The old Galactic open clusters FSR1716 and Czernik23
The old Galactic open clusters FSR1716 and Czernik23
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旧银河疏散星团 FSR1716 和 Czernik23
DOI：
10.1051/0004-6361:200810332
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发表时间：
2008
影响因子：
6.5
通讯作者：
E. Bica
中科院分区：
文献类型：
--
作者：
C. Bonatto;E. Bica
语境。年龄超过 ∼4 Gyr 的疏散星团在银河系中很少见。受一系列质量减少过程的影响，大多数疏散星团的恒星成分在小于~1 Gyr的时间尺度内溶解到场中。从这个意义上说，改进旧天体的统计数据可能为更好地理解疏散星团的动态消解提供约束。目标。我们的主要目的是研究候选球状星团 FSR 1716 的性质，该星团位于 � = 329.8 ° 和 b = -1.6 ° 。我们还推导了反中心疏散星团 Czernik 23 (FSR 834) 的参数。这两个天体均在 Froebrich、Scholz 和 Raftery 星团候选目录中被检测为恒星密度过高。方法。分析基于近红外色星等图和恒星径向密度剖面。应用于 2MASS J、H 和 Ks 光度测定的场星去污算法增强了固有颜色-幅度图形态。结果。等时线拟合表明，FSR 1716 更可能是一个古老（∼7 Gyr）且被吸收（AV = 6.3 ± 0.2）的疏散星团，位于太阳圈内约 0.6 kpc 处受污染的中心区域。然而，我们不能排除低质量、松散球状星团的可能性。 Czernik 23 被证明是一个几乎无吸收的疏散星团，年龄约为 5 吉里，距离反中心约 2.5 kpc。在这两种情况下，太阳和亚太阳 ([Fe/H] ∼− 0.5) 金属丰度等时线同样很好地代表了恒星序列。两个星团目前存储在恒星中的质量含量较低（<200 M�）。它们相对较小的核心和星团半径与年龄相近的其他疏散星团相当。这些结构参数可能是由于恒星演化、潮汐与盘的相互作用（以及 FSR 1716 中的凸起）以及可能的巨大分子云而导致的数吉里质量损失的结果。结论。 Czernik 23，尤其是 FSR 1716，是极端动态幸存者的罕见例子。两者的识别代表着银河系中已知年龄超过 4 吉里的疏散星团数量增加了约 10%。
Context. Open clusters older than ∼4 Gyr are rare in the Galaxy. Affected by a series of mass-decreasing processes, the stellar content of most open clusters dissolves into the field on a time-scale shorter than ∼1 Gyr. In this sense, improving the statistics of old objects may provide constraints for a better understanding of the dynamical dissolution of open clusters. Aims. Our main purpose is to investigate the nature of the globular cluster candidate FSR 1716, located at � = 329.8 ◦ and b = −1.6 ◦ . We also derive parameters of the anti-centre open cluster Czernik 23 (FSR 834). Both objects have been detected as stellar overdensities in the Froebrich, Scholz & Raftery star cluster candidate catalogue. Methods. The analyses are based on near-infrared colour−magnitude diagrams and stellar radial density profiles. The intrinsic colour−magnitude diagram morphology is enhanced by a field-star decontamination algorithm applied to the 2MASS J, H ,a nd Ks photometry. Results. Isochrone fits indicate that FSR 1716 is more probably an old (∼7 Gyr) and absorbed (AV = 6.3 ± 0.2) open cluster, located ≈0.6 kpc inside the solar circle in a contaminated central field. However, we cannot rule out the possibility of a low-mass, loose globular cluster. Czernik 23 is shown to be an almost absorption-free open cluster, ∼5 Gyr old, located about 2.5 kpc towards the anticentre. In both cases, solar and sub-solar ([Fe/H] ∼− 0.5) metallicity isochrones represent equally well the stellar sequences. Both star clusters have a low mass content (<200 M� ) presently stored in stars. Their relatively small core and cluster radii are comparable to those of other open clusters of similar age. These structural parameters are probably a consequence of the several Gyr of mass loss due to stellar evolution, tidal interactions with the disk (and bulge in the case of FSR 1716), and possibly giant molecular clouds. Conclusions. Czernik 23, and especially FSR 1716, are rare examples of extreme dynamical survivors. The identification of both as such represents an increase of ≈10% in the known population of open clusters older than ∼4 Gyr in the Galaxy.
FSR 0190：另一个古老的遥远星系团
DOI：
10.1111/j.1745-3933.2007.00409.x
发表时间：
2008
期刊：
Letters
影响因子：
--
作者：
Froebrich D
通讯作者：
Froebrich D