The Fermi Bubbles Revisited

Abstract

We analyze 60 months of all sky data from the Fermi-LAT. The Fermi Bubble structures discovered previously are clearly revealed by our analysis. With more data and, consequently, better statistics we can now divide each bubble into constant longitude slices to investigate their gross $\gamma$-ray spectral morphology. While the detailed spectral behaviour of each slice derived within our analysis is somewhat dependent on the assumed background model, we find, robustly, a relative deficit of the flux at low energies (i.e., hardening) towards the top of the South Bubble. In neither Bubble does the spectrum soften with longitude. The morphology of the Fermi Bubbles is also revealed to be energy dependent: at high energies they are more extended. We conclude from the gamma-ray spectrum at high latitudes that a low energy break in the parent cosmic ray population is required in both leptonic and hadronic models. We briefly discuss possible leptonic and hadronic interpretation of this phenomenology.

8 pages. 9 figures. Submitted to Astronomy & Astrophysics

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• Testing the millisecond pulsar scenario of the Galactic center gamma-ray excess with very high energy gamma-rays
• Unveiling the Origin of the Fermi Bubbles
• Search for Very High Energy Gamma Rays from the Northern $\text{Fermi}$ Bubble Region with HAWC
• The Accretion Wind Model of the Fermi Bubbles (II): Radiation
• Probing the Southern Fermi Bubble in Ultraviolet Absorption using Distant AGNs
• 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
• Fermi bubble edges: spectrum and diffusion function
• A Latitude-Dependent Analysis of the Leptonic Hypothesis for the Fermi Bubbles
• Cosmic Rays in a Galactic Breeze
• Galactic halo bubble magnetic fields and UHECR deflections
• Gamma-ray Production in the Extended Halo of the Galaxy and Possible Implications for the Origin of Galactic Cosmic Rays
• Signatures of Recent Cosmic-Ray Acceleration in the High-Latitude $\gamma$-Ray Sky
• Galactic Cosmic-Rays in a Breeze
• Giant lobes of Centaurus A as seen in radio and gamma-ray images obtained with the Fermi-LAT and Planck satellites
• Observations of the Fermi bubbles and the Galactic center excess with the DArk Matter Particle Explorer
• Satellite Infall and Mass Deposition on the Galactic Centre
• Multi-wavelength emission from leptonic processes in ageing galaxy bubbles
• Cosmic Ray (Stochastic) Acceleration from a Background Plasma