NOAO >   Observing Info >   Approved Programs >   2003B-0009

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Proposal Information for 2003B-0009


PI: C. R. O'Dell, Vanderbilt University, cr.odell@vanderbilt.edu
Address: Physics Department, Box 1807-B, Vanderbilt University, Nashville, TN 37235, USA

CoI: Lisa Frattare, STScI
CoI: Margaret Meixner, STScI
CoI: Peter McCullough, STScI

Title: Emission Line Imaging of the Helix Nebula

Abstract: The CTIO Mosaic-II CCD camera on the CTIO 4-m telescope presents the opportunity to make unprecedented calibrated emission-line images of the closest planetary nebula, the Helix Nebula, whose size (12\arcmin\ diameter) and low surface brightness has precluded its quantitative imaging in all the important diagnostic lines. Mosaic-II has the necessary field of view even when we use 4x4 inch filters (necessary for two of the lines). These images will supplement 0.05\arcsec images of the inner parts of the nebula with the HST's ACS-WFC obtained during the Leonids meteor stream passage in 2002. Although of high resolution, the HST optical data do not cover the most interesing outer regions of the nebula that were imaged in the infrared H_2 line at 2.12 (mu)m. These outer regions also contain the radiation shadows originating in the knots found closer to the central star. \newline \newline When combined with the HST data plus existing and forthcoming kinematic data on the nebula, we will be able to construct a realistic 3-D model. Such models are necessary for understanding the conditions surrounding the Cometary Knots, which contain about half of all the mass ejected from the central star. A realistic model of the nebula is necessary for determination of whether or not these knots will survive the planetary nebula stage and become components of the interstellar medium. If they do, they would be important contributors to the process of star formation.


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