Distribution of the He I Lambda 5876 H Beta Line Emission Ratio in the Crab Nebula
Abstract
Interference-filter images of the Crab Nebula have been employed to produce a map of the He I 5876 A/H-beta line-intensity ratio over the bright filamentary structure. Calibrations with published slit spectroscopy and theoretical calculations indicate that most of the nebular gas is characterized by at least a 75 percent helium mass fraction if the lines arise from recombination. However, collisional excitation of He I lines may be appreciable. The line ratio distribution is markedly nonuniform, including a large, patchy, low-helium region near the base of the tubular 'jet' structure and exceptionally high He I emitting areas defining an extended, broken strip across the pulsar.
- Publication:
-
The Astronomical Journal
- Pub Date:
- June 1987
- DOI:
- 10.1086/114431
- Bibcode:
- 1987AJ.....93.1511U
- Keywords:
-
- Crab Nebula;
- Emission Spectra;
- Line Spectra;
- Radiation Distribution;
- Filaments;
- H Beta Line;
- Helium;
- Interstellar Matter;
- Matched Filters;
- Pulsars;
- Spatial Distribution;
- Astrophysics;
- STARS: SUPERNOVAE