ON THE GALACTIC SPIN OF BARRED DISK GALAXIES

Abstract

We present a study of the connection between the galactic spin parameter (lambda(d)) and the bar fraction in a volume-limited sample of 10,674 disk galaxies drawn from the Sloan Digital Sky Survey Data Release 7. The galaxies in our sample are visually classified into one of three groups: non-barred galaxies and galaxies hosting long or short bars, respectively. We find that the spin distributions of these three classes are statistically different, with galaxies hosting long bars having the lowest lambda(d) values, followed by non-barred galaxies, while galaxies with short bars present typically high spin parameters. The bar fraction presents its maximum at low to intermediate lambda(d) values for the case of long bars, while the maximum for short bars is at high lambda(d). This bimodality is in good agreement with previous studies finding longer bars hosted by luminous, massive, red galaxies with a low content of cold gas, while short bars were found in low luminosity, low mass, blue galaxies that were typically gas rich. In addition, the rise and fall of the bar fraction as a function of lambda(d), within the long-bar sample shown in our results, can be explained as a result of two competing factors: the self-gravity of the disk that enhances bar instabilities and the support by random motions, instead of ordered rotational motion, that prevents the formation/growth of bars.