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arXiv 1202.4770astro-ph.CO
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基本金属丰度关系的物理学

The physics of the fundamental metallicity relation

Pratika Dayal, Andrea Ferrara, James S. Dunlop

摘要:

我们提出了一个简单的,红移无关的分析模型,解释当地的基本金属丰度关系(FMR),考虑到恒星形成的物理过程,流入的金属贫星系际介质(IGM)气体,和流出的金属丰富的星际介质(ISM)气体。我们证明了FMR的物理学可以概括如下:对于恒星质量M * >= 10^11太阳质量的大质量星系,由于恒星形成而导致的ISM金属富集被贫金属IGM气体的流入所补偿,导致气体金属丰度随恒星形成率(SFR)的恒定值;由于这些星系的大势阱,流出可以忽略不计。另一方面,由于SFR较小,质量较小的星系产生的重元素也较少,而这些重元素由于其浅势阱而更有效地被抛射,因此,对于给定的M *,气体金属丰度随SFR减小。对于这样的星系,外流效率决定的斜率,和膝盖的金属性SFR关系。在不改变任何参数的情况下,这个简单的模型也成功地与大约260个邻近星系的样本中观察到的气体分数-气体金属丰度关系相匹配。

英文摘要:

We present a simple, redshift-independent analytic model that explains the local Fundamental Metallicity Relation (FMR), taking into account the physical processes of star formation, inflow of metal-poor intergalactic medium (IGM) gas, and the outflow of metal rich interstellar medium (ISM) gas. We show that the physics of the FMR can be summarised as follows: for massive galaxies with stellar mass M_* >= 10^11 solar masses, ISM metal enrichment due to star formation is compensated by inflow of metal poor IGM gas, leading to a constant value of the gas metallicity with star formation rate (SFR); outflows are rendered negligible as a result of the large potential wells of these galaxies. On the other hand, as a result of their smaller SFR, less massive galaxies produce less heavy elements that are also more efficiently ejected due to their shallow potential wells; as a result, for a given M_*, the gas metallicity decreases with SFR. For such galaxies, the outflow efficiency determines both the slope, and the knee of the metallicity-SFR relation. Without changing any parameters, this simple model is also successfully matched to the gas fraction - gas metallicity relation observed for a sample of about 260 nearby galaxies.

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