Near- to mid-infrared spectroscopy for the giant elliptical galaxy NGC 1316 (FORNAX A) with the AKARI infrared camera

We present the near- to mid-infrared (similar to 2.5-13 mu m) spectrum of the giant elliptical galaxy NGC 1316 ( Fornax A) obtained with the Infrared Camera (IRC) on board AKARI. NGC 1316 is known to have a peculiar polycyclic aromatic hydrocarbon (PAH) emission spectrum with an unusually high ratio of the 11.3 mu m to the 7.7 mu m emission intensity through the Spitzer IRS observation. NGC 1316 is a 3 Gyr old merger remnant with a dormant nucleus that was rather active 0.1 Gyr ago; the relatively well-known evolutionary history makes the elliptical galaxy an ideal probe for studying long-term effects of past energetic events on the interstellar medium. We have found that there is no significant PAH emission feature at 3.3 mu m while we have confirmed the peculiar PAH emission spectrum in the mid-infrared. We have detected a strong absorption feature at 4.3 mu m, which may be attributed to solid-state CO2 in grain mantles. We discuss physical implications for those unusual emission and absorption features.