ExHaLe-jet: an extended hadro-leptonic jet model for blazars – I. Code description and initial results

Abstract

The processes operating in blazar jets are still an open question. Modelling the radiation emanating from an extended part of the jet allows one to capture these processes on all scales. Kinetic codes solving the Fokker–Planck equation along the jet flow are well suited to this task, as they can efficiently derive the radiation and particle spectra without the need for computationally demanding plasma physical simulations. Here, we present a new extended hadro-leptonic jet code – ExHaLe-jet– which considers simultaneously the processes of relativistic protons and electrons. Within a pre-set geometry and bulk flow, the particle evolution is derived self-consistently. Highly relativistic secondary electrons (and positrons) are created through γ–γ pair production, Bethe–Heitler pair production, and pion/muon decay. These secondaries are entrained in the jet flow decreasing the ratio of protons to electrons with distance from the jet base. For particle–photon interactions, we consider all internal and many external photon fields, such as the accretion disc, broad-line region, and the dusty torus. The external fields turn out to be the most important source for particle–photon interactions governing the resulting photon and neutrino spectra. In this paper, we present the code and an initial parameter study, while in follow-up works we present extensions of the code and more specific applications.

Blazars at Very High Energies: Emission Modelling

“…It should be noted that the treatment of the internal light-travel time effects becomes important when dealing with an extended emission region [66]. This more complex multizone approach, when extended to lepto-hadronic modelling, requires in addition the follow-up of several particle species over a large range of simulated cells (e.g., [67]).…”

Blazars at Very High Energies: Emission Modelling

“…It should be noted that the treatment of the internal light-travel time effects becomes important when dealing with an extended emission region [66]. This more complex multi-zone approach, when extended to lepto-hadronic modelling, requires in addition the follow-up of several particle species over a large range of simulated cells (e.g., [67]).…”

Studying the Influence of External Photon Fields on Blazar Spectra Using a One-Zone Hadro-Leptonic Time-Dependent Model

“…The code is based on the recently developed extended hadro-leptonic steady-state code ExHaLe-jet [19]. In fact, the fundamental equations governing the particle and radiation processes are the same, and we only provide a brief overview here describing the free parameters.…”

“…Equation ( 1) is solved with a Chang and Cooper routine [24]; for a detailed description, see [19,25].…”

“…During both decay processes, neutrinos are produced. The neutrino spectra are calculated following [19,26,27]. The secondary electrons produced in this decay chain are injected into the electron-Fokker-Planck equation along with the primary electrons.…”