Astronomy and Astrophysics – Astrophysics
Scientific paper
2003-10-06
Astron.Astrophys. 412 (2003) 157-174
Astronomy and Astrophysics
Astrophysics
36 pages, 8 figures, Astronomy and Astrophysics in press
Scientific paper
10.1051/0004-6361:20031370
Cornerstone molecules (CO, H_2CO, CH_3OH, HCN, HNC, CN, CS, SO) were observed toward seven sub-millimeter bright sources in the Orion molecular cloud in order to quantify the range of conditions for which individual molecular line tracers provide physical and chemical information. Five of the sources observed were protostellar, ranging in energetics from 1 - 500L_sun, while the other two sources were located at a shock front and within a photodissociation region (PDR). Statistical equilibrium calculations were used to deduce from the measured line strengths the physical conditions within each source and the abundance of each molecule. In all cases except the shock and the PDR, the abundance of CO with respect to H_2 appears significantly below (factor of ten) the general molecular cloud value of 10^-4. {Formaldehyde measurements were used to estimate a mean temperature and density for the gas in each source. Evidence was found for trends between the derived abundance of CO, H_2CO, CH_3OH, and CS and the energetics of the source, with hotter sources having higher abundances.} Determining whether this is due to a linear progression of abundance with temperature or sharp jumps at particular temperatures will require more detailed modeling. The observed methanol transitions require high temperatures (T>50 K), and thus energetic sources, within all but one of the observed protostellar sources. The same conclusion is obtained from observations of the CS 7-6 transition. Analysis of the HCN and HNC 4-3 transitions provides further support for high densities n> 10^7 cm^-3 in all the protostellar sources.
Boonman Annemieke M. S.
Johnstone Doug
van Dishoeck Ewine F.
No associations
LandOfFree
Astrochemistry of Sub-Millimeter Sources in Orion: Studying the Variations of Molecular Tracers with Changing Physical Conditions 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 Astrochemistry of Sub-Millimeter Sources in Orion: Studying the Variations of Molecular Tracers with Changing Physical Conditions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Astrochemistry of Sub-Millimeter Sources in Orion: Studying the Variations of Molecular Tracers with Changing Physical Conditions will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-320015