Evolutionary synthesis of simple stellar populations - Colours and indices

We construct evolutionary synthesis models for simple stellar populations using the evolutionary tracks from the Padova group (1993, 1994), theoretical colour calibrations from Lejeune et al. (1997, 1998) and t func- tions for stellar atmospheric indices from Worthey et al. (1994). A Monte-Carlo technique allows us to obtain a smooth time evolution of both broad band colours in UBVRIK and a series of stellar absorption features for Single Burst Stellar Populations (SSPs). We present colours and in- dices for SSPs with ages from 1 10 9 yrs to 1: 61 0 10 yrs and metallicities (M=H )= 2 :3, 1:7, 0:7, 0:4, 0.0 and 0.4. Model colours and indices at an age of about a Hubble time are in good agreement with observed colours and in- dices of the Galactic and M 31 GCs.