Galaxy density contrast as a function of z for the population of MPGs with reliable estimates of δ and R_e (gray circles, magenta squares, or cyan triangles). Solid lines indicate the median value of the (1 + δ) distribution, while the 25th and the 75th percentiles are indicated with long-dashed and dot-dashed lines, respectively. Magenta filled squares are MPGs with Σ ≤ 1000 M_⊙ pc⁻² (i.e., the low-Σ sample), cyan filled triangles are MPGs with Σ > 2000 M_⊙ pc⁻² (i.e., the high-Σ sample) and gray circles are MPGs with 1000 < Σ ≤ 2000 M_⊙ pc⁻².