Pregalactic formation of globular clusters in cold dark matter

We reconsider the pregalactic hypothesis for the formation of globular clusters in the light of Zinn's discovery published in 1985 of a two-component globular population in the Milky Way. For a cold dark matter spectrum, high-σ fluctuations of 10^5^-10^6^ M_sun_ are assumed to be the progenitors of the spheroidal population of globular clusters. The mass fraction of globular clusters in galaxies then requires that perturbations above roughly 2.8 σ survive as globulars, and their observed radii require baryonic collapse factors of order 10. Such an absolute density threshold for globular cluster formation achieves adequate fits to observed cluster radii and densities, the mass fraction of globulars versus Hubble type, the radial density profile of globulars within galaxies, and the globular luminosity function. However, a fixed density threshold criterion for cluster survival lacks convincing physical justification and does not by itself explain the homogeneous metallicities within clusters or the large metallicity variations from cluster to cluster and from galaxy to galaxy.