Effect of migration during (left) and after (right) a massive merger. Left column: top panel: changes in angular momentum in a time period of 2 Gyr encompassing the merger event. The vertical velocity dispersion profiles of inward migrators, outward migrators and the non-migrating population, as indicated, are shown in the second panel. The net effect of migrators can be seen in the third panel. Bottom panel: fractional change in velocity dispersion resulting from migration Δσ_z = (σ_z,all − σ_{z,non_mig}) /σ_z,all. Migrators cool the outer disk, thus working against disk flaring. Right column: same as on the left, but for stars born after the last massive merger event. Minimal effect from migration is seen on the disk vertical velocity dispersion.