The dark lane of the planetary nebula NGC 6302^*†

Abstract

The butterfly-shaped planetary nebula, NGC 6302, shows a unique, dense equatorial dark lane, which is presumably a dusty disc, obscuring an unobserved, very hot central star. We trace the structure of this disc using Hubble Space Telescope Hα and [N II] images, Very Large Telescope L-and M-band images at 0.4-arcsec resolution, including Brα and polycyclic aromatic hydrocarbon (PAH) images, and a James Clerk Maxwell Telescope 450-μm image. Extinction maps are derived from these images. Within the disc, the extinction is A_Hα= 5-7 mag and A_Brα= 1-2 mag. The 450-μm map shows a north-south elongated central core, tracing the massive dust disc, and extended emission from dust in the bipolar flows. A fit to the spectral energy distribution yields the disc dust mass of 0.03 M_solar. The innermost region shows an ionized shell. The orientation of the polar axis shows a marked change between shell, disc and inner and outer outflow. The structures are well described by the warped-disc model of Icke (2003). PAH images are presented: PAH emission is found in the shell but avoids the disc. An infrared source is found close to the expected location of the central star.