  We present a detailed numerical study of dynamical heterogeneities in the
aging regime of a simple binary Lennard-Jones glass former. For most waiting
times t_w and final times t, both the dynamical susceptibility \chi_4(t,t_w)
and the dynamical correlation length \xi_4(t,t_w) can be approximated as
products of two factors: i) a waiting time dependent scale that grows as a
power of t_w, and ii) a scaling function dependent on t,t_w only through the
value of the intermediate scattering function C(t,t_w). We find that
\chi_4(t,t_w) is determined *only in part* by the correlation volume.
