银河系中探测第一代恒星的几率

THE PROBABILITY TO DETECT THE FIRST GENERATIONS OF STARS IN THE GALAXY

第一代恒星是形成于宇宙大爆炸后的原始气体中的、不含重于碳元素的、寿命大于 1 4Gyr的、迄今尚未演化的最古老的恒星 .长期的观测结果表明银河系中尚未发现金属丰度 ([Fe/H] )为零、甚至金属丰度 [Fe/H]≤ - 6的恒星 .为解释这一观察现象 ,将以Tsuiimoto等人提出的银晕的化学演化模型为基础 ,假设形成第一代恒星的初始质量函数具有Miller Scalo的形式 ,从理论上预言和讨论探测第一代恒星的可能性 .利用已有的晕星的观测资料限定模型的参数 .如果形成恒星的云的质量为 1 0 6 M - 1 0 7M ,模型结果预言探测到第一代恒星的几率为 6 .1 4× 1 0 - 4 - 6 .1 4× 1 0 - 5 .

The first generation stars (FGS), which were formed from gas completely free of carbon and heavier elements, are unevolved and the oldest stars. In this paper, We try to explain why no FGS has been found in our Galaxy, even no star with metallicity [Fe/H]≤-6 has been found. We calculate and discuss the probability to detect FGS using the chemical evolution model of Galactic halo posed by Tsujimoto et al (TSY 99) under the assumption that the first generation star has Miller Scalo form of initial mass function. The parameter of model are confined by the observational data of the Galactic halo stars. The result suggests that the probability of identifying essentially meatal free stars in the local halo is around 6.14×10 -4 —6.14×10 -5 , providing that the star formation in the halo is confined to individual gas clouds with a mass of 10 5 M ?—10 6 M ?. We discussed the results of our calculation in last section.