...
首页> 外文期刊>The Astrophysical journal >SPACE VELOCITIES OF SOUTHERN GLOBULAR CLUSTERS. VI. NINE CLUSTERS IN THE INNER MILKY WAY
【24h】

SPACE VELOCITIES OF SOUTHERN GLOBULAR CLUSTERS. VI. NINE CLUSTERS IN THE INNER MILKY WAY

机译:南部球团的空间速度。 VI。内银河系中的九个集群

获取原文
   

获取外文期刊封面封底 >>

       

摘要

We have measured the absolute proper motions of nine low-latitude, inner Galaxy globular clusters, namely, NGC?6273 (M 19), NGC?6284, NGC?6287, NGC?6293, NGC?6333 (M 9), NGC?6342, NGC?6356, NGC?6388, and NGC?6441. These are the first determinations ever made for these clusters. The proper motions are on the International Celestial Reference System via Hipparcos. The proper-motion errors range between 0.4 and 0.9 mas yr–1 and are dominated by the number of measurable cluster members in these regions which are very crowded by the bulge/bar and the thick disk. This sample contains five metal-poor ([Fe/H] –1.0) and four metal-rich ([Fe/H] ≥ –1.0) clusters; seven clusters are located within ~4 kpc from the Galactic center, while the remaining two, namely NGC?6356 and NGC?6284, are in the background of the bulge at ~7.5 kpc from the Galactic center. By combining proper motions with radial velocities and distances from the literature we derive three-dimensional velocities. In a number of cases, distance uncertainties make the kinematical classification ambiguous. For the metal-poor group of clusters, we find that three clusters, namely NGC?6273, NGC?6287, and NGC?6293 are members of a kinematically hot system, the inner halo. As for the remaining two metal-poor clusters, NGC?6284 is located at ~7.5 kpc from the Galactic center and kinematically belongs to the thick disk, while NGC?6333, located in the inner ~2 kpc, has an uncertain membership (between halo and thick disk) due to the distance uncertainty. Within the metal-rich group of clusters, NGC?6356 and NGC?6342 have velocities compatible with membership in the thick disk; however, velocity uncertainties do not allow us to rule out their belonging to a hotter system. NGC?6342 is within ~2 kpc from the Galactic center, and thus it may belong to the bulge. NGC?6356 is at ~7.5 kpc from the Galactic center and thus its metallicity, kinematics, and location argue together in favor of thick-disk membership. The remaining two metal-rich clusters, NGC?6388 and NGC?6441, have velocities incompatible with membership in the thick disk or the bar of the Milky Way. They can be thought of as members of a kinematically hot system in the inner Galaxy. Curiously, both clusters have similar velocity components. Together with their similar Galactic location and peculiar but similar stellar-population characteristics, these two clusters may share a common origin. Their velocities are also very low indicating that the two clusters are now at apocenter, i.e., they will not leave the inner ~4 kpc of the Galaxy.
机译:我们测量了九个低纬度,内部银河系球状星团的绝对固有运动,分别是NGC?6273(M 19),NGC?6284,NGC?6287,NGC?6293,NGC?6333(M 9),NGC? 6342,NGC?6356,NGC?6388和NGC?6441。这些是对这些集群做出的第一个决定。适当的议案是通过Hipparcos在国际天文参考系统上进行的。适当运动误差的范围在0.4到0.9 mas yr–1之间,并且受这些区域中可测量的簇成员的数量支配,这些簇成员被凸起/条和厚磁盘非常拥挤。该样本包含五个金属贫乏([Fe / H]≤–1.0]和四个富金属([Fe / H]≥–1.0)的簇;七个星团位于距银河系中心约4 kpc的范围内,而其余两个星团,即NGC?6356和NGC?6284,位于距银河系中心约7.5 kpc处的凸起背景中。通过将适当的运动与径向速度和文献中的距离相结合,我们得出了三维速度。在许多情况下,距离的不确定性使运动学分类不明确。对于贫金属的团簇,我们发现三个团簇,即NGC?6273,NGC?6287和NGC?6293是运动热系统内环的成员。至于剩下的两个贫金属团簇,NGC?6284距银河系中心约7.5 kpc,在运动学上属于厚盘,而位于内部〜2 kpc的NGC?6333具有不确定的隶属关系(介于光晕和厚盘)由于距离不确定。在富含金属的团簇中,NGC?6356和NGC?6342的速度与厚盘中的成员资格兼容。但是,速度不确定性不允许我们排除它们属于较热系统的可能性。 NGC?6342距银河系中心约2 kpc以内,因此它可能属于凸出部分。 NGC?6356距银河系中心约7.5 kpc,因此其金属性,运动学和位置共同支持厚盘成员。剩下的两个富含金属的星团NGC?6388和NGC?6441具有与厚盘或银河系中的成员不兼容的速度。可以将它们视为内部银河系中运动热系统的成员。奇怪的是,两个星团都有相似的速度分量。加上它们相似的银河位置和特殊但相似的恒星种群特征,这两个星团可能具有相同的起源。它们的速度也很低,表明这两个星团现在处于中心位置,即它们将不会离开银河系内部约4 kpc。

著录项

获取原文

客服邮箱:kefu@zhangqiaokeyan.com

京公网安备:11010802029741号 ICP备案号:京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有
  • 客服微信

  • 服务号