Cygnus A: A Long-Wavelength Resolution of the Hot Spots

This paper presents observations of Cygnus A at 74 and 327 MHz at angularresolutions of approximately 10" and 3", respectively. These observations areamong the highest angular resolutions obtained below 1000 MHz for this object.While the angular resolution at 74 MHz is not sufficient to separate clearlythe hot spots from the lobes, guided by 151 and 327 MHz images, we haveestimated the 74 MHz emission from the hot spots. We confirm that the emissionfrom both the western and eastern hot spots flattens at low frequencies andthat there is a spectral asymmetry between the two. For the eastern hot spot, alow-energy cutoff in the electron energy spectrum appears to explain theflattening, which implies a cutoff Lorentz factor \gamma_min ~ 300, though wecannot exclude the possibility that there might be a moderate level offree-free absorption. For the western hot spot, the current observations arenot sufficient to distinguish between a free-free absorped power-law spectrumand a synchrotron self-absorbed spectrum.Comment: 7 pages, AASTeX, 3 figures; accepted in ApJ