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arXiv 2409.02501astro-ph.CO
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巡天空间变异性对星系红移分布及Rubin Legacy Survey of Space and Time (LSST)宇宙学$3\ imes2$-点统计量的影响

Impact of survey spatial variability on galaxy redshift distributions and the cosmological $3\times2$-point statistics for the Rubin Legacy Survey of Space and Time (LSST)

Qianjun Hang, Benjamin Joachimi, Eric Charles, John Franklin Crenshaw, Patricia Larsen, Alex I. Malz, Sam Schmidt, Ziang Yan, Tianqing Zhang, the LSST Dark Ener… 展开作者

Qianjun Hang, Benjamin Joachimi, Eric Charles, John Franklin Crenshaw, Patricia Larsen, Alex I. Malz, Sam Schmidt, Ziang Yan, Tianqing Zhang, the LSST Dark Energy Science Collaboration

AI总结:

本研究评估LSST巡天空间非均匀性对星系红移分布及宇宙学$3\ imes2$点统计的影响,发现Y3/Y5深度变化导致bin属性变化达10-40%,需将非均匀性降至3%以下以恢复无偏宇宙学约束。

摘要:

我们研究了空间巡天非均匀性对Rubin天文台Legacy Survey of Space and Time (LSST)未来数据发布中星系红移分布的影响。具体而言,我们构建了一个受Rubin OpSim观测条件退化的模拟测光数据集,并使用模板拟合光度红移估计器BPZ和机器学习方法FlexZBoost估计样本的光度红移。我们选取Gold样本(定义为10年LSST数据的$i<25.3$),每年调整星等截止值,并将其划分为五个层析红移bin,用于弱引力透镜透镜和源样本。我们量化了1年(Y1)、3年(Y3)和5年(Y5)数据中,随着叠加$i$波段深度变化,每个层析bin中天体数量、平均红移和宽度的变化。特别是,由于LSST的滚动观测模式,Y3和Y5具有较大的非均匀性,因此提供了非均匀性影响的最坏情况。我们发现这些量通常随深度增加而增加,在极端深度值下变化可达$10-40\%$。以Y3为例,我们将可变深度效应传播到弱引力透镜$3\ imes2$pt分析中,并通过Fisher预测评估对宇宙学参数的影响。我们发现星系聚集对可变深度最为敏感,非均匀性需降至$3\%$以下才能恢复无偏的宇宙学约束。鉴于预期的LSST Y3噪声,对星系-剪切和剪切-剪切功率谱的影响很小。

英文摘要:

We investigate the impact of spatial survey non-uniformity on the galaxy redshift distributions for forthcoming data releases of the Rubin Observatory Legacy Survey of Space and Time (LSST). Specifically, we construct a mock photometry dataset degraded by the Rubin OpSim observing conditions, and estimate photometric redshifts of the sample using a template-fitting photo-$z$ estimator, BPZ, and a machine learning method, FlexZBoost. We select the Gold sample, defined as $i<25.3$ for 10 year LSST data, with an adjusted magnitude cut for each year and divide it into five tomographic redshift bins for the weak lensing lens and source samples. We quantify the change in the number of objects, mean redshift, and width of each tomographic bin as a function of the coadd $i$-band depth for 1-year (Y1), 3-year (Y3), and 5-year (Y5) data. In particular, Y3 and Y5 have large non-uniformity due to the rolling cadence of LSST, hence provide a worst-case scenario of the impact from non-uniformity. We find that these quantities typically increase with depth, and the variation can be $10-40\%$ at extreme depth values. Using Y3 as an example, we propagate the variable depth effect to the weak lensing $3\times2$pt analysis, and assess the impact on cosmological parameters via a Fisher forecast. We find that galaxy clustering is most susceptible to variable depth, and non-uniformity needs to be mitigated below $3\%$ to recover unbiased cosmological constraints. There is little impact on galaxy-shear and shear-shear power spectra, given the expected LSST Y3 noise.

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