Neutral atomic carbon in the globules of the Helix
arXiv:astro-ph/9703116 · doi:10.1086/310677
Abstract
We report detection of the 609u line of neutral atomic carbon in globules of the Helix nebula. The measurements were made towards the position of peak CO emission. At the same position, we obtained high-quality CO(2-1) and 13CO(2-1) spectra and a 135" x 135" map in CO(2-1). The velocity distribution of CI shows six narrow (1 -> 2 km/sec) components which are associated with individual globules traced in CO. The CI column densities are 0.5 -> 1.2 x 10^16/cm^2. CI is found to be a factor of ~6 more abundant than CO. Our estimate for the mass of the neutral envelope is an order of magnitude larger than previous estimates. The large abundance of CI in the Helix can be understood as a result of the gradual photoionisation of the molecular envelope by the central star's radiation field.
5 pages, Latex, AAS macros, 3 EPS figures, to appear in Astrophysical Journal Letters
Cited by in corpus (13)
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- Chemistry and clumpiness in planetary nebulae
- Morphology and Composition of the Helix Nebula
- Detecting z > 10 objects through carbon, nitrogen and oxygen emission lines
- Photoevaporating flows from the cometary knots in the Helix nebula (NGC 7293)
- The Multitude of Molecular Hydrogen Knots in the Helix Nebula
- Atomic Carbon in the Envelopes of Carbon-Rich Post-AGB Stars
- VLA Observations of H I in the Helix Nebula (NGC 7293)
- CO in the C1 globule of the Helix nebula with ALMA
- Herschel spectral-mapping of the Helix Nebula (NGC 7293): Extended CO photodissociation and OH+ emission
- Detection of CI line emission from the detached CO shell of the AGB star R Sculptoris
- An optical absorption study of the Helix Planetary Nebula: NaI and CaII lines, and a search for diffuse bands