Balwdwin Effect

Studies of well-defined samples of quasars show that the equivalent width of the CIV 1549 emission line for flat-spectrum, radio-loud quasars follow the relation EW(CIV 1549) propto L(optical)-0.6, but the correlation is much weaker for other broad emission lines and for other categories of AGN.

Figure 1

Figure 1. The equivalent width of the broad CIV 1549 emission line versus luminosity in the adjacent continuum. The crosses are PG quasars with MB < -24 mag; the filled circles are an optical flux-limited subset of flat-spectrum radio quasars from the PKS ± 4 degree survey (Baldwin et al. 1989)


Baldwin, J.A. 1977 ApJ, 214, 679

Baldwin, J.A., Wampler, E.J., & Gaskelll, C.M. 1989, ApJ., 338, 630

Adapted from J. H. Krolik, Active Galactic Nuclei Princeton Series in Astrophysics, 1999