Unified model for the gamma-ray emission of supernova remnants

Abstract

Shocks of supernova remnants (SNRs) are important (and perhaps the dominant) agents for production of the Galactic cosmic rays. Recent $\gamma$-ray observations of several SNRs have made this case more compelling. However, these broadband high-energy measurements also reveal a variety of spectral shape demanding more comprehensive modeling of emissions from SNRs. According to the locally observed fluxes of cosmic ray protons and electrons, the electron-to-proton number ratio is known to be about 1%. Assuming such a ratio is universal for all SNRs and identical spectral shape for all kinds of accelerated particles, we propose a unified model that ascribes the distinct $\gamma$-ray spectra of different SNRs to variations of the medium density and the spectral difference between cosmic ray electrons and protons observed at Earth to transport effects. For low density environments, the $\gamma$-ray emission is inverse-Compton dominated. For high density environments like systems of high-energy particles interacting with molecular clouds, the $\gamma$-ray emission is ${\pi }^0$-decay dominated. The model predicts a hadronic origin of $\gamma$-ray emission from very old remnants interacting mostly with molecular clouds and a leptonic origin for intermediate age remnants whose shocks propagate in a low density environment created by their progenitors via e.g., strong stellar winds. These results can be regarded as evidence in support of the SNR-origin of the Galactic cosmic rays.

7 pages (two-column), 5 figures, 1 table; discussion added; accepted by ApJ

References in corpus (24)

• Discrepant hardening observed in cosmic-ray elemental spectra
• The cosmic-ray electron flux measured by the PAMELA experiment between 1 and 625 GeV
• Primary particle acceleration above 100 TeV in the shell-type Supernova Remnant RX J1713.7-3946 with deep H.E.S.S. observations
• The Expansion Asymmetry and Age of the Cassiopeia A Supernova Remnant
• Observations of the young supernova remnant RX J1713.7-3946 with the Fermi Large Area Telescope
• H.E.S.S. observations of the supernova remnant RX J0852.0-4622: shell-type morphology and spectrum of a widely extended VHE gamma-ray source
• Inverse Compton Emission from Galactic Supernova Remnants: Effect of the Interstellar Radiation Field
• Theory of cosmic ray production in the supernova remnant RX J1713.7-3946
• Gamma ray emission from SNR RX J1713.7-3946 and the origin of galactic cosmic rays
• In which shell-type SNRs should we look for gamma-rays and neutrinos from p-p collisions?
• Mechanism for spectral break in cosmic ray proton spectrum from Supernova remnant W44
• Discovery of the radio and X-ray counterpart of TeV Gamma-ray source HESS J1731-347
• Observations of the shell-type SNR Cassiopeia A at TeV energies with VERITAS
• AGILE detection of GeV gamma-ray emission from the SNR W28
• Exploring a SNR/Molecular Cloud Association Within HESS J1745-303
• The Distances of SNR W41 and overlapping HII regions
• VLA and XMM-Newton observations of the SNR W41/TeV Gamma-ray source HESS J1834-087
• Modeling the Multi-Wavelength Emission of Shell-Type Supernova Remnant RX J1713.7-3946
• Stochastic Electron Acceleration in Shell-Type Supernova Remnants II
• Arguments against a dominantly hadronic origin of the VHE radiation from the supernova remnant RX J1713-3946
• 3-D Model of Broadband Emission from Supernova Remnants Undergoing Non-linear Diffusive Shock Acceleration
• Non-thermal emission from old supernova remnants
• X-ray Hotspot Flares and Implications for Cosmic Ray Acceleration and Magnetic Field amplification in Supernova Remnants
• The multi-band nonthermal emission from the supernova remnant RX J1713.7-3946

Cited by in corpus (19)

• Identification of the TeV Gamma-ray Source ARGO J2031+4157 with the Cygnus Cocoon
• Discovery of the VHE gamma-ray source HESS J1832-093 in the vicinity of SNR G22.7-0.2
• Anomalous distributions of primary cosmic rays as evidence for time-dependent particle acceleration in Supernova remnants
• TeV cosmic ray nuclei acceleration in shell-type supernova remnants with hard $\gamma$-ray spectra
• Multi-wavelength study of the galactic PeVatron candidate LHAASO J2108+5157
• 3D simulations of the non-thermal broad-band emission from young supernova remnants including efficient particle acceleration
• Fermi Large Area Telescope observations of the supernova remnant HESS J1731-347
• Synchrotron Emission on FIRE: Equipartition Estimators of Magnetic Fields in Simulated Galaxies with Spectrally-Resolved Cosmic Rays
• Time evolution of broadband non-thermal emission from supernova remnants in different circumstellar environments
• Detection of GeV $\gamma$-ray emission in the direction of HESS J1731-347 with Fermi-LAT
• Evolution of High-Energy Particle Distribution in Mature Shell-Type Supernova Remnants
• Hadronic versus leptonic origin of gamma-ray emission from supernova remnants
• In-situ Measurement of the Energy Fraction in Supra-thermal and Energetic Particles at ACE, Wind, and PSP Interplanetary Shocks
• Supernova connection of unidentified ultra high energy gamma-ray source LHAASO J2108+5157
• Evidence for gamma-ray emission from the remnant of Kepler's supernova based on deep H.E.S.S. observations
• Origin of Cosmic Ray Electrons and Positrons
• G279.0+1.1: a new extended source of high-energy gamma rays
• Particle acceleration, escape and non-thermal emission from core-collapse supernovae inside non-identical wind-blown bubbles
• The structure of TeV-bright shell-type supernova remnants