Narrow-line Seyfert galaxies with permitted Fe II emission Markarian 507, 5C 3.100, and I Zw 1

Optical, X-ray and and/or IR spectra of Mrk 507, 5C 3.100 and I Zw 1 are compared in a discussion of the bases for classifications of Seyfert 1 and 2 galaxies. Einstein Observatory X ray data indicate that the Seyfert designation requires a continuum extending to X-rays in order to account for permitted Fe II lines observed in Seyfert galaxies. It is suggested that the IR luminosity of I Zw 1, which exceeds the X-ray luminosity by two orders of magnitude, may be accounted for by interaction between companion galaxies. The presence or absence of dense clouds such as those in I Zw 1 is identified as the factor which separates Seyfert galaxies into two mutually exclusive ranges in X-ray luminosity.