Day 813

Friday.

1501.01632
Cosmic variance of the galaxy cluster weak lensing signal
Gruen, Seitz, et al

Intrinsic variations of the projected density profiles of clusters of galaxies at fixed mass are a source of uncertainty for cluster weak lensing.  Present a semi-analytical model to account for this effect, based on a combination of variations in halo concentration, ellipticity and orientation, and the presence of correlated haloes.  Calibrate the parameters of the model at the 10% level to match the empirical cosmic variance of cluster profiles at M200m=1e14-15 Msun/h, z=0.25~0.5 in a cosmological simulation.  Show that WL measurements of clusters provide correct mass likelihoods.  Effects on the achievable accuracy of WL cluster mass measurements are particularly strong for the most massive clusters and deep observations (with ~20% uncertainty from cosmic variance alone at M200m=1e15 Msun/h and 0.25), but significant also under typical ground-based conditions.  Show that neglecting intrinsic profile variations leads to biases in the mass-observable relation constrained with WL, both for intrinsic scatter and overall scale (the latter at the 15% level).  These biases are in excess of the statistical errors of upcoming surveys and can be avoided if the cosmic variance of cluster profiles is accounted for.