  Molecular dynamics computer simulations of a binary Lennard-Jones glass under
shear are presented. The mechanical response of glassy states having different
thermal histories is investigated by imposing a wide range of external shear
rates, at different temperatures. The stress-strain relations exhibit an
overshoot at a strain of around 0.1, marking the yielding of the glass sample
and the onset of plastic flow. The amplitude of the overshoot shows a
logarithmic behavior with respect to a dimensionless variable, given by the age
of the sample times the shear rate. Dynamical heterogeneities having finite
lifetimes, in the form of shear bands, are observed as the glass deforms under
shear. By quantifying the spatial fluctuations of particle mobility, we
demonstrate that such shearbanding occurs only under specific combinations of
imposed shear-rate, age of glass and ambient temperature.
