R × t diagrams showing the radially averaged distribution of the mass and light as a function of the distance (in HLR units) from the nucleus and lookback time (in log units). The intensity of the map shows: stellar mass formed per unit area (M_⊙ pc^-2; right panels), and luminosity at 5635 Å per unit area (L_⊙ Å^-1 pc^-2; left panels). From top to bottom: Mice A, Mice B, IC 1623 W.