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Infrared and Millimeter Views of the Helix: the Nearest, Massive, Neutral Remnant of a Circumstellar Envelope

Published online by Cambridge University Press:  25 May 2016

P.J. Huggins ,
P. Cox ,
T. Forveille ,
R. Bachiller  and
K. Young
P.J. Huggins
Affiliation:
Physics Department, New York University, New York NY 10003, USA
P. Cox
Affiliation:
IAS, Université de Paris XI, 91405 Orsay, France
T. Forveille
Affiliation:
Observatoire de Grenoble, B.P. 53X, 38041 Grenoble Cedex, France
R. Bachiller
Affiliation:
IGN OAN, Apt 1143, 28800 Alcalá de Henares, Spain
K. Young
Affiliation:
SAO, 60 Garden Street, Cambridge, MA 02138, USA

Abstract

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We present new, infrared and millimeter views of the Helix nebula which illustrate the critical role of remnant, neutral AGB envelopes in the formation and evolution of planetary nebulae. Large scale ∼ 1 000″ mapping of the entire nebula in the CO (J = 2 − 1) line with the CSO reveals the global structure of the envelope. The CO emission forms the familiar ring structure seen in optical images of the Helix, and indicates a massive remnant with ≳ 50% the mass of the ionized nebula. High resolution CO mapping with the IRAM 30 m telescope shows that the whole envelope is fragmented into an intricate array of small clumps, closely related to the cometary globules seen in the central, ionized cavity. 5–17 μm spectroscopy of the Helix with ISOCAM reveals a remarkable near infrared spectrum, dominated by the pure (v = 0 − 0) rotational lines of H2. The H2 lines are excited to a temperature of ∼ 900 K, and likely arise in warm, outer layers of the small clumps seen in CO. Imaging of the H2 emission with ISOCAM over the whole nebula provides a striking portrait of the fragmented neutral envelope. 3-dimensional views of the envelope are also presented, based on CO mapping and using 3-dimensional visualization techniques. Point symmetries dominate the toroidal structure, and suggest an origin for the Helix in equatorial mass-loss on the AGB, shaped by the action of bipolar outflows or jets.

Type
Part 5. Non-Spherical Mass Loss, Binarity, Post-AGB Evolution
Information
Symposium - International Astronomical Union , Volume 191: Asymptotic Giant Branch Stars , 1999 , pp. 425 - 430
Copyright
Copyright © Astronomical Society of the Pacific 1999 

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