Time and Space Dependent Stochastic Acceleration Model for the Fermi Bubbles

TL;DR

This paper presents a time and space-dependent stochastic acceleration model that successfully explains both the gamma-ray Fermi Bubbles and the microwave WMAP haze by considering shock-related turbulence and electron escape dynamics.

Contribution

It introduces a novel model incorporating spatially and temporally varying stochastic acceleration and electron escape to reproduce observed phenomena.

Findings

Model reproduces Fermi Bubbles and WMAP haze characteristics

Accounts for shock-related turbulence and electron escape dynamics

Works under typical galactic magnetic fields

Abstract

Fermi-LAT reveals two huge gamma-ray bubbles existing in the Galactic Center, called 'Fermi Bubbles'. The existence of two microwave bubbles at the same region are also reported by the observation by WMAP, dubbed 'WMAP haze'. In order to explain these components, It has been argued that the gamma-rays arise from Inverse-Compton scattering of relativistic electrons accelerated by plasma turbulence, and the microwaves are radiated by synchrotron radiation. But no previous research reproduces both the Fermi Bubbles and WMAP haze under typical magnetic fields in the galaxy. We assume that shocks present in the bubbles and the efficiency of the acceleration by plasma turbulence, 'stochastic acceleration', changes with the distance from the shock front. The distance from the shock front increases with time, accordingly the efficiency of the acceleration changes with time. We also consider the time development of the electrons escape from the turbulence by diffusive loss. Our model succeed to reproduce both the observed characteristics of the Fermi Bubbles and WMAP haze under typical magnetic fields.