Formation and Evolution of Barred Galaxies

很大一部分螺旋星系都含有棒。棒的存在可以极大地影响宿主星系的演化。棒将气体引导到星系的中心，在那里它被转化为恒星。这些恒星中的核反应产生重元素（称为“金属”），当恒星在超新星中爆炸时，这些重元素被喷射到气体中。此外，如果在星系中心有一个超大质量黑洞，沿着棒沿着流动的气体可能会落在黑洞上，产生活动星系核（或AGN）。因此，我们预期棒星系比无棒星系有更高的中心星星形成率（SFR）、更高的中心金属丰度和更强烈的活动星系核活动。然而，最近的观察揭示了一个更复杂的情况。只有具有强棒的星系才显示出增强的中央星星形成，但并非所有星系都是如此：大质量棒星系（恒星质量大于100亿至300亿太阳质量）和低质量棒星系之间似乎存在显着差异。所有的棒星系都表现出中心金属丰度的增强，但低质量的棒星系在中心星星形成方面没有表现出相应的增强。一些大质量的棒星系有，但不是所有的。相反，一些具有强棒的大质量星系显示出中心星星形成的抑制。这表明，在某些情况下，酒吧可能会淬火星星形成的中心区域，而不是促进它。此外，我们观察到的星星形成和活动星系核活动之间的反相关在棒星系的中心。这些观测揭示了不同质量的星系，或者具有不同强度的棒的星系，可以有截然不同的星星形成历史。为了充分理解这些星系的演化，我们需要了解驱动这种演化的各种物理过程之间的相互作用。我们建议进行一个长期项目，研究棒星系的演化。我们将进行一系列星系演化的数值模拟。我们的目标是了解的物理过程，决定了历史的星星形成和金属在棒星系，并确定在淬火星星形成的反馈在一些棒星系中所发挥的作用。

A large fraction of spiral galaxies contain bars. The presence of a bar can greatly affect the evolution of the host galaxy. The bar channels gas into the center of galaxies, where it is converted into stars. The nuclear reactions in these stars produce heavy elements (called "metals"), that are then ejected into the gas when the stars explode in supernovae. Also, if there is a supermassive black hole in the center of the galaxy, the gas flowing along the bar might fall onto the black hole, producing an active galactic nuclei (or AGN). We would therefore expect barred galaxies to have higher central star formation rates (SFR), higher central metallicity, and more intense AGN activity than unbarred galaxies. However, recent observations reveal a more complex picture. Only galaxies with strong bars show enhanced central star formation, and not all of them do: There appears to be significant differences between massive barred galaxies (stellar masses larger than 10-30 billion solar masses) and low-mass ones. All barred galaxies show an enhancement in central metallicity, but low-mass barred galaxies do not show a corresponding enhancement in central star formation. Some high-mass barred galaxies do, but not all of them. Instead, some massive galaxies with strong bars show a suppression of central star formation. This suggests that bars might, under some circumstances, quench star formation in the central regions, instead of boosting it. Also, we observe an anti-correlation between star formation and AGN activity in the center of barred galaxies. These observations reveal that galaxies of different masses, or with bars of different strength, can have drastically different star formation histories. To fully understand the evolution of these galaxies, we need to understand the interplay between the various physical processes driving this evolution. We propose to pursue a long-term project to study the evolution of barred galaxies. We will perform a series of numerical simulations of galaxy evolution. Our goal is to understand the physical processes that determine the history of star formation and metallicity in barred galaxies, and determine the role played by feedback in quenching star formation in some barred galaxies.