COBE DIFFUSE INFRARED BACKGROUND EXPERIMENT OBSERVATIONS OF GALACTIC REDDENING AND STELLAR POPULATIONS

This Letter describes the results of an initial study of Galactic exti nction and the colors of Galactic stellar populations in the near-IR u sing the Diffuse Infrared Background Experiment (DIRBE) aboard the Cos mic Background Explorer (COBE) spacecraft. The near-IR reddening obser ved by DIRBE is consistent with the extinction law tabulated by Rieke and Lebofsky (1985). The distribution of dust and stars in most of the first and fourth quadrants of the Galactic plane (0 degrees < l < 90 degrees, and 270 degrees < l < 360 degrees, respectively) can be model ed as a stellar background source seen through up to similar to 4 mag of extinction at 1.25 mu m. The unreddened near-IR colors of the Galac tic disk are similar to those of late-K and M giants. The Galactic bul ge exhibits slightly bluer colors in the 2.2-3.5 mu m range, as noted by Terndrup et al. (1991). Star-forming regions exhibit colors that in dicate the presence of a similar to 900 K continuum produced by hat du st or PAHs contributing at wavelengths as short as 3.5 mu m.