Mass segregation in the hyades cluster
Mass segregation in the hyades cluster
复制标题
毕星团星团中的质量偏析
DOI：
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发表时间：
2022
影响因子：
4.8
通讯作者：
Semyeong Oh
中科院分区：
文献类型：
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作者：
N. Evans;Semyeong Oh
使用盖亚色星等图，我们分配质量的979确认成员的毕星团和尾巴的目录。通过拟合累积质量分布，潮汐半径内的恒星具有类似普卢默的分布，半质量半径rh为5.75 pc。尾巴的长度为rh = 69.35 pc，并且比Plummer的下降速度更慢，密度与距离成比例-1.36。在BP-RP =2或0.56M <$2处，星团星被分成两组，ar{M}} = 0.95 M_odot$）和低质量（${ar{M}} = 0.32 M_odot$）人口。我们证明：（i）高质量种群的半质量半径rh为4.88 pc，而低质量种群的半质量半径rh为8.10 pc;（ii）尽管空间范围不同，但高质量种群和低质量种群的运动学和二元性特性相似。它们具有各向同性的速度椭球，平均一维速度频散σ分别为0.427和0.415 km s−1。毕星团的动力学状态与能量均分（$sigma propto {ar{M}}^{-1/2}$）。我们确定了一个新的质量分离不稳定性的集团逃逸速度V。人口$V/sigma lesssim 2sqrt{2}$永远无法达到热平衡和均分。这个区域包含了许多银河系的疏散星团和球状星团。对于毕宿星团，必须有至少9.5 × 10− 4 M <$km 2 s− 2 Myr −1的向外能量通量才能维持其当前的配置。目前由于潮汐剥离造成的0.26M <$Myr−1的质量损失本身意味着大量的能量流超过了所需的量级。
Using the Gaia colour-magnitude diagram, we assign masses to a catalogue of 979 confirmed members of the Hyades cluster and tails. By fitting the cumulative mass profile, stars within the tidal radius have a Plummer-like profile with half-mass radius rh of 5.75 pc. The tails are extended with rh = 69.35 pc and fall off more slowly than Plummer with density proportional to distance−1.36. The cluster stars are separated into two groups at BP-RP =2 or 0.56M⊙ to give a high mass (${ar{M}} = 0.95 M_odot$) and a low mass (${ar{M}} = 0.32 M_odot$) population. We show that: (i) the high mass population has a half-mass radius rh of 4.88 pc, whilst the low mass population has rh = 8.10 pc; (ii) despite the differences in spatial extent, the kinematics and binarity properties of the high and low mass populations are similar. They have isotropic velocity ellipsoids with mean 1d velocity dispersions σ of 0.427 and 0.415 km s−1 respectively. The dynamical state of the Hyades is far from energy equipartition ($sigma propto {ar{M}}^{-1/2}$). We identify a new mass segregation instability for clusters with escape speed V. Populations with $V/sigma lesssim 2sqrt{2}$ can never attain thermal equilibrium and equipartition. This regime encompasses many Galactic open and globular clusters. For the Hyades, there must be an outward energy flux of at least 9.5 × 10−4M⊙ km2 s−2Myr−1 to maintain its current configuration. The present mass loss of 0.26M⊙Myr−1 due to tidal stripping by itself implies a substantial energy flow beyond the required magnitude.