标题： 球状星团中多群体的蒙特卡罗模拟：使用百万体模拟对冷却流与吸积情景的约束 显示英文标题

标题： Monte Carlo simulations of multiple populations in globular clusters: constraints on the cooling flow vs. accretion scenario using million bodies simulations

摘要： 我模拟了一个包含两个恒星种群的恒星系统的演化，其初始设置根据银河系球状星团中多重种群起源的两种主要情景来定义：(i) 从原始+污染气体的冷却流形成第二代恒星，以及(ii) 污染气体被吸积到部分低质量恒星的原恒星盘上。 为此，运行了包含从$10^{5}$到$3\cdot 10^{6}$粒子的蒙特卡洛模拟，包括恒星演化、双星相互作用、外部潮汐场以及对原恒星盘结构的详细建模。 早期气体吸积到原恒星盘上无法产生离散种群，也无法改变显著（$>10\%$）比例的恒星的化学组成，除非假设盘的寿命大于（$t_{disk}\sim20~Myr$）模型预测的寿命。 此外，在这种情景下，两个种群的混合时间尺度太短，无法再现化学富集种群的观测分异。 另一方面，在冷却流情景中运行的模拟在经过哈勃时间后可以演化成第一代与第二代质量比类似于球状星团中观测到的恒星系统，前提是采用初始填充因子$r_{h}/r_{J}>0.15$。 然而，在弱潮汐场条件下，预测的第二代恒星的径向分异比银河系球状星团在大银心距离处观测到的更强。 在遵循椭圆轨道并在现实轴对称势中的模拟中，这种差异消失了。 显示英文摘要

摘要： I simulate the evolution of a stellar system hosting two stellar populations whose initial set up is defined according to the two main scenarios proposed for the origin of multiple populations in Galactic globular clusters: (i) formation of a second generation from a cooling flow of pristine+polluted gas and (ii) accretion of polluted gas onto the proto-stellar disks of a fraction of low-mass stars. For this purpose, Monte Carlo simulations containing from $10^{5}$ up to $3\cdot 10^{6}$ particles have been run including the effect of stellar evolution, binary interactions, external tidal field and a detailed modelling of the proto-stellar disk structure. The early accretion of gas onto proto-stellar disks is unable to produce discrete populations and to alter the chemical composition of a significant ($>10\%$) fraction of stars unless a disk lifetime larger ($t_{disk}\sim20~Myr$) than that predicted by models is assumed. Moreover, in this scenario the mixing timescale of the two populations is too short to reproduce the observed segregation of the chemically enriched population. On the other hand, simulations run within the cooling flow scenario can evolve after a Hubble time into stellar systems with a first-to-second population mass ratio similar to that observed in globular clusters, provided that an initial filling-factor $r_{h}/r_{J}>0.15$ is adopted. However, in the weak tidal field regime a radial segregation of the second population stronger than what observed in Milky Way globular clusters at large Galactocentric distances is predicted. This discrepancy disappears in simulations following eccentric orbits in a realistic axisymmetric potential.