The high SNR rate in the Galactic Center: origin of the cosmic rays excess?

Abstract

AbstractThe center of our Galaxy hosts a Super-Massive Black Hole (SMBH) of about 4 × 106 M⊙. Since it has been argued that the SMBH might accelerate particles up to very high energies, its current and past activity could contribute to the population of Galactic cosmic-rays (CRs). Additionally, the condition in the Galactic Center (GC) are often compared with the one of a starburst system. The high supernovae (SN) rate associated with the strong massive star formation in the region must create a sustained CR injection in the GC via the shocks produced at the time of their explosion.The presence of an excess of very high energy (VHE) cosmic rays in the inner 100 pc of the Galaxy in close correlation with the massive gas complex known as the central molecular zone (CMZ) has been revealed in 2006 by the H.E.S.S. collaboration. Recently, by analysing 10 years of H.E.S.S. data, the H.E.S.S. collaboration confirmed the presence of this extended VHE diffuse emission and deduced a CR density peaked toward the GC. The origin of the CR over-abundance in the GC still remains mysterious: Is it due to a single accelerator at the center or to multiple accelerators filling the region?In order to investigate the presence of these multiple CR accelerators, and in particular the impact of their spatial distribution on the VHE emission morphology, we build a 3D model of CR injection and diffusive propagation with a realistic 3D gas distribution. We discuss the CR injection in the region by a spectral and morphological comparison with H.E.S.S. data.We show that a peaked γ-ray profile towards the GC center is obtained using a realistic SN spatial distribution taking into account the central massive star clusters. The contribution of theses sources cannot be neglected in particular at high longitudes. In order to fit the very central excess observed with H.E.S.S., another central VHE component is probably necessary.