Cosmological simulations for combined-probe analyses: covariance and neighbour-exclusion bias

Abstract

We present a public suite of weak lensing mock data, extending the Scinet\nLight Cone Simulations (SLICS) to simulate cross-correlation analyses with\ndifferent cosmological probes. These mocks include KiDS-450- and LSST-like\nlensing data, cosmic microwave background lensing maps and simulated\nspectroscopic surveys that emulate the GAMA, BOSS and 2dFLenS galaxy surveys.\nWith 844 independent realisations, our mocks are optimised for combined-probe\ncovariance estimation, which we illustrate for the case of a joint measurement\ninvolving cosmic shear, galaxy-galaxy lensing and galaxy clustering from\nKiDS-450 and BOSS data. With their high spatial resolution, the SLICS are also\noptimal for predicting the signal for novel lensing estimators, for the\nvalidation of analysis pipelines, and for testing a range of systematic effects\nsuch as the impact of neighbour-exclusion bias on the measured tomographic\ncosmic shear signal. For surveys like KiDS and DES, where the rejection of\nneighbouring galaxies occurs within ~2 arcseconds, we show that the measured\ncosmic shear signal will be biased low, but by less than a percent on the\nangular scales that are typically used in cosmic shear analyses. The amplitude\nof the neighbour-exclusion bias doubles in deeper, LSST-like data. The\nsimulation products described in this paper are made available at\nhttp://slics.roe.ac.uk/.\n