A preliminary study of photometric redshifts based on the Wide Field Survey Telescope

• Published in: arXiv.org 2023-09
• Main Authors: Liu, Yu, Xiao-zhi, Lin, Yong-quan, Xue, Huynh Anh N Le
• Format: Article
• Language: English
• Subjects: Astronomical catalogs; Bias; Lunar phases; Outliers (statistics); Photometry; Quality assessment; Red shift
• ISSN: 2331-8422

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 (\(\sigma_{\rm NMAD}\)) and outlier fraction (\(f_{\rm outlier}\)) of photometric redshifts in two typical WFST observational cases, the single 30-second exposure observations (hereafter shallow mode) and co-added 50-minute exposure observations (hereafter deep mode). We find bias\(\la0.006\), \(\sigma_{\rm NMAD}\la0.03\), and \(f_{\rm outlier}\la5\%\) in the shallow mode and bias\(\approx 0.005\), \(\sigma_{\rm NMAD}\approx 0.06\), and \(f_{\rm outlier}\approx 17\%\)--\(27\%\) 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 \(z_{\rm phot}\) results can be significantly improved, with \(f_{\rm outlier}\approx 1\%\) and \(\sigma_{\rm NMAD}\approx 0.02\).