Location of Repository

Preprint typeset using L ATEX style EmulateApJ- D. Benford’s version CHEMICAL EVOLUTION OF THE CIRCUMSTELLAR ENVELOPES OF CARBON-RICH POST-AGB OBJECTS

By F. Herpin, J. R. Goicoechea, J. R. Pardo and J. Cernicharo

Abstract

We have observed with the 30-m IRAM telescope, the CSO telescope and the ISO 4 satellite (Infrared Space Observatory) the rotational lines of CO at millimeter, submillimeter and far infrared wavelengths in the direction of C-rich stellar objects at different stages of evolution: CRL 2688 (a very young Proto-Planetary Nebula), CRL 618 (a Proto-Planetary Nebula), and NGC 7027 (a young Planetary Nebula). Several changes in the longwave emission of CO and other molecules are discussed here in relation with the degree of evolution of the objects. In the early stages, represented by CRL 2688, the longwave emission is dominated by CO lines. In the intermediate stage, CRL 618, very fast outflows are present which, together with the strong UV field from the central star, dissociate CO. The released atomic oxygen is seen via its atomic lines, and allows the formation of new O-bearing species, such as H2O and OH. The abundance of HNC is enhanced with respect to HCN as a result of the chemical processes occurring in the photo-dissociation region (PDR). At this stage, CO lines and [OI] lines are the dominant coolants, while the cooling effect of [CII] is rising. At the Planetary Nebula stage, NGC 7027, large parts of the old CO AGB material have been reprocessed. The spectrum is then dominated by atomic and ionic lines. New species such as CH + appear. Water has probably been reprocessed i

Topics: ∼ 5 − 25 kms −1, see, e.g, Loup et al. 1993). During this
Year: 2002
OAI identifier: oai:CiteSeerX.psu:10.1.1.315.6947
Provided by: CiteSeerX
Download PDF:
Sorry, we are unable to provide the full text but you may find it at the following location(s):
  • http://citeseerx.ist.psu.edu/v... (external link)
  • http://arxiv.org/pdf/astro-ph/... (external link)
  • Suggested articles


    To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.