NITROGEN-RICH AND SULFUR-RICH GAS IN THE CRAB-NEBULA

Long-slit, systematic spectroscopic mapping in the Crab Nebula superno va remnant provides evidence for large-scale distributions of nitrogen -rich and sulfur-rich gas. It is postulated that these components repr esent ejecta from the precursor star's helium mantle and a mixture inv olving products of oxygen burning, respectively. There is striking spa tial asymmetry, with the nitrogen-rich gas located primarily in the no rth-northwest part of the remnant and the sulfur-rich mixture found ma inly south of the pulsar. This implies directional ejection of the mor e highly processed material. The nitrogen-rich gas is also characteriz ed by higher velocities, as would be expected from an accelerating sho ck following core bounce.