Deep spectroscopy of planetary nebulae

In nebulae astrophysics, there are two long-standing discrepancies: 1) the ionic and elemental abundances of C, N, O, and Ne derived from optical recombination lines (ORLs) are systematically higher than those derived from collisionally excited lines (CELs); 2) the electron temperature derived from H I recombination continuum (e.g., Balmer jump at 3646 A) is always lower than that derived from CELs.  These two discrepancies have been observed in more than 100 Milky Way planetary nebulae.  A number of mechanisms have been proposed to explain them, but no consensus have been reached.  I present deep spectroscopy of several  Milky Way planetary nebulae (PNe) that have large ORL/CEL abundance discrepancies.  The  results have intriguing and lead us to better understand the problems. In order to investigate the origin of the substructures of M31, we carried out spectroscopic observations of three PNe in the Northern Spur of M31. The results also shed some light on the possible origin of Northern Spur.  Follow-up spectroscopy is required.
15/05/2014 - 14:30
Dr. Xuan Fang