The AKARI Extragalactic Large Area Survey Towards the North Ecliptic Pole

Large area surveys in the infrared wavelengths have revealed a significant evolution of the star formation activity of the universe in the past. Extragalactic surveys we have conduced with AKARI towards the north ecliptic pole (NEP) are unique, in terms of a comprehensive wavelength coverage from 2 to 24 mu m using all 9 photometric bands of the IRC. This includes new wavelength windows for extragalactic surveys, such as 18 mu m. We demonstrate that this IRC all-band photometry is capable of tracing a steep rise in the flux at the blue side of the polycyclic aromatic hydrocarbon (PAH) 6.2 mu m emission feature of infrared luminous galaxies at z < 1. Starburst-dominated ULIRGs are identified using IRC all-band photometry. The PAH-to-total IR luminosity ratio of these starburst ULIRGs is systematically higher than that of local ULIRGs. The nature of ULIRGs could be different from local ones even at z similar to 1.