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H_2 morphology of young planetary nebulae

Graham, James R. and Herbst, T. M. and Matthews, K. and Neugebauer, G. and Soifer, B. T. and Serabyn, E. and Beckwith, S. (1993) H_2 morphology of young planetary nebulae. Astrophysical Journal, 408 (2). L105-L107. ISSN 0004-637X.

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The distributions of H_2 1-0 S(l) emission in the young planetary nebulae BD +30°3639 and NGC 7027 show striking similarities: both have limb-brightened arcs of H_2 emission with radii that are about twice those of their H II regions. The extended H_2 emission in both nebulae is attributed to a photodissociation region. This implies that the neutral envelopes of these young planetaries extend well beyond the edge of the H II region, in contrast to older nebulae where the ionized and molecular gas are more nearly coextensive. The contrast between young and old planetaries can only be explained if the molecular envelope is inhomogeneous. We endorse a scenario for the evolution of a planetary nebula in which a photodissociation front propagates through the clumpy molecular envelope, leaving the ionized core embedded in an envelope of partially ionized atomic gas and dense molecular knots. In an evolved planetary, the H II region has expanded to engulf some of the dense molecular knots, which can be identified with bright [O I] and H_2 1-0 S(l) condensations, while the remnant of the photodissociated envelope may be detected as a faint optical halo.

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Additional Information:© 1993 American Astronomical Society. Received 1993 January 5; accepted 1993 February 24.
Subject Keywords:ISM: molecules planetary nebulae: general planetary nebulae individual (BD + 30°3639, NGC 7027)
Record Number:CaltechAUTHORS:20170301-070004355
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Official Citation:H2 morphology of young planetary nebulae Graham, J. R., Herbst, T. M., Matthews, K., Neugebauer, G., Soifer, B. T., Serabyn, E., , Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 408, no. 2, p. L105-L107.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74625
Deposited By: Ruth Sustaita
Deposited On:01 Mar 2017 15:50
Last Modified:01 Mar 2017 15:50

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