Maximum rotational velocity V_max versus intrinsic velocity dispersion σ_int. Objects from the AMAZE and LSD samples are marked with black and blue symbols, respectively. The σ_int value is obtained fitting the observed velocity dispersion map and error bars represent 1σ uncertainties. Overplotted the V_max = σ_int locus (dashed line), the V_max = k   σ_int loci (dotted lines), the mean value of V_max/σ for the local galaxies (continuous line) and the V_max/σ interval for the SINS sample at z ~ 2 (Förster Schreiber et al. 2009) (gray region).