论文标题
变色龙重力中的恒星溪流
Stellar Streams in Chameleon Gravity
论文作者
论文摘要
重力理论包含新的标量自由度通常需要筛选机制，以确保与太阳系测试一致。一种广泛研究的机制 - 变色龙 - 可能导致违反等价原理（EP），因为筛选和未经筛选的物体的下降不同。如果星星被筛选，但周围的暗物质不是，这会导致前进和尾流之间的不对称性。我们提供了对现实银河质量分布的这种效果幅度的分析估计。使用受限的N体密码，我们模拟了4个具有一系列质量和轨道的卫星，以及第五力量的各种强度以及银河系和卫星的筛选水平。可以根据模拟来计算，可以根据恒星数据来计算，恒星在前导和尾流中的累积数函数的比率是从卫星中计算的，并且可以提供直接测试。我们使用hu-sawicki重力的特定示例案例预测了大型中心距离的流的限制。具有100至200 kpc之间的启示性的流提供可实现的约束，在$ | f_ {r0} | = 10^{ - 7} $。如果考虑到卫星的环境筛查，则更加严格的约束在$ 10^{ - 7.5} $甚至$ 10^{ - 8} $的水平。这些将是迄今为止最严格的天体物理限制之一。我们注意到变色龙重力的进一步签名：（i）如果所有星星丢失了，（ii）在极端的第五力量制度中，落后的恒星流可能会与暗物质祖细胞分离，则可能会发展出恒星尾随的尾巴的条纹，（iii）（iii）如果卫星被完全筛分，则其轨道频率比相关的范围较低，以较低的范围，偏爱相关的差异。
Theories of gravity that incorporate new scalar degrees of freedom typically require screening mechanisms to ensure consistency with Solar System tests. One widely-studied mechanism -- the chameleon -- can lead to violations of the equivalence principle (EP), as screened and unscreened objects fall differently. If the stars are screened but the surrounding dark matter is not, this leads to asymmetry between leading and trailing streams. We provide analytic estimates of the magnitude of this effect for realistic Galactic mass distributions. Using a restricted N-body code, we simulate 4 satellites with a range of masses and orbits, together with a variety of strengths of the fifth force and screening levels of the Milky Way and satellite. The ratio of the cumulative number function of stars in the leading and trailing stream as a function of longitude from the satellite is computable from simulations, measurable from the stellar data and can provide a direct test. We forecast constraints for streams at large Galactocentric distances, using the specific example case of Hu-Sawicki gravity. Streams with apocentres between 100 and 200 kpc provide attainable constraints at the level of $|f_{R0}| = 10^{-7}$. Still more stringent constraints at the level of $10^{-7.5}$ or even $10^{-8}$ are plausible provided the environmental screening of the satellite is accounted for. These would be among the tightest astrophysical constraints to date. We note further signatures of chameleon gravity: (i) the trailing stellar stream may become detached from the dark matter progenitor if all the stars are lost, (ii) in the extreme fifth force regime, striations in the stellar trailing tail may develop, (iii) if the satellite is fully screened, its orbital frequency is lower than that of the associated dark matter, which is preferentially liberated into the leading tidal tail.
