Bridging 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 $\lesssim10\%$ of radio galaxies. XRGs are thought to emerge in galaxies
featuring a binary supermassive black hole ($\rm SMBH$), $\rm SMBH$ 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 $\rm SMBH$ sphere of influence
of radius $R_{\rm B}$ to the $\rm SMBH$ of gravitational radius $R_{\rm g}$, at
the largest scale separation $R_{\rm B}/R_{\rm g} = 10^3$ to date. Initially,
our axisymmetric system of constant-density hot gas contains weak vertical
magnetic field and rotates in an equatorial plane of a rapidly spinning $\rm
SMBH$. We seed the gas with small-scale $2\%$-level pressure perturbations.
Infalling gas forms an accretion disk, and the $\rm SMBH$ launches
relativistically-magnetized collimated jets reaching well outside $R_{\rm B}$.
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 $\rm SMBH$, becomes dynamically important, and leads to a magnetically
arrested disk state. The $\rm SMBH$ accretes at $2\%$ of the Bondi rate
($\dot{M}\simeq2.4\times10^{-3}M_{\odot}\,{\rm yr}^{-1}$ for M87*), and
launches twin jets at $\eta=150\%$ efficiency. These jets are powerful enough
($P_{\rm jets}\simeq2\times10^{44}\,{\rm erg\,s}^{-1}$) to escape along the
spin axis and end the short-lived jets state whose transient nature can account
for the rarity of XRGs
