Density and Radius of Dark Matter Halo in the Milky Way Galaxy from a Large-Scale Rotation Curve
Density and Radius of Dark Matter Halo in the Milky Way Galaxy from a Large-Scale Rotation Curve
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从大尺度旋转曲线看银河系暗物质晕的密度和半径
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发表时间：
2011
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通讯作者：
Sofue
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作者：
Sofue
重建了银河系的大尺度旋转曲线，覆盖了从银河系中心到本群，或从银河系中心半径R ~ 0 kpc到~ 1 Mpc的区域。银河系凸起、指数盘和暗晕的尺度半径和质量由旋转曲线的最小二乘拟合确定。鼓状+盘状系统的总质量只有Mb+Md≃3.3×10M⊙。采用暗晕的Navaro-Frenk-White （NFW）密度曲线，ρ = ρ0/([R/h)(1+(R/h))]， h和ρ0分别为尺度半径和尺度密度，最小二乘拟合得到h = 15.3±1.1 kpc和ρ0 =（7.18±0.90）×10M⊙pc−3。在R0 = 8 kpc时，太阳附近暗物质密度的局域值估计为ρ0 =（1.08±0.17）× 10M⊙pc−3 = 0.410±0.066 GeV cm−3。太阳圈内的暗物质质量为Mh(R≤8 kpc) ~ 3.9×10M⊙。在假定的银河系边界内R ~ 385 kpc的整个暗晕的总质量是Mh ~ 1.04×10M⊙，距离M31的一半。这导致重子与暗物质之比的最大值为(Mb + Md)/Mh ~ 3.1%。这个值远小于宇宙平均值19%(=4.6%/24%)，这意味着其余16% （~ 1.7×10M⊙）的重子在我们的银河系中失踪或看不见。
A large-scale rotation curve of the Milky Way Galaxy is reconstructed, which covers the area from Galactic Center to Local Group, or from galacto-centric radius R∼ 0 kpc to ∼ 1 Mpc. The scale radii and masses of the galactic bulge, exponential disk and dark halo are determined by least squares fitting to the rotation curve. The bulge+disk system is shown to have a total mass of only Mb+Md ≃3.3×10M⊙. The Navaro-Frenk-White (NFW) density profile for dark halo, ρ = ρ0/([R/h)(1+(R/h))] with h and ρ0 being the scale radius and scale density, respectively, is applied, and the least squares fit yields h = 15.3±1.1 kpc and ρ0 = (7.18±0.90)×10M⊙ pc−3. The local value of the dark matter density near the Sun at R0 = 8 kpc is estimated to be ρ0 = (1.08± 0.17)× 10M⊙ pc−3 = 0.410± 0.066 GeV cm −3. The dark matter mass inside the solar circle is Mh(R≤ 8 kpc)∼ 3.9×10M⊙. The total mass of the entire dark halo inside the supposed boundary of the Galaxy at R∼ 385 kpc, a half distance to M31, is Mh ∼ 1.04×10M⊙. This leads to an upper value of the baryon to dark matter ratio of (Mb + Md)/Mh ∼3.1%. This value is much smaller than the cosmic mean of 19%(=4.6%/24%), implying that the rest 16% (∼ 1.7×10M⊙) baryons are missing or invisible in our Galaxy.