The Extreme Ultraviolet Deficit and Magnetically Arrested Accretion in Radio Loud Quasars

Abstract

The Hubble Space Telescope composite quasar spectra presented in Telfer et al. show a significant deficit of emission in the extreme ultraviolet (EUV) for the radio loud component of the quasar population (RLQs), compared to the radio quiet component of the quasar population (RQQs). The composite quasar continuum emission between 1100 \AA\, and $\sim$580 \AA\, is generally considered to be associated with the innermost regions of the accretion flow onto the central black hole. The deficit between 1100 \AA\, and 580 \AA\, in RLQs has a straightforward interpretation as a missing or a suppressed innermost region of local energy dissipation in the accretion flow. It is proposed that this can be the result of islands of large scale magnetic flux in RLQs that are located close to the central black hole that remove energy from the accretion flow as Poynting flux (sometimes called magnetically arrested accretion). These magnetic islands are natural sites for launching relativistic jets. Based on the Telfer et al. data and the numerical simulations of accretion flows in Penna et al., the magnetic islands are concentrated between the event horizon and an outer boundary of $<2.8 M$ (in geometrized units) for rapidly rotating black holes and $< 5.5M$ for modestly rotating black holes.