Calibrating photometric redshift measurements with the Multi-channel
  Imager (MCI) of the China Space Station Telescope (CSST)
  The China Space Station Telescope (CSST) photometric survey aims to perform a
high spatial resolution (~0.15'') photometric imaging for the targets that
cover a large sky area (~17,500 deg^2) and wide wavelength range (from NUV to
NIR). It expects to explore the properties of dark matter, dark energy, and
other important cosmological and astronomical areas. In this work, we evaluate
whether the filter design of the Multi-channel Imager (MCI), one of the five
instruments of the CSST, can provide accurate photometric redshift (photo-z)
measurements with its nine medium-band filters to meet the relevant scientific
objectives. We generate the mock data based on the COSMOS photometric redshift
catalog with astrophysical and instrumental effects. The application of upper
limit information of low signal-to-noise ratio (SNR) data is adopted in the
estimation of photo-z. We investigate the dependency of photo-z accuracy on the
filter parameters, such as band position and width. We find that the current
MCI filter design can achieve good photo-z measurements with accuracy
sigma_z~0.017 and outlier fraction f_c~2.2%. It can effectively improve the
photo-z measurements of the main CSST survey using the Survey Camera (SC) to an
accuracy sigma_z~0.015 and outlier fraction f_c~1.5%. It indicates that the
original MCI filters are proper for the photo-z calibration.
