A Bipolar, Knotty Outflow with Velocities of 500 Kilometers per Second or above from the Engraved Hourglass Planetary Nebula M[CLC]y[/CLC]C[CLC]n[/CLC] 18

Abstract

High spectral resolution observations of the [N II] 6548 + 6584 Å and Hα emission lines from the young planetary nebula MyCn 18 have been obtained using the Manchester echelle spectrometer combined with the Anglo-Australian Telescope. These spatially resolved spectra reveal not only the kinematical characteristics of the two bright rings of emission, which define the well-known "engraved hourglass" structure of this object, but also the dramatic motions of the faint, irregular knots of emission observed outside the main nebular structure. The knots are moving with velocities ≥500 km s-1 away from the central star, an order of magnitude faster than the motions observed from the main nebula, making them among the highest velocity outflows ever observed from a planetary nebula. A bipolar, rotating, episodic jet mechanism is favored for their origin.