Extended radio AGN and how they bend it

October 8, 2021


Extended radio active galactic nuclei (AGN) are known for their gorgeous emission in the radio, a result of activity in the nucleus of galaxies, known as active galaxies. Relativistic jets shoot at distances way beyond the galaxy size, on opposite directions on a perpendicular plane.

These radio AGN come in different shapes and very often display bends in their otherwise straight radio appearance. The reason for the bend is not always clear, and is very often the topic of studies related to the environment surrounding these sources.

A team of COSMOS researchers in collaboration with simulation experts have performed a study (Vardoulaki et al. 2021b) to understand the reason behind the distortion in the radio shapes of AGN jets. They used radio observations from the Very Large Array (VLA) in COSMOS to measured the "bent angle" (the angle the jets form to each other in a two-sided source), and related it to the environment (Vardoulaki et al. 2021a). Probes of environment include 1) galaxy groups identified at X-rays in COSMOS using Chandra and XXM data, 2) the large-scale structure identified and 3) the cosmic web (clusters, filaments, field) identified from the distances of objects and their relative positions in the universe. In addition, they investigated the relation to the properties of the AGN host galaxy.

Contrary to other studies (e.g. radio Galaxy Zoo Garon et al. 2019), no strong relations to these environmental probes have been found. However, the comparison to magnetohydrodynamic simulations (ENZO-MHD; Vazza et al. 2021) of simulated radio sources shows that the dominant mechanism affecting the radio structures of extended radio AGN could be the evolution of the ambient medium, i.e., the environment which surrounds these objects. The properties of this medium allows for more space for jet interactions.

 And there you have it! This is how extended radio AGN bend it!

Image: Examples of three radio sources in COSMOS imaged by VLA (purple) including a straight (left) and bent (middle and right) extended radio AGN.