M31在167 kpc范围内由旋转曲线得到的质量分布
Mass Distribution of M31 from its Rotation Curve up to 167 kpc
- Peking University（北京大学）
- Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）
- University of Chinese Academy of Science（中国科学院大学）
- National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）
- Beijing Planetarium, Beijing Academy of Science and Technology（北京天文馆，北京市科学技术研究院）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
利用超过8500个示踪体约束M31在2-167 kpc的旋转曲线，在动力学平衡假设下测量其质量分布，并量化晕速度各向异性和暗物质轮廓选择带来的系统不确定性。
AI中文摘要：
仙女座星系（M31）的质量分布对于理解其暗物质含量、并合历史以及在本地群中的动力学作用至关重要。然而，对M31总质量的估计仍存在相当大的不确定性，部分原因在于大银心距处动力学约束有限。此外，M31最近的并合历史产生了丰富的潮汐子结构，并可能使其外晕偏离动力学平衡，从而使基于平衡态的质量估计复杂化。我们利用超过8500个具有视向速度的示踪体来约束M31在R=2--167 kpc范围内的旋转曲线（RC）。在盘面区域，我们使用金斯方程从干净的示踪体样本中推导出旋转曲线，并发现与之前的H I测量结果吻合良好。在晕区域，我们使用高斯混合模型来考虑潮汐子结构和银河系前景污染，并约束残余动力学热晕的运动学。假设该晕族可作为平衡态示踪体，我们推断出外旋转曲线，并在不同速度各向异性β和暗物质晕轮廓下约束M31的质量分布。NFW和Dekel--Zhao（DZ）模型在β=0.3--0.7时给出的总质量大致一致，范围为1.12(+0.11/-0.10)至1.63(+0.21/-0.17)x10^12太阳质量。相比之下，Einasto轮廓倾向于显著更低的质量，为0.41(+0.09/-0.06)至0.86(+0.21/-0.16)x10^12太阳质量，这表明质量估计对所采用的晕轮廓有显著依赖性，尽管在固定β下，Einasto解与基于M31卫星星系的独立质量估计相比，比NFW和DZ模型存在更大的张力。总体而言，我们的分析在动力学平衡假设下提供了M31质量分布的全面测量，同时量化了与晕速度各向异性和暗物质密度轮廓选择相关的系统不确定性。
英文摘要：
The mass distribution of the Andromeda galaxy (M31) is fundamental for understanding its dark matter content, assembly history, and dynamical role within the Local Group. However, estimates of M31's total mass remain quite uncertain, partly because of limited dynamical constraints at large galactocentric radii. Moreover, M31's recent merger history has produced abundant tidal substructures and may have left its outer halo out of dynamical equilibrium, complicating equilibrium-based mass estimates. We use over 8,500 tracers with line-of-sight velocities to constrain the rotation curve (RC) of M31 over R=2--167 kpc. In the disk, we derive the RC from a clean tracer sample using the Jeans equation and find good agreement with previous H I measurements. In the halo, we use Gaussian mixture modeling to account for tidal substructures and Galactic foreground contamination and constrain the kinematics of the residual dynamically hot halo. Assuming this halo population can be treated as an equilibrium tracer, we infer the outer RC and constrain M31's mass distribution for different velocity anisotropies beta and dark matter halo profiles. The NFW and Dekel--Zhao (DZ) models yield broadly consistent total masses ranging from 1.12(+0.11/-0.10) to 1.63(+0.21/-0.17)x10^12 Msun for beta=0.3--0.7. In contrast, the Einasto profile favors substantially lower masses of 0.41(+0.09/-0.06) to 0.86(+0.21/-0.16)x10^12 Msun, highlighting significant dependence on the adopted halo profile, although Einasto solutions are more in tension with independent mass estimates based on M31 satellite galaxies than the NFW and DZ models at fixed beta. Overall, our analysis provides a comprehensive measurement of M31's mass distribution under the assumption of dynamical equilibrium, while also quantifying the systematic uncertainties associated with halo velocity anisotropy and the choice of dark matter density profile.
