Environment distribution cumulative histograms of the environmental densities within a spherical volume including the fifth nearest neighbor to the target galaxy, for TNG50 and TNG100 mergers and non-mergers. From left to right: (a) environmental mass densities taking into account companions with mass ratio > 1:4 (major companions), and (b) environmental mass densities taking into account companions with mass ratio > 1:10 (major and minor companions). We also make the histograms for the observational data visible as reference where available, indicated by the dotted lines. KS test statistics between simulation mergers and non-mergers, as well as between confident mergers (merger probability > 0.8) and non-mergers (merger probability < 0.3) are indicated. Major companions (left panel): KS test (Simulation) statistic: 0.226, KS test (Observation) statistic: 0.131. Major and minor companions (right panel): KS test (Simulation) statistic: 0.194, KS test (Observation) statistic: 0.131.