Feedback between Sgr A and B: AGN-starburst connection in the galactic centre

Abstract

Propagation of fast-mode magnetohydrodynamic (MHD) compression waves is traced in the Galactic Centre. MHD waves produced by the active Galactic nucleus (Sgr A) focus on the molecular clouds such as Sgr B in the central molecular zone, which will trigger star formation, or possibly starburst. MHD waves newly excited by the starburst propagate backwards, and focus on the nucleus (Sgr A), where implosive waves compress the nuclear gas to promote fuelling the nucleus and may trigger nucleus activity. Echoing focusing of MHD waves between Sgr A (active galactic nucleus: AGN) and Sgr B (starburst) trigger each other at high efficiency by minimal energy requirement. It also solves the problem of angular momentum for AGN fuelling, as the focusing waves do not require global gas flow.