A near-infrared study of 2mass bars in local galaxies:: An anchor for high-redshift studies

We have measured the fraction of bars in nearby spiral galaxies using near-infrared J, H, and K-s images of 151 spiral galaxies from 2MASS. This local sample provides an anchor for the study of the evolution of the bar fraction and bar properties with redshift. We identify bars by analyzing the full two-dimensional light distribution and requiring a combined ellipticity and position angle signature. The combined "bar signature'' is found in 59% of the galaxies. The bar fraction increases to 67% when we include "candidate'' bars, where only the ellipticity signature is present. We also measure the change in the bar fraction as a function of bar size; the bar fraction drops to 31% for bars with a semimajor axis larger than 4 kpc. We find that infrared bars typically extend to one-third of the galactic disk, with a deprojected relative size of [a(bar)/R-25] similar to 0.3 +/- 0.2. Early-type spirals host significantly larger bars, consistent with earlier studies. The [a(bar)/R-25] is 2 times larger in early types than in late types. The typical bar axial ratio (b/a) is similar to 0.5, with a weak trend of higher axial ratios for larger bars.