The synergy between the Dark Energy Survey and the South Pole Telescope

Abstract: The Dark Energy Survey (DES) has recently completed the Science Verification phase (SV), collecting data over 150 sq. deg. of sky. In this work we analyze to what extent it is beneficial to supplement the analysis of DES data with CMB lensing data. We provide forecasts for both DES-SV and for the full survey covering 5000 sq. deg. We show that data presently available from DES-SV and SPT-SZ would allow a ~ 8% measurement of the linear galaxy bias in three out of four redshift bins. We further show that a joint analysis of cosmic shear, galaxy density and CMB lensing data allows to break the degeneracy between the shear multiplicative bias, the linear galaxy bias and the normalization of the matter power spectrum. We show that these observables can thus be self calibrated to the percent or sub-percent level, depending on the quality of available data, fraction of overlap of the footprints and priors included in the analysis.