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arXiv 1409.6348astro-ph.GA
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三个研究不足的星系团的径向速度和疏散星团的运动学

Radial Velocities of Three Poorly Studied Clusters and the Kinematics of Open Clusters

Christian R. Hayes, Eileen D. Friel

摘要:

我们目前的径向速度恒星在该领域的疏散星团伯克利44,伯克利81,和NGC 6802使用威斯康星州印第安纳州耶鲁大学NOAO(WIYN)3.5米望远镜获得的光谱。这些星系团的年龄处于中间(1-3 Gyr),位于太阳银河系中心半径内,并且之前没有径向速度测量。我们发现Be 44、Be 81和NGC 6802的平均径向速度分别为-9.6 +/- 3.0 km s ^-1、48.1 +/-2.0 km s ^-1和12.4 +/- 2.8 km s^-1。我们提出了一个广泛的年龄范围内的134个疏散星团的径向速度的分析使用本研究和文献中获得的数据。假设星系团系统围绕银河系中心以恒定速度旋转,我们发现较老的星系团比年轻的星系团具有更慢的旋转和更大的视线(LOS)速度色散。随着年龄的增长,星系团系统的旋转速度逐渐下降,伴随着一个平稳的增加,在LOS速度色散,我们解释为加热效果的疏散星团系统随着时间的推移。

英文摘要:

We present radial velocities for stars in the field of the open star clusters Berkeley 44, Berkeley 81, and NGC 6802 from spectra obtained using the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5 m telescope. These clusters are of intermediate age (1-3 Gyr), located within the solar Galactocentric radius, and have no previous radial velocity measurements. We find mean radial velocities of -9.6 +/- 3.0 km s^-1, 48.1 +/- 2.0 km s^-1, and 12.4 +/- 2.8 km s^-1 for Be 44, Be 81, and NGC 6802, respectively. We present an analysis of radial velocities of 134 open clusters of a wide range of ages using data obtained in this study and the literature. Assuming the system of clusters rotates about the Galactic center with a constant velocity, we find older clusters exhibit a slower rotation and larger line-of-sight (LOS) velocity dispersion than younger clusters. The gradual decrease in rotational velocity of the cluster system with age is accompanied by a smooth increase in LOS velocity dispersion, which we interpret as the effect of heating on the open cluster system over time.

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