Abandoning the assumption that light traces mass, I seek the location of the center of the Local Group of galaxies based solely on kinematic data and the plausible assumption of infall. The available set of positions and radial velocities is shown to be a misleading indicator of Local Group motions, giving a direction to the center offset from the true one; statistical techniques of moderate sophistication do not catch the offset. Corrected calculations show the center to lie in the direction to M31 within the uncertainty of the method, a few degrees. The distance to the center is not well determined, lying about 0.5 Mpc from the Milky Way. The pattern of observed (galactocentric) radial velocities excludes both dynamically important `orphan haloes' and any extended dark matter halo for the Group as a whole, and shows the Group to have formed from a much more extended volume than it presently occupies. Kinematics alone indicates that the mass of the Group is concentrated effectively in M31 and the Milky Way.
GHASP: an H$α$ kinematical survey of spiral galaxies - XI. Distribution of luminous and dark matter in spiral and irregular nearby galaxies using WISE photometry
我们提出了一个样本的质量分布的121个附近的星系与高质量的光学速度场和可用的红外$\it{WISE}$ 3.4 $μ$ m数据。与以前的研究相反,这个样本涵盖了所有的形态类型,并不偏向于晚型星系。这些星系是法布里-珀罗运动学$\it{GHASP}$调查的螺旋星系和不规则的附近星系的一部分。结合运动学数据的$\it{WISE}$表面亮度数据探测从老恒星人口的排放,我们推导出质量模型,使我们能够比较发光的暗物质晕质量分布在这些星系的光学区域。暗物质(DM)模型是利用等温核轮廓和Navarro-Frenk-White尖点轮廓建立的。我们允许重子盘的M/L变化或我们保持固定,恒星演化模型(WISE W $_1$ -W $_2$颜色)的约束,我们进行最佳拟合(BFM)和伪等温最大盘(MDM)模型。我们发现,MDM提供的M/L值比BFM高四倍,这表明平均而言,椎间盘成分往往是最大的。主要结果如下:(i)大多数星系的自转曲线更适合于核心而不是尖点轮廓;(ii)DM参数和发光物质组分参数之间的关系主要取决于形态类型。更准确地说,DM在星系内部的分布取决于星系是否有凸起。
The ESO Multi-Instrument Kinematic Survey (MIKiS) of Galactic Globular Clusters: solid body rotation and anomalous velocity dispersion profile in NGC 5986
GHASP: an H$α$ kinematical survey of spiral galaxies -- XIII. Distribution of luminous and dark matter in spiral and irregular nearby galaxies using H$α$ and HI rotation curves and WISE photometry
利用高分辨率的GHASP Fabry-Perot H $α$和扩展的WHISP HI混合旋转曲线以及3.4 $μ$ m WISE测光,给出了31个螺旋星系和不规则邻近星系的质量模型。我们的目的是比较的暗物质(DM)晕的光学半径内使用H $α$ RC的效果,包括和排除中性气体成分的质量贡献,当使用HI或混合RC。伪等温(ISO)的核心和Navarro-Frenk-White(NFW)的尖突DM晕配置文件与各种基准拟合程序。使用H $α$ RC(包括或不包括HI气体成分)的质量模型提供兼容的圆盘M/L。DM晕与重子参数之间的关联对RC的依赖性不强。显然,拟合过程之间的差异大于不同数据集之间的差异。与仅使用H $α$ RC时相比,混合RC和HI RC导致ISO和NFW最佳拟合模型的M/L值更高,但ISO光晕的中心密度更低,NFW光晕的浓度更高。与质量模型参数推导出的混合RC的协议,作为参考,是更好的HI比H $α$ RC。ISO密度曲线比NFW密度曲线更适合RC,特别是当使用H $α$或混合RC时。使用各种数据集确定的光学半径处的晕质量是相容的,即使它们倾向于被高估与H $α$ RC。因此,混合RC是研究光学半径内质量分布的理想选择。
3D kinematics of SMC star clusters: residual velocities disentangle kinematically perturbed clusters
Instituto Interdisciplinario de Ciencias Básicas (ICB), CONICET-UNCuyo(基础科学跨学科研究所 (ICB));Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)(国家科学研究委员会)
MIKiS: the Multi-Instrument Kinematic Survey of Galactic Globular Clusters. I. Velocity dispersion profiles and rotation signals of 11 globular clusters