Transition of the stellar initial mass function explored using binary population synthesis
Transition of the stellar initial mass function explored using binary population synthesis
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使用二元布居合成探索恒星初始质量函数的转变
DOI：
10.1093/mnrasl/slt033
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发表时间：
2013
影响因子：
--
通讯作者：
M. Y.
中科院分区：
文献类型：
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作者：
Suda;T.;Komiya;Y.;Yamada;S.;Katsuta;Y.;Aoki;W.; Gil-Pons;P.;Doherty;C. L.;Campbell;S. W.;Wood;P. R.;Fujimoto;M. Y.
恒星初始质量函数(IMF)在确定星系中存活恒星的数量、星际介质的化学成分和星系中的光分布方面起着至关重要的作用。一个关键的悬而未决的问题是，IMF在时间和空间上是否具有普遍性。在这里，我们使用最先进的恒星演化结果来表明，我们银河系的IMF在银河系形成的早期就从一个以大质量恒星为主的IMF过渡到了今天的IMF。恒星演化的最新结果已在二进制人口合成代码中实现，并与我们银河系中碳增强型贫金属(CEMP)恒星的观测结果进行了比较。我们发现，现今IMF对银晕恒星的应用引起了与渐近巨星演化有关的四个可观测量的严重矛盾。此外，将我们的计算结果与CEMP星的观测结果进行比较，可能有助于我们限制国际货币基金组织的跃迁金属丰度，我们将其暂定为[Fe/H]和≈−2。目前研究的一个新颖之处是，在低金属丰度的中等质量AGB星中包含了质量损失抑制。这大大减少了氮增强型恒星的过剩，这是之前研究中使用以大质量恒星为主的IMF时的一个主要问题。我们的结果还表明，在化学演化模型中一直使用现在的IMF导致了I.5型超新星的过量产生。更多关于恒星丰度的数据将有助于我们了解国际货币基金组织是如何变化的，以及是什么导致了这种转变。
The stellar initial mass function (IMF) plays a crucial role in the determination of the number of surviving stars in galaxies, of the chemical composition of the interstellar medium and of the distribution of light in galaxies. A key unsolved question is whether the IMF is universal in time and space. Here, we use the state-of-the-art results of stellar evolution to show that the IMF of our Galaxy made a transition from an IMF dominated by massive stars to the present-day IMF at an early phase of the Galaxy formation. Updated results from stellar evolution in a wide range of metallicities have been implemented in a binary population synthesis code, and compared with the observations of carbon-enhanced metal-poor (CEMP) stars in our Galaxy. We find that the application of the present-day IMF to Galactic halo stars causes serious contradictions with four observable quantities connected with the evolution of asymptotic giant branch (AGB) stars. Furthermore, a comparison between our calculations and the observations of CEMP stars might help us to constrain the transition metallicity for the IMF, which we tentatively set at [Fe/H] ≈−2. A novelty of the current study is the inclusion of mass-loss suppression in intermediate-mass AGB stars at low metallicity. This significantly reduces the overproduction of nitrogen-enhanced stars, which was a major problem in previous studies when using the IMF dominated by high-mass stars. Our results also demonstrate that the use of the present-day IMF for all time in chemical evolution models results in the overproduction of Type I.5 supernovae. More data on stellar abundances will help us to understand how the IMF has changed, and what caused such a transition.