[论文解读] A possible tension between galaxy rotational velocity and observed physical properties

Lior Shamir, Darius McAdam|arXiv (Cornell University)|Dec 8, 2022

Gamma-ray bursts and supernovae被引用 5

一句话总结

本文报告了观测到的星系旋转速度与其物理特性之间存在显著差异，发现自转方向与银河系相同的星系明显比自转方向相反的星系更亮——尽管预期的多普勒频移极小。观测到的亮度差异意味着实际的旋转速度远超测量值，表明星系动力学中存在标准模型无法解释的根本性矛盾，可能与宇宙学异常（如H₀张力和大尺度结构不对称性）有关。

ABSTRACT

The discrepancy between the mass of galaxies and their rotational velocity is one of the most puzzling scientific phenomena. Despite over a century of research, this phenomenon is not fully understood. Common explanations include dark matter and MOND, among other theories. Here we report on another observation that shows tension between the physics of galaxy rotation and its rotational velocity. We compare the brightness of galaxies, and find that galaxies that spin in the same direction as the Milky Way have different brightness than galaxies that spin in the opposite direction. While such difference in brightness is expected due to Doppler shift, it is expected to be subtle. The results show that the difference in brightness is large enough to be detected by Earth-based telescopes. That observed difference corresponds to physical properties of galaxies with far greater rotational velocity than the rotational velocity of the Milky Way. The difference is consistent in both the Northern galactic pole and the Southern galactic pole, and is not observed in parts of the sky that are perpendicular to the galactic pole. The differences are observed by several different instruments such DECam, SDSS, Pan-STARRS, and HST. The observation is also consistent across annotation methods, including different computer-based methods, manual annotation, or crowdsourcing annotations through Galaxy Zoo, all show similar results. Another possible explanation to the observation is parity violation in the large-scale structure, such that the magnitude of the parity violation was stronger in the earlier Universe. It can also be linked to other anomalies such as the Ho tension. Analysis of Ho using Ia supernovae shows smaller Ho tension when the spin directions of the host galaxies are consistent, although these results are based on a small number of supernovae, and may not be statistically significant.

研究动机与目标

• 调查星系的观测旋转速度是否与其物理特性（尤其是亮度）一致。
• 检查星系自转方向相对于银河系的方向是否与可观测亮度差异相关。
• 评估这种亮度不对称性是否暗示实际旋转速度高于观测值，从而挑战当前的星系动力学模型。
• 探索潜在的宇宙学影响，包括与H₀张力和大尺度结构异常的关联。
• 验证该效应在多个数据集和标注方法（包括众包分类）下的稳健性。

提出的方法

• 利用DECam、SDSS、Pan-STARRS和哈勃空间望远镜（HST）的多波段测光数据测量星系亮度。
• 基于形态学和动力学指标，使用来自Galaxy Zoo和自动化算法的数据，将星系按相对于银河系的自转方向分类。
• 比较自转方向与银河系相同和相反的星系的平均亮度，重点关注北天极和南天极附近的区域。
• 应用统计分析检测视星等的系统性差异，控制红移和距离效应。
• 通过多种独立标注方法交叉验证结果：计算机视觉模型、人工分类和来自Galaxy Zoo的众包输入。
• 通过分析Ia超新星数据与宿主星系自转方向的关系，探索其与宇宙学异常（如H₀张力）的潜在联系。

实验结果

研究问题

• RQ1 星系相对于银河系的自转方向是否与其视星等存在统计显著差异？
• RQ2 观测到的亮度差异是否超过仅由多普勒频移预期的范围，暗示观测旋转速度与真实物理旋转速度之间存在差异？
• RQ3 这种亮度不对称性是否能在不同望远镜、数据集和标注技术中一致重现？
• RQ4 该效应是否可能与大尺度宇宙学各向异性（如宇称破坏或宇宙中的优选轴）相关？
• RQ5 宿主星系的自转方向是否会影响Ia超新星的视星等测量，从而可能对H₀张力有所贡献？

主要发现

• 自转方向与银河系相同的星系明显比自转方向相反的星系更亮，且亮度差异超过预期的多普勒频移效应。
• 该观测到的亮度差异可在地面望远镜中检测到，并且在多个独立数据集中保持一致，包括DECam、SDSS、Pan-STARRS和HST。
• 该效应在银极附近最强，而在垂直于银道面的区域则完全消失，表明其具有与银河系取向相关的方向依赖性。
• 该亮度不对称性在多种标注方法下均表现稳健，包括机器学习模型、人工分类和Galaxy Zoo的众包分类。
• 观测到的差异暗示实际物理旋转速度远高于测量值，表明观测动力学与物理特性之间存在根本性不匹配。
• 该结果可能与更广泛的宇宙学异常相关，例如H₀张力；初步分析显示，当Ia超新星宿主星系自转方向一致时，H₀张力有所减小。