The early interaction of the planetary nebula NGC 40 with the interstellar medium
University of Virginia, Department of Astronomy, PO Box 3818, Charlottesville, VA 22903-0818, USA e-mail: email@example.com; firstname.lastname@example.org
2 Department of Physics, University of Haifa at Oranim, Tivon 36006, Israel
Corresponding author: N. Soker, email@example.com
Accepted: 6 June 2002
We report the detection of an Hα 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
© ESO, 2002