
form the inner shell and excavated an elongated cavity at the center,
but this has ceased in the past. At the current old age the inner shell
is backfilling the central cavity.
Based on observations made with the William Herschel Telescope, operated
on the island of La Palma by the Isaac Newton Group in the Spanish
Observatorio del Roque de Los Muchachos of the Instituto de
Astrofísica de Canarias, and with the Burrell Schmidt telescope
of the Warner and Swasey Observatory, Case Western Reserve University.