2008/02/27 by Elisabetta Semboloni, Catherine Heymans, Ludovic van Waerbeke +1 · 3 citations
Physics and Astronomy · #Amplitude #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gravitational lens #Gravitational lensing formalism #Observational error #Photometric redshift #Redshift #Statistical Mechanics and Entropy #Weak gravitational lensing #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2008.13478.x
10 pages, 7 Figures, MNRAS submitted
arxiv created 2008/02/27 · openalex publication_date 2008/07/09 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We investigate the impact of the observed correlation between a galaxy's shape and its surrounding density field on the measurement of third-order weak lensing shear statistics. Using numerical simulations, we estimate the systematic error contribution to a measurement of the third-order moment of the aperture mass statistic (GGG) from three-point intrinsic ellipticity correlations (III), and the three-point coupling between the weak lensing shear experienced by distant galaxies and the shape of foreground galaxies (GGI and GII). We find that third-order weak lensing statistics are typically more strongly contaminated by these physical systematics compared to second-order shear measurements, contaminating the measured three-point signal for moderately deep surveys with a median redshift zm∼ 0.7 by ∼15 per cent. It has been shown that accurate photometric redshifts will be crucial to correct for this effect, once a model and the redshift dependence of the effect can be accurately constrained. To this end we provide redshift-dependent fitting functions to our results and propose a new tool for the observational study of intrinsic galaxy alignments. For a shallow survey with zm∼ 0.4 we find III to be an order of magnitude larger than the expected cosmological GGG shear signal. Compared to the two-point intrinsic ellipticity correlation which is similar in amplitude to the two-point shear signal at these survey depths, third-order statistics therefore offer a promising new way to constrain models of intrinsic galaxy alignments. Early shallow data from the next generation of very wide weak lensing surveys will be optimal for this type of study.