论文标题
$ f（r）$重力中矮星系的动态
Dynamics of dwarf galaxies in $f(R)$ gravity
论文作者
论文摘要
我们在八个矮人球星系中使用星星的运动学数据来评估$ f（r）$重力是否可以符合这些系统的视线速度分散的观察到的曲线，而无需诉诸暗物质。我们的模型假设每个星系在球面上都是对称的，并且具有恒定的速度各向异性参数$β$和与恒星种群合成模型一致的恒定质量与光比。我们解决了球形牛仔裤方程，其中包括Yukawa样重力电势出现在$ F（R）$重力的弱场极限中，以及用于恒星分布的Plummer密度曲线。 $ f（r）$速度分散配置文件取决于两个参数：比例长度$ξ^{ - 1} $，在Yukawa术语的下方，重力场$Δ> -1 $的提升。 $δ$和$ξ$不是通用参数，但是它们在同一类对象中的变化预计将受到限制。 $ f（r）$速度分散配置文件符合数据$ $ξ^{ - 1} = 1.2^{+18.6} _ { - 0.9} $ mpc，用于整个星系样本。相反，$δ$的值显示了一个双峰分布，以$ \barδ= -0.986 \ pm0.002 $和$ \barΔ= -0.92 \ pm0.01 $。这两个值不同意$6σ$，并暗示$ f（r）$重重的严重张力。是否有待观察的是，改进的矮星系模型是通过未来的星体空间任务所测量的恒星的适当运动提供的其他约束，可以返回整个样品的一致$δ$并消除此张力。
We use the kinematic data of the stars in eight dwarf spheroidal galaxies to assess whether $f(R)$ gravity can fit the observed profiles of the line-of-sight velocity dispersion of these systems without resorting to dark matter. Our model assumes that each galaxy is spherically symmetric and has a constant velocity anisotropy parameter $β$ and constant mass-to-light ratio consistent with stellar population synthesis models. We solve the spherical Jeans equation that includes the Yukawa-like gravitational potential appearing in the weak field limit of $f(R)$ gravity, and a Plummer density profile for the stellar distribution. The $f(R)$ velocity dispersion profiles depend on two parameters: the scale length $ξ^{-1}$, below which the Yukawa term is negligible, and the boost of the gravitational field $δ>-1$. $δ$ and $ξ$ are not universal parameters, but their variation within the same class of objects is expected to be limited. The $f(R)$ velocity dispersion profiles fit the data with a value $ξ^{-1}= 1.2^{+18.6}_{-0.9}$ Mpc for the entire galaxy sample. On the contrary, the values of $δ$ show a bimodal distribution that picks at $\barδ=-0.986\pm0.002$ and $\barδ=-0.92\pm0.01$. These two values disagree at $6σ$ and suggest a severe tension for $f(R)$ gravity. It remains to be seen whether an improved model of the dwarf galaxies or additional constraints provided by the proper motions of stars measured by future astrometric space missions can return consistent $δ$'s for the entire sample and remove this tension.
