A new AGN classification based radio kinematics

Links to the paper: pdf ADS

Box plots of extended jets radio luminosities vs. core-extended jet luminosities ratio for the three kinematic classes. Horizontal black lines delimit regions where the luminosities of extended jets are typical of FR I or FR II radio morphologies (Hervet et al. 2016). Credit jet images: NRAO

The origin and location of zones where particle are accelerated in jets is still subject to controversy. The most studied scenarios are based on shock (stationary and/or moving) or on magnetic reconnections.

I started to focus my interest on the high energy zones location during my PhD at the Paris Observatory by studying radio maps of hundreds of jets from the North American telescope array VLBA. These radio data taken at 22 GHz are available to the scientific community by the MOJAVE collaboration.

The great angular resolution achieved by the VLBI technique allows jets observations at a scale of 0.1 milli-arcseconds, and then provide unique informations on jets structures and kinematics close to the supermassive black hole. This resolution is currently unachievable for energies above sub-millimeter.

By studying these sources I discovered a strong link between the radio VLBI kinematics and the synchrotron peak frequency of blazars.

This guided me to propose that blazars can, on top of being traditionally classified from spectral features, also be classified in a relevant way following radio kinematics features.

HBLs are characterized by a succession of quasi-stationary radio knots (Class I), FSRQs by relativistic knots ejected from a zone inside the radio core (Class II), and intermediate blazars by a knot-ejection zone further downstream the core with also the presence of stationary knots (Class I/II). This link indicates that observed knots (overdensities of plasma) are great candidates to host the main particle acceleration zones.

Temporal evolution of knot-core distances for three blazars representative of the three kinematic classes I, II and I/II, selected from the MOJAVE database (Hervet et al. 2016).

Since this publication, further independent evidences confirmed this classification, such as Lister et al. 2019 or Piner & Edward 2018.