{"title":"在不断膨胀的ΛCDM宇宙中权衡银河系和仙女座","authors":"David Benisty","doi":"10.1051/0004-6361/202449884","DOIUrl":null,"url":null,"abstract":"The dynamics of the Local Group (LG), especially the contribution of the Milky Way (MW) and Andromeda (M 31) galaxies, is sensitive to the presence of dark energy. This work analyzes the evolution of the LG by considering it as a two-body problem in a homogeneous and isotropic expanding spacetime in a full Λcold dark matter (ΛCDM) background. Using the timing argument (TA), which links LG dynamics to LG mass, we find that the full ΛCDM background predicts a ∼10% lower mass for the LG; whereas Λ alone predicts a ∼10% higher mass. The TA mass is modified by (i) simulations and (ii) the effect of the Large Magellanic Cloud (LMC) to alleviate the poorly constrained internal mass distributions of M 31 and the MW, their time evolution, and the unknown distribution of dark matter between them. First, using IllustrisTNG simulations, we accounted for the effects of two extended halos and their environment (rather than point particles) and predicted their mass (3.89 ± 0.62)×10<sup>12<sup/> <i>M<i/><sub>⊙<sub/>. Second, the LMC effectively changes the separation and velocities of M 31 towards the MW and reduces the predicted mass to (2.33 ± 0.72)×10<sup>12<sup/> <i>M<i/><sub>⊙<sub/>. Despite the uncertainties around dark matter between these galaxies, the overall estimated mass is compatible with the mere sum of the MW and M 31 masses. The total mass of the TA is compatible with other estimates, such as the Hubble flow and the Virial Theorem with other dwarf galaxies. The combined result shows, for the first time, that a lower mass estimate can be obtained from the TA, with a consistent embedding and other systematic effects, and without an additional dark matter halo around the galaxies.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":5.4000,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Weighing Milky Way and Andromeda in an expanding ΛCDM Universe\",\"authors\":\"David Benisty\",\"doi\":\"10.1051/0004-6361/202449884\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"The dynamics of the Local Group (LG), especially the contribution of the Milky Way (MW) and Andromeda (M 31) galaxies, is sensitive to the presence of dark energy. This work analyzes the evolution of the LG by considering it as a two-body problem in a homogeneous and isotropic expanding spacetime in a full Λcold dark matter (ΛCDM) background. Using the timing argument (TA), which links LG dynamics to LG mass, we find that the full ΛCDM background predicts a ∼10% lower mass for the LG; whereas Λ alone predicts a ∼10% higher mass. The TA mass is modified by (i) simulations and (ii) the effect of the Large Magellanic Cloud (LMC) to alleviate the poorly constrained internal mass distributions of M 31 and the MW, their time evolution, and the unknown distribution of dark matter between them. First, using IllustrisTNG simulations, we accounted for the effects of two extended halos and their environment (rather than point particles) and predicted their mass (3.89 ± 0.62)×10<sup>12<sup/> <i>M<i/><sub>⊙<sub/>. Second, the LMC effectively changes the separation and velocities of M 31 towards the MW and reduces the predicted mass to (2.33 ± 0.72)×10<sup>12<sup/> <i>M<i/><sub>⊙<sub/>. Despite the uncertainties around dark matter between these galaxies, the overall estimated mass is compatible with the mere sum of the MW and M 31 masses. The total mass of the TA is compatible with other estimates, such as the Hubble flow and the Virial Theorem with other dwarf galaxies. 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引用次数: 0
摘要
本星系群(LG)的动力学,尤其是银河系(MW)和仙女座星系(M 31)的动力学,对暗能量的存在非常敏感。这项工作把局域群看作是一个在完全Λ冷暗物质(ΛCDM)背景下的均质和各向同性膨胀时空中的双体问题,从而分析了局域群的演化。利用将LG动力学与LG质量联系起来的时序论证(TA),我们发现完整的ΛCDM背景预言的LG质量要低∼10%;而单独的Λ预言的LG质量要高∼10%。TA的质量是通过(i)模拟和(ii)大麦哲伦云(LMC)的影响来修正的,以减轻对M 31和MW内部质量分布、它们的时间演化以及它们之间未知的暗物质分布的约束。首先,利用IllustrisTNG模拟,我们考虑了两个扩展光环及其环境(而不是点粒子)的影响,并预测了它们的质量(3.89±0.62)×1012 M⊙。其次,LMC有效地改变了M 31向MW的分离和速度,并将预测质量降低到(2.33±0.72)×1012 M⊙。尽管这些星系之间的暗物质存在不确定性,但总体估计质量与MW和M 31的质量之和是一致的。TA的总质量与其他估计值相吻合,比如哈勃流和其他矮星系的室温定理。综合结果首次表明,在嵌入和其他系统效应保持一致的情况下,并且在星系周围没有额外暗物质晕的情况下,可以从 TA 得到较低的质量估计值。
Weighing Milky Way and Andromeda in an expanding ΛCDM Universe
The dynamics of the Local Group (LG), especially the contribution of the Milky Way (MW) and Andromeda (M 31) galaxies, is sensitive to the presence of dark energy. This work analyzes the evolution of the LG by considering it as a two-body problem in a homogeneous and isotropic expanding spacetime in a full Λcold dark matter (ΛCDM) background. Using the timing argument (TA), which links LG dynamics to LG mass, we find that the full ΛCDM background predicts a ∼10% lower mass for the LG; whereas Λ alone predicts a ∼10% higher mass. The TA mass is modified by (i) simulations and (ii) the effect of the Large Magellanic Cloud (LMC) to alleviate the poorly constrained internal mass distributions of M 31 and the MW, their time evolution, and the unknown distribution of dark matter between them. First, using IllustrisTNG simulations, we accounted for the effects of two extended halos and their environment (rather than point particles) and predicted their mass (3.89 ± 0.62)×1012M⊙. Second, the LMC effectively changes the separation and velocities of M 31 towards the MW and reduces the predicted mass to (2.33 ± 0.72)×1012M⊙. Despite the uncertainties around dark matter between these galaxies, the overall estimated mass is compatible with the mere sum of the MW and M 31 masses. The total mass of the TA is compatible with other estimates, such as the Hubble flow and the Virial Theorem with other dwarf galaxies. The combined result shows, for the first time, that a lower mass estimate can be obtained from the TA, with a consistent embedding and other systematic effects, and without an additional dark matter halo around the galaxies.
期刊介绍:
Astronomy & Astrophysics is an international Journal that publishes papers on all aspects of astronomy and astrophysics (theoretical, observational, and instrumental) independently of the techniques used to obtain the results.