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KiDS-Legacy calibration: Unifying shear and redshift calibration with the SKiLLS multi-band image simulations

Abstract:
We present SKiLLS, a suite of multi-band image simulations for the weak lensing analysis of the complete Kilo-Degree Survey (KiDS), dubbed KiDS-Legacy analysis. The resulting catalogues enable joint shear and redshift calibration, enhancing the realism and hence accuracy over previous efforts. To create a large volume of simulated galaxies with faithful properties and to a sufficient depth, we integrated cosmological simulations with high-quality imaging observations. We also improved the realism of simulated images by allowing the point spread function (PSF) to differ between CCD images, including stellar density variations and varying noise levels between pointings. Using realistic variable shear fields, we accounted for the impact of blended systems at different redshifts. Although the overall correction is minor, we found a clear redshift-bias correlation in the blending-only variable shear simulations, indicating the non-trivial impact of this higher-order blending effect. We also explored the impact of the PSF modelling errors and found a small yet noticeable effect on the shear bias. Finally, we conducted a series of sensitivity tests, including changing the input galaxy properties. We conclude that our fiducial shape measurement algorithm, lensfit, is robust within the requirements of lensing analyses with KiDS. As for future weak lensing surveys with tighter requirements, we suggest further investments in understanding the impact of blends at different redshifts, improving the PSF modelling algorithm and developing the shape measurement method to be less sensitive to the galaxy properties.Comment: 28 pages, 31 figures, 2 tables, minor revisions to match the final accepted versio
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1051/0004-6361/202245210

Authors

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Role:
Author
ORCID:
0000-0002-3827-0175
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Role:
Author
ORCID:
0000-0002-0641-3231
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Institution:
University of Oxford
Role:
Author
ORCID:
0000-0002-3376-6200
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Role:
Author
ORCID:
0000-0001-7023-3940


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Funder identifier:
https://ror.org/0472cxd90
Grant:
647112
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Funder identifier:
10.13039/501100001801
Grant:
Scholarship for International Research Fees and Ad Hoc Postgraduate Scholarship
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Funder identifier:
10.13039/501100000271
Grant:
ST/N000919/1
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Funder identifier:
10.13039/501100003246
Grant:
Vici grant 639.043.512


Publisher:
EDP Sciences
Journal:
Astronomy & Astrophysics More from this journal
Volume:
670
Pages:
A100-A100
Publication date:
2023-02-10
Acceptance date:
2022-12-20
DOI:
EISSN:
1432-0746
ISSN:
0004-6361


Language:
English
Keywords:
Pubs id:
1335203
Local pid:
pubs:1335203
Source identifiers:
W4313592864
Deposit date:
2026-05-05
ARK identifier:
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