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arXiv 1209.4462astro-ph.GA
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银河核球的化学演化:不同的恒星星族和可能的梯度

Chemical evolution of the Galactic bulge: different stellar populations and possible gradients

V. Grieco, F. Matteucci, A. Pipino, G. Cescutti

摘要:

我们计算了银河核球的化学演化,以解释最近观测到的两个主要恒星星族的存在。比较模型结果和观测数据后,我们认为,旧的更多的金属贫恒星星族形成非常快(在0.1-0.3 Gyr的时间尺度上)通过强烈的恒星形成的爆发和初始质量函数平坦比在太阳附近,而金属丰富的人口形成在一个较长的时间尺度(3 Gyr)。我们预测两个种群的平均丰度差异(<[Fe/H]>为-0.52 dex),这可以解释为金属丰度梯度。我们还预测了贫金属群本身内部的亚群之间Fe、O、Mg、Si、S和Ba的可能梯度(例如<[Fe/H]>为-0.145 dex)。最后,通过一个耗散坍缩后的化学动力学模型,我们预测在距离银河系中心500 pc以内,Fe的梯度为-0.26 dex kpc^{-1}。

英文摘要:

We compute the chemical evolution of the Galactic bulge to explain the existence of two main stellar populations recently observed. After comparing model results and observational data we suggest that the old more metal poor stellar population formed very fast (on a timescale of 0.1-0.3 Gyr) by means of an intense burst of star formation and an initial mass function flatter than in the solar vicinity whereas the metal rich population formed on a longer timescale (3 Gyr). We predict differences in the mean abundances of the two populations (-0.52 dex for <[Fe/H]>) which can be interpreted as a metallicity gradients. We also predict possible gradients for Fe, O, Mg, Si, S and Ba between sub-populations inside the metal poor population itself (e.g. -0.145 dex for <[Fe/H]>). Finally, by means of a chemo-dynamical model following a dissipational collapse, we predict a gradient inside 500 pc from the Galactic center of -0.26 dex kpc^{-1} in Fe.

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