Abstract

During January, 1981, the CT10 4-m telescope was used with a 6-detector bolometer array spectrometer (Gehrz, Hackwell, and Smith, 1976, P.A.S.P., 88, 971) to make maps of Eta Carina simultaneously at wavelengths of 8.1, 8.9, 10.2, 11.3, 12.2 and 13.1 microns, with a 1.8 arcsec FWHM beam. The maps were made using a fast raster scanning method (Grasdalen, et. al. Bull. A.A.S., 11, 712; Hackwell, Grasdalen, and Gehrz, 1982, Ap. J., 252, 250) in which the wobbling secondary mirror is stepped in declination under computer control, while chopping, to produce a scan line. After each scan line, the telescope is stepped by one pixel in right ascension to build a map. The measured intensity of each pixel is taken to be the difference between the signal beam and the displaced reference beam. For this project, we scanned a 32 × 32 raster centered on Eta Carina with a 0.8 arcsec pixel spacing, and an integration time per pixel of 0.4 seconds. Four frames were co-added to reduce high spatial frequency noise due to seeing, giving an overall integration time per pixel of 1.6 seconds and a final signal-to-noise ratio in the brightest regions of 500 at 13.1 microns and 2000 at 11.3 microns. Absolute calibration and beam profiles were determined by mapping standard stars from the list of Elias et. al. (1983 A. J., in press) at the same pixel spacing and chopper throw as for Eta Carina. Our measurements give integrated fluxes which agree well with those determined by other observers (e. g. Gehrz et. al. 1973, Ap. Lett., 13, 89).

© 1983 Optical Society of America