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Published September 2004 | Published
Journal Article Open

Infrared Array Camera (IRAC) Observations of Planetary Nebulae

Abstract

We present the initial results from the Infrared Array Camera (IRAC) imaging survey of planetary nebulae (PNs). The IRAC colors of PNs are red, especially in the 8.0 μm band. Emission in this band is likely due to contributions from two strong H2 lines and a [Ar III] line in that bandpass. IRAC is sensitive to the emission in the halos as well as in the ionized regions that are optically bright. In NGC 246, we have observed an unexpected ring of emission in the 5.8 and 8.0 μm IRAC bands not seen previously at other wavelengths. In NGC 650 and NGC 3132, the 8.0 μm emission is at larger distances from the central star compared to the optical and other IRAC bands, possibly related to the H2 emission in that band and the tendency for the molecular material to exist outside of the ionized zones. In the flocculi of the outer halo of NGC 6543, however, this trend is reversed, with the 8.0 μm emission bright on the inner edges of the structures. This may be related to the emission mechanism, where the H2 is possibly excited in shocks in the NGC 6543 halo, whereas H2 emission is likely fluorescently excited in the UV fields near the central star.

Additional Information

© 2004. The American Astronomical Society. Received 2004 March 30; accepted 2004 May 19. This work is based on observations made with the Spitzer Space Telescope, which is operated by JPL, Caltech, 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.

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