Model of collimated jets with high energy particles

TL;DR

This paper develops a gravitational model of highly collimated, high-energy particle jets originating from Kerr black holes, analyzing geodesics to explain jet structure and energetics in astrophysical contexts.

Contribution

It introduces a purely gravitational, Kerr spacetime-based model of collimated jets, focusing on unbound geodesics and their energy flux, providing a new theoretical framework for jet formation.

Findings

Derived expressions for jet energy flux and particle density.

Applied model to electrons, estimating jet parameters.

Linked geodesic properties to observed jet powers.

Abstract

The increasing data set of precise observations of very energetic and collimated jets, with black hole (BH) as putative central engine, at different astrophysical scales and in various environments, should soon permit to discriminate and classify current theoretical models able to describe the jets formation. We construct a purely gravitational theoretical model of perfectly collimated jets of high energy particles in the ideal case where the central engine is a Kerr BH of mass $M$ and angular momentum by unit of mass $a$. We study in Weyl coordinates ($\rho $, $z$) the unbound Kerr 2D-geodesics which are asymptotes to straight lines parallel to the $z$ axis of equations \rho =constant= \rho_{1}= [(a/M)^2+Q/(E^2-1)]^{1/2} of which existence was recently demonstrated (Gariel et al.,A & A, 2010). On these geodesics, flow test particles of energy $E$, with a Carter constant $Q$ and (necessarily) an angular momentum $L_{z}=0$. Studying the characteristics of the geodesics equations system, in the special case of a double root, we exhibit jets with a radial structure, whose energy flux can be calculated. From the observed data of the jet powers, we obtain the mean particles density, the particles flow, the speed and the Lorentz factor of the jets, for any charged or neutral test particle. Then, we numerically apply these results to electrons. We also discuss the domains of initial conditions for geodesics starting inside the ergosphere. All these results come from the Kerr spacetime structure, and enhance the Penrose process as a plausible origin for the high energy jets.