论文标题
当地小组的质量：可能只不过是其部分的总和
The Local Group's mass: probably no more than the sum of its parts
论文作者
论文摘要
本地组的总质量（LG）及其主要成分的质量，银河系和M31，是几个宇宙学问题的重要锚点。近年来，独立测量始终产生接近$ 10^{12} \ mathrm {m_ \ odot} $的MW，$ 1-2 \ times 10^{12} \ times 10^{12} \ mathrm {m_ \ odot} $，而M31的概述则来自$ 5的$ 5，以$ 5的参数为$ ginalemative yourder of airdiend $ niver of airdiend $ nitive of the the the the the tim the tim tive tim a tim night'tim tim tim tim a tim night' \ times 10^{12} \ mathrm {m_ \ odot} $。在这里，我们分析了极大的UCHUU模拟，以限制本地组及其两个最大成员的质量。首先，我们证明了选择LG类似物的重要性，其运动学以与LG相似的相互作用而占主导地位。采用观察到的分离和径向速度，我们获得了$ 75 _ { - 40}^{+65} $ kmms $^{ - 1} $的加权后部。通过高斯进程回归，我们推断总质量为$ 3.2^{+1.2} _ { - 0.9} \ times 10^{12} {12} \ Mathrm {M_ \ odot} $，显着低于计时参数预测。重要的是，我们表明，其余的不确定性不是植根于分析或观察性误差，而是源于运动学质量关系中不可还原的散布。我们进一步找到质量较小的光晕$ 0.9 _ { - 0.3}^{+0.6} \ times 10^{12} {12} \ Mathrm {m_ \ odot} $，以及更大的halo $ 2.3 _ { - 0.9}}}分别对MW和M31的质量进行独立测量。将MW的质量纳入额外的先验，使我们能够进一步限制所有测量结果，并确定MW很可能是两者的较低质量对象。
The total mass of the Local Group (LG) and the masses of its primary constituents, the Milky Way and M31, are important anchors for several cosmological questions. In recent years, independent measurements have consistently yielded halo masses close to $10^{12} \mathrm{M_\odot}$ for the MW, and $1-2 \times 10^{12} \mathrm{M_\odot}$ for M31, while estimates derived from the pair's kinematics via the `timing argument' have yielded a combined mass of around $5 \times 10^{12} \mathrm{M_\odot}$. Here, we analyse the extremely large Uchuu simulation to constrain the mass of the Local Group and its two most massive members. First, we demonstrate the importance of selecting LG analogues whose kinematics are dominated by mutual interactions to a similar extent as the LG. Adopting the observed separation and radial velocity, we obtain a weighted posterior of $75_{-40}^{+65}$ kms$^{-1}$ for the uncertain transverse velocity. Via Gaussian process regression, we infer a total mass of $3.2^{+1.2}_{-0.9} \times 10^{12} \mathrm{M_\odot}$, significantly below the timing argument prediction. Importantly, we show that the remaining uncertainty is not rooted in the analysis or observational errors, but in the irreducible scatter in the kinematics-mass relation. We further find a mass for the less massive halo of $0.9_{-0.3}^{+0.6} \times 10^{12} \mathrm{M_\odot}$ and for the more massive halo of $2.3_{-0.9}^{+1.0} \times 10^{12} \mathrm{M_\odot}$, consistent with independent measurements of the masses of MW and M31, respectively. Incorporating the mass of the MW as an additional prior allows us to further constrain all measurements and determine that the MW is very likely to be the lower mass object of the two.
