The Sobolev approximation in molecular clouds

Details The Sobolev approximation in molecular clouds The Sobolev approximation in molecular clouds

Oct 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997newa....2..365o&link_type=abstract

New Astronomy, vol. 2, no. 4, p. 365-385.

Astronomy and Astrophysics

Astronomy

14

Line: Formation, Radiative Transfer, Methods: Numerical, Radio Lines: Ism, Ism: Jets And Outflows

Scientific paper

To derive the physical properties of a molecular cloud from line observations, one has to know or assume the molecular excitation conditions. The Sobolev approximation neglecting nonlocal radiative interactions is often used for a simple estimate. It is based on the existence of large velocity gradients throughout the cloud.We have investigated the justification of the Sobolev approximation in situations where this condition is not strictly fulfilled. A semi-analytical extension of the Sobolev approximation for the line radiative transfer problem in molecular clouds and outflows is developed. It is applied to test the range of the validity of the ordinary Sobolev approximation and to solve problems beyond its limits.This linear approximation is able to treat configurations with moderate velocity gradients where the basic assumption of the Sobolev approximation, taking constant physical parameters within the radiative interaction region, is no longer justified.It turns out that the Sobolev approximation is quite accurate even far beyond the limits of its strict applicability. The computed energy densities deviate by less than a factor 2.5 in systems with a smooth, monotonic density and velocity structure. This maximum error is further reduced in regions with constant density gradients falling down to 20% for spherical homogeneous flows.For situations requiring high accuracies of the line intensity computations, a simple way for the improvement of results obtained by the ordinary Sobolev approximation is demonstrated.

Affiliated with

Also associated with

No associations

Rating

The Sobolev approximation in molecular clouds 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 The Sobolev approximation in molecular clouds, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Sobolev approximation in molecular clouds will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1157170