A comparison of the Orion nebula's physical conditions measured in the radio and optical domains.
Abstract
The core of M42 has been studied in the H-alpha and He I optical lines as well as in the H66-alpha and He 66-alpha radio lines. The results of this study show a large degree of internal consistency probably because the angular and spectral resolutions were nearly identical for the optical and radio experiments. In particular, effective-temperature values derived from the radio recombination lines under the LTE assumption agree remarkably well with the values derived from a width comparison of H-alpha and He I line profiles. On the basis of this and other recent studies, it is suggested that the bulk emission in the H50-alpha to H170-alpha recombination lines can be explained by a simple model of optically thin nebular gas largely homogeneous in temperature (9000-10,000 K) and density and hardly removed from LTE. This model contrasts with more complex models thar require radial variations in temperature and density and large departures from LTE.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- April 1977
- Bibcode:
- 1977A&A....56..385C
- Keywords:
-
- Abundance;
- Interstellar Matter;
- Light Emission;
- Nebulae;
- Radiative Recombination;
- Radio Spectra;
- Astronomical Maps;
- H Alpha Line;
- H Beta Line;
- Helium;
- Line Shape;
- Spectral Resolution;
- Astrophysics