SIMBAD references

Improvements in the accuracy of shape measurements are essential to exploit the statistical power of planned imaging surveys that aim to constrain cosmological parameters using weak lensing by large-scale structure. Although a range of tests can be performed using the measurements, the performance of the algorithm can only be quantified using simulated images. This yields, however, only meaningful results if the simulated images resemble the real observations sufficiently well. In this paper, we explore the sensitivity of the multiplicative bias to the input parameters of Euclid-like image simulations. We find that algorithms will need to account for the local density of sources. In particular, the impact of galaxies below the detection limit warrants further study because magnification changes their number density, resulting in correlations between the lensing signal and multiplicative bias. Although achieving sub-per cent accuracy will require further study, we estimate that sufficient archival HubbleSpace Telescope data are available to create realistic populations of galaxies.