Simulations to study the minimum S/N to obtain reliable measurements of the velocity dispersion, plotting Δσ/σ (defined as (σ_o − σ_i)/σ_i), the relative error introduced when measuring the σ of a galaxy as a function of S/N. Different colours show different σ for the simulated galaxies and it assumes a stellar population of 4 Gyr and Z = −0.4.