超越由内而外的增长：磁盘郊区的形成和演变
Beyond Inside-Out Growth: Formation and Evolution of Disk Outskirts
摘要：
我们对一个理想星系进行了高质量和力分辨率的模拟，该星系是由嵌入球形暗物质晕中的气体耗散坍缩形成的。模拟包括恒星形成和恒星反馈的影响。在我们的模拟中，一个恒星盘的形式与表面密度分布组成的内部指数打破一个陡峭的外部指数。破裂在早期形成，并在整个演化过程中持续存在，随着更多的气体能够冷却并增加圆盘的质量而向外移动。破裂的参数与观测结果非常吻合。这个突变对应于恒星形成率的快速下降，这与冷却气体表面密度的下降有关，但是外部指数是由从内盘通过螺旋臂在近圆形轨道上向外散射的恒星组成的。因此，由此产生的配置文件及其相关的突破是一个径向恒星形成截止和长期过程的恒星质量重新分配之间的相互作用的结果。这样的演变的一个后果是一个急剧变化的径向平均恒星年龄分布在断裂半径。
英文摘要：
We have performed a high mass and force resolution simulation of an idealized galaxy forming from dissipational collapse of gas embedded in a spherical dark matter halo. The simulation includes star formation and effects of stellar feedback. In our simulation a stellar disk forms with a surface density profile consisting of an inner exponential breaking to a steeper outer exponential. The break forms early on and persists throughout the evolution, moving outward as more gas is able to cool and add mass to the disk. The parameters of the break are in excellent agreement with observations. The break corresponds with a rapid drop in the star formation rate associated with a drop in the cooled gas surface density, but the outer exponential is populated by stars that were scattered outward on nearly circular orbits from the inner disk by spiral arms. The resulting profile and its associated break are therefore a consequence of the interplay between a radial star formation cutoff and redistribution of stellar mass by secular processes. A consequence of such evolution is a sharp change in the radial mean stellar age profile at the break radius.
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