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

摘要

Long-slit, systematic spectroscopic mapping in the Crab Nebula supernova remnant provides evidence for large-scale distributions of nitrogen-rich and sulfur-rich gas. It is postulated that these components represent ejecta from the precursor star's helium mantle and a mixture involving products of oxygen burning, respectively. There is striking spatial asymmetry, with the nitrogen-rich gas located primarily in the north-northwest part of the remnant and the sulfur-rich mixture found mainly south of the pulsar. This implies directional ejection of the more highly processed material. The nitrogen-rich gas is also characterized by higher velocities, as would be expected from an accelerating shock following core bounce.