标题： 矮星系中的修改引力测试 显示英文标题

标题： Tests of Modified Gravity with Dwarf Galaxies

摘要： 在试图解释宇宙加速膨胀的修改引力理论中，低密度环境中的矮星系可能受到增强的作用力。标量-张量理论这一类理论，包括f(R)引力，预测了这种作用力增强（像银河系这样的大质量星系可以通过一种屏蔽机制来避免这种“第五种”力对星系内部的影响）。我们研究了在引力作用下运动的晚型矮星系盘中对广义相对论的可观测偏差。第五种力作用于暗物质和HI气体盘，但不作用于恒星盘，因为主序星的自屏蔽效应保护了星系内部免受这种“第五种”力的影响。我们在这种盘星系中发现了四种明显的可观测效应：1. 恒星盘与HI盘的位移。2. 恒星盘沿外部力方向的扭曲。3. 与恒星盘相比，从HI气体测量的旋转曲线有所增强。4. 恒星盘旋转曲线的不对称性。我们估计，在落入的矮星系中，空间效应可达1千秒差距，旋转速度效应约为10公里/秒。这些偏差是可以测量的：我们预计，通过对附近矮星系样本进行仔细分析，可以将天体物理对引力理论的约束提高三个数量级，甚至将太阳系的约束提高一个数量级。因此，可以利用低红移星系对Hui等人（2009）和Jain（2011）所提出的引力测试方法进行有效的检验，尽管在理解可能的天体物理效应带来的复杂性时必须谨慎。 显示英文摘要

摘要： In modified gravity theories that seek to explain cosmic acceleration, dwarf galaxies in low density environments can be subject to enhanced forces. The class of scalar-tensor theories, which includes f(R) gravity, predict such a force enhancement (massive galaxies like the Milky Way can evade it through a screening mechanism that protects the interior of the galaxy from this "fifth" force). We study observable deviations from GR in the disks of late-type dwarf galaxies moving under gravity. The fifth-force acts on the dark matter and HI gas disk, but not on the stellar disk owing to the self-screening of main sequence stars. We find four distinct observable effects in such disk galaxies: 1. A displacement of the stellar disk from the HI disk. 2. Warping of the stellar disk along the direction of the external force. 3. Enhancement of the rotation curve measured from the HI gas compared to that of the stellar disk. 4. Asymmetry in the rotation curve of the stellar disk. We estimate that the spatial effects can be up to 1 kpc and the rotation velocity effects about 10 km/s in infalling dwarf galaxies. Such deviations are measurable: we expect that with a careful analysis of a sample of nearby dwarf galaxies one can improve astrophysical constraints on gravity theories by over three orders of magnitude, and even solar system constraints by one order of magnitude. Thus effective tests of gravity along the lines suggested by Hui et al (2009) and Jain (2011) can be carried out with low-redshift galaxies, though care must be exercised in understanding possible complications from astrophysical effects.