Hadronic origin of multi-TeV gamma rays and neutrinos from low-luminosity active galactic nuclei: Implications of past activities of the Galactic center

Yutaka Fujita, Shigeo S. Kimura, Kohta Murase
2015 Physical Review D  
Radiatively inefficient accretion flows (RIAFs) in low-luminosity active galactic nuclei (LLAGNs) have been suggested as cosmic-ray and neutrino sources that may largely contribute to the observed diffuse neutrino intensity. We show that this scenario naturally predicts hadronic multi-TeV gamma-ray excesses around Galactic centers. The protons accelerated in the RIAF in Sagittarius A^* (Sgr A^*) escape and interact with dense molecular gas surrounding Sgr A^*, which is known as the central
more » ... ular zone (CMZ), and produce gamma rays as well as neutrinos. Based on a theoretical model that is compatible with the IceCube data, we calculate gamma-ray spectra of the CMZ and find that the gamma rays with ≳ 1 TeV may have already been detected with the High Energy Stereoscopic System, if Sgr A^* was more active in the past than it is today as indicated by various observations. Our model predicts that neutrinos should come from the CMZ with a spectrum similar to the gamma-ray spectrum. We also show that such a gamma-ray excess is expected for some nearby galaxies hosting LLAGNs.
doi:10.1103/physrevd.92.023001 fatcat:frhu7nl37jcftid5dms7acb2ou