Argelander Institut für Astronomie, Auf dem Hügel 71, Bonn D-53121, Germany.
Department of Physics and Astronomy, University of California, Irvine, California 92697, USA.
Phys Rev Lett. 2018 Jun 29;120(26):261301. doi: 10.1103/PhysRevLett.120.261301.
The radial acceleration measured in bright galaxies tightly correlates with that generated by the observed distribution of baryons, a phenomenon known as the radial acceleration relation (RAR). Dwarf spheroidal satellite galaxies have been recently found to depart from the extrapolation of the RAR measured for more massive objects but with a substantially larger scatter. If confirmed by new data, this result provides a powerful test of the theory of gravity at low accelerations that requires robust theoretical predictions. By using high-resolution hydrodynamical simulations, we show that, within the standard model of cosmology (ΛCDM), satellite galaxies are expected to follow the same RAR as brighter systems but with a much larger scatter which does not correlate with the physical properties of the galaxies. In the simulations, the RAR evolves mildly with redshift. Moreover, the acceleration due to the gravitational field of the host has no effect on the RAR. This is in contrast with the external field effect in modified Newtonian dynamics (MOND) which causes galaxies in strong external fields to deviate from the RAR. This difference between ΛCDM and MOND offers a possible way to discriminate between them.
在亮星系中测量到的径向加速度与观测到的重子分布产生的加速度密切相关，这种现象被称为径向加速度关系（RAR）。最近发现，矮椭球星状伴星系偏离了对更大质量物体测量的 RAR 外推，但具有更大的离散度。如果这一结果被新数据所证实，这将为低加速度下的引力理论提供一个强有力的检验，这需要强有力的理论预测。通过使用高分辨率的流体动力学模拟，我们表明，在标准宇宙学模型（ΛCDM）中，卫星星系预计将遵循与更亮系统相同的 RAR，但离散度要大得多，且与星系的物理性质无关。在模拟中，RAR 随红移的演化很轻微。此外，宿主星系引力场的加速度对 RAR 没有影响。这与修正牛顿动力学（MOND）中的外部场效应形成了对比，后者导致处于强外部场中的星系偏离 RAR。ΛCDM 和 MOND 之间的这种差异为它们之间的区分提供了一种可能的方法。
