Shocked Molecular Gas Near the Galactic Center

Abstract

A 3′ × 6′ field centered ~4′ south of the Galactic center and a ~2′ × 4′ field east of the Galactic center have been mapped using the 4_-1 → 3₀ E line (36.169 GHz) of methanol (CH₃OH). Line profiles typically consist of broad (~10-20 km s^-1) components, as well as narrow (~1 km s^-1),spike-like components. The narrow features are bright and unresolved with 60″ resolution, and are probably due to maser activity. We found maser activity immediately adjacent to the non-thermal “wisp” (SgrA-E) ~4′ south of SgrA-West, the secondary knot at SgrA-F, and the eastern edge of SgrA-East. Position-velocity diagrams suggest that the molecular material has been shocked to a higher velocity in the same vicinities. We propose that the maser activity, and the shift in velocity south of the Galactic center, heretofore interpreted as an increasingly steep velocity gradient toward the Galactic center, may be due to the impact of a SNR and the resulting shock of the ambient molecular material. The dynamical effects on the molecular gas of such a shock may have implications on gas feeding toward the nucleus.