The evolution of embedded star clusters
The evolution of embedded star clusters
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嵌入式星团的演化
DOI：
10.1111/j.1365-2966.2011.20137.x
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发表时间：
2011
影响因子：
4.8
通讯作者：
S. Zwart
中科院分区：
文献类型：
--
作者：
F. I. Pelupessy;S. Zwart
研究了嵌入式集群的演化过程。在考虑恒星演化和气体含量的流体动力学影响的情况下，采用直接N体积分法求解星团内恒星的运动方程。恒星的引力和周围的气体自洽地耦合在一起，从而实现了星系团的真实动态演化。在求解运动方程的同时，恒星演化代码会跟踪恒星质量、光度和半径的变化。恒星风和超新星释放出的气体将质量和能量储存到星系团所在的气藏中。我们检查了有1000颗恒星的星团模型，但我们改变了恒星形成效率(在0.05和0.5之间)、星团半径(0.1-1.0pC)、初始恒星群的维里支持程度(0-100%)和反馈的强度。我们发现初始恒星比例M★/MTOTGT0.05是星系团生存所必需的。如果气体没有被超新星猛烈地吹出，并且星系团在放出气体的过程中有时间接近维里平衡，那么存活的可能性更大。当星系团被嵌入时，动力摩擦在星系团中早期有效地驱动质量分离。M≳2和M⊙的恒星优先保留，代价是损失质量较小的恒星。我们的结论是，昂宿星团等疏散星系团的质量分离程度不是长期演化的结果，而是其嵌入阶段的残余。
We study the evolution of embedded clusters. The equations of motion of the stars in the cluster are solved by direct N-body integration while taking the effects of stellar evolution and the hydrodynamics of the natal gas content into account. The gravity of the stars and the surrounding gas are coupled self-consistently to allow the realistic dynamical evolution of the cluster. While the equations of motion are solved, a stellar evolution code keeps track of the changes in stellar mass, luminosity and radius. The gas liberated by the stellar winds and supernovae deposits mass and energy into the gas reservoir in which the cluster is embedded. We examine cluster models with 1000 stars, but we varied the star formation efficiency (between 0.05 and 0.5), cluster radius (0.1–1.0 pc), the degree of virial support of the initial population of stars (0–100 per cent) and the strength of the feedback. We find that an initial star fraction M★/Mtot > 0.05 is necessary for cluster survival. Survival is more likely if gas is not blown out violently by a supernova and if the cluster has time to approach virial equilibrium during outgassing. While the cluster is embedded, dynamical friction drives early and efficient mass segregation in the cluster. Stars of m≳ 2 M⊙ are preferentially retained, at the cost of the loss of less massive stars. We conclude that the degree of mass segregation in open clusters such as the Pleiades is not the result of secular evolution but a remnant of its embedded stage.