Two-dimensional parameter space, given by central rotation strength χ vs. concentration Ψ, of differentially rotating models defined by ; the remaining parameters are fixed at . The upper solid line marks the maximum admitted values of χ, for given values of concentration Ψ, that is the underlying area indicates pairs (Ψ,χ) for which models can be constructed. The intermediate and the lower solid lines mark the values of , respectively. The gray, wide-striped, and thin-striped areas represent the extreme, rapid, and moderate rotation regimes, respectively.