We study the asymptotic behaviour of the partial density function associated to sections of a positive hermitian line bundle that vanish to a particular order along a fixed divisor Y. Assuming the data in question is invariant under an S 1 -action (locally around Y) we prove that this density function has a distributional asymptotic expansion that is in fact smooth upon passing to a suitable real blow-up. Moreover we recover the existence of the "forbidden region" R on which the density function is exponentially small, and prove that it has an "error-function" behaviour across the boundary ∂ R . As an illustrative application, we use this to study a certain natural function that can be associated to a divisor in a Kähler manifold.