Effects of overlapping sources on cosmic shear estimation: Statistical sensitivity and pixel-noise bias
Abstract
The next generation of dark-energy imaging surveys - so called "Stage-IV" surveys, such as that of the Rubin Observatory Legacy Survey of Space and Time (LSST) - will cross a threshold in the number density of detected sources on the sky that requires qualitatively different image analysis and measurement techniques compared to the current generation of Stage-III surveys. In Stage-IV surveys, a significant amount of the cosmologically useful information is due to sources whose images overlap with those of other sources on the sky. We focus on the weak gravitational lensing probe, for which we expect the largest impact since the cosmic shear signal is primarily encoded in the estimated shapes of observed galaxies and thus directly impacted by overlaps. We introduce a framework based on the Fisher formalism to analyze the effect of the overlapping sources ("blending") on the estimation of cosmic shear. This method gives concrete predictions for the minimum loss of information due to noise and blending for any choice of "deblending" scheme and shape-measurement algorithm. Our studies account for undetected sources but do not address their full effects and biases they may introduce.
- Publication:
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Journal of Cosmology and Astroparticle Physics
- Pub Date:
- July 2021
- DOI:
- 10.1088/1475-7516/2021/07/043
- arXiv:
- arXiv:2103.02078
- Bibcode:
- 2021JCAP...07..043S
- Keywords:
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- gravitational lensing;
- redshift surveys;
- weak gravitational lensing;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- Accepted for publication in JCAP. 45 pages, 19 figures