Near- to mid-Infrared Observations of Galaxy Mergers: NGC2782 and
  NGC7727
  We present the results of near- to mid-infrared (NIR to MIR) imaging and NIR
spectroscopic observations of two galaxy mergers, NGC 2782 (Arp 215) and NGC
7727 (Arp 222), with the Infrared Camera on board AKARI. NGC 2782 shows
extended MIR emission in the eastern side of the galaxy, which corresponds to
the eastern tidal tail seen in the HI 21 cm map, while NGC 7727 shows extended
MIR emission in the north of the galaxy, which is similar to the plumes seen in
the residual image at the K-band after subtracting a galaxy model. Both
extended structures are thought to have formed associated with their merger
events. They show excess emission at 7--15 micron, which can be attributed to
emission from polycyclic aromatic hydrocarbons (PAHs), while the observed
spectral energy distributions decline longward of 24 micron, suggesting that
very small grains (VSGs) are deficient. These characteristics of the observed
MIR spectral energy distribution may be explained if PAHs are formed by
fragmentation of VSGs during merger events. The star formation rate is
estimated from the MIR PAH emission in the eastern tail region of NGC 2782 and
it is in fair agreement with those estimated from Halpha and [CII] 158 micron.
MIR observations are efficient for the study of dust processing and structures
formed during merger events.
