The Kinematics and Dynamics of the Globular Clusters and Planetary Nebulae of NGC 5128
The Kinematics and Dynamics of the Globular Clusters and Planetary Nebulae of NGC 5128
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NGC 5128 球状星团和行星状星云的运动学和动力学
DOI：
10.1086/518788
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
G. Harris
中科院分区：
文献类型：
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作者：
K. Woodley;W. Harris;M. Beasley;E. Peng;T. Bridges;D. Forbes;G. Harris
提出了对巨型椭圆星系 NGC 5128 晕的新运动学和动力学研究。从经光谱确认的 340 个球状星团和 780 个行星状星云样本中，确定了 NGC 5128 晕的旋转幅度、旋转轴、速度色散和总动力质量。通过将球状星团样本细分为 158 个富金属 ([Fe/H] > -1.0) 和 178 个，搜索球状星团运动学的径向依赖性和金属丰度依赖性贫金属 ([Fe/H] < -1.0) 球状星团。我们的结果表明，富金属和贫金属亚群的运动学非常相似：在 0-50 kpc 的投影半径上，富金属和贫金属亚群的平均旋转幅度分别为 47 ± 15 和 31 ± 14 km s-1。 0-5 kpc 范围内的迹象表明，贫金属星团的旋转信号比星系外部区域的低。旋转轴在 5 kpc 处显示出有趣的扭曲，与 Peng 和同事提出的零速度曲线一致。在5 kpc以内，富金属和贫金属群体的旋转轴几乎平行于南北方向，即0°，而超过5 kpc，旋转轴扭曲~180°。两种金属丰度种群的速度色散均显示出随星系中心半径的稳定增加，对于富金属和贫金属种群，在 15 kpc 的预计半径内，平均值为 111 ± 6 和 117 ± 6 km s-1；然而，最外围区域的统计数据较少且存在空间偏差。行星状星云的运动学略有不同。在距 NGC 5128 中心 90 kpc 的投影半径范围内，行星状星云具有 76 ± 6 km s-1 的较高旋转幅度和北偏东 170° ± 5° 的旋转轴，在任一确定的量中都没有显着的径向偏差。速度色散随着银河系中心距离的增加而减小。 NGC 5128 的总质量是使用 Evans 等人描述的示踪质量估计器找到的，以确定内部随机运动支持的质量，并使用 Jeans 方程的球形分量确定旋转支持的质量。我们从行星状星云数据中发现总质量为 (1.0 ± 0.2) × 1012 M⊙，延伸至投影半径 90 kpc。富金属和贫金属球状星团的相似运动学使我们能够将两个子群结合起来，以确定总质量的独立估计，给出 (1.3 ± 0.5) × 1012 M⊙ 的投影半径为 50 kpc。最后，我们在 NGC 5128 中发布了已知球状星团的新的同质目录。该目录结合了之前所有来自径向速度研究和 HST 成像研究的明确星团识别，以及来自 M. A. Beasley 等人的研究的 80 个具有径向速度的新球状星团。 （准备中）。
A new kinematic and dynamic study of the halo of the giant elliptical galaxy NGC 5128 is presented. From a spectroscopically confirmed sample of 340 globular clusters and 780 planetary nebulae, the rotation amplitude, rotation axis, velocity dispersion, and total dynamical mass are determined for the halo of NGC 5128. The globular cluster kinematics were searched for both radial dependence and metallicity dependence by subdividing the globular cluster sample into 158 metal-rich ([Fe/H] > -1.0) and 178 metal-poor ([Fe/H] < -1.0) globular clusters. Our results show that the kinematics of the metal-rich and metal-poor subpopulations are quite similar: over a projected radius of 0-50 kpc, the mean rotation amplitudes are 47 ± 15 and 31 ± 14 km s-1 for the metal-rich and metal-poor populations, respectively. There is a indication within 0-5 kpc that the metal-poor clusters have a lower rotation signal than in the outer regions of the galaxy. The rotation axis shows an interesting twist at 5 kpc, agreeing with the zero-velocity curve presented by Peng and coworkers. Within 5 kpc both metal-rich and metal-poor populations have a rotation axis nearly parallel to the north-south direction, which is 0°, while beyond 5 kpc the rotation axis twists ∼180°. The velocity dispersion displays a steady increase with galactocentric radius for both metallicity populations, with means of 111 ± 6 and 117 ± 6 km s-1 within a projected radius of 15 kpc for the metal-rich and metal-poor populations; however, the outermost regions suffer from low number statistics and spatial biases. The planetary nebula kinematics are slightly different. Out to a projected radius of 90 kpc from the center of NGC 5128, the planetary nebulae have a higher rotation amplitude of 76 ± 6 km s-1 and a rotation axis of 170° ± 5° east of north, with no significant radial deviation in either determined quantity. The velocity dispersion decreases with galactocentric distance. The total mass of NGC 5128 is found using the tracer mass estimator, described by Evans et al., to determine the mass supported by internal random motions and the spherical component of the Jeans equation to determine the mass supported by rotation. We find a total mass of (1.0 ± 0.2) × 1012 M⊙ from the planetary nebula data extending to a projected radius of 90 kpc. The similar kinematics of the metal-rich and metal-poor globular clusters allow us to combine the two subpopulations to determine an independent estimate of the total mass, giving (1.3 ± 0.5) × 1012 M⊙ out to a projected radius of 50 kpc. Lastly, we publish a new and homogeneous catalog of known globular clusters in NGC 5128. This catalog combines all previous definitive cluster identifications from radial velocity studies and HST imaging studies, as well as 80 new globular clusters with radial velocities from a study of M. A. Beasley et al. (in preparation).