Maps of average EM-weighted velocity along the LoS for shocked Si (upper panel) and Fe (lower panel) at the age of Cas A for model W15-2-cw-IIb-HD+dec. The approximate velocity range is ± 5000 km s⁻¹ (see color bar on the right in units of 1000 km s⁻¹). The solid contours mark the cuts of the forward and reverse shocks in the plane of the sky passing through the center of the explosion. These images correspond to the effective Doppler maps derived from observations.