Left: distribution of the local density Σ for galaxies in A2255 (dotted line) and in the ANWS (dashed line). Right: comparison between the local density Σ _0.5 Mpc adopted in this work, which is the number density within a projected distance of 0.5 Mpc, and Σ _1.0 Mpc within a projected distance of 1.0 Mpc (upper) and within a projected distance to the 5th-nearest neighbor (lower). The neighbors were identified among all members (black solid lines) and massive (log  M _*/ M _☉ > 10) ones (red dotted lines) within Δ v < 1000 km s ⁻¹. The Spearman rank correlation coefficient r _s between local densities is printed in the bottom right of each panel.