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

Along with a brief analysis we present data obtained from BVRI and Ks imagesof a sample of 19 galaxies (18 barred and 1 unbarred) which will be furtherexplored in a future paper. We measured the lengths and colors of the bars,created color maps and estimated global color gradients. Applying a methoddeveloped in a companion paper, we could distinguish for 7 galaxies in oursample those whose bars have been recently formed from the ones with alreadyevolved bars. We estimated an average difference in the optical colors betweenyoung and evolved bars that may be translated to an age difference of the orderof 10 Gyr, meaning that bars may be, at least in some cases, long standingstructures. Moreover, our results show that, on average, evolved bars arelonger than young bars. This seems to indicate that, during its evolution, abar grows longer by capturing stars from the disk, in agreement with recentnumerical and analytical results. Although the statistical significance ofthese results is low, and further studies are needed to confirm them, wediscuss the implications from our results on the possibility of bars being arecurrent phenomenon. We also present isophotal contours for all our images aswell as radial profiles of relevant photometric and geometric parameters.