Black hole jets
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Black Hole Jets: Mechanisms and Observations
Introduction to Black Hole Jets
Black hole jets are powerful streams of plasma that are ejected from the regions surrounding black holes. These jets can travel at relativistic speeds and emit radiation across the entire electromagnetic spectrum. Understanding the mechanisms behind their formation and propagation is crucial for astrophysics.
Mechanisms of Jet Formation
Energy Sources: Accretion Disk and Black Hole Rotation
The energy driving black hole jets can originate from two primary sources: the accretion disk or the rotating black hole itself. Magnetohydrodynamic (MHD) simulations have shown that jets can extract energy from a black hole if the plasma near it is threaded by large-scale magnetic flux. This process involves the creation of large magnetic stresses that are released as relativistic jets, depleting the black hole's rotational energy1.
Binary Black Holes and Dual Jets
When galaxies merge, their central black holes can form a binary system before coalescing into a single black hole. During this process, the combined accretion disks form a circumbinary disk that anchors a magnetic field. Numerical simulations indicate that the interaction of orbiting binary black holes with this magnetic field can generate collimated beams of electromagnetic radiation, which eventually transition into a single jet as the black holes merge2.
Small-Scale Magnetic Flux Loops
Another proposed mechanism for jet formation involves small-scale magnetic flux loops sustained by disc turbulence. These loops are forced to inflate and open due to differential rotation between the black hole and the accretion flow. This process does not require a large-scale net magnetic flux and can operate effectively in many systems, especially when the accretion flow is retrograde3.
Observational Evidence and Simulations
Event Horizon Telescope Observations
High-resolution observations of the jet in the galaxy M87 using the Event Horizon Telescope have provided insights into the structures near the black hole's event horizon. These observations suggest that the accretion disk powering the jet orbits in the same direction as the black hole's spin, supporting the theory that the jet is powered by the accretion disk5.
Plasma Simulations and Pair Creation
General-relativistic collisionless plasma simulations of Kerr-black-hole magnetospheres have shown that black holes can drive powerful plasma jets to relativistic velocities. These simulations begin from vacuum conditions and inject electron-positron pairs based on local unscreened electric fields, leading to steady states with electromagnetically powered jets6.
Magnetically Arrested Discs
Simulations of magnetically arrested discs (MADs) demonstrate that when a large amount of magnetic flux is transported to the center, it impedes accretion and leads to powerful outflows. For rapidly spinning black holes, the efficiency of energy generation in jets and winds can exceed 100%, indicating the extraction of spin energy from the black hole10.
Impacts and Implications
Primordial Black Holes and Dark Matter
Primordial black holes (PBHs) formed in the early Universe are considered potential candidates for dark matter. In the gaseous environment of the interstellar medium, PBHs with accretion disks can launch outflows such as winds and jets. These jets can efficiently deposit kinetic energy and heat the surrounding gas, providing novel tests and setting new limits on PBHs4.
Intermediate-Mass Black Holes
The detection of an off-nuclear intermediate-mass black hole (IMBH) in the spiral galaxy NGC 2276, with a powerful jet, confirms that the accretion physics is mass invariant. This discovery suggests that seed IMBHs in the early Universe possibly had powerful jets that were significant sources of feedback9.
Conclusion
The study of black hole jets involves understanding complex interactions between magnetic fields, accretion disks, and black hole rotation. Observations and simulations have provided significant insights into the mechanisms driving these jets and their implications for astrophysics. As technology advances, future observations and simulations will continue to unravel the mysteries of black hole jets.
Sources and full results
Most relevant research papers on this topic
Simulations of Jets Driven by Black Hole Rotation
Magnetohydrodynamic simulations show a well-defined jet that extracts energy from a black hole, driven by magnetic stresses created by large-scale magnetic flux near the black hole.
Highly CitedDual Jets from Binary Black Holes
Merging black holes may produce a detectable electromagnetic signature, as they stir the plasma surrounding them, generating collimated beams of electromagnetic radiation that transition to a single jet as they merge due to gravitational waves.
Highly CitedBlack hole jets without large-scale net magnetic flux
Small-scale magnetic flux loops can launch relativistic jets from rotating black holes without large-scale net magnetic flux, potentially responsible for hard X-ray emission.
Impacts of Jets and winds from primordial black holes
Primordial black holes with significant spin can sustain powerful relativistic jets and generate associated cocoons, setting new limits on their mass range and establishing a new method for identifying spinning black holes.
Jet-Launching Structure Resolved Near the Supermassive Black Hole in M87
The relativistic jet in M87 is powered by an accretion disk in a prograde orbit around a spinning black hole, as observed by the Event Horizon Telescope.
Highly CitedFirst-Principles Plasma Simulations of Black-Hole Jet Launching.
Black hole jets can be effectively simulated using collisionless plasma, potentially aiding in understanding future submillimeter and infrared observations.
New constraints on the structure and dynamics of black hole jets
This study reveals a linear relationship between jet power and radius, and a bimodal distribution of accretion rates in black hole jets, constraining their basic dynamical and structural properties.
General relativistic magnetohydrodynamic simulations of the jet formation and large-scale propagation from black hole accretion systems
The study reveals that black hole accretion systems can produce Poynting-dominated jets with minimal instability, potentially explaining their ability to extend to large distances without completely disrupting.
Highly CitedThe powerful jet of an off-nuclear intermediate-mass black hole in the spiral galaxy NGC 2276
An off-nuclear intermediate-mass black hole in NGC 2276 has a powerful jet, confirming that accretion physics is mass invariant and that seed IMBHs in the early Universe may have had powerful jets as a source of feedback.
Highly CitedEfficient Generation of Jets from Magnetically Arrested Accretion on a Rapidly Spinning Black Hole
Magnetically arrested accretion on a rapidly spinning black hole can efficiently generate outflowing energy in jets and winds, potentially explaining active galactic nuclei with apparent few 100 per cent.
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