COBE DIFFUSE INFRARED BACKGROUND EXPERIMENT OBSERVATIONS OF THE GALACTIC BULGE

Low angular resolution maps of the Galactic bulge at 1.25, 2.2, 3.5, and 4.9 mu m obtained by the Diffuse Infrared Background Experiment (DIRBE) onboard NASA's Cosmic Background Explorer (COBE) are presented. After correction for extinction and subtraction of an empirical model for the Galactic disk, the surface brightness distribution of the bulge resembles a flattened ellipse with a minor-to-major axis ratio of approximate to 0.6. The bulge minor axis scale height is found to be 2.degrees 1 +/- 0.degrees 2 for all four near-infrared wavelengths. Asymmetries in the longitudinal distribution of bulge brightness contours are qualitatively consistent with those expected for a triaxial bar with its near end in the first Galactic quadrant (0 degrees < l < 90 degrees). There is no evidence for an out-of-plane tilt of such a bar.