The Central Region of the Barred Spiral Galaxy NGC1097 Probed by AKARI
  Near-Infrared Spectroscopy
  With the Infrared Camera on board AKARI, we carried out near-infrared
(2.5-5.0 micron) spectroscopy of the central kiloparsec region of the barred
spiral galaxy, NGC1097, categorized as Seyfert 1 with a circumnuclear starburst
ring. Our observations mapped the area of ~50"*10" with the resolution of ~5",
covering about a half of the ring and the galactic center. As a result, we
spatially resolve the starburst ring in the polycyclic aromatic hydrocarbon 3.3
micron, the aliphatic hydrocarbon 3.4-3.6 micron features, and the hydrogen Br
alpha 4.05 micron emission. They exhibit spatial distributions significantly
different from each other, indicating that the environments vary considerably
around the ring. In particular, the aliphatic features are enhanced near the
bar connecting the ring with the nucleus, where the structure of hydrocarbon
grains seems to be relatively disordered. Near the center, the continuum
emission and the CO/SiO absorption features are strong, which indicates that
the environments inside the ring are dominated by old stellar populations. The
near-infrared spectra do not show any evidence for the presence of nuclear
activity.
