Spectral indices and evolutionary properties derived for our galaxies. Upper left: variation in Balmer and 4000 Å breaks for CSPs as a function of their age using BC03 templates at solar metallicity. Lighter curves mark the evolution for a truncated SFH with increasing duration of star formation. The effect of adopting templates of different metallicity is displayed for the values that produce the largest variation, i.e., 2.5Z_⊙ (triangles). Dotted and solid grey curves show the behaviour of a constant SFH for the two breaks, respectively. Upper right: individual values of D_B and D_n4000 for our targets. The red track shows their evolution with age and is attenuated by 1 mag. The dashed grey line marks the 1:1 relation. Lower left: variation of the index ratio as a function of age for an SSP-like template. The effect of smoothing templates to the HST resolution is shown by the dashed black curve. The effect of a A_V = 1 mag attenuation is instead shown by the red curve. The full transition between a Balmer-dominated and a 4000 Å -dominated spectrum is flagged when D_B/D_n4000 = 1 (dashed grey line), which occurs around 1.3 Gyr of passive evolution. Dark grey triangles mark the evolution for 2.5Z_⊙ templates. Lower right: best-fit values for the dust attenuation and mass-weighted age from the combined fit. Chandra X-ray, VLA 3GHz, and Spitzer/MIPS 24 μm detections are marked by black crosses and yellow and black hexagons, respectively.