On the galactic spin of barred disk galaxies

TL;DR

This study investigates how the galactic spin parameter influences the presence and type of bars in disk galaxies, revealing a correlation between spin values and bar morphology, with implications for galaxy evolution.

Contribution

It provides the first detailed analysis linking galactic spin parameters to the prevalence and type of bars in a large SDSS galaxy sample, highlighting a bi-modal relationship.

Findings

Long bars are associated with low spin parameters.

Short bars are associated with high spin parameters.

Bar fraction peaks at different spin values for long and short bars.

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 galaxies hosting long or short bars, and non-barred galaxies. We find that the spin distributions of these three classes are statistically different, with galaxies hosting long bars with 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 bi-modality is in good agreement with previous studies finding longer bars hosted by luminous, massive, red galaxies with low content of cold gas, while short bars are found in low luminosity, low mass, blue galaxies, usually 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.