Testing photometric redshift measurements with filter definition of the Chinese Space Station Optical Survey (CSS-OS)

Abstract

The Chinese Space Station Optical Survey (CSS-OS) is a major science project\nof the Space Application System of the China Manned Space Program. This survey\nis planned to perform both photometric imaging and slitless spectroscopic\nobservations, and it will focus on different cosmological and astronomical\ngoals. Most of these goals are tightly dependent on the accuracy of photometric\nredshift (photo-z) measurement, especially for the weak gravitational lensing\nsurvey as a main science driver. In this work, we assess if the current filter\ndefinition can provide accurate photo-z measurement to meet the science\nrequirement. We use the COSMOS galaxy catalog to create a mock catalog for the\nCSS-OS. We compare different photo-z codes and fitting methods that using the\nspectral energy distribution (SED) template-fitting technique, and choose to\nuse a modified LePhare code in photo-z fitting process. Then we investigate the\nCSS-OS photo-z accuracy in certain ranges of filter parameters, such as band\nposition, width, and slope. We find that the current CSS-OS filter definition\ncan achieve reasonably good photo-z results with sigma_z~0.02 and outlier\nfraction ~3%.\n