Redshift evolution of the function β − β_DW. All galaxies reported in the plot have S/N > 5. Furthermore, the 407 green galaxies shown satisfy the condition M_UV < −18.6. The orange points represent the median values of the green points in redshift bins. On the right panel, a histogram of the green points is shown, fit by a Gaussian function with μ = 0.042 ± 0.002 and σ = 0.038 ± 0.001.