VLA OH Observations of High Negative Velocity Gas towards The Galactic Center
Session 22 -- Galactic Structure; Galactic Center
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

## [22.18] VLA OH Observations of High Negative Velocity Gas towards The Galactic Center

J.-H. Zhao (CfA), W. M. Goss (NRAO), P. T. P. Ho (CfA)

The high-negative-velocity cloud at --180 km s$^{-1}$ was discussed by G\"usten \& Downes (1981) more than a decade ago. Since then, numerous observations were carried out to determine the properties of this component; however the nature of this feature was uncertain due to the lack of high angular resolution observations. Recently we have carried out VLA observations of this feature in the 1667 MHz line of OH at V$_{\rm LSR}$=--180 km s$^{-1}$ with an angular resolution of several arc seconds. Both the structure and the kinematics have been determined and we show that the high-negative-velocity absorbing gas is well mixed with the ionized gas in the center of the Galaxy. The observed kinematics are not consistent with ejection, outflow, or a possible association with the expanding molecular ring at V$_{\rm LSR}$=--135 km s$^{-1}$. The mass of neutral gas seen in absorption at --180 km s$^{-1}$ is about 5$\times$10$^3$ M$_\odot$, only a small fraction of the entire cloud observed in CO emission. Based on a numerical model, we demonstrate that the high velocity gas flows towards the Galactic center and interacts with the central gravitational potential which can distort the kinematics of the high velocity gas projected in front of Sgr A West.