论文标题
模拟的高红移星系中的圆盘厚度的演变
Evolution of Disc Thickness in Simulated High-Redshift Galaxies
论文作者
论文摘要
我们使用一套宇宙学模拟研究了银河系大小星系的恒星盘的生长。我们计算恒星种群的半质量轴长度和轴轴比例，在带有恒星质量$ m_* = 10^7-10^{10} {10} m _ {\ odot} $的孤立星系中分裂的年龄，在Redshifts $ z $> 1.5。我们发现，在我们的模拟中，恒星始终以相对较薄的圆盘形成，在100岁以下的年龄在半质量的高度$ z_ {1/2} $ 〜0.1 kpc和短对长轴比$ z_ {1/2}/x__ {1/2} $ 〜0.15中。圆盘厚度随着恒星种群的年龄而增加，达到中位数$ z_ {1/2} $ 〜0.8 kpc和$ z_ {1/2}/x_ {1/2} $ 〜0.6 $ 〜0.6 $ 〜0.6，年龄超过500 MYR。我们在模拟快照上追踪相同的恒星，并明确表明它们的内在形状会随着时间的流逝而增长。我们确定了一种有助于观察到的圆盘厚度的新机制：银河平面的方向的快速变化混合了年轻恒星的构型。经常提到的银河盘的“倒置”形成场景，它认为年轻的恒星在高红移时已经在已经厚的圆盘中形成，可能会缺少这种额外的快速盘膨胀机制。相当薄的平面内恒星的实际形成与燃料恒星形成的致密分子气的相应平坦构型一致。
We study the growth of stellar discs of Milky Way-sized galaxies using a suite of cosmological simulations. We calculate the half-mass axis lengths and axis ratios of stellar populations split by age in isolated galaxies with stellar mass $M_* = 10^7 - 10^{10} M_{\odot}$ at redshifts $z$ > 1.5. We find that in our simulations stars always form in relatively thin discs, and at ages below 100 Myr are contained within half-mass height $z_{1/2}$ ~ 0.1 kpc and short-to-long axis ratio $z_{1/2}/x_{1/2}$ ~ 0.15. Disc thickness increases with the age of stellar population, reaching median $z_{1/2}$ ~ 0.8 kpc and $z_{1/2}/x_{1/2}$ ~ 0.6 for stars older than 500 Myr. We trace the same group of stars over the simulation snapshots and show explicitly that their intrinsic shape grows more spheroidal over time. We identify a new mechanism that contributes to the observed disc thickness: rapid changes in the orientation of the galactic plane mix the configuration of young stars. The frequently mentioned "upside-down" formation scenario of galactic discs, which posits that young stars form in already thick discs at high redshift, may be missing this additional mechanism of quick disc inflation. The actual formation of stars within a fairly thin plane is consistent with the correspondingly flat configuration of dense molecular gas that fuels star formation.
