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Optical identification of 15 μm sources in the AKARI performance verification field toward the north ecliptic pole

Matsuhara, Hideo; Wada, Takehiko; Pearson, Chris P.; Oyabu, Shinki; Im, Myungshin; Imai, Koji; Takagi, Toshinobu; Kang, Eugene; Hwang, Narae; Jeong, Woong-Seob; Lee, Hyung Mok; Lee, Myung Gyoon; Pak, Soojong; Serjeant, Stephen; Nakagawa, Takao; Hanami, Hitoshi; Inami, Hanae; 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 and Watarai, Hidenori (2007). Optical identification of 15 μm sources in the AKARI performance verification field toward the north ecliptic pole. Publications of the Astronomical Society of Japan, 59 S543-S555.

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We present the results of optical identifications for 257 mid-infrared sources detected with a deep 15 μm survey over approximately 80 arcmin2 area in the AKARI performance verification field near the North Ecliptic Pole. The 15 μm fluxes of the sources range from 1 mJy down to 40 μJy, approximately one half of which are below 100 μJy. Optical counterparts were searched for within a 200–300 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 that the B - R and R - z' colors 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 15 μm sources show colors with 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 15 μm sample is much larger than that in our brighter 15 μm sources, which is consistent with the evolving mid-infrared luminosity function derived by recent studies based on Spitzer 24 μm deep surveys. Based on an SED fitting technique, the nature of the faint 15 μm sources is further discussed for a selected number of sources with available Ks-band data

Item Type: Journal Item
Copyright Holders: 2007 Astronomical Society of Japan
ISSN: 0004-6264
Keywords: evolution; galaxies; statistics; infrared galaxies; space vehicles; instruments
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: Space
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Item ID: 25497
Depositing User: Tracy Bartlett
Date Deposited: 02 Mar 2011 09:32
Last Modified: 20 Nov 2019 19:09
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