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arXiv 2502.04449astro-ph.CO
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KiDS-1000:利用层析弱引力透镜探测纯冷暗物质功率谱的偏差

KiDS-1000: Detection of deviations from a purely cold dark matter power spectrum with tomographic weak gravitational lensing

Patrick Simon, Lucas Porth, Pierre Burger, Konrad Kuijken

AI总结:

本研究利用KiDS巡天数据重建三维功率谱,发现其与纯冷暗物质ΛCDM模型存在偏差,不同红移区间结构增长特征不一致,为宇宙学模型验证和系统误差分析提供了新观测依据。

摘要:

非线性结构增长的模型不确定性限制了当前宇宙学参数的探测能力。为更深入地揭示非线性尺度的物理机制,我们仅依托背景宇宙学、源红移分布以及源的内禀对齐(IA)振幅(及其不确定性),从千度巡天(Kilo-Degree Survey, KiDS)的透镜数据中重建了精细分箱的三维功率谱。我们采用的Tikhonov正则化方法稳定了反投影过程,使得在独立红移区间内进行贝叶斯重建成为可能。在详细介绍算法并利用模拟数据完成性能测试后,我们给出了功率谱相对于仅包含冷暗物质结构增长的ΛCDM参考谱的相对偏差结果。对z≲1的全区间取平均时,与Planck卫星结果一致的参考模型需要在k=0.05–10 h Mpc⁻¹的非线性尺度上存在高达20%–30%的显著抑制,才能匹配KiDS-1000的观测结果(68%置信区间,CI)。相反,采用S₈≈0.73的更低值的参考模型无需引入抑制效应,即可在20%的容差范围内匹配KiDS-1000的功率谱。然而,当将数据拆分为三个红移区间分析时,无论采用何种参考模型,我们仅在z≈0.4–0.13区间探测到结构增长,在z≈0.7–0.4区间未探测到结构增长。这可能表明KiDS-1000数据中存在虚假的系统误差、内禀对齐(IA)模型存在偏差,或者暗示存在一种结构增长延迟的非标准宇宙学模型。在不久的将来,利用我们的算法分析第四阶段(Stage IV)巡天数据,有望实现精度显著提升的功率谱重建。

英文摘要:

Model uncertainties in the non-linear structure growth limit current probes of cosmological parameters. To shed more light on the physics of non-linear scales, we reconstructed the finely binned three-dimensional power-spectrum from lensing data of the Kilo-Degree Survey (KiDS), relying solely on the background cosmology, the source redshift distributions, and the intrinsic alignment (IA) amplitude of sources (and their uncertainties). The adopted Tikhonov regularisation stabilises the deprojection, enabling a Bayesian reconstruction in separate $z$-bins. Following a detailed description of the algorithm and performance tests with mock data, we present our results for the power spectrum as relative deviations from a $Λ\rm CDM$ reference spectrum that includes only structure growth by cold dark matter. Averaged over the full range $z\lesssim1$, a \emph{Planck}-consistent reference then requires a significant suppression on non-linear scales, $k=0.05$--$10\,h\,\rm Mpc^{-1}$, of up to $20\%$--$30\%$ to match KiDS-1000 ($68\%$ credible interval, CI). Conversely, a reference with a lower $S_8\approx0.73$ avoids suppression and matches the KiDS-1000 spectrum within a $20\%$ tolerance. When resolved into three $z$-bins, however, and regardless of the reference, we detect structure growth only in the range $z\approx0.4$--$0.13$, but not in the range $z\approx0.7$--$0.4$. This could indicate spurious systematic errors in KiDS-1000, inaccuracies in the intrinsic alignment (IA) model, or potentially a non-standard cosmological model with delayed structure growth. In the near future, analysing data from Stage IV surveys with our algorithm promises a substantially more precise reconstruction of the power spectrum.

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