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Abstract X-shaped radio galaxies (XRGs) produce misaligned X-shaped jet pairs and make up ≲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 ̇ ≃ 2.4 × 10 − 3 M ⊙ yr − 1 for M87*) and launches twin jets at η = 150% efficiency. These jets are powerful enough ( P jets ≃ 2 × 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.
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How to Turn Jets into Cylinders near Supermassive Black Holes in 3D General Relativistic Magnetohydrodynamic Simulations
Abstract Accreting supermassive black holes (SMBHs) produce highly magnetized relativistic jets that tend to collimate gradually as they propagate outward. However, recent radio interferometric observations of the 3C 84 galaxy reveal a stunning, cylindrical jet already at several hundred SMBH gravitational radii,r≳ 350rg. We explore how such extreme collimation emerges via a suite of 3D general relativistic magnetohydrodynamic simulations. We consider an SMBH surrounded by a magnetized torus immersed in a constant-density ambient medium that starts at the edge of the SMBH sphere of influence, chosen to be much larger than the SMBH gravitational radius,rB= 103rg. We find that radiatively inefficient accretion flows (e.g., M87) produce winds that collimate the jets into parabolas near the black hole. After the disk winds stop collimating the jets atr≲rB, they turn conical. Once outsiderB, the jets run into the ambient medium and form backflows that collimate the jets into cylinders some distance beyondrB. Interestingly, for radiatively efficient accretion, as in 3C 84, the radiative cooling saps the energy out of the disk winds; at early times, they cannot efficiently collimate the jets, which skip the initial parabolic collimation stage, start out conical near the SMBH, and turn into cylinders already atr≃ 300rg, as observed in 3C 84. Over time, the jet power remains approximately constant, whereas the mass accretion rate increases; the winds grow in strength and start to collimate the jets, which become quasi-parabolic near the base, and the transition point to a nearly cylindrical jet profile moves outward while remaining insiderB.
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- PAR ID:
- 10492984
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal Letters
- Volume:
- 963
- Issue:
- 1
- ISSN:
- 2041-8205
- Format(s):
- Medium: X Size: Article No. L29
- Size(s):
- Article No. L29
- Sponsoring Org:
- National Science Foundation
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