Potential scientific synergies in weak lensing studies between the CSST and Euclid space probes

Aims. With the next generation of large surveys poised to join the ranks of observational cosmology in the near future, it is important to explore their potential synergies and to maximize their scientific outcomes. In this study, we aim to investigate the complementarity of two upcoming space missions: Euclid and the China Space Station Telescope (CSST), both of which will be focused on weak gravitational lensing for cosmology. In particular, we analyze the photometric redshift (photo-z) measurements by combining NUV, 2006;gy bands from CSST with the VIS, Y,2006;J,2006;H bands from Euclid, and other optical bands from the ground-based Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) and Dark Energy Survey. We also consider the advantages of combining the two space observational data in simplifying image deblending. For Euclid, weak lensing measurements use the broad optical wavelength range of 550-900 nm, for which chromatic point-spread function (PSF) effects are significant. For this purpose, the CSST narrow-band data in the optical can provide valuable information for Euclid to obtain more accurate PSF measurements and to calibrate the color and color-gradient biases for galaxy shear measurements.