Preliminary Study of Photometric Redshifts Based on the Wide Field Survey Telescope

• Published in: Research in astronomy and astrophysics 2023-12, Vol.23 (12), p.125011-152
• Main Authors: Liu, Yu, Lin, Xiao-Zhi, Xue, Yong-Quan, Le, Huynh Anh N.
• Format: Article
• Language: English
• Subjects: Astronomical catalogs; Bias; Galaxies; galaxies: distances and redshifts; galaxies: high-redshift; galaxies: photometry; Lunar phases; Outliers (statistics); Photometry; Polls & surveys; Quality assessment; Red shift
• ISSN: 1674-4527; 2397-6209
• DOI: 10.1088/1674-4527/acf544

The Wide Field Survey Telescope (WFST) is a dedicated time-domain multi-band ( u , g , r , i , and z ) photometric survey facility under construction. In this paper, we present a preliminary study that assesses the quality of photometric redshifts based on WFST by utilizing mock observations derived with the galaxy catalog in the COSMOS/UltraVISTA field. We apply the template fitting technique to estimate photometric redshifts by using the ZEBRA photometric-redshift code and adopting a modified set of adaptive templates. We evaluate the bias (median relative offset between the output photometric redshifts and input redshifts), normalized median absolute deviation ( σ NMAD ) and outlier fraction ( f outlier ) of photometric redshifts in two typical WFST observational cases, the single 30 s exposure observations (hereafter shallow mode) and co-added 50 minutes exposure observations (hereafter deep mode). We find bias ≲0.006, σ NMAD ≲ 0.03, and f outlier ≲ 5% in the shallow mode and bias ≈0.005, σ NMAD ≈ 0.06, and f outlier ≈ 17%–27% in the deep mode, respectively, under various lunar phases. Combining the WFST mock observational data with that from the upcoming CSST and Euclid surveys, we demonstrate that the z phot results can be significantly improved, with f outlier ≈ 1% and σ NMAD ≈ 0.02.