The X-shaped radio galaxy J0725+5835 is associated with an AGN pair

TL;DR

This study uses high-resolution radio observations to identify a dual AGN system in an X-shaped radio galaxy, supporting jet re-orientation as the cause of its morphology.

Contribution

It provides the first detailed radio imaging evidence of dual active nuclei in an X-shaped radio galaxy, linking jet re-orientation to the galaxy's peculiar shape.

Findings

Detection of dual radio cores with optical counterparts.

Identification of a bridge and jet bending indicating galaxy interaction.

Discovery of an arcsecond-scale jet in the companion galaxy.

Abstract

X-shaped radio galaxies (XRGs) are those that exhibit two pairs of unaligned radio lobes (main radio lobes and "wings"), one of the promising models for the peculiar morphology is jet re-orientation. To clarify it, we conducted the European VLBI Network (EVN) 5 GHz observation of an XRG J0725+5835, which resembles the archetypal binary AGNs 0402+379 in radio morphology but it is larger in angular size. In our observation, two milliarcsec (mas) scale radio components with non-thermal radio emission are detected, each of them coincides with an optical counterpart with similar photometric redshift and (optical and infrared) magnitude, corresponding to dual active nuclei. Furthermore, with the improved VLA images, we find a bridge between the two radio cores and a jet bending in the region surrounding the companion galaxy, which further supports the interplay between the main and companion galaxies. In addition, we also report the discovery of an arcsec-scale jet in the companion. Given the projected separation of $\sim100$ kpc between the main and companion galaxies, XRG J0725+5835 is likely associated with a dual jetted-AGN system. In both EVN and VLA observations, we find signatures that the jet is changing its direction, which is likely responsible for the X-shaped morphology. On the origin of jet re-orientation, several scenarios are discussed.