Relative orientation of the spin vectors of neighboring halos. Upper panel: cosine of the mean angle (cos ⟨θ⟩) between the spin vectors of CHs and their NN1, in bins of R_isol/r_vir. Lower panel: frequency distribution of cos θ for close neighbors where CHs are separated from their NN1 by 1 < R_isol/r_vir < 4 (red) and for extremely isolated halos where CHs are separated from their NN1 by 30 < R_isol/r_vir < 70 (blue).