Simultaneous Spectral and Spatial Modelling of Young Pulsar Wind Nebulae

TL;DR

This paper presents a comprehensive, time-dependent multi-zone model for pulsar wind nebulae that simultaneously fits spectral and spatial data, providing new insights into their physical properties.

Contribution

The authors develop and calibrate a novel multi-zone model incorporating spatially-dependent magnetic fields and particle dynamics, enabling simultaneous spectral and spatial fitting of PWN data.

Findings

Model successfully fits PWN G0.9+0.1 spectral energy distribution

Simultaneous spectral and size fitting constrains nebula parameters

Incorporates convection, diffusion, and radiative losses in modeling

Abstract

We model the morphology and spectrum of a pulsar wind nebula using a leptonic emission code. This code is a time-dependent, multi-zone model that investigates the changes in the particle spectrum as they traverse the nebula. We calculate the synchrotron and inverse Compton emissivities at different positions in the nebula, obtaining the surface brightness versus the radius, and also the size of the nebula as a function of energy. We incorporate a time and spatially-dependent $B$-field, spatially-dependent bulk particle speed implying convection and adiabatic losses, diffusion, as well as radiative losses. We calibrate our new model using two independent models. We then apply the model to PWN G0.9+0.1 and show that simultaneously fitting the spectral energy distribution and the energy-dependent source size may lead to constraints on several model parameters pertaining to the spatial properties of the PWN.