2015ApJ...808...86M

The gas traced by the SiO 1-0 emission appears to not have a direct connection or interaction with the circumnuclear disk (CND). In contrast, higher-resolution observations of the SiO 5-4 emission confirm the dissymmetric gas distribution of the CND, as well as a large concentration of gas in the CND's southwest region. In particular, the SiO 5-4 emission peaks toward what is likely the ''convergent'' position, where the west arc of Sgt A West overlaps with the CND. We think that this is the position where several incoming and outgoing gas flows interact with each other. The high angular resolution () observations of the SiO 5-4 emission show several emission clumps with sizes. These clumps have different velocities that may have resulted from a collision with incoming clouds. We confirm that the overall fractional abundance of SiO is about 10^–9 relative to the total H₂, and it probably resulted from the large-scale shocks prevalent in the Galactic center region. A comparison of the SiO fractional abundance suggests that in addition to the dense ambient cloud component, which surrounds but does not interact much with the CND, there are separate gas components that have more interactions with the CND.