The Fermi bubbles from stochastic acceleration of electrons in a Galactic outflow

Abstract

The discovery of the Fermi bubbles---a huge bilobular structure seen in GeV gamma-rays above and below the Galactic center---implies the presence of a large reservoir of high energy particles at $\sim 10\text{kpc}$ from the disk. The absence of evidence for a strong shock coinciding with the edge of the bubbles, and constraints from multi-wavelength observations point towards stochastic acceleration by turbulence as a likely mechanism of acceleration. We have investigated the time-dependent acceleration of electrons in a large-scale outflow from the Galactic centre. For the first time, we present a detailed numerical solution of the particle kinetic equation that includes the acceleration, transport and relevant energy loss processes. We also take into account the addition of shock acceleration of electrons at the bubble's blast wave. Fitting to the observed spectrum and surface brightness distribution of the bubbles allows determining the transport coefficients, thereby shedding light on the origin of the Fermi bubbles.

14 pages, 11 figures; submitted to A&A

References in corpus (17)

• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• The Fermi Galactic Center GeV Excess and Implications for Dark Matter
• The Spectrum and Morphology of the Fermi Bubbles
• The Fermi Bubbles: Giant, Multi-Billion-Year-Old Reservoirs of Galactic Center Cosmic Rays
• Extended Anomalous Foreground Emission in the WMAP 3-Year Data
• Giant Magnetized Outflows from the Centre of the Milky Way
• On the Momentum Diffusion of Radiating Ultrarelativistic Electrons in a Turbulent Magnetic Field
• The Starburst Contribution to the Extra-Galactic Gamma-Ray Background
• Fermi Bubbles Inflated by Winds Launched from the Hot Accretion Flow in Sgr A*
• The Interaction of the Fermi Bubbles with the Milky Way's Hot Gas Halo
• The Spatially Uniform Spectrum of the Fermi Bubbles: the Leptonic AGN Jet Scenario
• A Hadronic-Leptonic Model for the Fermi Bubbles: Cosmic-Rays in the Galactic Halo and Radio Emission
• Multi-wavelength Emission from the Fermi Bubble III. Stochastic (Fermi) Re-Acceleration of Relativistic Electrons Emitted by SNRs
• Multi-wavelength Emission from the Fermi Bubble II. Secondary Electrons and the Hadronic Model of the Bubble
• Multi-wavelength Emission from the Fermi Bubble I. Stochastic acceleration from Background Plasma
• Fermi bubble edges: spectrum and diffusion function
• Systematic effects in the extraction of the 'WMAP haze'

Cited by in corpus (10)

• Fermi and eRosita bubbles as relics of the past activity of the Galactic black hole
• Evolution of cosmic ray electron spectra in magnetohydrodynamical simulations
• Simulating the Fermi Bubbles as Forward Shocks Driven by AGN Jets
• Fermi bubbles: the collimated outburst needed to explain forward-shock edges
• A numerical study of the interplay between Fermi acceleration mechanisms in radio lobes of FR-II radio galaxies
• The Important Role of Cosmic-Ray Re-Acceleration
• Galactic breeze origin for the Fermi bubbles emission
• Magnetohydrodynamic turbulence and the associated spatial diffusion tensor of cosmic rays in dynamical galactic halos
• Numerical modeling and physical interplay of stochastic turbulent acceleration for non-thermal emission processes
• On the high-energy protons regular acceleration in the Fermi Bubbles