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Barred galaxies frequently exhibit central starburst activity, typically concentrated in circumnuclear rings. Much of direct and circumstantial evidence speaks in favor of bar-induced fueling of star-forming activity in these galaxies. We present results, partly preliminary, for three galaxies which were studied through high-resolution imaging in the optical and near-infrared (NIR), and through numerical modeling.
In particular, we have been able to reproduce the main features observed in the central region of NGC~4321. In the NIR, we see a large-scale (4~kpc) bar, disected by a 1--1.3 kpc diameter oval region of strongly enhanced star formation, formed by two tightly wound spirals. The NIR isophotes are aligned with the bar both inside and outside the ``ring''. Two leading armlets are seen in the NIR ($K$) and both culminate in regions of intense star formation at the inner boundary of the ``ring''. The morphology of the circumnuclear region is consistent with being regulated by a pair of inner Lindblad resonances.
We also show new optical, NIR, and molecular data of two additional barred galaxies: NGC~1300 and NGC~6951, which have circumnuclear star-forming regions of similar size as NGC~4321. Although these regions are more ring-like and do not exhibit spiral structure, we show that similar mechanisms as described for the first galaxy regulate the structure and star formation in these two galaxies.
The fact that NGC~6951 hosts a Seyfert nucleus may provide an important test of the relevance of bar-induced inflows, such as observed in these barred galaxies, to active galactic nuclei. Implications and observational and theoretical prospects are discussed.
