The optical spectra of 3C 227 and other broad-line radio galaxies

Measured emission-line profiles, relative line intensities, and continuum intensities are reported for 3C 227, 3C 382, and 3C 445, and are compared with previously obtained data for 3C 390.3. The spectra of these four radio galaxies are found to be remarkably similar in overall qualitative aspects; all have broad H I and He I emission lines, similar forbidden-line spectra, and continuous spectra with relatively weak absorption lines. The most striking features in all four spectra are the broad Balmer-line emission profiles, which are not the same in the four galaxies. It is argued that the broad line profiles must result from the Doppler effect, due to either thermal velocities, mass-motion velocities, or radial velocities of injected high-energy protons. The irregularities in the profiles imply that there is a relatively small number of 'currents', 'streams', or 'clouds', and that thermal Doppler broadening cannot be the main contributor. Photoionization is assumed to be the most plausible energy-input mechanism in all four galaxies.