On the origin of jet-like features in bow shock pulsar wind nebulae

TL;DR

This paper investigates the origin of jet-like features in bow shock pulsar wind nebulae by modeling particle escape and trajectories, revealing that beamed, asymmetric, and charge-separated escape can explain observed jets.

Contribution

It introduces a detailed 3D relativistic MHD model to study particle escape, showing that beamed and asymmetric escape can produce jet-like features in pulsar wind nebulae.

Findings

Beamed escape of high-energy particles is possible.

Escape can be asymmetric and charge-separated.

These features can explain observed jet-like structures.

Abstract

Bow shock pulsar wind nebulae are a large class of non-thermal synchrotron sources associated to old pulsars, that have emerged from their parent supernova remnant and are directly interacting with the interstellar medium. Within this class a few objects show extended X-ray features, generally referred as "jets", that defies all the expectations from the canonical MHD models, being strongly misaligned respect to the pulsar direction of motion. It has been suggested that these jets might originate from high energy particles that escape from the system. Here we investigate this possibility, computing particle trajectories on top of a 3D relativistic MHD model of the flow and magnetic field structure, and we show not only that beamed escape is possible, but that it can easily be asymmetric and charge separated, which as we will discuss are important aspects to explain known objects.