Martinet, NicolasNicolasMartinetSchneider, PeterPeterSchneiderHildebrandt, HendrikHendrikHildebrandtShan, HuanYuanHuanYuanShanAsgari, MarikaMarikaAsgariDietrich, Jörg P.Jörg P.DietrichHarnois-Déraps, JoachimJoachimHarnois-DérapsErben, ThomasThomasErbenGRADO, ANIELLOANIELLOGRADOHeymans, CatherineCatherineHeymansHoekstra, HenkHenkHoekstraKlaes, DominikDominikKlaesKuijken, KonradKonradKuijkenMERTEN, JULIANJULIANMERTENNakajima, ReikoReikoNakajima2021-01-112021-01-1120180035-8711http://hdl.handle.net/20.500.12386/29649We study the statistics of peaks in a weak-lensing reconstructed mass map of the first 450 deg<SUP>2</SUP> 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 (Ω<SUB>m</SUB>, σ<SUB>8</SUB>) plane perpendicularly to its main degeneracy. We estimate S<SUB>8</SUB> = 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 S<SUB>8</SUB> compared to the shear two-point correlation functions alone, highlighting the great potential of peaks as a cosmological probe.STAMPAenArticle10.1093/mnras/stx27932-s2.0-85040005029000424339500053https://academic.oup.com/mnras/article-abstract/474/1/712/45665302018MNRAS.474..712MFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_6 Stars and stellar systems