Molecular tracers of the central 12 parsecs of the Galactic center

We have used the BIMA array to image the Galactic center with a 19 pointing mosaic in HCN(1-0), HCO+ (1-0), and H 42 alpha emission with 5 km s(-1) ve locity resolution and 13" x 4" angular resolution. The 5' field includes th e circumnuclear ring (CND) and parts of the 20 and 50 km s(-1) clouds. HCN( 1-0) and HCO+ trace the CND and nearby giant molecular clouds, while the H 42 alpha emission traces the ionized gas in Sgr A West. We find that the CN D has a definite outer edge in HCN and HCO+ emission at similar to 45" radi us and appears to be composed of two or three distinct streams of molecular gas rotating around the nucleus. Outside the CND, HCN and HCO+ trace dense clumps of high-velocity gas in addition to optically thick emission from t he 20 and 50 km s(-1) clouds. A molecular ridge of compressed gas and dust, traced in NH3 emission and self-absorbed HCN and HCO+, wraps around the ea stern edge of Sgr A East. Just inside this ridge are several arcs of gas th at have been accelerated by the impact of Sgr A East with the 50 km s(-1) c loud. HCN and HCO+ emission trace the extension of the northern arm of Sgr A West, which appears to be an independent stream of neutral and ionized ga s and dust originating outside the CND. Broad line widths and OH maser emis sion mark the intersection of the northern arm and the CND. Comparison to p revious NH3 and 1.2 mm dust observations shows that HCN and HCO+ preferenti ally trace the CND and are weaker tracers of the GMCs than NH3 and dust. We discuss possible scenarios for the emission mechanisms and environment at the Galactic center that could explain the differences in these images.