SIMBAD references

Images of the Crab Nebula have been obtained through custom interference filters that transmit emission from the expanding supernova remnant in He II λ4686, Hβ, He I λ5876, [O I] λλ6300, 6364, [N II] λλ6548, 6583, [S II] λλ6716, 6731, [S III] λ9069, and [C I] λλ9823, 9850. We present both raw and flux-calibrated emission-line images. Arrays of 19,440 photoionization models, with extensive input abundance ranges, were matched pixel by pixel to the calibrated data in order to derive corresponding element abundance or mass-fraction distributions for helium, carbon, nitrogen, oxygen, and sulfur. These maps show distinctive structure, and they illustrate regions of gas in which various stages of nucleosynthesis have apparently occurred, including the CNO cycle, helium burning, carbon burning, and oxygen burning. It is hoped that the calibrated observations and chemical abundance distribution maps will be useful for developing a better understanding of the precursor star evolution and the supernova explosive process.