Homogenization of the Stellar Population along Late-Type Spiral Galaxies

Abstract

We present a study of the broadband UBV color profiles for 257 Sbc barred and non-barred galaxies. In our sample, the color gradients are negative (reddish inward) in approximately 59% of the objects, are almost null in 27%, and are positive in 14%, considering only the face-on galaxies, which represent approximately 51% of the sample. We have also found that barred galaxies are over-represented among the objects having null or positive gradients, indicating that bars act as a mechanism of homogenization of the stellar population. A correlation between the total and bulge colors was found, which is a consequence of an underlying correlation between the colors of bulges and disks found by others. Moreover, the mean total color is the same irrespective of the gradient regime, while bulges are bluer in galaxies with null or positive gradients, which indicates an increase of the star formation rate in the central regions of these objects. We found no correlation between color and O/H abundance gradients. We discuss this result considering a picture in which bars are a relatively fast recurrent phenomenon. These results are not compatible with a pure classical monolithic scenario for bulge and disk formation. On the contrary, they favor a scenario where both these components are evolving in a correlated process, in which stellar bars play a crucial role.(Abridged)