Metallicity versus age in spiral nuclei

It has recently been proposed that the blue nuclei of late-type spiral galaxies are old, metal-poor stellar systems in which the horizontal branch dominates the light. This is contrary to the conventional interpretation which holds that the blueness results from the presence of a substantial young (<1 Gyr) stellar population. Left unresolved, such a fundamental disagreement casts grave doubts on our ability to understand composite stellar systems--e.g., galaxies in earlier stages of evolution of high redshifts. In this paper we show that straightforward comparison of narrow-band scanner colors for Sc nuclei and globular culsters in the Local Group excludes the possibility that the nuclei are old, metal-poor systems. Photometric precisions higher than 5% are in general necessary for such a distinction to be made, however