Abstract
Accreting black holes produce collimated outflows, or jets, that traverse many orders of magnitude in distance, accelerate to relativistic velocities, and collimate into tight opening angles. Of these, perhaps the least understood is jet collimation due to the interaction with the ambient medium. In order to investigate this interaction, we carried out axisymmetric general relativistic magnetohydrodynamic simulations of jets produced by a large accretion disc, spanning over 5 orders of magnitude in time and distance, at an unprecedented resolution. Supported by such a disc, the jet attains a parabolic shape, similar to the M87 galaxy jet, and the product of the Lorentz factor and the jet half-opening angle, γ θ ≪ 1, similar to values found from very long baseline interferometry (VLBI) observations of active galactic nuclei (AGNs) jets; this suggests extended discs in AGNs. We find that the interaction between the jet and the ambient medium leads to the development of pinch instabilities, which produce significant radial and lateral variability across the jet by converting magnetic and kinetic energy into heat. Thus pinched regions in the jet can be detectable as radiating hotspots and may provide an ideal site for particle acceleration. Pinching also causes gas from the ambient medium to become squeezed between magnetic field lines in the jet, leading to enhanced mass loading and deceleration of the jet to non-relativistic speeds, potentially contributing to the spine-sheath structure observed in AGN outflows.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 2200-2218 |
| Number of pages | 19 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 490 |
| Issue number | 2 |
| DOIs | |
| State | Published - Dec 1 2019 |
Funding
We thank the anonymous referee for helpful suggestions in improving the text. We thank O. Bromberg, A. Philippov, O. Porth, and E. Sobacchi for helpful discussions. KC thanks M. Lucchini, T. Beuchert, F. Krau\u00DF, and T.D. Russell for providing useful insights for the background study. This research was made possible by National Science Foundation (NSF) PRAC award no. 1615281, OAC-1811605, NSF AST-1911080, AST-1910248, and AST-1910451 at the Blue Waters sustained-petascale computing project and supported in part under grant no. NSF PHY-1125915. KC and SM are supported by the Netherlands Organization for Scientific Research (NWO) VICI grant (no. 639.043.513), ML is supported by the NWO Spinoza Prize and AT by Northwestern University, the TAC and NASA Einstein (grant no. PF3-140131) postdoctoral fellowships and the NSF grant 1815304 and NASA grant 80NSSC18K0565. KC thanks the Leids Kerkhoven-Bosscha Fonds (LKBF) subsidy no. 17.2.100 for travel funding. The simulation data presented in this work are available on request to AT at [email protected]. 1615281, OAC-1811605, NSF AST-1911080, AST-1910248, and AST-1910451 at the Blue Waters sustained-petascale computing project and supported in part under grant no. NSF PHY-1125915. KC and SM are supported by the Netherlands Organization for Scientific Research (NWO) VICI grant (no. 639.043.513), ML is supported by the NWO Spinoza Prize and AT by Northwestern University, the TAC and NASA Einstein (grant no. PF3-140131) postdoctoral fellowships and the NSF grant 1815304 and NASA grant 80NSSC18K0565. KC thanks the Leids Kerkhoven-Bosscha Fonds (LKBF) subsidy no. 17.2.100 for travel funding.
Keywords
- Accretion
- Accretion discs
- Galaxies: individual: (M87)
- MHD
- Methods: numerical
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science