Observations of NGC 7027 from 5.2 to 7.5 microns - The detection of NI II and additional dust features

Abstract

The authors have observed NGC 7027 with a multichannel grating spectrometer from 5.2 to 7.5 μm at a spectral resolving power of 120 - 200. Two new dust emission features are resolved at 5.62 and 6.95 μm, and for the first time the Ni II fine-structure line at 6.64 μm is detected. It is shown that a single molecular dust constituent might account for six of the nine observed dust features between 2 and 14 μm. The strength of the Ni II line indicates either that Ni is not depleted in the neutral gas, or that the line is formed at high density.