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Description
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 D_H{beta}_=FWHM/{sigma}_H{beta}_, the ratio of full width at half maximum to the dispersion of broad H{beta}, reflects the dynamics of the broad-line region (BLR) and correlates with the dimensionless accretion rate (dM/dt) or Eddington ratio (L_bot_/L_Edd_). At the same time, dM/dt and (L_bot_/L_Edd_ correlate with R_Fe_, the ratio of optical Fe ii to H{beta} line flux emission. Assembling all AGNs with reverberation mapping measurements of broad H{beta}, both from the literature and from new observations reported here, we find a strong bivariate correlation of the form log((dM/dt.L_bot_/L_Edd_)={alpha}+{beta}D_H{beta}_+{gamma}R_Fe_ where {alpha}=(2.47,0.31), {beta}=-(1.59,0.82), and {gamma}=(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.
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