Young Populations in the Nuclei of Barred Galaxies
  We have conducted a $UBVRI$ and $H_{\alpha}$ CCD photometry of 5 barred galaxies, NGC 2523, NGC 2950, NGC 3412, NGC 3945 and NGC 5383, along with SPH simulations, in order to understand the origin of young stellar populations in the nuclei of barred galaxies. The $H_{\alpha}$ emissions which are thought to be emitted by young stellar populations are either absent or strongly concentrated on the nuclei of early type galaxies (NGC 2950, NGC 3412, NGC 3945), while they are observed in the nuclei and circumnuclear regions of intermediate type galaxies with strong bars (NGC 2523, NGC 5383). SPH simulations of realistic mass models for these galaxies show that some disk material can be driven into the nuclear regions by strong bar potentials. This implies that the young stellar populations in the circumnuclear regions of barred galaxies can be formed out of such gas. The existence of the nuclear dust lanes is an indication of an on-going gas inflow and extremely young stellar populations in these galaxies, because the nuclear dust lanes such as those in NGC 5383 are not long-lasting features according to our simulations. 
H. B. Ann (PNU, Korea)