Project Details
Projekt
Jet Composition under Scrutiny
Subject Area
Astrophysics and Astronomy
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 443220636
Our goal is to shed light on the long-standing issue of plasma composition in AGN jets. In the seminal work by Blandford and Znajek (1977), mass loading of the jets was assumed by photon-photon pair creation close to the ergosphere and by mass entrainment from the ambient medium. Using fluid-dynamical jet models endowed with Lagrangian relativistic test particles together with combinations of mixed-composition floor models, we propose to study the evolution of the resulting MHD accretion-ejection flows and relativistic jets by computing line-of-sight integrals that can be compared with observations to constrain the assumed compositions. While it has been shown during the 1st phase of the research unit, that this is technically feasible, a number of specific issues remain that still need further research. Among them, the following stand out as the most straight forward ones, (i) implementing a more refined model for particle acceleration at oblique shocks in the jet simulations, (ii) computing polarised radiation transport to predict composition-sensitive signatures such as birefringent polarisation conversion, (iii) including accelerated protons with gyro radii exceeding the computing grid cell-sizes and the relevant hadronic emission processes, and (iv) taking into account resistive effects, in particular reconnection. We will also study the contribution of pair injection due to particle acceleration by intermittent vacuum gaps in the launching region and by magnetic reconnection in the turbulent nozzle region of the current-carrying inner jet to the plasma composition on parsec scales. Here, our ansatz is to use the resistive MHD code combined with PIC-motivated parameterisations for the non-thermal particle distributions to estimate the pair yields from the cascades initiated by them. In this way, we can improve from the assumption of a generic to a physical floor model for the jet simulations.
DFG Programme
Research Units
Subproject of
FOR 5195:
Relativistic Jets in Active Galaxies
International Connection
India
Cooperation Partner
Professor Dr. Bhargav Vaidya
