The Most Massive Active Black-Holes at z~1.5-3.5 Have High Spins and Radiative Efficiencies

Understand

The radiative efficiencies ($\eta$) of 72 luminous unobscured Active Galactic Nuclei (AGNs) at $z\sim1.5-3.5$, powered by some of the most massive black holes (BHs), are constrained.

• The analysis is based on accretion disk (AD) models, which link the continuum luminosity at rest-frame optical wavelengths and the black hole mass ($M_{\rm BH}$) to the accretion rate through the AD, $\dot{M}_{\rm AD}$.
• The data are gathered from several literature samples with detailed measurements of the ${\rm H}\beta$ emission line complex, observed at near-IR bands.
• When coupled with standard estimates of bolometric luminosities ($L_{\rm bol}$), the analysis suggests high radiative efficiencies, with most of the sources showing $\eta>0.2$ - that is, higher than the commonly assumed value of 0.1, and the expected value for non-spinning BHs ($\eta=0.057$).