Assessing the large-scale angular clustering of UNIONS Lyman Break Galaxies via cross-correlations

[2607.09943] Assessing the large-scale angular clustering of UNIONS Lyman Break Galaxies via cross-correlations Skip to main content Search Submit Donate Log in Astrophysics > Cosmology and Nongalactic Astrophysics arXiv:2607.09943 (astro-ph) [Submitted on 10 Jul 2026 ( v1 ), last revised 25 Aug 2026 (this version, v3)] Title: Assessing the large-scale angular clustering of UNIONS Lyman Break Galaxies via cross-correlations Authors: Constantin Payerne , Christophe Yèche , William d'Assignies Doumerg , Hendrik Hildebrandt , Martin Kilbinger , Calum Murray , Thomas de Boer , Kenneth C. Chambers , Scott Chapman , Michael J. Hudson , Alan W. McConnachie View PDF HTML (experimental) Abstract: Lyman-break galaxies (LBGs), selected via the strong spectral break blueward of the Lyman limit, are powerful tracers of large-scale structure at redshifts $z>2$. In this work, we assess the feasibility of using LBGs selected from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS) multi-band photometric catalog as cosmological probes of the high-redshift Universe using two-point statistics. We demonstrate that spatially varying imaging systematics, driven by variations in PSF depth, seeing across the UNIONS footprint, limit robust measurements of the LBG auto-angular power spectrum on large scales, even after correcting the LBG field with linear or non-linear mitigation techniques. This study shows that clustering analyses of faint galaxy samples close to survey depth are challenging. We therefore turn to cross-correlation measurements with external tracers, in particular the \textit{Planck} CMB lensing convergence and quasars from DESI DR1 and \textit{Quaia}, which are less sensitive to the angular imaging systematics. Using both data and mock catalogues, we demonstrate that the LBG--CMB lensing cross-power spectrum can be measured more robustly than the auto-spectrum, with an amplitude consistent with theoretical predictions. Residual systematics primarily manifest as excess variance at large angular scales, without introducing a significant bias in the recovered signal. Taken together, these results establish UNIONS-selected LBGs as reliable tracers for cross-correlation cosmology at $z\sim 2.5$, and highlight cross-correlation techniques as a powerful and robust avenue for extracting cosmological information from photometric high-redshift galaxy samples in the presence of complex imaging systematics. Comments: 20 pages, 19 figures, to be submitted to The Open Journal of Astrophysics Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO) Cite as: arXiv:2607.09943 [astro-ph.CO] (or arXiv:2607.09943v3 [astro-ph.CO] for this version) https://doi.org/10.48550/arXiv.2607.09943 Focus to learn more arXiv-issued DOI via DataCite Submission history From: Constantin Payerne Mr [ view email ] [v1] Fri, 10 Jul 2026 19:49:34 UTC (3,822 KB) [v2] Wed, 15 Jul 2026 12:28:21 UTC (3,824 KB) [v3] Tue, 25 Aug 2026 09:13:18 UTC (3,824 KB) Full-text links: Access Paper: View PDF HTML (experimental) TeX Source view license Current browse context: astro-ph.CO < prev | next > new | recent | 2026-07 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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