The Most Massive Active Galactic Nuclei at $1\lesssim z\lesssim 2$

Abstract

We obtained near-infrared spectra of 26 SDSS quasars at $0.7<z<2.5$ with reported rest-frame ultraviolet $M_{\mathrm{BH}}\sim 10^{10}{M}_{\odot }$ to critically examine the systematic effects involved with their mass estimations. We find that AGNs heavier than $10^{10}{M}_{\odot }$ often display double-peaked H$\alpha$ emission, extremely broad FeII complex emission around MgII, and highly blueshifted and broadened CIV emission. The weight of this evidence, combined with previous studies, cautions against the use of $M_{\mathrm{BH}}$ values based on any emission line with a width over 8000 km/s. Also, the $M_{\mathrm{BH}}$ estimations are not positively biased along the presence of ionized narrow line outflows, anisotropic radiation, or the use of line FWHM instead of $\sigma$ for our sample, and unbiased with variability, scatter in broad line equivalent width, or obscuration for general type-1 quasars. Removing the systematically uncertain $M_{\mathrm{BH}}$ values, $\sim 10^{10}{M}_{\odot }$ BHs in $1\lesssim z\lesssim 2$ AGNs can still be explained by anisotropic motion of the broad line region from $\sim 10^{9.5}{M}_{\odot }$ BHs, although current observations support they are intrinsically most massive, and overmassive to the host's bulge mass.

21 pages, accepted to ApJ

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