The crab-like supernova remnant G21.5-0.9 at millimeter wavelengths

We present a BIMA array image of the supernova remnant G21.5-0.9 at 94 GHz with angular resolution. 8 " .6 x 4 " .5. On scales larger than our synthes ized beam, our results do not indicate any radial or local variations in th e acceleration or synchrotron loss processes for the relativistic particles emitting at radio wavelengths. However, the FWHM size of the radio remnant is significantly greater than that of the X-ray remnant. Either any low-fr equency spectral break is distributed across the remnant or, more probably, the break frequency is in fact higher than 100 GHz.