2017ApJ...838...41J

We obtained near-infrared spectra of 26 Sloan Digital Sky Survey quasars at 0.7 z 2.5 with reported rest-frame ultraviolet M_BH ∼ 10¹⁰ M_☉ to critically examine the systematic effects involved with their mass estimations. We find that active galactic nuclei (AGNs) heavier than 10¹⁰ M_☉ often display double-peaked Hα emission, extremely broad Fe II complex emission around Mg II, and highly blueshifted and broadened C 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, ∼10¹⁰ 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.