M 2-9: moving dust in a fast bipolar outflow *
Hugo E. Schwarz 1, 2,
Colin Aspin 1, 3,
Romano L.M. Corradi 4 and
Bo Reipurth 2
Received 29 April 1996 / Accepted 30 July 1996
Using optical images and spectra of the bipolar nebula M 2-9 we show that, in addition to the well-known bright inner nebula, the object has fast, highly collimated outflows reaching a total extent of . These radially opposed and point-symmetric outer lobes are both redshifted, leading us to model the radiation from them in terms of light reflected from moving dust, rather than intrinsic emission. Our polarization images show that the lobes are 60% linearly polarized in a direction perpendicular to the long axis of M 2-9. This high polarization indicates optically thin scattering, and lends weight to our dust scattering model.
Use of this model then allows us to determine the distance to M 2-9 directly from the measured proper motions on images taken over a period of more than 16 yrs. The physical and geometrical parameters of the nebula then follow. M 2-9 is at a distance of 650 pc, is 0.4 pc long, has a luminosity of 550 , and its outer nebula has a dynamical age of 1200 yrs, in round numbers.
Using the fact that the central object has been constrained to be of low luminosity but of a sufficiently high temperature to make the observed OIII, we argue that the central object of M 2-9 has to contain a compact, hot source, and is probably a binary.
Key words: ISM: M 2-9 planetary nebulae: M 2-9 ISM: jets and outflows polarisation dust circumstellar matter
Send offprint requests to: H. E. Schwarz, at the NOT address
© European Southern Observatory (ESO) 1997
Online publication: July 3, 1998