AI 中文总结
研究通过两点统计评估UNIONS中LBGs作为高红移宇宙探测器的可行性，因成像系统误差大尺度LBG自角功率谱测量受限，转而采用与外部探测器交叉相关测量，结果表明该方法更稳健，确立LBGs为可靠追踪器，突出交叉相关技术优势。
AI 中文摘要
莱曼断点星系（LBGs）是红移$z>2$时大尺度结构的有力追踪器。本文利用两点统计评估从紫外近红外光学北方巡天（UNIONS）多波段测光目录中选取的LBGs作为高红移宇宙宇宙学探测器的可行性。结果表明，PSF深度和视场变化导致的空间变化成像系统误差限制了大尺度上LBG自角功率谱的可靠测量。因此转向与外部追踪器的交叉相关测量，如普朗克CMB透镜会聚和DESI DR1及Quaia的类星体，其对角度成像系统误差不太敏感。利用数据和模拟目录证明，LBG - CMB透镜交叉功率谱比自谱测量更稳健，幅度与理论预测一致。这些结果确立了UNIONS选择的LBGs作为$z\sim2.5$交叉相关宇宙学的可靠追踪器，并突出了交叉相关技术在存在复杂成像系统误差时从高红移测光星系样本中提取宇宙学信息的强大且稳健的途径。
英文摘要
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.
Comments20 pages, 19 figures, to be submitted to The Open Journal of Astrophysics
