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

TL;DR

This paper investigates the EUV deficit in radio loud quasars, attributing it to magnetically arrested accretion near the black hole, which suppresses inner accretion regions and facilitates jet launching.

Contribution

It proposes that magnetic islands near the black hole cause the EUV deficit in RLQs, linking magnetic flux, accretion flow suppression, and jet formation.

Findings

EUV deficit correlates with magnetic flux near black hole

Magnetic islands are located within 2.8 to 5.5 gravitational radii

Suppressed inner accretion regions explain EUV emission differences

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.