Probing cosmology with weak lensing peak counts
Abstract
We propose counting peaks in weak lensing (WL) maps, as a function of their height, to probe models of dark energy and to constrain cosmological parameters. Because peaks can be identified in twodimensional WL maps directly, they can provide constraints that are free from potential selection effects and biases involved in identifying and determining the masses of galaxy clusters. As a pilot study, we have run cosmological Nbody simulations to produce WL convergence maps in three models with different constant values of the dark energy equationofstate parameter, w=0.8, 1, and 1.2, with a fixed normalization of the primordial power spectrum (corresponding to presentday normalizations of σ_{8}=0.742, 0.798, and 0.839, respectively). By comparing the number of WL peaks in eight convergence bins in the range of 0.1<κ<0.4, in multiple realizations of a single simulated 3×3 degree field, we show that the first (last) pair of models differ at the 95% (85%) confidence level. A survey with depth and area comparable to those expected from the Large Synoptic Survey Telescope should have a factor of ≈50 better parameter sensitivity. These results warrant further investigation, in order to assess the constraints available when marginalization over other uncertain parameters is included, and with the specifications of a realistic survey folded into the analysis. Here we find that relatively lowamplitude peaks (κ∼0.03), which typically do not correspond to a single collapsed halo along the line of sight, account for most of the parameter sensitivity. We study a range of smoothing scales and source galaxy redshifts (z_{s}). With a fixed source galaxy density of 15arcmin^{2}, the best results are provided by the smallest scale we can reliably simulate, 1 arcmin, and z_{s}=2 provides substantially better sensitivity than z_{s}≤1.5.
 Publication:

Physical Review D
 Pub Date:
 February 2010
 DOI:
 10.1103/PhysRevD.81.043519
 arXiv:
 arXiv:0907.0486
 Bibcode:
 2010PhRvD..81d3519K
 Keywords:

 98.80.k;
 95.36.+x;
 95.80.+p;
 98.65.Dx;
 Cosmology;
 Dark energy;
 Astronomical catalogs atlases sky surveys databases retrieval systems archives etc.;
 Superclusters;
 largescale structure of the Universe;
 Astrophysics  Cosmology and Extragalactic Astrophysics
 EPrint:
 16 pages, submitted to Phys. Rev. D