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arXiv 1909.04038astro-ph.GAastro-ph.CO
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御夫座宇宙学模拟中的气体吸积和星系喷泉流:angular momentum和金属再分布

Gas accretion and galactic fountain flows in the Auriga cosmological simulations: angular momentum and metal re-distribution

Robert J. J. Grand, Freeke van de Voort, Jolanta Zjupa, Francesca Fragkoudi, Facundo A. Gómez, Guinevere Kauffmann, Federico Marinacci, Rüdiger Pakmor, Volker S… 展开作者

Robert J. J. Grand, Freeke van de Voort, Jolanta Zjupa, Francesca Fragkoudi, Facundo A. Gómez, Guinevere Kauffmann, Federico Marinacci, Rüdiger Pakmor, Volker Springel, Simon D. M. White

摘要:

利用一组15个高分辨率的磁流体动力学宇宙学模拟银河系的形成,我们调查的起源重子物质中发现的恒星在红移为零。我们发现,大约一半的这种材料来自subhalo/卫星系统和一半是顺利地从星系间介质(IGM)吸积。在所有物质中,大约有$90 \%$至少有一次在星系风中被喷射和重新吸积。绝大多数顺利吸积的气体进入银河系喷泉,延伸到银河系中心距离中位数为$\sim 20$ kpc,再循环时间中位数为$\sim 500$ Myr。我们证明,在大多数情况下,银河喷泉获得角动量通过混合低角动量,风回收气体与高角动量气体在环银河介质(CGM)。顺行合并通过帮助调整圆盘和CGM旋转轴来促进这种活动,而逆行合并导致喷泉失去角动量。喷泉流,促进角动量的增长是有利于顺利的轨道上的演化准平行于光盘序列的恒星质量特定的角动量平面,而逆行的未成年人合并,主要合并和酒吧驱动的长期演化移动星系的膨胀序列。最后,我们证明了喷泉流的作用,扁平化和缩小的径向金属丰度梯度和金属丰度分散盘星,分别。因此,星系喷泉的演化强烈地依赖于宇宙学的合并历史,并且对于银河系大小的盘状星系的化学动力学演化至关重要。

英文摘要:

Using a set of 15 high-resolution magnetohydrodynamic cosmological simulations of Milky Way formation, we investigate the origin of the baryonic material found in stars at redshift zero. We find that roughly half of this material originates from subhalo/satellite systems and half is smoothly accreted from the Inter-Galactic Medium (IGM). About $90 \%$ of all material has been ejected and re-accreted in galactic winds at least once. The vast majority of smoothly accreted gas enters into a galactic fountain that extends to a median galactocentric distance of $\sim 20$ kpc with a median recycling timescale of $\sim 500$ Myr. We demonstrate that, in most cases, galactic fountains acquire angular momentum via mixing of low-angular momentum, wind-recycled gas with high-angular momentum gas in the Circum-Galactic Medium (CGM). Prograde mergers boost this activity by helping to align the disc and CGM rotation axes, whereas retrograde mergers cause the fountain to lose angular momentum. Fountain flows that promote angular momentum growth are conducive to smooth evolution on tracks quasi-parallel to the disc sequence of the stellar mass-specific angular momentum plane, whereas retrograde minor mergers, major mergers and bar-driven secular evolution move galaxies towards the bulge-sequence. Finally, we demonstrate that fountain flows act to flatten and narrow the radial metallicity gradient and metallicity dispersion of disc stars, respectively. Thus, the evolution of galactic fountains depends strongly on the cosmological merger history and is crucial for the chemo-dynamical evolution of Milky Way-sized disc galaxies.

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