We present velocity measurements for 107 star clusters in the nearby, low-luminosity spiral galaxy M33, from a homogeneous data set taken with the WIYN HYDRA spectrograph. The target clusters were chosen primarily from our previous catalogs based on multiband Hubble Space Telescope WFPC2 imaging and therefore have previous age estimates based on integrated colors. Our sample includes objects spanning the entire range of cluster ages found in M33, allowing us to study cluster kinematics as a function of age. We find that the cluster velocity dispersion with respect to the local disk motion increases dramatically with age. The young clusters have a maximum circular velocity of 87 +- 11 km s~(-1), similar to the previous rotation solution for H Ⅱ regions in M33. When clusters are divided into age groups, the old clusters clearly have very different kinematics from the young population and from the gas disk. Monte Carlo simulations comparing synthetic disk plus halo systems with the observed velocity distribution for our old M33 clusters suggest that old clusters are likely to be composed of two distinct subpopulations, an 85% +- 5% halo component plus a 15% +- 5% disk component. This is the first evidence for distinct kinematic subpopulations among the old M33 clusters, and this galaxy appears to have a higher halo/bulge fraction of old stellar objects than found in the Galaxy. To further study the properties of halo clusters in M33, we use spectroscopic line index measurements for 17 clusters with the largest departure from disk motion, and thus the most pristine halo objects in our sample, to determine ages and approximate metal abundances. When compared with the Worthey models and with similar measurements for 12 Galactic globulars, our clusters have an age spread of ～5-7 Gyr, ～2 times as large as the spread among the Galactic sample. This small halo sample shows little evidence for a progression in metal abundance with age. There is also some support for different size (core radius) distributions when comparing "young" and "old" halo M33 clusters. We discuss these findings in the context of different galaxy formation models.
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机译：我们根据来自WIYN HYDRA光谱仪的同质数据集，对附近低光度旋涡星系M33中的107个星团进行了速度测量。目标星团主要是从我们先前的基于多波段哈勃太空望远镜WFPC2成像的目录中选择的，因此具有基于综合颜色的先前年龄估计。我们的样本包括跨越M33中发现的整个星团年龄范围的对象，这使我们能够研究星团运动随年龄变化的函数。我们发现，相对于局部磁盘运动的簇速度散布随着年龄的增长而急剧增加。幼小团簇的最大圆周速度为87±11 km s〜（-1），类似于先前对M33中HⅡ区的旋转解。将星团分为年龄组时，显然旧星团的运动学与年轻人口和气碟的运动学有很大不同。蒙特卡洛模拟将合成磁盘加光晕系统与我们的旧M33簇的观察到的速度分布进行了比较，表明旧簇可能由两个不同的亚群组成，即85％+-5％的光晕分量加上15％+-5％磁盘组件。这是在旧的M33集群中发现不同运动学亚群的第一个证据，而且这个星系似乎比星系中的旧恒星物体具有更高的光晕/凸起部分。为了进一步研究M33中的光晕团簇的属性，我们使用光谱线指数测量了17个离磁盘运动最远的团簇，因此也是样本中最原始的光晕物体，以确定年龄和近似的金属丰度。与沃思（Worthey）模型进行比较并对12个银河小球进行相似的测量后，我们的星团的年龄分布为〜5-7 Gyr，约为银河样品之间的分布的〜2倍。这个小的光环样本几乎没有证据表明金属的丰度随着年龄的增长而增加。比较“年轻”和“旧”光环M33群集时，还支持不同大小（核心半径）分布。我们在不同的星系形成模型的背景下讨论这些发现。
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