The Nature of the Crab Nebula Filaments

The Crab Nebula is the nearest and brightest supernova remnant. It is exceptional because it is still in the early stages of its evolution where the ejecta are dominated by the supernova environment rather than the shock interaction with the interstellar medium. We are performing the first extensive study of the molecular cores associated with the filaments. These constitute a new phase of interstellar matter, where warm dusty gas, irradiated by intense X and gamma rays, and surrounded by high-energy ionizing particles, has developed a rich molecular inventory. Many features, including the optical low-ionization spectrum, strong molecular hydrogen lines in the IR, and the morphology, are strikingly similar to the filaments seen around brightest cluster galaxies in cool core galaxy clusters. The Crab filaments provide a laboratory to understand molecular gas under extreme duress. This is a NASA-data interpretation effort aimed at complementing an existing ADP project that is compiling the extensive set of space-based observations of the Crab. That project began a year and a half ago and will soon have enough of a foothold on the data to begin the modeling and analysis. The project proposed here is that analysis and modeling effort. We will use the plasma simulation code Cloudy, which can self-consistently treat ions, molecules, and dust irradiated by ionizing particles and photons to reproduce the X-ray through FIR spectrum. This project is highly leveraged by existing NASA funded efforts so can make rapid progress at modest cost, a graduate student who will do this as a thesis. The central questions we expect to answer include the following: Excitation processes and the molecular cores. These constitute a new phase of the ISM, which molecules and dust exposed to intense energetic ionizing photon and particles. Grain properties and high redshift galaxies: The dust formed in the Crab is our best chance to study grain formation at high redshift, The mass of the filaments: The ionized mass of the observed nebula is surprisingly low. Do the molecular cores solve this problem? The chemical composition will be a byproduct of our simulation. Many elements are formed in supernovae like the Crab. Cloudy and the microphysics of the filaments; this is a laboratory to test our understanding of processes in extreme conditions, and finally filaments in cool-core clusters of galaxies, the Crab filaments are spectrally and morphologically similar to filaments around Brightest cluster galaxies in cool core galaxy clusters. What can each tell us about the other?