Multi-wavelength analysis of 18 mu m-selected galaxies in the AKARI/Infrared-Camera monitor field towards the North Ecliptic Pole

作者：Takagi Toshinobu^*; Matsuhara Hideo; Wada Takehiko; Oyabu Shinki; Imai Koji; Pearson Chris P; Hanami Hitoshi; Onaka Takashi; Fujishiro Naofumi; Ishihara Daisuke; Ita Yoshifusa; Kataza Hirokazu; Kim Woojung; Matsumoto Toshio; Murakami Hiroshi; Ohyama Youichi; Sakon Itsuki; Tanabe Toshihiko; Uemizu Kazunori; Ueno Munetaka; Watarai Hindenori; Usui Fumihiko; Lee Hyung Mok; Im Myungshin; Serjeant Stephen; Savage Richard S; Tange Tsutomu; Nakagawa Takao

来源：Publications of the Astronomical Society of Japan, 2007, 59: S557-S569.

• galaxies : active
• galaxies : evolution
• galaxies : starburst
• infrared : galaxies

We present an initial analysis of AKARI 18 mu m-selected galaxies using all 9 photometric bands at 2-24 mu m available in the Infrared Camera (IRC), in order to demonstrate new capabilities of AKARI cosmological surveys with this unprecedented wavelength coverage at mid-infrared (MIR) bands. We detected 72 sources at 18 mu m in an area of 50.2 arcmin(2) in the AKARI/IRC monitor field towards the North Ecliptic Pole (NEP). From this sample, 25 galaxies with probable redshifts of z greater than or similar to 0.5 were selected with a single colour cut (N2 -N3 > 0.1) for a detailed spectral energy distribution (SED) analysis with ground-based BVRi'z' JK data. Using an SED radiative transfer model of starbursts covering the wavelength range UV-submm, we derived photometric redshifts from the optical-MIR SEDs of 18 mu m-selected galaxies. From the best-fit SED models, we showed that the 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. This indicates that the IRC all-band photometry is useful to constrain the redshift of infrared galaxies, specifically for dusty galaxies with a less prominent 4000 A break. Also, we found that the flux dip between the PAH 7.7 and 11.2 mu m emission feature is recognizable in the observed SEDs of galaxies at z similar to 1. This pilot study suggests the possibility of detecting many interesting galaxy properties in the NEP-Deep and Wide surveys, such as a systematic difference in SEDs between high- and low-z Ultra-Luminous InfraRed Galaxies, and a large variation of the PAH inter-band strength ratio in galaxies at high redshifts.

• 出版日期2007