The Effect of Density Variations on Elemental Abundance Ratios in Gaseous Nebulae
Abstract
Using numerical analysis it is demonstrated that when there are changes in gas density within a nebulae various empirical methods for determining the electron density can give different results. Eleven different species are considered which have line pair ratios that are well-known electron density (Ne) diagnostic tools. In the presence of varying density, there is a progression in inferred values of Ne from N+ (122/204 microns) at the lowest to C(2+) (1906/1909 A) at the highest. For many of the 11 species there is a fixed order in the inferred density, while for others the order can change somewhat for different mixes of densities. When there are nonconstant density conditions, it is shown that systematic biases may occur in the empirical determination of chemical abundance ratios. Tabular material is presented that delineates the maximum bias that can occur in the determination of a particular abundance ratio in a two-component model.
- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- April 1989
- DOI:
- 10.1086/191330
- Bibcode:
- 1989ApJS...69..897R
- Keywords:
-
- Abundance;
- Gas Density;
- H Ii Regions;
- Nebulae;
- Electron Density (Concentration);
- Nitrogen Ions;
- Numerical Analysis;
- Oxygen Ions;
- Astrophysics;
- NEBULAE: ABUNDANCES;
- NEBULAE: H II REGIONS