MEASUREMENTS OF THE MILLIMETER-WAVE SPECTRUM OF INTERSTELLAR DUST EMISSION

We report measurements of the differential brightness of interstellar dust emission near the Galactic plane and at high Galactic latitudes. The data were obtained as part of a program to measure anisotropy in the cosmic microwave background (CMB). The measurements were made with a 0.degrees 5 beam size and a 1.degrees 3 p-p sinusoidal chop, in broad bands (Delta nu/nu similar to 0.3) centered near frequencies of 6, 9, and 12 cm-l. A measurement made toward the Galactic plane, at longitude l = 23.degrees 7, is compared with the contrast observed in the 100 mu m IRAS data. Assuming the dust emission has a brightness I-nu proportional to nu(n)B(nu)(T-d), where B-nu is the Planck function, a best fit yields n = 1.6 +/- 0.4, T-d = 24 +/- 5 K. In a region near the star mu Pegasi (mu PEG l = 91 degrees, b = -31 degrees), the comparison of our data with the 100 mu m IRAS data yields n = 1.4 +/- 0.4, and T-d = 18 +/- 3 K. In a second region near the star gamma Ursa Minoris (GUM l = 108 degrees, b = 41 degrees), an upper limit is placed on contrast in dust emission. This upper limit is consistent with the spectrum measured at mu PEG and the IRAS 100 mu m emission contrast at GUM, which is similar to 8 times lower than mu PEG.