Evidence for the uniformity of globular cluster populations

The distribution of the colours of globular clusters in our own Galaxy, in the spiral galaxy M31, and in the giant elliptical galaxy M87 (NGC 4486) are re-examined in terms of the reddening-free photometric parameter R. It is shown that the distribution of cluster colour for these populations is entirely consistent with a unique intrinsic distribution, with the observed differences being understood in terms of the random errors of photometric measurement. In particular, the suggestion that the relative numbers of globular clusters of different metallicities in M31 and the Galaxy are significantly different is not substantiated. (author)