Research Question

Do the radio properties of Active Galactic Nuclei (AGN) show a similar evolution to the radio jets in X-ray Binaries (XRBs) and do they correspond to analogous accretion states of XRBs?

Quick Summary

I am investigating whether particular AGN radio jet morphologies correspond to specific accretion states of XRBs.

Video Summary

  • A 10 minute video explaining what a radio galaxy is with the public being the intended audience: Radio Galaxies

More Details

Background and Motivation

Black holes that accrete surrounding matter are some of the brightest objects in the sky and allow us to study physical processes under conditions of extreme gravity and high orbital velocities. Black holes usually come in two varieties: stellar mass black holes, which are often found in X-ray binaries (see in left panel of image below), and supermassive black holes which are at the centres of galactic nuclei (see right panel of image below). But the question is, are these black hole systems analogous to each other, and differ only in scale?

XRB vs AGN.

Image credit: Left: NASA/CXC/M.Weiss. Right:ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray).

Our research group at the Astronomical Institute of the Czech Academy of Sciences is exploring the similarities and differences between the accretion around stellar mass (those in X-ray binaries) and supermassive black holes (those in AGN) to examine whether black holes across the mass scale can be unified in their accretion states. We want to answer the question, are these black hole systems analogous to each other, and differ only in scale? The unification between AGNs and XRBs is important for understanding the accretion processes in both kinds of objects. In our work, we investigate the inherent similarities and differences between AGN & XRB – what can be scaled up or down to understand these two classes of black holes. Our primary tool is to compare various states & properties of XRBs with different classes of AGN.

Comparing Radio Galaxies to XRBs

One of the manifestations of the different accretion states of the stellar mass black holes in the X-ray binaries is the presence of the radio jets. The XRBs are often seen to evolve from the ‘low-hard’ state to the ‘high’ state accompanied by the launching and presence of radio jets, which eventually get quenched as the state transitions to ‘high-soft’ state (see image below). Conversely, supermassive black holes in AGN also often appear with large radio jets showing current (powerful jet) or past (bright lobes) radio activity (FR Is and FR IIs). My work focuses on the question, do the radio properties of AGN show a similar evolution to XRBs as the radio jets in XRBs and do these radio properties correspond to analogous accretion states? I explore this question with the analysis of the radio properties of AGN (e.g. morphology) and their location in a diagram called the hardness (of Xray emission)-intensity (total luminosity) diagram. To this end, I have collected ~15-20 catalogs of radio galaxies that either have morphological or HERG/LERG classifications. I analyze of the radio properties of these AGN and their location in the hardness-intensity diagram and compare them to XRBs.

XRB HID

Image credit: Fender+04. This figure represents an X-ray hardness–intensity diagram (HID); ‘HS’ indicates the ‘high/soft state’ and ‘LS’ the ‘low/hard state’.