Impact and interplay of $Λ$CDM analysis choices for LSST cosmic shear

[2602.21863] Impact and interplay of $Λ$CDM analysis choices for LSST cosmic shear Skip to main content Search Submit Donate Log in Astrophysics > Cosmology and Nongalactic Astrophysics arXiv:2602.21863 (astro-ph) [Submitted on 25 Feb 2026 ( v1 ), last revised 27 Aug 2026 (this version, v3)] Title: Impact and interplay of $Λ$CDM analysis choices for LSST cosmic shear Authors: N. C. Robertson , C. Heymans , J. Zuntz , P. Burger , C. D. Leonard , I. G. McCarthy , J. G. Paine , J. Salcido , N. Šarčević , M. Schaller , J. Schaye , M. P. van Daalen (for The FLAMINGO team and The LSST Dark Energy Science Collaboration) View PDF HTML (experimental) Abstract: We forecast cosmological parameter constraints for a cosmic shear analysis of the Rubin Observatory Legacy Survey of Space and Time (LSST), defining an analysis framework that can accurately recover the $\Lambda$CDM model in the presence of astrophysical and data-related systematics. When accounting for our present uncertainty on the suppression of the non-linear matter power spectrum through baryon feedback, we find that the error on the composite parameter $S_8=\sigma_8\sqrt{\Omega_{\rm m}/0.3}$ almost doubles compared to an LSST analysis which neglects this astrophysical phenomenon. After the first year of observations, LSST will extend beyond the magnitude limit of existing representative spectroscopic calibration samples, requiring photometric redshifts to be calibrated using an alternative strategy. Adopting literature measurements of the reduced redshift calibration precision found from galaxy cross-correlation techniques, combined with current levels of baryon feedback uncertainty, we forecast final year LSST cosmic shear constraints that barely improve upon the first year analysis. This forecast therefore serves as encouragement to the community to develop methodology and observations to constrain models of baryon feedback and enhance photometric redshift calibration at depths where spectroscopy is unrepresentative. With tight priors on both these systematic terms, we forecast that LSST cosmic shear can deliver constraints on $S_8$ that are more than five times as constraining as existing cosmic shear surveys. Comments: 22 pages, 13 figures, Published in the Open Journal of Astrophysics Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO) Cite as: arXiv:2602.21863 [astro-ph.CO] (or arXiv:2602.21863v3 [astro-ph.CO] for this version) https://doi.org/10.48550/arXiv.2602.21863 Focus to learn more arXiv-issued DOI via DataCite Related DOI : https://doi.org/10.33232/001c.168762 Focus to learn more DOI(s) linking to related resources Submission history From: Naomi Robertson Dr [ view email ] [v1] Wed, 25 Feb 2026 12:44:02 UTC (4,899 KB) [v2] Mon, 2 Mar 2026 15:36:15 UTC (4,899 KB) [v3] Thu, 27 Aug 2026 09:49:40 UTC (4,904 KB) Full-text links: Access Paper: View PDF HTML (experimental) TeX Source view license Current browse context: astro-ph.CO < prev | next > new | recent | 2026-02 Change to browse by: astro-ph References & Citations INSPIRE HEP SciX Google Scholar Semantic Scholar export BibTeX citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer ( What is the Explorer? ) Connected Papers Toggle Connected Papers ( What is Connected Papers? ) Litmaps Toggle Litmaps ( What is Litmaps? ) scite.ai Toggle scite Smart Citations ( What are Smart Citations? ) Code, Data, Media Code, Data and Media Associated with this Article alphaXiv Toggle alphaXiv ( What is alphaXiv? ) Links to Code Toggle CatalyzeX Code Finder for Papers ( What is CatalyzeX? ) DagsHub Toggle DagsHub ( What is DagsHub? ) GotitPub Toggle Gotit.pub ( What is GotitPub? ) Huggingface Toggle Hugging Face ( What is Huggingface? ) ScienceCast Toggle ScienceCast ( What is ScienceCast? ) Demos Demos Replicate Toggle Replicate ( What is Replicate? ) Spaces Toggle Hugging Face Spaces ( What is Spaces? ) Spaces Toggle TXYZ.AI ( What is TXYZ.AI? ) Related Papers Recommenders and Search Tools Link to Influence Flower Influence Flower ( What are Influence Flowers? ) Core recommender toggle CORE Recommender ( What is CORE? ) IArxiv recommender toggle IArxiv Recommender ( What is IArxiv? ) Author Venue Institution Topic About arXivLabs arXivLabs: experimental projects with community collaborators arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website. 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