A 2.5-5 {\mu}m Spectroscopic Study of Hard X-ray Selected AGNs using
  AKARI InfraRed Camera
  We present results of the 2.5-5 {\mu}m spectroscopy of a sample of hard X-ray
selected active galactic nuclei (AGNs) using the grism mode of the InfraRed
Camera (IRC) on board the infrared astronomical satellite AKARI. The sample is
selected from the 9-month Swift/BAT survey in the 14-195 keV band, which
provides a fair sample of AGNs including highly absorbed ones. The 2.5-5 {\mu}m
spectroscopy provide a strong diagnostic tool for the circumnuclear environment
of AGNs through the continuum shapes and emission/absorption features such as
the 3.3 {\mu}m polycyclic aromatic hydrocarbon (PAH) emission and the broad 3.1
{\mu}m H2O ice, 3.4 {\mu}m bare carbonaceous dust, 4.26 {\mu}m CO2 and 4.67
{\mu}m CO absorptions. As our first step, we use the 3.3 {\mu}m PAH emission as
a proxy for the star-formation activity and searched for possible difference of
star-formation activity between type 1 (unabsorbed) and type 2 (absorbed) AGNs.
We found no significant dependence of the 3.3 {\mu}m PAH line luminosity,
normalized by the black hole mass, on optical AGNs types or the X-ray measured
column densities.
