THE FUNDAMENTAL PLANE OF THE BROAD-LINE REGION IN ACTIVE GALACTIC NUCLEI

Abstract

ABSTRACT Broad emission lines in active galactic nuclei (AGNs) mainly arise from gas photoionized by continuum radiation from an accretion disk around a central black hole. The shape of the broad-line profile, described by  H β = FWHM / &sgr; H β ?> , the ratio of full width at half maximum to the dispersion of broad Hβ, reflects the dynamics of the broad-line region (BLR) and correlates with the dimensionless accretion rate ( M · ?> ) or Eddington ratio ( L bol ?> / L Edd ?> ). At the same time, M · ?> and L bol ?> / L Edd ?> correlate with  Fe ?> , the ratio of optical Fe ii to Hβ line flux emission. Assembling all AGNs with reverberation mapping measurements of broad Hβ, both from the literature and from new observations reported here, we find a strong bivariate correlation of the form log ( M · , L bol / L Edd ) = &agr; + β  H β + γ  Fe , ?> where α = (2.47, 0.31), β = −(1.59, 0.82), and γ = (1.34, 0.80). We refer to this as the fundamental plane of the BLR. We apply the plane to a sample of z < 0.8 quasars to demonstrate the prevalence of super-Eddington accreting AGNs are quite common at low redshifts.