a)−c): True-color SDSS image composites of the type i+ ETGs under study. The overlaid contours depict the morphology of the spiral-like star-forming features, as revealed by applying an unsharp-masking technique. The outermost contour corresponds to a surface brightness level μ_r ≃ 25 mag/□″ for NGC 1167 and ≃26 mag/□″ for NGC 1349 and NGC 3106, and the vertical line to a linear scale of 2 R_eff in the SDSS r band. Bright foreground stars (panel a)) and a dwarf galaxy at the redshift of NGC 3106 (panel c)) are shown with crosses, and the edges of the CALIFA field of view are delineated in white color. d)–f): EW(Hα) maps, as derived from CALIFA IFS data, overlaid with the same contours as in panels a)−c). Radial profiles of the intensity of the stellar continuum, normalized to its central value (g)−i)), EW(Hα) (j)–k)) and mass fraction M₁₀₀ (%) of stars younger than 100 Myr (m)–o)).