Detection of cosmic magnification via galaxy sheargalaxy number density correlation from HSC survey data
Abstract
We propose a novel method to detect cosmic magnification signals by crosscorrelating foreground convergence fields constructed from galaxy shear measurements with background galaxy positional distributions—namely, shearnumber density correlation. We apply it to the Hyper SuprimeCam Subaru Strategic Program (HSCSSP) survey data. With 27 nonindependent data points and their full covariance, χ_{0}^{2}≈34.1 and χ_{T}^{2}≈24.0 with respect to the null and the cosmological model with the parameters from HSC shear correlation analyses in Hamana et al. [Publ. Astron. Soc. Jpn. 72, 16 (2020), 10.1093/pasj/psz138], respectively. The Bayes factor of the two is log_{10}B_{T 0}≈2.2 assuming equal model probabilities of null and HSC cosmology, showing a clear detection of the magnification signals. Theoretically, the ratio of the shearnumber density and shearshear correlations can provide a constraint on the effective multiplicative shear bias m ¯ using internal data themselves. We demonstrate the idea with the signals from our HSCSSP mock simulations and rescale the statistical uncertainties to a survey of 15000 deg^{2}. For twobin analyses with background galaxies brighter than m_{lim}=23 , the combined analyses lead to a forecasted constraint of σ (m ¯)∼0.032 , 2.3 times tighter than that found when using the shearshear correlation alone. Correspondingly, σ (S_{8}) with S_{8}=σ_{8}(Ω_{m}/0.3 )0.^{5} is tightened by ∼2.1 times. Importantly, the joint constraint on m ¯ is nearly independent of cosmological parameters. Our study therefore points to the importance of including the shearnumber density correlation in weak lensing analyses, which can provide valuable consistency tests of observational data, and thus to solidify the derived cosmological constraints.
 Publication:

Physical Review D
 Pub Date:
 June 2021
 DOI:
 10.1103/PhysRevD.103.123504
 arXiv:
 arXiv:2104.13595
 Bibcode:
 2021PhRvD.103l3504L
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 9 pages, 4 figures