What is the Origin of the Baldwin Effect in the BLR and the NLR?

Abstract

The origin of the luminosity dependence of the strength of broad and narrow emission lines in AGN (i.e. the Baldwin effect) is not firmly established yet. We explore this question using the Boroson & Green sample of the 87 z<=0.5 PG quasars. UV spectra of the C IV region with a sufficient S/N are available for 81 of the objects. We use these spectra to explore the dependence of the C IV EW on M_BH and L_Edd, as deduced from optical spectra of the H beta region. We find a strong correlation of the C IV EW with L_Edd. This may be the primary correlation which drives the Baldwin effect for C IV. A similar correlation analysis using the C IV FWHM instead of the H beta FWHM, yields an insignificant correlation. This suggests that the C IV FWHM provides a significantly less accurate estimate of M_BH compared to the H Beta FWHM. We also measured the [O III] 4363 /[O III] 5007 line ratio for 72 objects in this sample, and use it to determine whether density or covering factor control the large range in [O III] 5007 strength in AGN.