N. R. ZEIGLER, L. M. ZIURYS, Department of Chemistry, University of Arizona, PO Box 210041, 1306 East University Blvd, Tucson, AZ, 85721, USA; L. N. ZACK, Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
The Helix Nebula, NGC 7293, has been mapped in HCO+ J = 1 0 emission with a 70'' spatial resolution (1.68 km s-1 velocity resolution) using the Arizona Radio Observatory (ARO) 12 m telescope on Kitt Peak. Over 200 individual positions covering an area of roughly 1000 × 800 '' were observed down to a 3 noise level of \textasciitilde 20 mK. HCO+ was detected at over three-quarters of the positions, with the majority of spectra showing multiple velocity components indicative of a complex kinematic structure. The column density of HCO+ across the Helix ranges from Ntot 1.4 × 1011 to 2.4 × 1012 cm-2, with an average Ntot 4 × 1011 cm-2. The HCO+ distribution, which traces gas with densities \textasciitilde 105 cm-3, is similar to that of CO and H2 , with certain point symmetries and red– and blue–shifted regions common in all three molecules; these data are also consistent with observations of atomic lines. The HCO+ emission appears to trace two ring-like structures emanating from the central star: one is blue-shifted and the other red-shifted with respect to the star, and possibly trace the edges of a bipolar outflow.