Evolution of the Unidentified Infrared Bands in the Nucleus of the
  Starburst Galaxy NGC 1097
  We present the analysis of the Unidentified Infrared Bands (UIB) in the
starburst galaxy NGC 1097. We have combined spectral maps observed with the
AKARI/IRC and Spitzer/IRS instruments, in order to study all of the most
prominent UIBs, from 3 to 20 micron. Such a complete spectral coverage is
crucial to remove the common degeneracies between the effects of the variations
of the size distribution and of the charge state of the grains. By studying
several UIB ratios, we show evidence that the average size of the UIB carriers
is larger in the central region than in the circumnuclear ring. We interpret
this result as the selective destruction of the smallest grains by the hard
radiation from the central active galactic nucleus.
