The jet-disk symbiosis. II. Interpreting the Radio/UV correlations in quasars

TL;DR

This study explores the correlation between UV and radio emissions in quasars, revealing that radio and UV emissions share a common energy source and that jet power is a significant fraction of disk luminosity, with implications for understanding quasar classifications.

Contribution

It introduces a model linking radio and UV emissions in quasars, quantifies jet power relative to disk luminosity, and explains different quasar classes through jet physics and relativistic boosting.

Findings

Radio core emission scales with disk luminosity, especially in radio weak quasars.

Radio loud jets carry at least one-third of the disk luminosity as jet power.

Radio intermediate quasars are likely relativistically boosted radio weak quasars.

Abstract

We investigate the correlation between the accretion disk (UV) luminosity and the radio core emission of a quasar sample. In a radio/$L_{\rm disk}$ plot we find the quasars to be separated into four classes: core dominated quasars (CDQ), lobe dominated quasars (LDQ), radio-intermediate quasars (RIQ) and radio weak quasars. In general the radio core emission scales with the disk luminosity, especially in the radio weak quasars. This shows that radio and UV emission have a common energy source and that the difference between radio loud and radio weak is established already on the parsec scale. We investigate the possibility that radio jets are responsible for the radio core emission in radio loud and radio weak quasars. Comparing our data with a simple jet emission model that takes the limits imposed by energy and mass conservation in a coupled jet-disk system into account, we find that radio loud jets carry a total power $Q_{\rm jet}$ that is at least 1/3 of the observed disk luminosity $L_{\rm disk}$. For the electron population one is forced to postulate an efficient process producing a large number of pairs and/or injecting electrons with a distribution with low-energy cut-off around 50 MeV -- secondary pair production in hadronic cascades could be such a process. The bulk Lorentz factor of the jet is limited to a narrow region ($3\la\gamma_{\rm j}\la10$)). The radio emission of radio weak quasars can be explained with exactly the same parameters for a powerful relativistic jet if secondary pair production, as suggested for radio loud jets, is inhibited. There is evidence that RIQ are the relativistically boosted population of radio weak quasar jets. We can estimate the hidden disk luminosity of FR II galaxies and find that this is consistent with FRII being misdirected quasars.