On the nature of radio filaments near the Galactic Center

Maxim Barkov,Maxim Lyutikov

doi:10.1088/1742-6596/1623/1/012001

Abstract

We suggest that narrow, long radio filaments near the Galactic Center arise as kinetic jets - streams of high energy particles escaping from ram-pressure confined pulsar wind nebulae (PWNe). The reconnection between the PWN and interstellar magnetic field allows pulsar wind particles to escape, creating long narrow features. They are the low frequency analogues of kinetic jets seen around some fast-moving pulsars, such as The Guitar and The Lighthouse PWNe. The radio filaments trace a population of pulsars also responsible for the Fermi GeV excess produced by the Inverse Compton scattering by the pulsar wind particles. The magnetic flux tubes are stretched radially by the large scale Galactic winds. In addition to PWNe accelerated particles can be injected at supernovae remnants. The model predicts variations of the structure of the largest filaments on scales of ∼ dozens of years - smaller variations can occur on shorter time scales. We also encourage targeted observations of the brightest sections of the filaments and of the related unresolved point sources in search of the powering PWNe and pulsars.

Highlights

The most natural explanation for the radio filaments is that of a magnetic flux tube populated by highly relativistic particles (Yusef-Zadeh et al 1984; Yusef-Zadeh & Morris 1987; Morris & Serabyn 1996)
Using 3D relativistic MHD simulations Barkov et al (2019a,b) showed that these features can’t have hydrodynamical origin and have to be kinetically streaming pulsar wind particles that escaped into the interstellar medium (ISM) due to reconnection between the PWN and ISM magnetic fields (see Bandiera (2008a))
An important advantage of the present model over previous suggestions (e.g. tails of bow shock PWN/analogues of cometary tails (Shore & LaRosa 1999), or other hydrodynamic flows (Rosner & Bodo 1996)) is that the non-thermal particles and magnetic field within the non-thermal filaments (NTFs) should not be in a pressure balance with the surrounding mediums

Summary

INTRODUCTION

The central part of the Galaxy shows numerous non-thermal filaments (NTFs) (Yusef-Zadeh et al 1984; Yusef-Zadeh & Morris 1987; Morris & Serabyn 1996; MeerKAT Collaboration 2018), the largest been the Snake, G359.1-00.2, (Gray et al 1995). The most natural explanation for the radio filaments is that of a magnetic flux tube populated by highly relativistic particles (Yusef-Zadeh et al 1984; Yusef-Zadeh & Morris 1987; Morris & Serabyn 1996). And we favor this interpretations, the observed filaments are the magnetic flux tubes that happen to be illuminated by the local injection of relativistic particles (Morris & Serabyn 1996). Using 3D relativistic MHD simulations Barkov et al (2019a,b) showed that these features can’t have hydrodynamical origin and have to be kinetically streaming pulsar wind particles that escaped into the interstellar medium (ISM) due to reconnection between the PWN and ISM magnetic fields (see Bandiera (2008a)). An effective “hole” appears in the PWN through which particles accelerated at the termination shock can escape into the ISM (Barkov et al 2019b)

Length and brightness estimates

Possible kinks in the NTFs

Fermi and VHE excess towards the GC

Predictions

DISCUSSION