The Nuclear Ring in the Barred Spiral Galaxy IC 4933
  We present infrared imaging from IRIS2 on the Anglo-Australian Telescope that
shows the barred spiral galaxy IC 4933 has not just an inner ring encircling
the bar, but also a star-forming nuclear ring 1.5 kpc in diameter. Imaging in
the u' band with GMOS on Gemini South confirms that this ring is not purely an
artifact due to dust. Optical and near-infrared colours alone however cannot
break the degeneracy between age, extinction, and burst duration that would
allow the star formation history of the ring to be unraveled. Integral field
spectroscopy with the GNIRS spectrograph on Gemini South shows the equivalent
width of the Pa-beta line to peak in the north and south quadrants of the ring,
indicative of a bipolar azimuthal age gradient around the ring. The youngest
star-forming regions do not appear to correspond to where we expect to find the
contact points between the offset dust lanes and the nuclear ring unless the
nuclear ring is oval in shape, causing the contact points to lead the bar by
more than 90 degrees.
