The photometric structure of the inner

The light distribution in the inner few kiloparsecs of the Milky Way is recovered non-parametrically from a dust-corrected near-infrared COBE/DIRBE surface brightness map of the inner Galaxy. The best ts to the photometry are obtained when the Sun is assumed to lie 14 4 pc below the plane. The recovered density distributions clearly show an elongated three-dimensional bulge set in a highly non-axisymmetric disk. In the favoured models, the bulge has axis ratios 1:0:6:0:4 and semi-major axis length 2 kpc. Its nearer long axis lies in the rst quadrant. The bulge is surrounded by an elliptical disk that extends to 2 kpc on the minor axis and 3:5 kpc on the major axis. In all models there is a local density minimum 2:2 kpc down the minor axis. The subsequent maximum 3 kpc down the minor axis (corresponding to l ' 22 and l ' 17) may be associated with the Lagrange point L 4. From this identiication and the length of the bulge-bar, we infer a pattern speed b ' 60 70 km s 1 kpc 1 for the bar. Experiments in which pseudo-data derived from models with spiral structure were deprojected under the assumption that the Galaxy is either eight-fold or four-fold symmetric, indicate that the highly non-axisymmetric disks recovered from the COBE data could reeect spiral structure within the Milky Way if that structure involves density contrasts greater than > 3 at NIR wavelengths. These experiments indicate that the angle 0 between the Sun{centre line and a major axis of the bulge lies near 20 .