1996A&A...309..715J

We analyse the evolution of galactic disks from the vertical luminosity and colour profiles of edge-on galaxies. The analysis is based on a self-gravitating disk composed of isothermal subpopulations with different ages according to the star formation history. The velocity dispersion increases with age determined by a disk heating process. The luminosity of the stars is computed using photometric evolutionary synthesis and the dust extinction is modeled by an exponential dust distribution. The star formation rate and metal enrichment are based on disk formation scenarios. Exponential luminosity profiles give strong evidence for a constant or moderately declining star formation rate. The intrinsic colour gradients from red (old outer parts) to blue (young inner parts) can be observed even if there is strong dust extinction in the inner parts, since the reddening of an exponential disk is constant in the optically thick parts. The colour gradients are weakened by the metal enrichment but the well known age-metallicity degeneracy can be solved by a spatial analysis of the colour distribution using multi-colour profiles including infrared bands and the tool of generalized colours. For the edge-on galaxy IC 2531 we find a similar composition as in the solar neighbourhood. The model with the same star formation history, the same metal enrichment but a different heating function leads to a good fit of the published luminosity and colour profiles of IC 2531. The mean heating of the disk, measured by the maximum velocity dispersion of the disk, is comparable to that of our Galaxy.