Galactic diffuse gamma-ray emission at TeV energy

Abstract

Measuring the diffuse Galactic gamma-ray flux in the TeV range is difficult for ground-based gamma-ray telescopes because of the residual cosmic-ray background, which is higher than the gamma-ray flux by several orders of magnitude. Its detection is also challenging for space-based telescopes because of low signal statistics. We characterize the diffuse TeV flux from the Galaxy using decade-long exposures of the Fermi Large Area Telescope. Considering that the level of diffuse Galactic emission in the TeV band approaches the level of residual cosmic-ray background, we estimated the level of residual cosmic-ray background in the SOURCEVETO event selection and verified that the TeV diffuse Galactic emission flux is well above the residual cosmic-ray background up to high Galactic latitude regions. We study spectral and imaging properties of the diffuse TeV signal from the Galactic plane. We find much stronger emission from the inner Galactic plane than in previous HESS telescope estimates (lower bound). We also find a significant difference in the measurement of the Galactic longitude and latitude profiles of the signal measured by Fermi and HESS. These discrepancies are presumably explained by the fact that regions of background estimate in HESS have non-negligible gamma-ray flux. Comparing Fermi measurements with those of ARGO-YBJ, we find better agreement, with the notable exception of the Cygnus region, where we find much higher flux (by a factor 1.5). We also measure the TeV diffuse emission spectrum up to high Galactic latitude and show that the spectra of different regions of the sky have spectral slopes consistent with Gamma=2.34+/- 0.04. We discuss the possible origin of the hard slope of the TeV diffuse emission. Fermi/LAT provides reliable measurements of the diffuse Galactic emission spectrum in the TeV range.

10 pages, 7 figures, accepted to A&A

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Cited by in corpus (16)

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• Gamma rays as probes of cosmic-ray propagation and interactions in galaxies
• Constraints on the models of the origin of high-energy astrophysical neutrinos
• Origin of Galactic sub-PeV diffuse gamma-ray emission: Constraints from high-energy neutrino observations
• LHAASO sensitivity for diffuse gamma-ray signals from the Galaxy
• Pion decay model of TIBET-AS$\gamma$ PeV gamma-ray signal
• Shimmering gravitons in the gamma-ray sky
• High-energy neutrinos from cosmic ray interactions in the Local Bubble
• Sensitivity of the Cherenkov Telescope Array to TeV photon emission from the Large Magellanic Cloud
• Neutrinos from the gamma-ray source eHWC J1825-134: predictions for Km${}^3$ detectors
• Constraints on the $e^{\pm }$ Pair Injection of Pulsar Halos: Implications from the Galactic Diffuse Multi-TeV Gamma-ray Emission
• Mapping large-scale diffuse gamma-ray emission in 10-100 TeV band with Cherenkov telescopes
• Signatures of anisotropic diffusion around PeVatrons in 100 TeV gamma-ray data
• Revisiting the propagation of highly-energetic gamma rays in the Galaxy
• Leptonic and hadronic models of high-energy nebula around V4641 Sgr
• Probing the Dark Matter of Three-loop Radiative Neutrino Mass Generation Model with the Cherenkov Telescope Array