A Near-Infrared Study of 2MASS Bars in Local Galaxies: An Anchor for High Redshift Studies

Abstract

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 36% for bars with a semi-major 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}> ~ 0.3 +/- 0.2. Early-type spirals host significantly larger bars, consistent with earlier studies. The <a_{bar}/R_{25}> is two times larger in early-types than in late-types. The typical bar axial ratio (b/a) is \~0.5, with a weak trend of higher axial ratios for larger bars.