Infrared Observations of the Helix Planetary Nebula
Abstract
We have mapped the Helix (NGC 7293) planetary nebula (PN) with the IRAC instrument on the Spitzer Space Telescope. The Helix is one of the closest bright PNs and therefore provides an opportunity to resolve the small-scale structure in the nebula. The emission from this PN in the 5.8 and 8 μm IRAC bands is dominated by the pure rotational lines of molecular hydrogen, with a smaller contribution from forbidden line emission such as [Ar III] in the ionized region. The IRAC images resolve the "cometary knots," which have been previously studied in this PN. The "tails" of the knots and the radial rays extending into the outer regions of the PN are seen in emission in the IRAC bands. IRS spectra on the main ring and the emission in the IRAC bands are consistent with shock-excited H_2 models, with a small (~10%) component from photodissociation regions. In the northeast arc, the H_2 emission is located in a shell outside the Hα emission.
Additional Information
© 2006 American Astronomical Society. Received 2006 May 10; accepted 2006 July 20. We gratefully thank Mark Wolfire and Michael Kaufman for providing us with their latest calculations of the H2 line strengths. We thank M. S. Kelley for providing his IRS extended source correction to us. This work is based in part on the IRAC post-BCD processing software IRAC_proc developed by Michael Schuster, Massimo Marengo, and Brian Patten at the Smithsonian Astrophysical Observatory. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA through contract 1256790 issued by JPL/Caltech. Support for the IRAC instrument was provided by NASA through contract 960541 issued by JPL. This work made use of the Two Micron All Sky Survey (2MASS) database, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. H. A. S. acknowledges partial support from NASA grant NAG5-10654. Facilities: SpitzerAttached Files
Published - HORapj06.pdf
Erratum - 0004-637X_656_1_629.pdf
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Additional details
- Eprint ID
- 18850
- Resolver ID
- CaltechAUTHORS:20100629-095313531
- 1256790
- NASA/JPL/Caltech
- NAG5-10654
- NASA
- Created
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2010-06-29Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field