2018/05/31 by Ryuichi Takahashi, Takahiro Nishimichi, Masahiro Takada +2
Environmental Science · Physics and Astronomy · #Astrophysics #Climate variability and models #Correlation function (quantum field theory) #Cosmology and Gravitation Theories #Covariance #Dark matter #Galaxies: Formation, Evolution, Phenomena #Galaxy #Halo #Matter power spectrum #Physics #Quantum mechanics #Redshift #Statistics #Weak gravitational lensing #astro-ph.CO
paper · pdf · doi:10.1093/mnras/sty2962
26 pages, 11 figures, accepted for publication in MNRAS
arxiv created 2018/10/26 · openalex publication_date 2018/11/01 · arxiv updated 2018/11/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
In this study, we measure the response of matter and halo projected power spectra |P\rm 2D\rm XY(k)| (X, Y are matter and/or haloes) to a large-scale density contrast, δb, using separate universe simulations. We show that the fractional response functions, i.e. |dln P\rm 2D\rm XY(k)/dδ \rm b|, are identical to their respective 3D power spectra within simulation measurement errors. Then, using various N-body simulation combinations (small-box simulations with periodic boundary conditions and sub-volumes of large-box simulations) to construct mock observations of projected fields, we study how supersurvey modes, in both parallel and perpendicular directions to the projection direction, affect the covariance matrix of |P\rm 2D\rm XY(k)|, known as supersample covariance (SSC). Our results indicate that the SSC term provides dominant contributions to the covariances of matter–matter and matter–halo spectra at small scales but does not provide significant contributions in the halo–halo spectrum. We observe that the large-scale density contrast in each redshift shell causes most of the SSC effect, and we did not observe an SSC signature arising from the large-scale tidal field within the levels of measurement accuracy. We also develop a response approach to calibrate the SSC term for the cosmic shear correlation function and galaxy–galaxy weak lensing and validate the method by comparison with the light-cone ray-tracing simulations. Our method provides a reasonably accurate, albeit computationally inexpensive, way to calibrate the covariance matrix for clustering observables available from wide-area galaxy surveys.