VHE \gamma-rays from the Galactic center generated by cosmic rays
Abstract
Through observations in very-high-energy (VHE) $\gamma$-rays, the High Energy Stereoscopic System (HESS) allowed studying the properties of the VHE $\gamma$-ray emission from the Galactic center (GC) between 0.1~TeV and 100~TeV. HESS observed a $\gamma$-ray diffuse emission strongly correlated with the central molecular zone (CMZ) morphology, showing energies above 30~TeV. The best scenario to generate the $\gamma$-ray diffuse emission is hadronic interaction between cosmic rays (CR) and the ambient gas. The observed $\gamma$-ray spectrum implies that the intrinsic CR spectrum could extend to energies $\sim 1\,\mathrm{PeV}$. The CR density profile in the CMZ shows an increased density towards the GC that is consistent with a source within the central 10 pc, with a continuous injection of CR over at least $10^4$ years. Protons could be accelerated close to the supermassive black hole Sagittarius A* or inside the clusters of young massive stars of Arches, Quintuplet and Nuclear. The problem is that current diffusion models are spherical and isotropic, but the CR diffusion in the CG is anisotropic. We plan to model the VHE $\gamma$-ray emission from the CMZ between 0.1 TeV and 100 TeV, generated by CR, considering different geometries, time dependence, and spectra of CR injection. We will include different diffusion coefficients, polar advection, and compute the interaction of CR with observed ambient gas. From the model, we will get the $\gamma$-ray morphology and spectrum observed by HESS in the CMZ, and predict $\gamma$-rays observation by the Cherenkov Telescope Array in the CMZ and other molecular clouds. Finally, we will identify multi-wavelength and multi-messenger contributions.
- Publication:
-
Boletin de la Asociacion Argentina de Astronomia La Plata Argentina
- Pub Date:
- August 2020
- Bibcode:
- 2020BAAA...61Q..99S
- Keywords:
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- gamma rays: general;
- cosmic rays;
- Galaxy: center