A Possible Hadronic Origin of TeV Photon Emission from SNR G106.3+2.7

TL;DR

This paper models particle acceleration in SNR G106.3+2.7 using nonlinear diffusive shock acceleration, explaining multi-band photon emissions from electrons and protons, and supports a hadronic origin for TeV gamma rays.

Contribution

It introduces a detailed NLDSA model that accounts for particle acceleration and multi-region emission, explaining the hadronic origin of high-energy gamma rays in SNR G106.3+2.7.

Findings

Gamma-ray emission below 1 TeV is from inside the SNR via proton-proton interactions.

Gamma-ray emission above 1 TeV is from escaped protons interacting with molecular clouds.

The model successfully reproduces observed multi-band emissions.

Abstract

In our model, the acceleration and propagation of particles from the Bohm-like diffusion region inside the SNR to the Galactic diffusion region outside the SNR are described through nonlinear diffusive shock acceleration (NLDSA). The main content of our NLDSA model is to solve the hydrodynamic equations numerically for gas density, gas velocity, gas pressure as well as the equation for the quasi-isotropic particle momentum distribution. The consequent multi-band non-thermal emission is from two different regions, namely the acceleration region and the escaping region. Our model is capable of explaining the multi-band photon emission via the dominant synchrotron radiation of the electrons accelerated inside the SNR; and the photons with energy of $\gtrsim$ GeV are naturally produced by the protons inside and outside the SNR. Moreover, the photons in the energy range of $\sim 1 - \sim 100$ TeV are due to the interaction of escaped protons with dense molecular clouds. For the photons with energy of $E_\gamma \gtrsim $ 1 GeV from SNR G106.3+2.7, our results here favor a hadronic origin, where the photons in the energy range of $\sim 1$ GeV to $\sim 1$ TeV are produced inside the SNR through proton-proton interaction, while the photons with $E_\gamma \gtrsim 1$ TeV originate from the interaction of escaped protons with a dense molecular cloud.