An aperture synthesis map of the Crab Nebula at 23 gigahertz

A map of the polarization and total brightness distribution of the Crab Nebula at 23 GHz with a resolution of 7 x 8 arcsec is presented. The total intensity distribution is quite similar to that at 5 GHz and shows radio ridges which have a similar spectral index to the general background, consistent with a model in which the enhanced radio emission of the ridges is due to an increased magnetic field near the optical filaments. The polarized brightness distribution at 23 GHz lacks the detailed structure visible at 5 GHz which is attributed to Faraday rotation at frequencies lower than 23 GHz. In the north of the nebula and in the region of the east optical bay, there appears to be substantial depolarization between the optical and 23 GHz emission, which implies somewhat higher rotation measures than have been previously suggested.