1609.03973
Do dark matter haloes explain lensing peaks?
Matilla, Haiman, Hsu, Gupta, Petri
Investigate a recently proposed halo-based model Camelus for predicting WL peak counts, and compared its results over a collection of 12 cosmologies with those from N-body sims. While counts from both models agree for peaks with S/N>1 (where S/N is the ratio of the park height to the rms shape noise), find ~50% fewer counts for peaks near S/N=0 and significantly higher counts in the negative S/N tail. Adding shape noise reduces the differences to within 20% for all cosmologies. Also found larger covariances that are more sensitive to cosmo parameters. As a result, credibility regions in the (Omega_m, sigma8) are ~30% larger. Even though the credible contours are commensurate, each model draws its predictive power from different types of peaks. Low peaks, especially those with 2<S/N<3, convey important cosmo information in N-body data, as shown in DeitrichHartlap, Kratochivil10, but Camelus constrains cosmology almost exclusively from high significance peaks (S/N>3). The results confirm the importance of using a cosmology-dependent covariance with at least a 14% improvement in parameter constraints. Identify the covariance estimation as the main driver behind differences in inference, and suggest possible ways to make Camelus even more useful as a highly accurate peak count emulator.
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