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LibraryG.C. Soan (NASA Ames), C.E. Woodward (WIRO), Jesse Bregman (NASA Ames)
1994, BAAS, 26, 1392
We have observed the Red Rectangle with the Cryogenic Spectrometer (CRSP) at the 2.1 m telescope of Kitt Peak National Observatory. The Red Rectangle is a well-known source of the infrared emission features associated with polycyclic aromatic hydrocarbons (PAHs). Our long-slit spectra cover the 3.2-3.6 micron regime, which includes the strong PAH band at 3.29 microns, a weaker component at 3.40 microns and an emission plateau which continues out to 3.6 microns. Emission in the PAH bands extends several arcseconds to the north and south of the central source (HD 44179). The seeing during our observations was approximately 1.5 arcseconds, but we have deconvolved the point spread function from our spectral images at each wavelength using maximum entropy reconstruction, allowing us to examine the relative behavior of these emission components at finer spatial scales. With the new 256×256 array installed on CRSP, each pixel covers 0.6 arcseconds of sky. Our reconstructions reveal that the strength of the small 3.4 micron emission feature increases with respect to the 3.3 micron feature as the distance from the central source increases. In particular, there appears to be a region of enhanced 3.4 micron emission roughly 3 arcsec to the north and south of the central source. We are analyzing our results in terms of the competing models for the origin of the 3.4 micron emission feature, which could be a vibrational overtone of the 3.3 micron feature, or could result from the attachment of molecular sidegroups to the PAH molecule.
We presented the above abstract at the January, 1995 meeting of the AAS in Tucson, and have continued to produce and analyze maximum entropy reconstructions of the spectral images. We now see that the 3.4 micron feature consists of two features at 3.40 and 3.43 microns. As the distance from the central source increases, first the 3.43 micron feature, then the 3.40 micron feature peak. This result is consistent with the conclusion of Geballe et al. (1994, Ap J, 434, L15) that the 3.40 micron feature arises from attached aliphatic side-groups and the 3.43 micron feature arises from a hot band (v=2-1).
Last modified 27 May, 2008. © Gregory C. Sloan and others.