Non-thermal emission from relativistic MHD simulations of PWNe: from synchrotron to inverse Compton

TL;DR

This paper extends diagnostic tools for synchrotron sources to include inverse Compton radiation, investigates gamma-ray emission in pulsar wind nebulae using relativistic MHD simulations, and explores jet-torus morphology and variability.

Contribution

It introduces a method to compute inverse Compton emission in pulsar wind nebulae simulations, incorporating multiple photon targets and detailed particle energy distributions.

Findings

The gamma-ray emission shape matches observations but exceeds flux levels.

Jet-torus morphology appears in high-resolution gamma-ray maps.

Simulated nebular magnetic fields influence the TeV emission excess.

Abstract

In this paper we complete the set of diagnostic tools for synchrotron emitting sources presented by Del Zanna et al. (Astron. Astrophys. 453, 621, 2006) with the computation of inverse Compton radiation from the same relativistic particles. Moreover we investigate, for the first time, the gamma-ray emission properties of Pulsar Wind Nebulae in the light of the axisymmetric jet-torus scenario. The method consists in evolving the relativistic MHD equations and the maximum energy of the emitting particles. The particle energy distribution function is split in two components: the radio one connected to a relic population born at the outburst of the supernova and the other associated to the wind population continuously accelerated at the termination shock and emitting up to the gamma-ray band. We consider the general Klein-Nishina cross section and three different photon targets: the nebular synchrotron photons, far-infrared thermal ones and the cosmic microwave background. The overall synchrotron spectrum is fitted assuming an excess of injected particles and a steeper power law with respect to previous models. The TeV emission has the correct shape but is in excess of the data. This is due to the nebular magnetic field structure as obtained by the simulations. The jet-torus morphology is visible in high-resolution gamma-ray synthetic maps too. We present a preliminary exploration of time variability in the X and gamma-ray bands.