Description
The UBVRI images of 26 bright spiral galaxies were decomposed in disks and bulges. Correlations of the resulting structural parameters are investigated, giving clues to the formation history of the bulges. We confirm that the large and bright bulges of early-type spirals are similar to elliptical galaxies. They were probably formed prior to the disks in a monolithic collapse or via early mergers. Late-type spirals have tiny and faint bulges with disk-like profiles. These bulges were probably formed after the disk in secular evolution processes, e.g. from a disk instability. The comparison of the color indices of corresponding spirals and bulges with population synthesis computations support above formation scenarios.
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