The Effects of Cosmic-Ray Protons on Galactic Nonthermal Filaments

Abstract

Abstract The Galactic center (GC) contains a collection of filaments that are typically tens of parsecs in length, illuminated by synchrotron radiation from cosmic rays (CRs). The origin of these nonthermal filaments (NTFs) is unclear. We aim to distinguish two injection mechanisms: the first mechanism posits that NTFs are fueled either by jets from pulsar wind nebulae and are lepton dominated; the second mechanism posits that NTFs are fueled by accelerated particles from interstellar shocks and are proton dominated. We explore these mechanisms using the magnetohydrodynamics (MHD) code Athena++ , modified to account for radiative and collisional losses, to simulate CR propagation with lepton and proton CR species. We vary parameters such as magnetic field strength, plasma density, and the CR diffusion coefficient to determine how the range of conditions present in the GC can affect CRs’ propagation, heating, plasma flow, and the observed synchrotron emission. We find few observable differences between the proton- and lepton-dominated cases, but comparing the models with observed filament properties motivates consideration of a third formation mechanism: the generation of NTFs arising from intermittent structures in GC turbulence.