论文标题

使用3D和2D分析在星系自旋方向上分析大规模不对称

Using 3D and 2D analysis for analyzing large-scale asymmetry in galaxy spin directions

论文作者

Shamir, Lior

论文摘要

星系自旋的性质尚不完全清楚。 IYE等人(2021)将3D分析应用于过去用于光度分析的明亮SDSS星系数据集。他们表明,螺旋星系的自旋方向的分布是随机的,提供了一个低统计显着性为0.29 $σ$的偶极子轴。但是,为了显示随机分布,做出了两个决定,每个决定都可以导致随机分布,而不管星系的自旋方向的实际分布如何。第一个决定是将数据集任意限制为z $ <$ 0.1,这是一个红移范围,在该范围内,以前的文献已经表明了预期的随机分布。更重要的是,虽然3D分析需要每个星系进行红移,但分析是通过光度红移进行的。如果存在不对称性,则预期其信号的数量级弱于显影红移的误差,因此预期在这些条件下的较低统计信号。当使用完全相同的数据而不限制为$ z_ {phot} <0.1 $,并且不使用光度红移时,该数据集中的旋转方向的分布显示出$>2σ$的统计信号。用于复制分析的代码和数据已公开可用。这些结果与SDS,PAN-STARRS,HST和DESI传统调查的其他实验一致。本文还研究了其他先前的研究,这些研究显示了星系自旋方向的随机分布。尽管需要进一步的研究,但目前的证据表明,不能排除顺时针和逆时针星系数量之间的大规模不对称性。

The nature of galaxy spin is still not fully known. Iye et al (2021) applied a 3D analysis to a dataset of bright SDSS galaxies that was used in the past for photometric analysis. They showed that the distribution of spin directions of spiral galaxies is random, providing a dipole axis with low statistical significance of 0.29$σ$. However, to show random distribution, two decisions were made, each can lead to random distribution regardless of the real distribution of the spin direction of galaxies. The first decision was to limit the dataset arbitrarily to z$<$0.1, which is a redshift range in which previous literature already showed that random distribution is expected. More importantly, while the 3D analysis requires the redshift of each galaxy, the analysis was done with the photometric redshift. If the asymmetry existed, its signal is expected to be an order of magnitude weaker than the error of the photometric redshift, and therefore the low statistical signal under these conditions is expected. When using the exact same data without limiting to $z_{phot}<0.1$ and without using the photometric redshift, the distribution of the spin directions in that dataset shows a statistical signal of $>2σ$. Code and data for reproducing the analysis are publicly available. These results are in agreement with other experiments with SDSS, Pan-STARRS, HST, and the DESI Legacy Survey. The paper also examines other previous studies that showed random distribution in galaxy spin directions. While further research will be required, the current evidence suggest that large-scale asymmetry between the number of clockwise and counterclockwise galaxies cannot be ruled out.

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