来自GD-1流的星系加速表明存在倾斜的暗物质晕

Jacob Nibauer and Ana Bonaca
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引用次数: 0

摘要

冷暗物质晕预计是三轴的,并且通常相对于恒星盘倾斜。恒星流提供了银河系光晕形状的敏感示踪剂,尽管银河系潜力的模型通常局限于简单、对称的功能形式。在这里,我们沿着GD-1流测量银河系加速度场,使用流在相空间中的轨迹的直接微分。使用来自Gaia,斯隆数字巡天,LAMOST和DESI的流成员的完全数据驱动目录,我们在6D相位空间中映射流。我们将样条曲线拟合到流轨迹上,并推断出圆柱加速度分量,az = - 1.8±0.1,aϕ = 0.2±0.1 km s - 1 Myr−1 at (R, z, ϕ) = (11.9 kpc, 7.3 kpc, 171)。我们测量了1.4±0.1 × 1011 M⊙的14 kpc范围内的质量和z轴密度平坦度,两者都与先前的估计一致。然而,我们发现与轴对称加速度场有2σ偏差,这可以用轴比为1:0.75:0.70的三轴暗物质晕来解释。日晕的长轴与银道面上方太阳方向的18°倾斜是一致的。倾斜的大小和方向与高分辨率光晕调查中盖亚和赫克歇勒的恒星光晕测量结果一致。倾斜的三轴晕对基于轨道积分的银河系研究具有重要意义,并且可以通过从多个流中推导加速度约束来进一步验证。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Galactic Accelerations from the GD-1 Stream Suggest a Tilted Dark Matter Halo
Cold dark matter halos are expected to be triaxial and often tilted relative to the stellar disk. Stellar streams provide a sensitive tracer of the Milky Way’s halo shape though models for the Galactic potential are typically limited to simple, symmetric functional forms. Here, we measure the Galactic acceleration field along the GD-1 stream using a direct differentiation of the stream’s track in phase space. Using a fully data-driven catalog of stream members from Gaia, Sloan Digital Sky Survey, LAMOST, and DESI, we map the stream in 6D phase space. We fit splines to the stream track and infer cylindrical acceleration components , az = −1.8 ± 0.1, and aϕ = 0.2 ± 0.1 km s−1 Myr−1 at (R, z, ϕ) = (11.9 kpc, 7.3 kpc, 171 1). We measure mass enclosed within 14 kpc of 1.4 ± 0.1 × 1011 M⊙ and z-axis density flattening of , both consistent with previous estimates. However, we find a 2σ deviation from an axisymmetric acceleration field, which can be explained by a triaxial dark matter halo with axis ratios 1:0.75:0.70. The major axis of the halo is consistent with a tilt of 18° above the Galactic plane in the direction of the Sun. The magnitude and direction of the tilt are consistent with measurements of the stellar halo from Gaia and the Hectochelle in the Halo at High Resolution survey. A tilted triaxial halo has important consequences for orbit-integration-based studies of the Galaxy and can be further tested by deriving acceleration constraints from multiple streams.
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