On the Lengths, Colors, and Ages of 18 Face-on Bars

Along with a brief analysis we present data obtained from BVRI and Ks images of a sample of 19 galaxies (18 barred and 1 unbarred), which will be further explored in a future paper. We measured the lengths and colors of the bars, created color maps, and estimated global color gradients. Applying a method developed in a companion paper, we could distinguish for seven galaxies in our sample those whose bars have been recently formed from the ones with already evolved bars. We estimated an average difference in the optical colors between young and evolved bars that may be translated to an age difference of the order of 10 Gyr, meaning that bars may be, at least in some cases, long-standing structures. Moreover, our results show that, on average, evolved bars are longer than young bars. This seems to indicate that, during its evolution, a bar grows longer by capturing stars from the disk, in agreement with recent numerical and analytical results. Although the statistical significance of these results is low, and further studies are needed to confirm them, we discuss the implications from our results on the possibility of bars being a recurrent phenomenon. We also present isophotal contours for all our images as well as radial profiles of relevant photometric and geometric parameters.