PAH chemistry and IR emission from circumstellar disks

Details PAH chemistry and IR emission from circumstellar disks PAH chemistry and IR emission from circumstellar disks

2007-01-22

arxiv.org/abs/astro-ph/0701606v1

Astronomy and Astrophysics

Astrophysics

13 pages, 8 figures, accepted for publication in A&A

Scientific paper

10.1051/0004-6361:20066829

Aims. The chemistry of, and infrared (IR) emission from, polycyclic aromatic hydrocarbons (PAHs) in disks around Herbig Ae/Be and T Tauri stars are investigated. The equilibrium distribution of the PAHs over all accessible charge/hydrogenation states depends on the size and shape of the PAHs and on the physical properties of the star and surrounding disk. Methods. A chemistry model is created to calculate this equilibrium distribution. Destruction of PAHs by ultraviolet (UV) photons, possibly in multi-photon absorption events, is taken into account. The chemistry model is coupled to a radiative transfer code to provide the physical parameters and to combine the PAH emission with the spectral energy distribution (SED) from the star+disk system. Results. Normally hydrogenated PAHs in Herbig Ae/Be disks account for most of the observed PAH emission, with neutral and positively ionized species contributing in roughly equal amounts. Close to the midplane, the PAHs are more strongly hydrogenated and negatively ionized, but these species do not contribute to the overall emission because of the low UV/optical flux deep inside the disk. PAHs of 50 carbon atoms are destroyed out to 100 AU in the disk's surface layer, and the resulting spatial extent of the emission does not agree well with observations. Rather, PAHs of about 100 carbon atoms or more are predicted to cause most of the observed emission. The emission is extended on a scale similar to that of the size of the disk. Furthermore, the emission from T Tauri disks is much weaker and concentrated more towards the central star than that from Herbig Ae/Be disks. Positively ionized PAHs are predicted to be largely absent in T Tauri disks because of the weaker radiation field.

Affiliated with

Also associated with

No associations

Rating

PAH chemistry and IR emission from circumstellar disks does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with PAH chemistry and IR emission from circumstellar disks, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and PAH chemistry and IR emission from circumstellar disks will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-515742