The structure and stellar population of the Galactic nuclear bulge

Deep CCD photometry of stars in the Galactic nuclear bulge has been obtained on four lines of sight near l = 0 deg with b from -3.9 deg to -10 deg. Although the steep decline noted in the volume density of the bulge K and M giants cannot be explained by the spheroid of the two-component model, it does, however, match more complicated models that account for the rotation curve of the Galaxy by including a massive central component. For an assumed distance of 7 kpc, a mean stellar age derived from the main-sequence turnoff of 11-14 Gyr is obtained. It is suggested that the evolution of bulge stars on the giant branch may take place at bluer colors or higher luminosities than currently predicted.