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Dynamical Constraints on the Formation of NGC 4472 and Its Globular Clusters

机译:NGC 4472及其球状星团形成的动力学约束

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We present new radial velocities for 87 globular clusters around the elliptical galaxy NGC 4472 and combine these with our previously published data to create a data set of velocities for 144 globular clusters around NGC 4472. We utilize this data set to analyze the kinematics of the NGC 4472 globular cluster system. The new data confirm our previous discovery that the metal-poor clusters have significantly higher velocity dispersion than the metal-rich clusters in NGC 4472. We also find very little or no rotation in the more spatially concentrated metal-rich population, with a resulting upper limit for this population of (v/σ)proj 0.34 at a 99% confidence level. The very small angular momentum in the metal-rich population requires efficient angular momentum transport during the formation of this population, which is spatially concentrated and chemically enriched. Such angular momentum transfer can be provided by galaxy mergers, but it has not been achieved in other extant models of elliptical galaxy formation that include dark matter halos. We also calculate the velocity dispersion as a function of radius and show that it is consistent with roughly isotropic orbits for the clusters and the mass distribution of NGC 4472 inferred from X-ray observations of the hot gas around the galaxy.
机译:我们为椭圆星系NGC 4472周围的87个球状星团提供了新的径向速度,并将它们与我们先前发布的数据结合起来,为NGC 4472周围的144个球状星团创建了速度数据集。我们利用该数据集来分析NGC的运动学4472球状星团系统。新数据证实了我们先前的发现,即贫金属团簇的速度弥散度明显高于NGC 4472中富金属团簇的速度散布。我们还发现,在空间上更集中的富金属团簇中旋转很少或没有旋转,从而导致(v /σ)proj <0.34的总体限制,置信度为99%。富含金属的族群中很小的角动量需要在该族群的形成过程中进行有效的角动量传输,该角动量在空间上是集中的并化学富集。这种角动量传递可以通过星系合并来提供,但是在包括暗物质光晕的椭圆形星系形成的其他现有模型中尚未实现。我们还计算了速度分散度与半径的函数关系,并表明它与星团周围的大致各向同性轨道以及从银河系周围热气的X射线观测推断出的NGC 4472的质量分布一致。

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