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arXiv 2003.10420astro-ph.CO
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从本动局域宇宙内部进行宇宙学推断

Cosmological inference from within the peculiar local universe

Roya Mohayaee, Mohamed Rameez, Subir Sarkar

AI总结:

针对局域强相干整体流与 $\Lambda$CDM 预期不符的问题,本文利用 Dark Sky 模拟分析异常局域环境,发现其增强 JLA 超新星相关并显著影响宇宙学常数与 $S_8$ 推断。

摘要:

宇宙结构形成所导致的“本动”速度的存在,标志着真实宇宙与通常假定的 Friedmann-Lemaítre-Robertson-Walker 度规之间存在一个不一致之处;后者只容纳大尺度上平滑的 Hubble 膨胀。在标准 $\Lambda$CDM 模型框架中,Ia 型超新星数据通常会针对观测者和超新星宿主星系相对于宇宙静止参考系的本动速度进行“校正”,以便从其 Hubble 图中推断膨胀率加速的证据。然而,观测表明存在一个强而相干的局域整体流,并且该整体流向外持续到红移 $z \gtrsim 0.1$ 仍不衰减,这与 $\Lambda$CDM 的预期相反。通过查询 Dark Sky Hubble-volume N-body 模拟的晕目录,我们发现,一个处于类似我们局域宇宙这种异常环境中的观测者所看到的 JLA 目录中超新星之间的相关性,会比典型的或 Copernican 观测者所看到的强 2–8 倍。这解释了我们的发现:本动速度校正对从超新星数据推断出的宇宙学常数数值有很大影响。我们还证明,类似局域宇宙中的观测者通过比较密度场和速度场,会推断出一个向下有偏的聚类参数 $S_8$ 值。因此,对本动局域宇宙进行更真实的建模,对于正确解释宇宙学数据至关重要。

英文摘要:

The existence of 'peculiar' velocities due to the formation of cosmic structure marks a point of discord between the real Universe and the usually assumed Friedmann-Lemaítre-Robertson-Walker metric which accomodates only the smooth Hubble expansion on large scales. In the standard $Λ$CDM model framework, Type Ia supernovae data are routinely "corrected" for the peculiar velocities of both the observer and the supernova host galaxies relative to the cosmic rest frame, in order to infer evidence for acceleration of the expansion rate from their Hubble diagram. However observations indicate a strong, coherent local bulk flow that continues outward without decaying out to a redshift $z \gtrsim 0.1$, contrary to the $Λ$CDM expectation. By querying the halo catalogue of the Dark Sky Hubble-volume N-body simulation, we find that an observer placed in an unusual environment like our local Universe should see correlations between supernovae in the JLA catalogue that are 2-8 times stronger than seen by a typical or Copernican observer. This accounts for our finding that peculiar velocity corrections have a large impact on the value of the Cosmological Constant inferred from supernova data. We also demonstrate that local Universe-like observers will infer a downward biased value of the clustering parameter $S_8$ from comparing the density and velocity fields. More realistic modelling of the peculiar local Universe is thus essential for correctly interpreting cosmological data.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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