4.3.2. FR I radio galaxies
FR Is generally have Liner-type spectra (Laing et al. 1994). However, two FR Is are known which have either a Seyfert 1 spectrum: S52116+81 () or a Seyfert 2 spectrum: PKS2014-55 (; ); to the best of our knowledge, these are the only known cases. The other FR I emission line nebulae are extended (~ 5 kpc) (); the emission lines are weak; the emission line luminosity does not correlate with the radio luminosity ().
There are no obvious differences between the emission line spectra of radio quiet E galaxies, LERGs and most FR Is; FR I and radio quiet E galaxies of the same optical magnitude produce similar line luminosities (; ).