Nested and Single Bars in Seyfert and Non‐Seyfert Galaxies

Abstract

We analyze the observed properties of nested and single stellar bar systems\nin disk galaxies. The 112 galaxies in our sample comprise the largest matched\nSeyfert vs. non-Seyfert sample of nearby galaxies with complete near-infrared\nor optical imaging sensitive to lengthscales ranging from tens of pc to tens of\nkpc. We find that a significant fraction of the sample galaxies, 17% +/- 4%,\nhas more than one bar, and that 28% +/- 5% of barred galaxies have nested bars.\nThe bar fractions appear to be stable according to reasonable changes in our\nadopted bar criteria. For these nested bars, we detect a clear division in\nlength between the large-scale (primary) bars and small-scale (secondary) bars,\nboth in absolute and normalized (to the size of the galaxy) length. We argue\nthat this bimodal distribution can be understood within the framework of the\ninner Lindblad resonances (ILRs), which are located where the gravitational\npotential of the innermost galaxy switches effectively from 3D to 2D. While\nprimary bars are found to correlate with the host galaxy sizes, no such\ncorrelation is observed for the secondary bars. Moreover, we find that\nsecondary bars differ morphologically from single bars. Overall, our matched\nSeyfert and non-Seyfert samples show a statistically significant excess of bars\namong the Seyfert galaxies at practically all lengthscales. We confirm our\nprevious result that Seyfert galaxies always show a preponderance of "thick"\nbars compared to the bars in non-Seyfert galaxies. Finally, no correlation is\nobserved between the presence of a bar and that of companion galaxies, even\nrelatively bright ones.\n