Let {fλ}{λ ∈ Λ} be any algebraic family of rational maps of a fixed degree, with a marked

critical point c(λ). We first prove that the hypersurfaces of the parameter space Λ on

which c(λ) is periodic converge as a sequence of positive closed (1, 1) currents to the

bifurcation current attached to c and defined by DeMarco.

We then turn our attention to the parameter space of polynomials of a fixed degree d,

with all critical points marked. By intersecting the d − 1 currents attached to the critical

points, we obtain a positive measure µbif of finite mass, supported on the connectedness

locus (which was already studied by Bassanelli and Berteloot). We give several characterizations of this measure, already well known in the unicritical case. In particular we show

that its support is precisely the closure of the set of strictly critically finite polynomials

(i.e. of Misiurewicz points).

This is joint work with Charles Favre.