Fermi Bubbles and Bubble-like emission from the Galactic Plane

Abstract

The diffuse gamma-ray sky revealed 'Bubbles' of emission above and below the Galactic Plane symmetric around the centre of the Milky Way with a height of 10 kpc in both directions. At present there is no convincing explanation for the origin. To understand the role of the Galactic Centre (GC) one has to study the Bubble spectrum inside the disc, a region which has been excluded from previous analysis because of the large foreground. From a novel template fit, which allows a simultaneous determination of the signal and foreground in any direction, we find that bubble-like emission is not only found in the halo, but in the Galactic Plane as well with a width in latitude coinciding with the molecular clouds. The longitude distribution has a width corresponding to the Galactic Bar with an additional contribution from the Scutum-Centaurus arm. The energy spectrum of the Bubbles coincides with the predicted contribution from CRs trapped in sources (SCRs). Also the energetics fits well. Hence, we conclude that the bubble-like emission has a hadronic origin, which arises from SCRs and the Bubbles in the halo arise from hadronic interactions in advected gas. Evidence for advection is provided by the ROSAT X-rays from hot gas in the Bubble region.

14 pages, 5 figures, this version accepted for ApJL. It includes section on energetics, finer latitude distribution showing that the bubble-like emission in the Plane originates in the molecular clouds, detailed comparison of ratio of "Soruce CRs" with diffuse CRs and more references

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Cited by in corpus (6)

• Gamma-ray sky points to radial gradients in cosmic-ray transport
• A Unified Model of the Fermi Bubbles, Microwave Haze, and Polarized Radio Lobes: Reverse Shocks in the Galactic Center's Giant Outflows
• The Denoised, Deconvolved, and Decomposed Fermi $\gamma$-ray sky - An application of the D${}^3$PO algorithm
• The start of the Sagittarius spiral arm (Sagittarius origin) and the start of the Norma spiral arm (Norma origin) - model-computed and observed arm tangents at galactic longitudes -20 degrees < l < +23 degrees
• Supernova explosions of massive stars and cosmic rays
• Molecular Clouds as the Origin of the Fermi Gamma-Ray GeV-Excess