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Article Contents

ABSTRACT

1.INTRODUCTION

2.DETERMINATION OF PHYSICAL PARAMETERS
2.1.Measurements of Relative Emission Line Strengths and Errors
2.2.Determination of Reddening and Underlying H I Absorption from Balmer Lines
2.3.Electron Temperature Determinations from Collisionally Excited Lines
2.4.Electron Density Determinations from Collisionally Excited Lines

3.CONVERTING INDIVIDUAL HE I LINES INTO HE/H ABUNDANCES
3.1.He I and H I Emissivities
3.2.Collisional Enhancement of He I Emission Lines
3.3.The Effects of Underlying Stellar Absorption
3.4.He I Optical Depth Effects
3.5.Ionization Correction Factors

4.SELF-CONSISTENT METHODS FOR EXTRACTING THE 4 He ABUNDANCE
4.1.Using 3 Lines
4.2.Using 5 Lines
4.3.Using 6 Lines

5.TEST CASES AND EXAMPLES
5.1.Cases with no Systematic Errors
5.2.Cases with Systematic Errors in I(lambda3889)
5.3.Cases with Systematic Errors in I(lambda7065)

6.DISCUSSION

A.MONTE CARLO ESTIMATES OF REDDENING AND UNDERLYING BALMER ABSORPTION

B.MONTE CARLO ESTIMATES OF REDDENING AND UNDERLYING BALMER ABSORPTION IN REAL OBSERVATIONS

C.MONTE CARLO ESTIMATES OF SELF-CONSISTENT HELIUM LINE RATIOS

REFERENCES