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arXiv 1607.01800astro-ph.GAastro-ph.CO
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质量差-加速度关系的统计研究

A statistical investigation of the mass discrepancy-acceleration relation

Harry Desmond

摘要:

我们使用质量差-加速度关系(星系中总质量与可见质量之比与加速度之间的相关性; MDAR)来检验星系晕之间的联系。我们使用一组16个统计数据来分析MDAR,这些统计数据量化了它的四个最重要的特征:它的形状,它的散射,“特征加速度尺度”的存在,以及它的残差与其他星系属性的相关性。我们构建了一个经验框架的星系晕连接LCDM产生预测这些统计数据,从传统的相关性(晕丰度匹配; AM),并在需要时介绍更多。通过与实验数据的比较,我们发现:1)MDAR的近似形状很容易被AM模拟再现,并且没有证据表明暗物质变得可以忽略的加速度在数据中的分布比在AM模拟中的分布小; 2)即使在保守的假设下,AM也显著高估了关系中的分散及其在低加速度下的归一化,此外,平均而言,暗物质的位置过于靠近星系的中心; 3)MDAR提供了2 σ证据,证明星系大小和哈勃类型与晕质量或在固定恒星质量下的浓度之间存在正相关关系。我们的分析奠定了基础,自下而上的确定的星系晕连接的关系,如MDAR,提供具体的统计检验特定的星系形成模型,并带来了更清晰的焦点,相对证据符合星系运动学LCDM和修改重力的替代品。

英文摘要:

We use the mass discrepancy-acceleration relation (the correlation between the ratio of total-to-visible mass and acceleration in galaxies; MDAR) to test the galaxy-halo connection. We analyse the MDAR using a set of 16 statistics that quantify its four most important features: its shape, its scatter, the presence of a "characteristic acceleration scale," and the correlation of its residuals with other galaxy properties. We construct an empirical framework for the galaxy-halo connection in LCDM to generate predictions for these statistics, starting with conventional correlations (halo abundance matching; AM) and introducing more where required. Comparing to the SPARC data, we find that: 1) the approximate shape of the MDAR is readily reproduced by AM, and there is no evidence that the acceleration at which dark matter becomes negligible has less spread in the data than in AM mocks; 2) even under conservative assumptions, AM significantly overpredicts the scatter in the relation and its normalisation at low acceleration, and furthermore positions dark matter too close to galaxies' centres on average; 3) the MDAR affords 2 sigma evidence for an anticorrelation of galaxy size and Hubble type with halo mass or concentration at fixed stellar mass. Our analysis lays the groundwork for a bottom-up determination of the galaxy-halo connection from relations such as the MDAR, provides concrete statistical tests for specific galaxy formation models, and brings into sharper focus the relative evidence accorded by galaxy kinematics to LCDM and modified gravity alternatives.

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