New Determination of Photometric Redshifts over the NEPW field based on the Deep Optical Survey using Hyper Suprime-Cam

Chien-Chang Ho^1*, Tomotsugu Goto¹, Nagisa Oi², Seong Jin Kim¹, Matthew A. Malkan³, Agnieszka Pollo⁴, Tetsuya Hashimoto¹, Yoshiki Toba^5,6,7, Helen K. Kim³, Ho-Seong Hwang⁸, Hyunjin Shim⁹, Ting-Chi Huang¹⁰, Eunbin Kim⁸, Ting-Wen Wang¹

¹Institute of Astronomy, National Tsing Hua University, Hsinchu city, Taiwan
²Faculty of Science Division II, Tokyo University of Science, Tokyo, Japan
³Department of Physics and Astronomy, UCLA, Los Angeles, CA, USA
⁴The Andrzej Soltan National Centre for Nuclear Research, Warsaw, Poland
⁵Department of Astronomy, Kyoto University, Kyoto, Japan
⁶Academia Sinica Institute of Astronomy and Astrophysics, Taipei City, Taiwan
⁷Research Center for Space and Cosmic Evolution, Ehime University, Ehime, Japan
⁸Korea Astronomy and Space Science Institute, Daejeon, Korea
⁹Department of Earth Science Education, Kyungpook National University, Buk-gu Daegu, Korea
¹⁰Department of space and astronautical science, SOKENDAI (The Graduate University for Advanced Studies), Kanagawa, Japan

* Presenter:Chien-Chang Ho, email:hosimon259@gmail.com

The North Ecliptic Pole Wide (NEPW) field has been observed in almost all the wavelength bands using various telescopes from ultraviolet (UV) to sub-millimetre (submm). However, the fainter infrared (IR) sources observed by AKARI telescope have remained unidentified until we derive new photometric redshifts (photo-z) based on recently obtained optical survey by Subaru/Hyper Suprime-Cam (HSC). In this work, we present the analyses, methodology, and new photo-z based on the deeper HSC data, along with all available ancillary data over this region, 24-filter combination from CFHT, Maidanak, KPNO, Spitzer and WISE. A χ² template-fitting method code (Le PHARE) was used. We use 2026 spectroscopic redshifts at 0 < z < 5 from the NEPW Survey as a calibration and assess the accuracy the photo-z. At z < 1.5, we achieve an accuracy of σ_Δz/(1+z) = 0.0493 with η = 9.27% of catastrophic errors (η is defined strictly as those objects with |Δz|/1 + z_spec > 0.15). We discuss the photo-z of active galactic nuclei (AGNs), stellarity of the sources, and the reliability of photo-z for faint sources. AGNs and high-stellarity objects in our catalogue do not affect our photo-z performance much. Therefore, we decided to keep them. This NEPW-24-band photo-z enables the full exploitation of this survey for studies of galaxy and large-scale structure.

Keywords: catalogues, redshifts, infrared: galaxies