[Fe III] emission lines in the planetary nebula NGC 2392

Abstract

NGC2392 is a young double-shell planetary nebula (PN). Its intrinsic structure and shaping mechanism are still not fully understood. In this paper we present new spectroscopic observations of NGC2392. The slits were placed at two different locations to obtain the spectra of the inner and outer regions. Several [Fe III] lines are clearly detected in the inner region. We infer that NGC2392 might have an intrinsic structure similar to the bipolar nebula Mz3, which also exhibits a number of [Fe III] lines arising from the central regions. In this scenario, the inner and outer regions of NGC2392 correspond to the inner lobes and the outer outflows of Mz3, respectively. We construct a three-dimensional morpho-kinematic model to examine our hypothesis. We also compare the physical conditions and chemical composition of the inner and outer regions, and discuss the implications on the formation of this type of PN. © 2012. The American Astronomical Society. All rights reserved.