THE SPATIAL DISTRIBUTION OF C2, C3, AND NH IN COMET 2P/ENCKE

Abstract

We examine the spatial distribution of C{sub 2}, C{sub 3}, and NH radicals in the coma of comet Encke in order to understand their abundances and distributions in the coma. The observations were obtained from 2003 October 22-24, using the 2.7 m telescope at McDonald Observatory. Building on our original study of CN and OH, we have used our modified version of the vectorial model, which treats the coma as one large cone, in order to reproduce Encke's highly aspherical and asymmetric coma. Our results suggest that NH can be explained by the photodissociation of NH{sub 2}, assuming that NH{sub 2} is produced rapidly from NH{sub 3} in the innermost coma. Our modeling of C{sub 2} and C{sub 3} suggests a multi-generational photodissociation process may be required for their production. Using the results of our previous study, we also obtain abundance ratios with respect to OH and CN. Overall, we find that Encke exhibits typical carbon-chain abundances, and the results are consistent with other studies of comet Encke.