The analysis of radio emission from H II regions: consequences of improper analytic methods.
Abstract
The analytic methods and approximations which have been used to deduce hot cores in H II regions and a gradient in nebular temperatures across the Galaxy from radio recombination-line and continuum emission are critiqued. In particular, it is shown that standard analyses of single-dish flux density measurements are vitiated by the effects of beam convolution and uncertainties in nebula size; other problems arise when the local thermodynamic equilibrium assumption is applied to recombination-line emission and when nebulae are considered to be plane-parallel, isothermal homogeneous objects. These invalid assumptions lead to an apparent decrease in the average electron density of nebulae with distance from the sun, and to an increase in their electron temperature with frequency and distance from the center of a nebula.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1978
- DOI:
- 10.1086/156131
- Bibcode:
- 1978ApJ...222..153L
- Keywords:
-
- Astronomical Spectroscopy;
- H Ii Regions;
- Nebulae;
- Radio Emission;
- Continuous Spectra;
- Emission Spectra;
- Line Spectra;
- Milky Way Galaxy;
- Radio Spectra;
- Thermodynamic Equilibrium;
- Astrophysics;
- H II Regions:Radio Radiation;
- H II Regions:Recombination Lines