The Most Massive Active Galactic Nuclei at 1 ≲ z ≲ 2

Abstract

We obtained near-infrared spectra of 26 Sloan Digital Sky Survey quasars at with reported rest-frame ultraviolet M BH  ∼ 10 10 M ⊙ to critically examine the systematic effects involved with their mass estimations. We find that active galactic nuclei (AGNs) heavier than 10 10 M ⊙ often display double-peaked H α emission, extremely broad Fe ii complex emission around Mg ii , and highly blueshifted and broadenedC iv emission. The weight of this evidence, combined with previous studies, cautions against the use of M BH values based on any emission line with a width over 8000 km s −1 . Also, the M BH estimations are not positively biased by the presence of ionized narrow line outflows, anisotropic radiation, or the use of line FWHM instead of σ for our sample, and unbiased with variability, scatter in broad line equivalent width, or obscuration for general type-1 quasars. Removing the systematically uncertain M BH values, ∼10 10 M ⊙ black holes (BHs) in 1 ≲  z  ≲ 2 AGNs can still be explained by anisotropic motion of the broad line region from ∼10 9.5 M ⊙ BHs, although current observations support that they are intrinsically most massive, and overmassive to the host’s bulge mass.