Leptonic origin of the 100 MeV gamma-ray emission from the Galactic Centre

Abstract

The Galactic centre is a bright gamma-ray source with the GeV-TeV band spectrum composed of two distinct components in the 1-10 GeV and 1-10 TeV energy ranges. The nature of these two components is not clearly understood. We investigate the gamma-ray properties of the Galactic centre to clarify the origin of the observed emission. We report imaging, spectral, and timing analysis of data from 74 months of observations of the Galactic centre by FERMI/LAT gamma-ray telescope complemented by sub-MeV data from approximately ten years of INTEGRAL/PICsIT observations. We find that the Galactic centre is spatially consistent with the point source in the GeV band. The tightest 3 sigma upper limit on its radius is 0.13 degree in the 10-300 GeV energy band. The spectrum of the source in the 100 MeV energy range does not have a characteristic turnover that would point to the pion decay origin of the signal. Instead, the source spectrum is consistent with a model of inverse Compton scattering by high-energy electrons. In this a model, the GeV bump in the spectrum originates from an episode of injection of high-energy particles, which happened ~300 years ago. This injection episode coincides with the known activity episode of the Galactic centre region, previously identified using X-ray observations. The hadronic model of source activity could be still compatible with the data if bremsstrahlung emission from high-energy electrons was present in addition to pion decay emission.

To match the accepted version

References in corpus (4)

• X-ray hiccups from SgrA* observed by XMM-Newton. The second brightest flare and three moderate flares caught in half a day
• Inverse Compton Scenarios for the TeV Gamma-Ray Emission of the Galactic Centre
• PANGU: A High Resolution Gamma-ray Space Telescope
• A Possible Link Between the Galactic Center HESS Source and Sgr A*

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• Gamma-Ray Emission from Molecular Clouds Generated by Penetrating Cosmic Rays
• Milky Way White Dwarfs as Sub-GeV to Multi-TeV Dark Matter Detectors
• Fermi LAT observations of Sagittarius A*: Imaging Analysis
• Optimal Celestial Bodies for Dark Matter Detection
• Constraints on late-forming exploding black holes
• Detection of positron in-flight annihilation from the Galaxy
• Constraints on Axion-like Particles from the gamma-ray observation of the Galactic Center
• Bounds on ALP-Mediated Dark Matter Models from Celestial Objects
• Shocking Signals of Dark Matter Annihilation
• A GeV-TeV particle component and the barrier of cosmic-ray sea in the Central Molecular Zone
• Origin of X-ray and gamma-ray emission from the Galactic central region
• High Energy Emission from the Galactic Center