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On testing CDM and geometry-driven Milky Way rotation curve models with Gaia DR2
Monthly Notices of the Royal Astronomical Society ( IF 4.8 ) Pub Date : 2020-06-02 , DOI: 10.1093/mnras/staa1511
Mariateresa Crosta 1 , Marco Giammaria 1, 2 , Mario G Lattanzi 1 , Eloisa Poggio 1
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Flat rotation curves in disk galaxies represent the main evidence for large amounts of surrounding dark matter. Despite of the difficulty in identifying the dark matter contribution to the total mass density in our Galaxy, stellar kinematics, as tracer of gravitational potential, is the most reliable observable for gauging different matter components. This work tests the flatness of the MW rotation curve with a simple general relativistic model suitable to represent the geometry of a disk as a stationary axisymmetric dust metric at a sufficiently large distance from a central body. Circular velocities of unprecedented accuracy were derived from the Gaia DR2 data for a carefully selected sample of disk stars. We then fit these velocities to both the classical, i.e. including a dark matter halo, rotation curve model and a relativistic analogue, as derived form the solution of Einstein's equation. The GR-compliant MW rotational curve model results statistically indistinguishable from its state-of-the-art DM analogue. This supports our ansatz that a stationary and axisymmetric galaxy-scale metric could "fill the gap" in a baryons-only Milky Way, suggestive of star orbits dragged along the background geometry. We confirmed that geometry is a manifestation of gravity according to the Einstein theory, in particular the weak gravitational effect due to the off-diagonal term of the metric could mimic for a "DM-like" effect in the observed flatness of the MW rotation curve. In the context of Local Cosmology, our findings are suggestive of a Galaxy phase-space as the exterior gravitational field of a Kerr-like source (inner rotating bulge) without the need of extra-matter.

中文翻译:

使用 Gaia DR2 测试 CDM 和几何驱动的银河系旋转曲线模型

盘状星系中平坦的旋转曲线代表了大量周围暗物质的主要证据。尽管很难确定暗物质对我们银河系总质量密度的贡献,但恒星运动学作为引力势的示踪剂,是测量不同物质成分的最可靠的观测指标。这项工作使用一个简单的广义相对论模型来测试 MW 旋转曲线的平坦度,该模型适合将圆盘的几何形状表示为距中心体足够远的静止轴对称尘埃度量。从盖亚 DR2 数据中为精心挑选的盘状星样本得出了前所未有的精度的圆速度。然后我们将这些速度拟合到经典的,即包括暗物质晕,旋转曲线模型和相对论模拟,作为从爱因斯坦方程的解导出的。符合 GR 的 MW 旋转曲线模型结果与其最先进的 DM 模拟在统计上无法区分。这支持了我们的观点,即静止且轴对称的星系尺度度量可以“填补”只有重子的银河系中的空白,暗示恒星轨道沿着背景几何形状拖动。根据爱因斯坦理论,我们证实几何是引力的一种表现,特别是由于度量的非对角线项而产生的弱引力效应可以模拟观察到的 MW 旋转曲线平坦度中的“类 DM”效应. 在局域宇宙学的背景下,我们的发现表明星系相空间是类克尔源(内部旋转凸起)的外部引力场,不需要额外物质。
更新日期:2020-06-02
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