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[16.08] Spectral Line Mapping Observations of 18-cm OH Lines in Comets

A. J. Lovell (Agnes Scott College), E. S. Howell (NAIC/Arecibo Obs.), F. P. Schloerb (FCRAO/UMass Amherst)

Using the 300m Arecibo telescope, we have obtained observations of 18-cm OH emission in six long-period comets, and observations of comet P/Wirtanen are underway. Spectra are obtained at the ephemeris position of the nucleus for all observed comets, and whenever the observed nucleus-centered lines are strong, maps are also made. These maps contain 7 positions: the nuclear position, and a hexagonal pattern of points offset by the width of one beam (approximately 4 arcminutes). Here we present mapping results for comets C/1999 S4 LINEAR, C/2001 A2/B LINEAR, C/1999 T1 McNaught-Hartley, C/2002 C1 Ikeya-Zhang, and C/2002 F1 Utsunomiya. OH lines are detected with estimated OH production rates as low as log(Q) = 27.5. We also present derived OH parent velocities and quenching radii from best-fit models. In these moderate-production comets, our models are consistent with little or no quenching of OH emission. This research is supported by NASA.

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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.