Integral Field Spectroscopy of the B and C Fragments of Comet 73P/Schwassmann-Wachmann 3

In May 2006, comet 73P/ Schwassmann-Wachmann 3 (SW3) made the closest approach (0.075 AU) to the Earth of a short period comet in more than 75 years. During this period the comet, which had split into several active sub-fragments during its 1995/1996 apparition, displayed strikingly different activity profiles from its 2 brightest remaining remnants, SW3-B and SW3-C. In particular, fragment SW3-B was observed to undergo several outburst events in the April-May timeframe that were also characterized by significant ejections of dusty debris, while SW3-C followed a less stochastic activity pattern.

We performed observations of SW3-B and SW3-C using the Hydra integral field spectrograph at the WIYN telescope during the period from May 8-15, 2006. This period is significant due to its proximity to perigee, our overlap with other complementary observations, and its coincidence with the onset and decline-phase of a major outburst from SW3-B. Each Hydra measurement contained 80 individual spectra obtained from fibers placed at increasing radial distance from the nucleus over the 1-degree field of view of the WIYN telescope. From May 8 to 11 the spectrograph was used in low dispersion mode, covering a bandpass from 370-650 nm that included detectable emissions from several diagnostic coma species. From May 12 to 15 the spectrograph was used in high (R 15000) resolution mode to map the acceleration of water ions and the band structure of NH2. We report here on the preliminary analysis of these data, including discussion of the radial distribution of emissions, a comparison activity levels between the two fragments, and a comparison with complementary production rate measurements made over the same period.