Galactic chemical evolution in hierarchical formation models - I. Early-type galaxies in the local Universe GCE in SAMs
Galactic chemical evolution in hierarchical formation models - I. Early-type galaxies in the local Universe GCE in SAMs
复制标题
分层形成模型中的星系化学演化 - I. SAM 中局域宇宙 GCE 中的早期型星系
DOI：
10.1111/j.1365-2966.2009.15924.x
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发表时间：
2010
影响因子：
4.8
通讯作者：
Arrigoni M
中科院分区：
文献类型：
--
作者：
Arrigoni M
在星系形成的层次范式下，我们在宇宙学半解析模型（SAMs）中研究了早型星系的金属丰度和丰度比。为了实现这一目标，我们实施了一个详细的星系化学演化模型，现在可以预测在半解析模拟星系的个别元素的丰度。这是第一次一个SAM的反馈，从活动星系核包括化学演化处方，放松瞬时循环近似。我们发现新模型能够再现观测到的质量-金属丰度（M★-[Z/H]）关系，并且首次在SAM中再现了观测到的质量-丰度比（M★-[α/Fe]）关系的正斜率。我们的结果表明，为了同时匹配早期星系的这些观测结果，似乎需要使用非常轻微的头重脚轻的初始质量函数（即x = 1.15的斜率，而不是标准x = 1.3）和较低比例的爆炸为Ia型超新星（SNe Ia）的双星。我们还检查了模拟星系中SN爆炸的速率。在早期型（非恒星形成）星系，我们的预测也与观测到的SNe率一致。然而，在恒星形成的星系，一个更高的比例的超新星Ia双星比我们首选的模型是需要匹配的数据。然而，如果我们偏离经典模型，并引入一个人口的SNe Ia与非常短的延迟时间，我们的模型同时产生一个很好的匹配所观察到的金属丰度，丰度比和SN率。
We study the metallicities and abundance ratios of early-type galaxies in cosmological semi-analytic models (SAMs) within the hierarchical galaxy formation paradigm. To achieve this we implemented a detailed galactic chemical evolution model and can now predict abundances of individual elements for the galaxies in the semi-analytic simulations. This is the first time a SAM with feedback from active galactic nuclei has included a chemical evolution prescription that relaxes the instantaneous recycling approximation. We find that the new models are able to reproduce the observed mass–metallicity (M★–[Z/H]) relation and, for the first time in a SAM, we reproduce the observed positive slope of the mass–abundance ratio (M★–[α/Fe]) relation. Our results indicate that in order to simultaneously match these observations of early-type galaxies, the use of both a very mildly top-heavy initial mass function (i.e. with a slope ofx= 1.15 as opposed to a standardx= 1.3), and a lower fraction of binaries that explode as Type Ia supernovae (SNe Ia) appears to be required. We also examine the rate of SN explosions in the simulated galaxies. In early-type (non-star-forming) galaxies, our predictions are also consistent with the observed SNe rates. However, in star-forming galaxies, a higher fraction of SN Ia binaries than in our preferred model is required to match the data. If, however, we deviate from the classical model and introduce a population of SNe Ia with very short delay times, our models simultaneously produce a good match to the observed metallicities, abundance ratios and SN rates.