37th DPS Meeting, 4-9 September 2005
Session 16 Comets
Poster, Monday, September 5, 2005, 6:00-7:15pm, Music Recital Room

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[16.13] Wide-field spectroscopic observations of comets in the UV: GALEX observations of C/2004 Q2 (Machholz)

J. P. Morgenthaler, W. M. Harris (University of Washington), M. R. Combi (University of Michigan), H. A. Weaver (Johns Hopkins University/APL), P. D. Feldman (Johns Hopkins University)

We report on UV observations of comet C/2004 Q2 (Machholz) made UT 2005 March 1 with the GALEX spacecraft. GALEX is a Small Explorer (SMEX) designed to map the history of star formation in the Universe using two modes: two-band photometry (1350--1750~Å, 1750--2800~Å) and integrated field grism spectroscopy (10--20~Å\ resolution). The 1~degree FOV diameter and high sensitivity to extended sources makes GALEX ideally suited to cometary coma studies. Preliminary reduction of the data shows the bright UV lines \ion{C}{1} 1657, CS 2576, and OH 3080~Å\ are easily detected to angular separations of >20 arcmin (200,000~km) from the nucleus. Detailed modeling of the integrated brightness and spatial extent of each emission line is planned. These models may allow extraction of the fainter emission lines expected in the data (e.g. \ion{S}{1} 1807--1826~Å, the CO fourth positive group near 1500~Å, and the CO Cameron bands near 2000~Å). Even if CO extraction is not possible, with strong detections of CS and \ion{C}{1} to large cometocentric distances, these data will provide important constraints on models seeking to address the carbon parentage problem. This work was made possible by the GALEX guest investigator program.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.