SPATIALLY RESOLVED SPECTRA OF THE UNIDENTIFIED INFRARED FEATURES AROUND HD-44179 (THE RED RECTANGLE)

We have observed HD 44179 and the surrounding unidentified infrared (U IR) emission with a long-slit 10 mum spectrometer. By applying maximum entropy reconstruction methods to our images, we have found spatial v ariations in the spectra not apparent in previous work with beam sizes of several arcseconds diameter. We find that no UIR emission arises i n the innermost regions of the source; instead, we observe only cool c ontinuum emission. After its abrupt appearance 0.5'' from the central source, the UIR emission decays steadily with distance, except for an enhancement in the intensity of the 11.3 mum feature approximately 1.5 '' away from the central source. The intensity of the 7.7 mum feature drops more quickly with distance than the intensity of the 8.6 and 11. 3 mum features, and the wavelength of peak intensity of this feature a ppears to shift from 7.9 mum near the central source to approximately 7.4 mum further away. These observations indicate that we have detecte d the formation of the carriers of the UIR emission features and chang es in their emission properties as they move outward. In particular, t he behavior of the 8.6 and 11.3 mum features suggest the material is g rowing increasingly hydrogenated with distance. We suggest that all th e unusual spectral properties of this sytem can be explained in terms of an accretion disk around a degenerate object.