The nature of the radio emission from the star-gas-dust complex W1

Results are presented of a low-frequency radio survey of the radio source W1, corresponding to the emission nebula GS 285, an extended gas-dust complex. The brightness distribution was mapped at 102 MHz by the 187 x 384 m Pushchino radio telescope. Comparison of the present flux densities with those observed at higher frequencies reveals the nebula S 171, the central and brightest component of GS 285, to have a thermal emission structure, thus ruling out the possibility of a supernova remnant. Distance estimation indicates S 171 to be at the same distance as the Cep IV stellar association (850 pc), evidence of a genetic link. The DN + N component of the nebula NGC 7822 within GS 285 is found to exhibit an apparently nonthermal spectral index, which may be explained as an interaction between the shock wave of an old supernova remnant and the H II region of the nebula. The major portion of NGC 7822 emission is thermal, however, so that the total radiation of W1 above 100 MHz is expected to have a thermal spectrum, inconsistent with a supernova remnant.