Quantifying the Impact of the Large Magellanic Cloud on the Structure of the Milky Way’s Dark Matter Halo Using Basis Function Expansions
Quantifying the Impact of the Large Magellanic Cloud on the Structure of the Milky Way’s Dark Matter Halo Using Basis Function Expansions
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DOI：
10.3847/1538-4357/ac0b44
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
N. Garavito-Camargo;G. Besla;C. Laporte;A. Price-Whelan;E. Cunningham;K. Johnston;M. Weinberg;F. Gómez
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文献类型：
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作者：
N. Garavito-Camargo;G. Besla;C. Laporte;A. Price-Whelan;E. Cunningham;K. Johnston;M. Weinberg;F. Gómez
整个银河系（MW）的不平衡的迹象突出了需要紧凑，灵活，非参数描述的相空间分布的星系。我们提出了一个新的表示目前的暗物质（DM）的分布和潜力来自N体模拟的MW和大麦哲伦云（LMC）系统使用基函数展开（BFE）。我们采用的方法，以最大限度地提高物理信号的表示。结果表明，对108个DM粒子的模拟可以用236（2067）个系数来描述，这108个DM粒子代表了MW（MW+LMC）畸变系统。我们发现，LMC诱导不对称扰动（奇数l，m）的MW的晕，这是不一致的扁，长，或三轴晕。此外，高阶偶模（l，m > 2）的能量与宇宙学模拟中发现的平均三轴晕相似。因此，必须考虑MW的光环对LMC的响应，以恢复其组装历史的印记。LMC导致外晕（>30 kpc）从盘质心（COM）移动了15-25 kpc，在BFE和晕星的径向速度中表现为偶极子。在30 kpc以内，无论LMC的质量如何，晕示踪物都将围绕MW盘的COM轨道运行。大麦哲伦星系的晕也被扭曲的MW潮汐，我们讨论了其质量损失的影响和随后对当前麦哲伦卫星的影响。
Indications of disequilibrium throughout the Milky Way (MW) highlight the need for compact, flexible, non-parametric descriptions of phase–space distributions of galaxies. We present a new representation of the current dark matter (DM) distribution and potential derived from N-body simulations of the MW and Large Magellanic Cloud (LMC) system using basis function expansions (BFEs). We incorporate methods to maximize the physical signal in the representation. As a result, the simulations of 108 DM particles representing the distorted MW(MW+LMC) system can be described by ∼236(2067) coefficients. We find that the LMC induces asymmetric perturbations (odd l, m) to the MW’s halo, which are inconsistent with oblate, prolate, or triaxial halos. Furthermore, the energy in high order even modes (l, m > 2) is similar to average triaxial halos found in cosmological simulations. As such, the response of the MW’s halo to the LMC must be accounted for in order to recover the imprints of its assembly history. The LMC causes the outer halo (>30 kpc) to shift from the disk center of mass (COM) by ∼15–25 kpc at present day, manifesting as a dipole in the BFE and in the radial velocities of halo stars. The shift depends on the LMC’s infall mass, the distortion of the LMC’s halo and the MW halo response.Within 30 kpc, halo tracers are expected to orbit the COM of the MW’s disk, regardless of LMC infall mass. The LMC’s halo is also distorted by MW tides; we discuss the implications for its mass loss and the subsequent effects on current Magellanic satellites.