The bipolar planetary nebula IC 4406 : CO, optical and dust emission.
Abstract
The CO J = 1-0 and 2-1 line emission towards the Type I planetary nebula IC 4406 was mapped, and high-quality images of the nebula in H-alpha + forbidden N II and O III line emission were obtained. The CO data show the presence of a high-velocity outflow directed along the major axis of the optical nebula, which, together with the spatial distribution of the H2 emission, indicate that the high-velocity outflow has been collimated by an equatorial density enhancement in the circumstellar envelope of the progenitor AGB star. The optical images show that the ionized nebula is cylindrical in shape, with a radius of 16 arcsec (0.12 pc), and contains a relatively dense equatorial torus. From modeling of the velocity and intensity variations of the CO profiles, it is found that the cavity is inclined (to the plane of the sky) by 11.5 +/-3 deg, its walls have a radius of 20 arcsec and a thickness of 5.5 +/-2.5 arcsec, and it contains a nonnegligible amount of molecular gas. It is suggested that the equatorial tori observed or deduced in IC 4406 results from 'born again' disks formed through the destruction of planetary systems at the end of the AGB evolutionary phase.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1991
- Bibcode:
- 1991A&A...251..560S
- Keywords:
-
- Bipolarity;
- Line Spectra;
- Planetary Nebulae;
- Radio Spectra;
- Stellar Envelopes;
- Stellar Mass Ejection;
- Carbon Monoxide;
- Cosmic Dust;
- Ionized Gases;
- Light Emission;
- Molecular Gases;
- Astrophysics