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arXiv 2008.12439astro-ph.COastro-ph.HE
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用Pantheon样品和高红移类星体测试宇宙各向异性

Testing cosmic anisotropy with Pantheon sample and quasars at high redshifts

J. P. Hu, Y. Y. Wang, F. Y. Wang

备注：
16 pages, 8 figure2, 2 tables, accepted for publication in A&A
发表信息：
A&A 643, A93 (2020)
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摘要：

本文利用半球比较（HC）方法和偶极子拟合（DF）方法，研究了由Pantheon样品和类星体组成的SN-Q样品的宇宙各向异性。与Pantheon样本相比，新样本具有更大的红移范围，更均匀的分布和更大的样本量。对于HC方法，我们发现在（$l$，$b$）= $({316.08^{\circ}}^{+27.41}_{-129.48}$，${4.53^{\circ}}^{+26.29}_{-64.06})$方向上的最大各向异性能级为$AL_{max}=0.142\pm0.026$.各向异性的大小是$A$ =（$-$ 8.46 $^{+4.34}_{-5.51}$）$\times$ $10^{-4}$，而对于DF方法得到的类星体样本，相应的优选方向指向$(l$，$b)$ =（$29.31^{\circ}$ $^{+30.59}_{-30.54}$，$71.40^{\circ}$ $^{+9.79}_{-9.72}$）。SN和类星体的组合样本与各向同性假设一致。数据集的分布可能会影响偶极子结果的首选方向。结果是弱依赖于红移层析分析的红移。在SN-Q样品中没有宇宙各向异性的证据。虽然从类星体样品中得到的一些结果与标准宇宙学模型不一致，但我们仍然没有在SN-Q样品中发现任何明显的宇宙各向异性证据。

英文摘要：

In this paper, we investigate the cosmic anisotropy from the SN-Q sample, consisting of the Pantheon sample and quasars, by employing the hemisphere comparison (HC) method and the dipole fitting (DF) method. Compared to the Pantheon sample, the new sample has a larger redshift range, a more homogeneous distribution, and a larger sample size. For the HC method, we find that the maximum anisotropy level is $AL_{max}=0.142\pm0.026$ in the direction ($l$, $b$) = $({316.08^{\circ}}^{+27.41}_{-129.48}$, ${4.53^{\circ}}^{+26.29}_{-64.06})$. The magnitude of anisotropy is $A$ = ($-$8.46 $^{+4.34}_{-5.51}$)$\times$$10^{-4}$ and the corresponding preferred direction points toward $(l$, $b)$ = ($29.31^{\circ}$$^{+30.59}_{-30.54}$, $71.40^{\circ}$$^{+9.79}_{-9.72}$) for the quasar sample from the DF method. The combined SN and quasar sample is consistent with the isotropy hypothesis. The distribution of the dataset might impact the preferred direction from the dipole results. The result is weakly dependent on the redshift from the redshift tomography analysis. There is no evidence of cosmic anisotropy in the SN-Q sample. Though some results obtained from the quasar sample are not consistent with the standard cosmological model, we still do not find any distinct evidence of cosmic anisotropy in the SN-Q sample.

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