Relativistic Jets in Active Galactic Nuclei und Microquasars

TL;DR

This paper reviews the current understanding of relativistic jets in active galactic nuclei and microquasars, highlighting key physical processes, open questions, and differences between these astrophysical sources.

Contribution

It provides a comprehensive overview of the knowns and unknowns in jet physics, comparing Galactic and extragalactic jet sources and discussing their underlying mechanisms.

Findings

Identifies key unresolved questions in jet launching and acceleration.

Highlights the role of magnetic fields in jet collimation and particle acceleration.

Summarizes observational evidence for high-energy particle acceleration in jets.

Abstract

Collimated outflows (jets) appear to be a ubiquitous phenomenon associated with the accretion of material onto a compact object. Despite this ubiquity, many fundamental physics aspects of jets are still poorly understood and constrained. These include the mechanism of launching and accelerating jets, the connection between these processes and the nature of the accretion flow, and the role of magnetic fields; the physics responsible for the collimation of jets over tens of thousands to even millions of gravitational radii of the central accreting object; the matter content of jets; the location of the region(s) accelerating particles to TeV (possibly even PeV and EeV) energies (as evidenced by gamma-ray emission observed from many jet sources) and the physical processes responsible for this particle acceleration; the radiative processes giving rise to the observed multi-wavelength emission; and the topology of magnetic fields and their role in the jet collimation and particle acceleration processes. This chapter reviews the main knowns and unknowns in our current understanding of relativistic jets, in the context of the main model ingredients for Galactic and extragalactic jet sources. It discusses aspects specific to active Galactic nuclei (especially blazars) and microquasars, and then presents a comparative discussion of similarities and differences between them.