论文标题
用Lamost DR5和Gaia DR2测量局部暗物质密度
Measuring the local dark matter density with LAMOST DR5 and Gaia DR2
论文作者
论文摘要
我们将垂直牛仔裤方程式应用于太阳能邻域的银河系星的运动学，以测量局部暗物质密度。从Lamost DR5和Gaia DR2的交叉匹配样品中选择了超过90,000 G型和K型矮星。应用的质量模型由单个指数恒星盘，剃须刀薄的气盘和恒定的暗物质密度组成。我们首先考虑简化的垂直牛仔裤方程，该方程式忽略了倾斜项并假定平坦的旋转曲线。在总恒星表面密度上的高斯先验下，马尔可夫链蒙特卡洛模拟推断出的局部暗物质密度为$ 0.0133 _ { - 0.0022}^{+0.0024} \ {\ rm m} _ {\ rm m} _ {\ odot} \，{\ odot} \，{\ rm rm pc} $ -10^{\ circ} <ϕ <5^{\ circ} $在方位角的局部暗物质密度在其1 $σ$错误中是一致的。但是，由于北部和南部垂直速度分散曲线的高原，北部和南部的子样本显示出很大的差异。这些高原可能是北部和南部之间暗物质密度不同估计的原因。考虑到倾斜术语对参数估计几乎没有影响，也不能解释北部和南方的不对称性。将$σ_{z} $概况差的一半差为未知的系统错误，然后我们获得了北部和南部子样本的一致测量。我们讨论垂直数据范围，示踪剂种群的尺度，恒星的垂直分布以及样本量对局部暗物质密度确定的不确定性的影响。
We apply the vertical Jeans equation to the kinematics of Milky Way stars in the solar neighbourhood to measure the local dark matter density. More than 90,000 G- and K-type dwarf stars are selected from the cross-matched sample of LAMOST DR5 and Gaia DR2 for our analyses. The mass models applied consist of a single exponential stellar disc, a razor thin gas disc and a constant dark matter density. We first consider the simplified vertical Jeans equation which ignores the tilt term and assumes a flat rotation curve. Under a Gaussian prior on the total stellar surface density, the local dark matter density inferred from Markov Chain Monte Carlo simulations is $0.0133_{-0.0022}^{+0.0024}\ {\rm M}_{\odot}\,{\rm pc}^{-3}$. The local dark matter densities for subsamples in an azimuthal angle range of $-10^{\circ} < ϕ< 5^{\circ}$ are consistent within their 1$σ$ errors. However, the northern and southern subsamples show a large discrepancy due to plateaux in the northern and southern vertical velocity dispersion profiles. These plateaux may be the cause of the different estimates of the dark matter density between the north and south. Taking the tilt term into account has little effect on the parameter estimations and does not explain the north and south asymmetry. Taking half of the difference of $σ_{z}$ profiles as unknown systematic errors, we then obtain consistent measurements for the northern and southern subsamples. We discuss the influence of the vertical data range, the scale height of the tracer population, the vertical distribution of stars and the sample size on the uncertainty of the determination of the local dark matter density.
