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arXiv 1606.01908astro-ph.GA
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半解析模型中初始质量函数的变化:对GAEA模型中星系质量组装和化学富集的影响

Variations of the initial mass function in semi-analytical models: implications for the mass assembly and the chemical enrichment of galaxies in the GAEA model

Fabio Fontanot, Gabriella De Lucia, Michaela Hirschmann, Gustavo Bruzual, Stephane Charlot, Stefano Zibetti

摘要:

在这项工作中,我们调查的综合银河系范围内的恒星初始质量函数(IGIMF)的方法的半分析模型GAEA(银河系演化和组装),其特点是化学富集和恒星反馈的详细治疗的框架内的影响。IGIMF提供了恒星IMF形状对星系中恒星形成速率的依赖性的解析描述。我们发现,我们的模型与一个普遍的IMF预测一个相当平坦的[ $α$ /Fe]恒星质量的关系。模型假设的IGIMF,而不是,能够再现所观察到的增加$α$ -增强与恒星质量,与以前的研究。这主要是由于大质量星系在高红移时具有较大的恒星形成率,导致相对于低质量星系有较强的$α$增强。与此同时,IGIMF假说并没有显著影响更大质量星系的恒星形成时间尺度更短的趋势。我们认为,在IGIMF的情况下,[ $α$ /Fe]比是最高的恒星形成事件的良好示踪剂。我们的模型大质量星系的最终恒星质量和质光比大于合成测光估计假设一个普遍的IMF,提供了一个自洽的解释类似的最近的结果,基于本地早型星系的动力学分析。

英文摘要:

In this work, we investigate the implications of the Integrated Galaxy-wide stellar Initial Mass Function (IGIMF) approach in the framework of the semi-analytic model GAEA (GAlaxy Evolution and Assembly), which features a detailed treatment of chemical enrichment and stellar feedback. The IGIMF provides an analytic description of the dependence of the stellar IMF shape on the rate of star formation in galaxies. We find that our model with a universal IMF predicts a rather flat [$α$/Fe]-stellar mass relation. The model assuming the IGIMF, instead, is able to reproduce the observed increase of $α$-enhancement with stellar mass, in agreement with previous studies. This is mainly due to the fact that massive galaxies are characterized by larger star formation rates at high-redshift, leading to stronger $α$-enhancement with respect to low-mass galaxies. At the same time, the IGIMF hypothesis does not affect significantly the trend for shorter star formation timescales for more massive galaxies. We argue that in the IGIMF scenario the [$α$/Fe] ratios are good tracers of the highest star formation events. The final stellar masses and mass-to-light-ratio of our model massive galaxies are larger than those estimated from the synthetic photometry assuming a universal IMF, providing a self-consistent interpretation of similar recent results, based on dynamical analysis of local early type galaxies.

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