Diffuse gamma-ray emission from the Galactic center and implications of its past activities

TL;DR

This paper models gamma-ray emission from the Galactic center, suggesting past activity of Sgr A* accelerated cosmic-ray protons that produce gamma-rays consistent with observations.

Contribution

It introduces a model linking Sgr A*'s past activity to gamma-ray emission via cosmic-ray proton diffusion and interactions in the CMZ.

Findings

Gamma-ray luminosity matches observations if Sgr A* was active in the past.

Cosmic-ray protons from Sgr A* can explain the observed gamma-ray spectrum.

The model supports the idea of historical activity of the Galactic center.

Abstract

It has been indicated that low-luminosity active galactic nuclei (LLAGNs) are accelerating high-energy cosmic-ray (CR) protons in their radiatively inefficient accretion flows (RIAFs). If this is the case, Sagittarius A* (Sgr A*) should also be generating CR protons, because Sgr A* is a LLAGN. Based on this scenario, we calculate a production rate of CR protons in Sgr A* and their diffusion in the central molecular zone (CMZ) around Sgr A*. The CR protons diffusing in the CMZ create gamma-rays through pp interaction. We show that the gamma-ray luminosity and spectrum are consistent with observations if Sgr A* was active in the past.