  We study an approximate version of the Schwinger-Dyson equation that controls
the nonperturbative behavior of the ghost-gluon vertex, in the Landau gauge. In
particular, we focus on the form factor that enters in the dynamical equation
for the ghost dressing function, in the same gauge, and derive its integral
equation, in the "one-loop dressed" approximation. We consider two special
kinematic configurations, which simplify the momentum dependence of the unknown
quantity; in particular, we study the soft gluon case, and the well-known
Taylor limit. When coupled with the Schwinger-Dyson equation of the ghost
dressing function, the contribution of this form factor provides considerable
support to the relevant integral kernel. As a consequence, the solution of this
coupled system of integral equations furnishes a ghost dressing function that
reproduces the standard lattice results rather accurately, without the need to
artificially increase the value of the gauge coupling.
