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Paper: Galactic and Extragalactic Sources in the North Ecliptic Pole: Wide Field Survey
Volume: 418, AKARI, a Light to Illuminate the Misty Universe
Page: 291
Authors: Lee, H. M.; Kim, S. J.; Im, M.; Lee, M. G.; Wada, T.; Matsuhara, H.; Oyabu, S.; the NEP Survey Team
Abstract: The North Ecliptic Pole (NEP) Wide Survey was carried out for about one year starting from May 2006 with 9 passbands from 2.5 to 24 μm and the areal coverage of about 5.8 sq. degrees centered on NEP. We present the initial results of the data analysis of all passbands except for the 24 μm. The survey depth reaches to around 22 magnitude (AB) at the near infrared (NIR) bands, and ∼ 18.5 magnitude at the mid infrared (MIR) bands such as 15 and 18 μm. We matched our infrared sources with the optical sources detected in CFHT imaging survey of about 2 sq. degree area that lies inside the NEP-Wide survey region in order to characterize the nature of infrared sources. The stars are identified by the stellarity parameter of CFHT’s r’-band image data given by SExtractor. The fraction of the stars among the infrared sources are found to dependent sensitively on the brightness as well as the wavelength. For example, the majority of bright sources in 9 and 11 μm are stars while stellar fraction decreases toward fainter sources. The stellar fraction at longer 15 and 18 μm bands remains to be less than 10% regardless of the brightness. Most of the non-stellar objects detected in mid-infrared are found to be star forming disk galaxies, with smaller fraction of early type galaxies and AGNs.
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