Bridging the Bondi and Event Horizon Scales: 3D GRMHD Simulations Reveal X-shaped Radio Galaxy Morphology

X-shaped radio galaxies (XRGs) produce misaligned X-shaped jet pairs and make up less than or similar to 10% of radio galaxies. XRGs are thought to emerge in galaxies featuring a binary supermassive black hole (SMBH), SMBH merger, or large-scale ambient medium asymmetry. We demonstrate that XRG morphology can naturally form without such special, preexisting conditions. Our 3D general-relativistic magnetohydrodynamic (GRMHD) simulation for the first time follows magnetized rotating gas from outside the SMBH sphere of influence of radius R-B to the SMBH of gravitational radius R-g at the largest scale separation, R-B/R-g = 10(3), to date. Initially, our axisymmetric system of constant-density hot gas contains a weak vertical magnetic field and rotates in the equatorial plane of a rapidly spinning SMBH. We seed the gas with small-scale 2% level pressure perturbations. Infalling gas forms an accretion disk, and the SMBH launches relativistically magnetized collimated jets reaching well outside R-B. Under the pressure of the infalling gas, the jets intermittently turn on and off, erratically wobble, and inflate pairs of cavities in different directions, resembling an X-shaped jet morphology. Synthetic X-ray images reveal multiple pairs of jet-powered shocks and cavities. Large-scale magnetic flux accumulates on the SMBH, becomes dynamically important, and leads to a magnetically arrested disk state. The SMBH accretes at 2% of the Bondi rate ((M) over dot similar or equal to 2.4 x 10(-3) M-circle dot yr(-1) for M87*) and launches twin jets at eta= 150% efficiency. These jets are powerful enough (P-jets similar or equal to 2 x 10(44) erg s(-1)) to escape along the SMBH spin axis and end the short-lived intermittent jet state, whose transient nature can account for the rarity of XRGs.

Automated summary

X-shaped radio galaxies (XRGs) are a type of galaxy that produces misaligned X-shaped jet pairs. These galaxies account for less than or similar to 10% of all radio galaxies. It has been suggested that XRGs are formed in galaxies that have binary supermassive black holes, black hole mergers, or large-scale asymmetries in the surrounding environment. However, our study shows that XRG morphology can naturally form without the need for such special conditions. Through a 3D general-relativistic magnetohydrodynamic (GRMHD) simulation, we tracked the movement of magnetized rotating gas from outside the sphere of influence of the supermassive black hole to its gravitational radius. Our results demonstrate that X-shaped jet morphology can be produced through the interaction between the infalling gas and the rotating black hole, without the need for preexisting conditions.