Triple Bars and Complex Central Structures in Disk Galaxies

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Abstract
We present an analysis of ground-based and Hubble Space Telescope images of three early-type barred galaxies. The first, NGC 2681, may be the clearest example yet of a galaxy with three concentric bars. The two other galaxies were previously suggested to be triple barred. Our analysis shows that while NGC 3945 is probably double barred, NGC 4371 has only one bar; but both have intriguing central structures. NGC 3945 has a large, extremely bright disk inside its primary bar, with patchy dust lanes, a faint nuclear ring or pseudoring within the disk, and an apparent secondary bar crossing the ring. NGC 4371 has a bright nuclear ring that is only marginally bluer than the surrounding bulge and bar. There is no evidence for significant dust or star formation in either of these nuclear rings. The presence of stellar nuclear rings suggests that the centers of these galaxies are dynamically cool and disklike.
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