Optical Identification of 15 Micron Sources in the AKARI Performance Verification Field toward the North Ecliptic Pole
Abstract
We present the results of optical identifications for 257 mid-infrared sources detected with a deep 15um survey over approximately 80 arcmin^2 area in the AKARI performance verification field near the North Ecliptic Pole. The 15um fluxes of the sources range from 1 mJy down to 40 uJy, approximately a half of which are below 100 uJy. Optical counterparts were searched for within a 2-3 arcsec radius in both the BVRi'z' catalog generated by using the deep Subaru/Suprime-cam field which covers one-third of the performance verification field, and the g'r'i'z' catalog based on observations made with MegaCam at CFHT. We found B-R and R-z' colours of sources with successful optical identifications are systematically redder than that of the entire optical sample in the same field. Moreover, approximately 40% of the 15um sources show colours R-L15>5, which cannot be explained by the spectral energy distribution (SED) of normal quiescent spiral galaxies, but are consistent with SEDs of redshifted (z>1) starburst or ultraluminous infrared galaxies. This result indicates that the fraction of the ultraluminous infrared galaxies in our faint 15um sample is much larger than that in our brighter 15um sources, which is consistent with the evolving mid-infrared luminosity function derived by recent studies based on the Spitzer 24um deep surveys. Based on an SED fitting technique, the nature of the faint 15um sources is further discussed for a selected number of sources with available K_s-band data.
Keywords
Cite
@article{arxiv.0708.3140,
title = {Optical Identification of 15 Micron Sources in the AKARI Performance Verification Field toward the North Ecliptic Pole},
author = {Hideo Matsuhara and Takehiko Wada and Chris P. Pearson and Shinki Oyabu and Myungshin Im and Koji Imai and Toshinobu Takagi and Eugene Kang and Narae Hwang and Woong-Seob Jeong and Hyung Mok Lee and Myung Gyoon Lee and Soojong Pak and Stephen Serjeant and Takao Nakagawa and Hitoshi Hanami and Hanae Inami and Takashi Onaka and Naofumi Fujishiro and Daisuke Ishihara and Yoshifusa Ita and Hirokazu Kataza and Woojung Kim and Toshio Matsumoto and Hiroshi Murakami and Youichi Ohyama and Itsuki Sakon and Toshihiko Tanabe and Kazunori Uemizu and Munetaka Ueno and Hidenori Watarai},
journal= {arXiv preprint arXiv:0708.3140},
year = {2015}
}