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arXiv 1106.4556astro-ph.COastro-ph.GA
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富气星系相互作用期间的化学演化

Chemical evolution during gas-rich galaxy interactions

Josefa Perez, Leo Michel-Dansac, Patricia Tissera

备注：
13 pages, 13 figures, accepted for publication in MNRAS
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摘要：

我们分析了一组星系的相互作用，使用自洽的化学流体动力学模型，其中包括恒星形成，超新星反馈和化学演化。与以前的工作一致，我们发现，潮汐引起的低金属丰度气体流入稀释中心的氧丰度，并有助于平坦的金属丰度梯度。潮汐引起的流入触发星爆，这增加了SN II反馈的影响，注入新的化学元素和驱动银河风，调节金属丰度分布。虽然$α$ -增强的中心区域检测到的诱导星爆与以前的工作一致的结果，我们的模拟表明，这个参数只能提供一个时间的第一近心点主要是非逆行的遭遇。为了再现低和高红移下的湿主合并，我们分别用20%和50%的气体形式的圆盘进行了模拟。我们发现，更多的气体丰富的遭遇表现类似于不太丰富的，在第一和第二近心点之间的低金属含量的气体流入被触发。然而，在更富气体的相互作用中触发的更高强度的流入产生更大的金属稀释因子，这些因子随后被超新星的新化学产物调制。我们发现，更多的气体丰富的相互作用开发暴力和clusified恒星形成引发的本地不稳定性之前的第一个近心点，因此，如果这些星系被观察到在这些早期阶段，没有重要的潮汐诱导的流入已经能够发展，他们往往会表现出过剩的氧气。我们发现一个全球平均相关的中心丰度和梯度的强度的恒星形成活动。[删节]

英文摘要：

We analyse a set of galaxy interactions performed by using a self-consistent chemo-hydrodynamical model which includes star formation, Supernova feedback and chemical evolution. In agreement with previous works, we find that tidally-induced low-metallicity gas inflows dilute the central oxygen abundance and contribute to the flattening of the metallicity gradients. The tidally-induced inflows trigger starbursts which increase the impact of SN II feedback injecting new chemical elements and driving galactic winds which modulate the metallicity distribution. Although $α$-enhancement in the central regions is detected as a result of the induced starbursts in agreement with previous works, our simulations suggest that this parameter can only provide a timing of the first pericentre mainly for non-retrograde encounters. In order to reproduce wet major mergers at low and high redshifts, we have run simulations with respectively 20 and 50 percent of the disc in form of gas. We find that the more gas-rich encounters behave similarly to the less rich ones, between the first and second pericentre where low-metallicity gas inflows are triggered. However, the higher strength of the inflows triggered in the more gas-rich interactions produces larger metal dilutions factors which are afterward modulated by the new chemical production by Supernova. We find that the more gas-rich interaction develops violent and clumpy star formation triggered by local instabilities all over the disc before the first pericentre, so that if these galaxies were observed at these early stages where no important tidally-induced inflows have been able to develop yet, they would tend to show an excess of oxygen. We find a global mean correlation of both the central abundances and the gradients with the strength of the star formation activity. [abridged]

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