跨越宇宙恒星形成历史高峰的恒星盘的升降：合并与平滑吸积
The rise and fall of stellar discs across the peak of cosmic star formation history: mergers versus smooth accretion
摘要：
从一个国家的最先进的宇宙流体动力学模拟，地平线-AGN星系合并树，我们进行了统计研究如何合并和平滑吸积驱动星系的形态特性以上$z > 1$。更具体地说，我们研究恒星的密度，有效半径和形状参数来自惯性张量取决于合并不同的质量比。我们发现了强有力的证据表明，在宇宙时间内，平滑的吸积往往会使小星系变平，从而形成盘。另一方面，合并，而不仅仅是主要的合并，表现出膨胀和破坏恒星盘的倾向，证实了椭圆星系的起源。我们还发现，椭圆星系更容易通过合并比盘星系的尺寸质量演化$r \prop M^{1.2}$而不是$r \prop M^{-0.5} - M^{0.5}$取决于合并质量比的大小增长。气体含量驱动的大小质量的演变，由于合并与气体贫星系$r \prop M^2$比气体丰富的星系$r \prop M$更快的大小增长。
英文摘要：
Building galaxy merger trees from a state-of-the-art cosmological hydrodynamics simulation, Horizon-AGN, we perform a statistical study of how mergers and smooth accretion drive galaxy morphologic properties above $z > 1$. More specifically, we investigate how stellar densities, effective radii and shape parameters derived from the inertia tensor depend on mergers of different mass ratios. We find strong evidence that smooth accretion tends to flatten small galaxies over cosmic time, leading to the formation of disks. On the other hand, mergers, and not only the major ones, exhibit a propensity to puff up and destroy stellar disks, confirming the origin of elliptical galaxies. We also find that elliptical galaxies are more susceptible to grow in size through mergers than disc galaxies with a size-mass evolution $r \prop M^{1.2}$ instead of $r \prop M^{-0.5} - M^{0.5}$ depending on the merger mass ratio. The gas content drive the size-mass evolution due to merger with a faster size growth for gas-poor galaxies $r \prop M^2$ than for gas-rich galaxies $r \prop M$.
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