Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-06-24
Astron.Astrophys. 425 (2004) 577-589
Astronomy and Astrophysics
Astrophysics
Accepted for publication in A&A. 13 pages, 10 figures
Scientific paper
10.1051/0004-6361:20048091
We have studied the influence of far ultraviolet (UV) radiation from a massive young stellar object (YSO) on the chemistry of its own envelope by extending the models of Doty et al. (2002) to include a central source of UV radiation. The models are applied to the massive star-forming region AFGL 2591 for different inner UV field strengths. Depth-dependent abundance profiles for several molecules are presented and discussed. We predict enhanced column densities for more than 30 species, especially radicals and ions. Comparison between observations and models is improved with a moderate UV field incident on the inner envelope, corresponding to an enhancement factor G0~10-100 at 200 AU from the star with an optical depth tau~15-17. Subtle differences are found compared with traditional models of Photon Dominated Regions (PDRs) because of the higher temperatures and higher gas-phase H2O abundance caused by evaporation of ices in the inner region. In particular, the CN/HCN ratio is not a sensitive tracer of the inner UV field, in contrast with the situation for normal PDRs: for low UV fields, the extra CN reacts with H2 in the inner dense and warm region and produces more HCN. It is found that the CH+ abundance is strongly enhanced and grows steadily with increasing UV field. High-J lines of molecules like CN and HCN are most sensitive to the inner dense region where UV radiation plays a role. Thus, even though the total column density affected by UV photons is small, comparison of high-J and low-J lines can selectively trace and distinguish the inner UV field from the outer one. In addition, future Herschel-HIFI observations of hydrides can sensitively probe the inner UV field.
Benz Arnold O.
Doty Steven D.
Jorgensen Jes K.
Stauber Pascal
van Dishoeck Ewine F.
No associations
LandOfFree
Influence of UV radiation from a massive YSO on the chemistry of its envelope 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 Influence of UV radiation from a massive YSO on the chemistry of its envelope, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Influence of UV radiation from a massive YSO on the chemistry of its envelope will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-101052