A comparison of the emission line properties between quasars and type 1 Seyfert galaxies

For quasars and Seyfert galaxies, the equivalent width of C IV lambda 1550 increases as the continuum luminosity of an object decreases. A reasonable interpretation is that the covering factor increases as luminosity decreases. This is consistent with the fact that the L alpha and C IV equivalent widths for Seyferts are a factor of 2 larger than those for high redshift quasars. The C IV/C III ratio, which is a sensitive indicator of the ionization parameter, is about 5 for many Seyferts while it is about 2 for high redshift quasars.