The Quasar Accretion Disk Size  Black Hole Mass Relation
Abstract
We use the microlensing variability observed for nine gravitationally lensed quasars to show that the accretion disk size at 2500 Angstroms is related to the black hole mass by log(R_2500/cm) = (15.6+0.2) + (0.54+0.28)log(M_BH/10^9M_sun). This scaling is consistent with the expectation from thin disk theory (R ~ M_BH^(2/3)), but it implies that black holes radiate with relatively low efficiency, log(eta) = 1.29+0.44 + log(L/L_E) where eta=L/(Mdot c^2). These sizes are also larger, by a factor of ~3, than the size needed to produce the observed 0.8 micron quasar flux by thermal radiation from a thin disk with the same T ~ R^(3/4) temperature profile. More sophisticated disk models are clearly required, particularly as our continuing observations improve the precision of the measurements and yield estimates of the scaling with wavelength and accretion rate.
 Publication:

arXiv eprints
 Pub Date:
 July 2007
 DOI:
 10.48550/arXiv.0707.0305
 arXiv:
 arXiv:0707.0305
 Bibcode:
 2007arXiv0707.0305M
 Keywords:

 Astrophysics
 EPrint:
 5 pages, 3 figures, submitted to ApJL