The hot spots of Cygnus A at 230 GHz

We have imaged Cygnus A at 230 GHz with similar to1 angular resolution, using the BIMA array. The hot spots have structures similar to those seen in images at 87, 15, and 5 GHz, but they are more compact and show spectral index gradients indicating local synchrotron aging of the radiating electron population. Bright 230 GHz features, and the flattest spectra, are seen in and near compact hot spots B and E. There are no marked spectral breaks above 5 GHz for the hot spot spectra as a whole, so that relativistic electrons with energies greater than similar to10 GeV are injected into both the compact and the extended hot spots on timescales of less than 50,000 yr. The X-ray emission of the hot spots, as measured by Chandra, more closely resembles the 5 GHz than the 230 GHz radio structures, as expected from an inverse Compton interpretation of the X-ray emission. However, hot spots A and B are overbright in X-rays relative to their 230 GHz emission. This may reflect a magnetic field and an electron population different from those in hot spot D.