Fast-moving pulsars as probes of interstellar medium

• Published in: Monthly notices of the Royal Astronomical Society 2020-09, Vol.497 (3), p.2605-2615
• Main Authors: Barkov, Maxim V, Lyutikov, Maxim, Khangulyan, Dmitry
• Format: Article
• Language: English
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/staa1601

ABSTRACT Pulsars moving through interstellar medium (ISM) produce bow shocks detected in hydrogen H α line emission. The morphology of the bow shock nebulae allows one to probe the properties of ISM on scales ∼0.01 pc and smaller. We performed 2D relativistic magnetohydrodynamic modelling of the pulsar bow shock and simulated the corresponding H α emission morphology. We find that even a mild spatial inhomogeneity of ISM density, δρ/ρ ∼ 1, leads to significant variations of the shape of the shock seen in H α line emission. We successfully reproduce the morphology of the Guitar Nebula. We infer quasi-periodic density variations in the warm component of ISM with characteristic length of ∼0.1 pc. Structures of this scale might be also responsible for the formation of the fine features seen at the forward shock of Tycho supernova remnant (SNR) in X-rays. Formation of such short periodic density structures in the warm component of ISM is puzzling, and bow-shock nebulae provide unique probes to study this phenomenon.