Edge detection method. The figure presents the stellar mass density map in Cartesian and polar coordinates (top left and top central panels), and the averaged surface stellar mass density profile (bottom left panel) of a simulated disk, computed in three different cases as is explained in the main text. The first derivative of the stellar mass density profile (bottom central panel) and the second derivative in both 2D (upper right) and 1D (bottom right) are also shown. Gray lines represent the surface stellar mass density and its derivatives using 10° wedges along azimuthal angles. Dashed red lines indicate R_edge, corresponding to the minimum of the second derivative.