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A "firework" of H2 knots in the planetary nebula NGC7293 (The helix nebula)

Matsuura, M., Speck, A.K., McHunu, B.M., Tanaka, I., Wright, N.J., Smith, M.D., Zijlstra, A.A., Viti, S., Wesson, R. (2009) A "firework" of H2 knots in the planetary nebula NGC7293 (The helix nebula). Astrophysical Journal, 700 (2). pp. 1067-1077. ISSN 0004-637X. (doi:10.1088/0004-637X/700/2/1067) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided. (Contact us about this Publication)
Official URL
http://dx.doi.org/10.1088/0004-637X/700/2/1067

Abstract

We present a deep and wide field-of-view (4? × 7?) image of the planetary nebula (PN) NGC7293 (the Helix Nebula) in the 2.12 ?m H 2 v = 1 ? 0 S(1) line. The excellent seeing (04) at the Subaru Telescope, allows the details of cometary knots to be examined. The knots are found at distances of 22-64 from the central star (CS). At the inner edge and in the inner ring (up to 45 from the CS), the knot often show a "tadpole" shape, an elliptical head with a bright crescent inside and a long tail opposite to the CS. In detail, there are variations in the tadpole shapes, such as narrowing tails, widening tails, meandering tails, or multipeaks within a tail. In the outer ring (45-64 from the CS), the shapes are more fractured, and the tails do not collimate into a single direction. The transition in knot morphology from the inner edge to the outer ring is clearly seen. The number density of knots governs the H2 surface brightness in the inner ring: H2 exists only within the knots. Possible mechanisms which contribute to the shaping of the knots are discussed, including photoionization and streaming motions. A plausible interpretation of our images is that inner knots are being overrun by a faster wind, but that this has not (yet) reached the outer knots. Based on H2 formation and destruction rates, H2 gas can survive in knots from formation during the late asymptotic giant branch phase throughout the PN phase. These observations provide new constraints on the formation and evolution of knots, and on the physics of molecular gas embedded within ionized gas.

Item Type: Article
DOI/Identification number: 10.1088/0004-637X/700/2/1067
Uncontrolled keywords: Infrared: ISM ISM: globules ISM: molecules planetary nebulae: individual (NGC 7293)
Subjects: Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Giles Tarver
Date Deposited: 11 Aug 2015 09:29 UTC
Last Modified: 29 May 2019 15:54 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/50105 (The current URI for this page, for reference purposes)
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