The contribution of Galactic TeV pulsar wind nebulae to Fermi-LAT diffuse emission

Abstract

The large-scale diffuse $\gamma -$ray flux observed by Fermi-LAT in the 1-100 GeV energy range, parameterized as $\propto E^{-\Gamma }$, has a spectral index $\Gamma$ that depends on the distance from the Galactic center. This feature, if attributed to the diffuse emission produced by cosmic rays (CR) interactions with the interstellar gas, can be interpreted as the evidence of a progressive CR spectral hardening towards the Galactic center. This interpretation challenges the paradigm of uniform cosmic rays diffusion throughout the Galaxy. We report on the implications of TeV Pulsar Wind Nebulae observed by the HESS Galactic Plane Survey in the 1-100 TeV energy range for the interpretation of Fermi-LAT data. We argue that a relevant fraction of this population cannot be resolved by Fermi-LAT in the GeV domain providing a relevant contribution to the large-scale diffuse emission, viz. $\sim 30\%$ of the total diffuse $\gamma$-ray emission in the inner Galaxy. This additional component naturally accounts for a large part of the spectral index variation observed by Fermi-LAT, weakening the evidence of CR spectral hardening in the inner Galaxy.

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• Modelling the Galactic very-high-energy $\gamma$-ray source population
• Modeling the γ-ray Pulsar Wind Nebulae population in our Galaxy
• Probing the Cosmic Ray density in the inner Galaxy
• The TeV gamma-ray luminosity of the Milky-Way and the contribution of H.E.S.S. unresolved sources to VHE diffuse emission
• Reconciling the diffuse Galactic gamma-ray and the cosmic ray spectra

Cited by in corpus (13)

• Diffuse Emission of Galactic High-Energy Neutrinos from a Global Fit of Cosmic Rays
• Population synthesis of pulsar wind nebulae and pulsar halos in the Milky Way -- Predicted contributions to the very-high-energy sky
• Milky Way as a Neutrino Desert Revealed by IceCube Galactic Plane Observation
• Unveiling the nature of galactic TeV sources with IceCube results
• Multi-Component Imaging of the Fermi Gamma-ray Sky in the Spatio-spectral Domain
• On the Contribution of Unresolved Pulsars to the Ultra-high-energy Galactic Diffuse Gamma-Ray Emission
• Setting an upper limit for the total TeV neutrino flux from the disk of our Galaxy
• Constraints on the $e^{\pm }$ Pair Injection of Pulsar Halos: Implications from the Galactic Diffuse Multi-TeV Gamma-ray Emission
• The Origin of the Very-High-Energy Diffuse $\gamma$-Ray Emission: The Case for Galactic Source Cocoons
• Galactic diffuse emission from radio to ultra-high-energy gamma rays in light of up-to-date cosmic ray measurements
• Galactic Gamma-Ray Diffuse Emission at TeV energies with HAWC Data
• Interpreting the LHAASO Galactic diffuse emission data
• Hunting Star-Forming Galaxies in the Gamma-Ray Domain