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arXiv 1601.07433astro-ph.GAastro-ph.CO
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星系团中星系的潮汐诱导棒

Tidally induced bars of galaxies in clusters

Ewa L. Lokas, Ivana Ebrova, Andres del Pino, Agnieszka Sybilska, E. Athanassoula, Marcin Semczuk, Grzegorz Gajda, Sylvain Fouquet

摘要:

利用N体模拟方法研究了团簇中盘状星系潮汐诱导棒的形成和演化。我们的祖先是一个巨大的,晚型星系类似于银河系,由指数盘和NFW暗物质晕组成。我们将星系置于室女座星系团的四个不同轨道上,并将其演化10 Gyr。作为一个参考案例,我们也孤立地发展了相同的模型。潮汐诱导的酒吧形成后不久,所有的轨道上的第一个近心通道,并生存,直到进化结束。它们出现得更早、更强、更长,并且在更紧的轨道上具有更低的模式速度。只有最紧的轨道的属性的酒吧控制的方向的潮汐扭矩从集群在pericenters。这些条的形成机制是角动量从星系的恒星成分转移到它的晕。当潮汐力较强时,所有的杆都经历了较长时间的屈曲不稳定性,这种屈曲不稳定性发生得更早,并导致更明显的方形/花生形。使用所有的模拟输出的星系在不同的演化阶段,我们构建了一个玩具模型的星系团中的人口和测量的平均酒吧强度和酒吧分数作为一个函数的团心半径。两者都被发现是半径的轻度减少的功能。我们的结论是,潮汐力可以触发酒吧形成在星系团的核心,但不是在外围,从而导致更大的浓度棒星系团的中心。

英文摘要:

Using N-body simulations we study the formation and evolution of tidally induced bars in disky galaxies in clusters. Our progenitor is a massive, late-type galaxy similar to the Milky Way, composed of an exponential disk and an NFW dark matter halo. We place the galaxy on four different orbits in a Virgo-like cluster and evolve it for 10 Gyr. As a reference case we also evolve the same model in isolation. Tidally induced bars form on all orbits soon after the first pericenter passage and survive until the end of the evolution. They appear earlier, are stronger, longer and have lower pattern speeds for tighter orbits. Only for the tightest orbit the properties of the bar are controlled by the orientation of the tidal torque from the cluster at pericenters. The mechanism behind the formation of the bars is the angular momentum transfer from the galaxy stellar component to its halo. All bars undergo extended periods of buckling instability that occur earlier and lead to more pronounced boxy/peanut shapes when the tidal forces are stronger. Using all simulation outputs of galaxies at different evolutionary stages we construct a toy model of the galaxy population in the cluster and measure the average bar strength and bar fraction as a function of clustercentric radius. Both are found to be mildly decreasing functions of radius. We conclude that tidal forces can trigger bar formation in cluster cores, but not in the outskirts, and thus cause larger concentrations of barred galaxies towards cluster center.

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