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°.5 beam size and a 1°.3 p-p sinusoidal chop, in broad bands (Δv/v ∼ 0.3) centered near frequencies of 6, 9, and 12 cm^-1. A measurement made toward the Galactic plane, at longitude l = 23°7, is compared with the contrast observed in the 100 μm IRAS data. Assuming the dust emission has a brightness I_v ∝ VⁿB_v(T_d), where B_v is the Planck function, a best fit yields n = 1.6 ± 0.4, T_d = 24 ± 5 K. In a region near the star μ Pegasi (μPEG l = 91°, b = -31°), the comparison of our data with the 100 μn IRAS data yields n = 1.4 ± 0.4, and T_d = 18 ± 3 K. In a second region near the star γ Ursa Minoris (GUM 1 = 108°, b = 41°), an upper limit is placed on contrast in dust emission. This upper limit is consistent with the spectrum measured at μPEG and the IRAS 100 μm emission contrast at GUM, which is ∼8 times lower than μPEG.