Radio Evidence for AGN Activity: Relativistic as Tracers of SMBHs

TL;DR

This paper discusses how relativistic jets observed via radio interferometry serve as indicators of supermassive black holes in quasars, revealing high velocities, collimation, and brightness temperatures that challenge existing models.

Contribution

It provides detailed radio observational evidence linking relativistic jets to SMBHs and highlights discrepancies in brightness temperature explanations.

Findings

Relativistic jets are direct tracers of SMBHs in quasars.

Observed jet velocities reach up to 50c, indicating near-light speeds.

Brightness temperatures exceed inverse Compton limits, suggesting additional mechanisms.

Abstract

Although the radio emission from most quasars appears to be associated with star forming activity in the host galaxy, about ten percent of optically selected quasars have very luminous relativistic jets apparently powered by a SMBH which is located at the base of the jet. When these jets are pointed close to the line of sight their apparent luminosity is enhanced by Doppler boosting and appears highly variable. High resolution radio interferometry shows directly the outflow of relativistic plasma jets from the SMBH. Apparent transverse velocities in these so called blazars are typically about 7c but reach as much as 50c indicating true velocities within one percent of the speed of light. The jets appear to be collimated and accelerated in regions as much as a hundred parsecs downstream from the SMBH. Measurements made with Earth to space interferometers indicate apparent brightness temperatures of about 10E14 K or more. This is well in excess of the limits imposed by inverse Compton cooling. The modest Doppler factors deduced from the observed ejection speeds appear to be inadequate to explain the high observed brightness temperatures in terms of relativistic boosting.