  We present results from a photometric H-alpha survey of 22 nuclear rings,
aiming to provide insight into their star formation properties, including age
distribution, dynamical timescales, star formation rates, and galactic bar
influence. We find a clear relationship between the position angles and
ellipticities of the rings and those of their host galaxies, which indicates
the rings are in the same plane as the disk and circular. We use population
synthesis models to estimate ages of each H-alpha emitting HII region, which
range from 1 Myr to 10 Myrs throughout the rings. We find that approximately
half of the rings contain azimuthal age gradients that encompass at least 25%
of the ring, although there is no apparent relationship between the presence or
absence of age gradients and the morphology of the rings or their host
galaxies. NGC1343, NGC1530, and NGC4321 show clear bipolar age gradients, where
the youngest HII regions are located near the two contact points of the bar and
ring. We speculate in these cases that the gradients are related to an
increased mass inflow rate and/or an overall higher gas density in the ring,
which would allow for massive star formation to occur on short timescales,
after which the galactic rotation would transport the HII regions around the
ring as they age. Two-thirds of the barred galaxies show correlation between
the locations of the youngest HII region(s) in the ring and the location of the
contact points, which is consistent with predictions from numerical modeling.
