KiDS-450: cosmological constraints from weak-lensing peak statistics - II: Inference from shear peaks using N-body simulations

Nicolas Martinet, Peter Schneider, Hendrik Hildebrandt, HuanYuan Shan, Marika Asgari, Jörg P. Dietrich, Joachim Harnois-Déraps, Thomas Erben, Aniello Grado, Catherine Heymans, Henk Hoekstra, Dominik Klaes, Konrad Kuijken, Julian Merten, Reiko Nakajima

Research output: Contribution to journalArticlepeer-review


We study the statistics of peaks in a weak-lensing reconstructed mass map of the first 450 deg2 of the Kilo Degree Survey (KiDS-450). The map is computed with aperture masses directly applied to the shear field with an NFW-like compensated filter. We compare the peak statistics in the observations with that of simulations for various cosmologies to constrain the cosmological parameter S_8 = σ _8 √{Ω _m/0.3}, which probes the (Ωm, σ8) plane perpendicularly to its main degeneracy. We estimate S8 = 0.750 ± 0.059, using peaks in the signal-to-noise range 0 ≤ S/N ≤ 4, and accounting for various systematics, such as multiplicative shear bias, mean redshift bias, baryon feedback, intrinsic alignment, and shear-position coupling. These constraints are ˜ 25 per cent tighter than the constraints from the high significance peaks alone (3 ≤ S/N ≤ 4) which typically trace single-massive haloes. This demonstrates the gain of information from low-S/N peaks. However, we find that including S/N <0 peaks does not add further information. Our results are in good agreement with the tomographic shear two-point correlation function measurement in KiDS-450. Combining shear peaks with non-tomographic measurements of the shear two-point correlation functions yields a ˜20 per cent improvement in the uncertainty on S8 compared to the shear two-point correlation functions alone, highlighting the great potential of peaks as a cosmological probe.
Original languageEnglish
Pages (from-to)712-730
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - 26 Oct 2017


  • gravitational lensing: weak
  • surveys
  • cosmological parameters
  • cosmology: observations


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