论文标题
基于动作的分布功能建模，用于限制银河系暗物质的形状
Action-based distribution function modelling for constraining the shape of the Galactic dark matter halo
论文作者
论文摘要
我们通过使用Gaia Dr2的Halo RR Lyrae星的Astrestoric数据来估算出$ r \ Lessim 30 $ kpc内的银河暗物质（DM）光环的3D密度曲线。我们完全考虑了RR Lyre恒星的恒星光环分布函数和银河电位，并充分考虑了调查选择功能，观察误差以及缺少的视线速度数据。使用贝叶斯MCMC方法，我们推断出模型参数，包括DM Halo $ Q $的密度平坦，这被认为是半径的函数。我们发现，$ Q $的99 \％的后验分布位于$ Q> 0.963 $，这极大地散布了扁平的DM光环。我们不能就$ r \ lyssim 30 $ kpc的银河系halo是庞大的结论得出任何结论，因为我们将自己限制在轴对称性的halo模型上，$ q \ leq1 $。我们的结果与宇宙流体动力学模拟的预测不一致，这些模拟的预测更加碎肉（$ \ langle {q} \ rangle \ sim0.8 \ pm 0.15 $ 0.15 $）DM Halos在$ \ sim 15 \％$ \％的病毒半径$ \％$ halos in virial Radius for Milky-Day尺寸大小的Galaxies。基于我们和宇宙学模拟的验证测试的另一种可能性是，银河系光环的真实值$ q $可能与宇宙学模拟一致，但是银河系潜力的不平衡是使我们的量子计量$ Q $ 0.1-0.2。作为我们分析的副产品，我们的模型将太阳邻域中的DM密度限制为$ρ_ {\ Mathrm {dm}，\ odot}，\ odot} =（9.01^{+0.18} _ { - 0.20} _ { - 0.20}） 0.342^{+0.007} _ { - 0.007} $ $ \; \ MATHRM {GEV} \ MATHRM {CM}^{ - 3} $。
We estimate the 3D density profile of the Galactic dark matter (DM) halo within $r \lesssim 30$ kpc from the Galactic centre by using the astrometric data for halo RR Lyrae stars from Gaia DR2. We model both the stellar halo distribution function and the Galactic potential, fully taking into account the survey selection function, the observational errors, and the missing line-of-sight velocity data for RR Lyrae stars. With a Bayesian MCMC method, we infer the model parameters, including the density flattening of the DM halo $q$, which is assumed to be constant as a function of radius. We find that 99\% of the posterior distribution of $q$ is located at $q>0.963$, which strongly disfavours a flattened DM halo. We cannot draw any conclusions as to whether the Galactic DM halo at $r \lesssim 30$ kpc is prolate, because we restrict ourselves to axisymmetric oblate halo models with $q\leq1$. Our result is inconsistent with predictions from cosmological hydrodynamical simulations that advocate more oblate ($\langle{q}\rangle \sim0.8 \pm 0.15$) DM halos within $\sim 15\%$ of the virial radius for Milky-Way-sized galaxies. An alternative possibility, based on our validation tests with a cosmological simulation, is that the true value $q$ of the Galactic halo could be consistent with cosmological simulations but that disequilibrium in the Milky Way potential is inflating our measurement of $q$ by 0.1-0.2. As a by-product of our analysis, our model constrains the DM density in the Solar neighbourhood to be $ρ_{\mathrm{DM},\odot} = (9.01^{+0.18}_{-0.20})\times10^{-3}M_\odot \mathrm{pc}^{-3} = 0.342^{+0.007}_{-0.007}$ $\;\mathrm{GeV} \mathrm{cm}^{-3}$.
