EDP Sciences
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Volume 391, Number 2, August IV 2002
Page(s) 689 - 692
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20020848

A&A 391, 689-692 (2002)
DOI: 10.1051/0004-6361:20020848

The early interaction of the planetary nebula NGC 40 with the interstellar medium

J. Martin1, K. Xilouris1 and N. Soker1, 2

1  University of Virginia, Department of Astronomy, PO Box 3818, Charlottesville, VA 22903-0818, USA
    e-mail: jrm7w@virginia.edu; kx8u@virginia.edu
2  Department of Physics, University of Haifa at Oranim, Tivon 36006, Israel

(Received 20 March 2002 / Accepted 6 June 2002 )

We report the detection of an H $\alpha$ emission-line structure in the upstream side of the planetary nebula NGC 40, which is predicted by numerical simulations, and which is attributed to Rayleigh-Taylor instability. Such a Rayleigh-Taylor instability is expected to occur at early stages of the interaction process between the interstellar medium (ISM) and a fast moving planetary nebula, as is the case for NGC 40. We resolved the Rayleigh-Taylor instability "tongues", as well as the flatness of the nebula around the "tongues", which results from the deceleration by the ISM.

Key words: planetary nebulae: general -- ISM: structure -- planetary nebulae: individual: NGC 40 -- instabilities

Offprint request: N. Soker, soker@physics.technion.ac.il

© ESO 2002