Nearby galaxies with Seyfert-like nuclei.

Seyfert galaxies are defined as that class of objects which show strong, broad emission lines arising in a bright semistellar nucleus. In connection with their obvious spectroscopic similarities to QSOs, Seyfert galaxies have become the objective of numerous investigations at all wavelengths. The discovery of narrow-line X-ray galaxies suggested that many other nearby galaxies with Seyfert-like nuclear activity may have gone undetected. The decision was made to examine this possibility by observing 24 emission-line galaxies identified as being of 'high excitation' by Sandage (1978) in his spectroscopic survey of 666 nearby galaxies. The present investigation is concerned with new optical, X-ray, and radio data for these galaxies and also for a comparison sample of four galaxies with 'normal' H II region nuclei. Attention is also given to the degree to which the nuclear activity in the Sandage high-excitation galaxies is related to the nonthermal activity found in classical Seyferts.