220 research outputs found
Cosmological Information in Weak Lensing Peaks
Recent studies have shown that the number counts of convergence peaks
N(kappa) in weak lensing (WL) maps, expected from large forthcoming surveys,
can be a useful probe of cosmology. We follow up on this finding, and use a
suite of WL convergence maps, obtained from ray-tracing N-body simulations, to
study (i) the physical origin of WL peaks with different heights, and (ii)
whether the peaks contain information beyond the convergence power spectrum
P_ell. In agreement with earlier work, we find that high peaks (with amplitudes
>~ 3.5 sigma, where sigma is the r.m.s. of the convergence kappa) are typically
dominated by a single massive halo. In contrast, medium-height peaks (~0.5-1.5
sigma) cannot be attributed to a single collapsed dark matter halo, and are
instead created by the projection of multiple (typically, 4-8) halos along the
line of sight, and by random galaxy shape noise. Nevertheless, these peaks
dominate the sensitivity to the cosmological parameters w, sigma_8, and
Omega_m. We find that the peak height distribution and its dependence on
cosmology differ significantly from predictions in a Gaussian random field. We
directly compute the marginalized errors on w, sigma_8, and Omega_m from the
N(kappa) + P_ell combination, including redshift tomography with source
galaxies at z_s=1 and z_s=2. We find that the N(kappa) + P_ell combination has
approximately twice the cosmological sensitivity compared to P_ell alone. These
results demonstrate that N(kappa) contains non-Gaussian information
complementary to the power spectrum.Comment: 24 pages, 12 figures, 14 tables. Accepted for publication in PRD
(version before proofs
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