The dust and molecular gas cloud surrounding a planetary nebula: NGC 7027
We have searched for millimeter-wave emission from nine molecules in the planetary nebula NGC 7027: CN, CS, C/sub 2/H, HC/sub 3/N, SiS, C/sup 18/O, SiCC, /sup 13/CH/sub 3/OH, and H/sub 2/CO. A search for the J, K = (1,1) line of NH/sub 3/ and the J = 21..-->..20 transition of HC/sub 7/N was undertaken at 1.3 cm. Only the N = 1..-->..0 line of CN was positively detected. Limits on integrated line strengths, column densities, and relative abundances are calculated for most of the molecules. Abundances calculated for the planetary nebula are compared with those found for the evolved carbon star, IRC+10/sup 0/216. Differences between the apparent chemical compositions of the two objects may be explained by a lower maximum volume density in NGC 7027 and the effect of the radiation field of its central star. An analysis of the extinction in the circumstellar cloud shows that the abundance ratio, (dust)/(CO), has nearly the same value in NGC 7027, a number of highly evolved stars, and diffuse interstellar molecular clouds. This result is not easy to reconcile with abundance predictions made on the basis of purely gas-phase chemistry, and it is likely that gas-grain chemistry is important in many astronomical environments.
- Research Organization:
- Wyoming Infrared Observatory, University of Wyoming
- OSTI ID:
- 5961708
- Journal Information:
- Astrophys. J.; (United States), Vol. 300:2
- Country of Publication:
- United States
- Language:
- English
Similar Records
MOLECULAR SURVIVAL IN EVOLVED PLANETARY NEBULAE: DETECTION OF H{sub 2}CO, c-C{sub 3}H{sub 2}, AND C{sub 2}H IN THE HELIX
Molecular envelope of the planetary nebula NGC 7027
Related Subjects
GENERAL PHYSICS
CARBON MONOXIDE
COSMOCHEMISTRY
CYANOGEN
PLANETARY NEBULAE
ABUNDANCE
AMMONIA
CARBON STARS
COSMIC DUST
COSMIC GASES
EMISSION
ENERGY-LEVEL TRANSITIONS
SPECTRA
SULFIDES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMISTRY
DUSTS
FLUIDS
GASES
HYDRIDES
HYDROGEN COMPOUNDS
MAIN SEQUENCE STARS
NEBULAE
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
OXIDES
OXYGEN COMPOUNDS
STARS
SULFUR COMPOUNDS
640105* - Astrophysics & Cosmology- Galaxies