THE CONNECTING MOLECULAR RIDGE in the GALACTIC CENTER

We report new observations of multiple transitions of the CS molecular lines in the SgrA region of the Galactic center, at an angular resolution of 40″ (=1.5 pc). The objective of this paper is to study the polar arc (PA), which is a molecular ridge near the SgrA region with apparent non-coplanar motions and a velocity gradient perpendicular to the Galactic plane. With our high resolution dense-gas maps, we search for the base and the origin of the PA, which is expected to be embedded in the Galactic disk. We find that the PA is connected to a continuous structure from one of the disk rings/arms in both the spatial and velocity domains. This structure near SgrA∗ has high CS(J = 4-3)/CS(J = 2-1) ratios The fact that this structure has eluded detection in previous observations is likely due to the combination of high excitation and low surface brightness temperature. We call this new structure the connecting ridge. We discuss the possible mechanism for forming this structure and for lifting the gas above the Galactic plane.