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arXiv 0709.3511astro-ph
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星系质量比对并合驱动的星暴的影响

The effect of galaxy mass ratio on merger--driven starbursts

T. J. Cox, Patrik Jonsson, Rachel S. Somerville, Joel R. Primack, Avishai Dekel

摘要:

我们利用星系合并的数值模拟来探讨星系质量比对合并驱动的星暴的影响。我们的数值模拟包括气体的辐射冷却,恒星的形成,和恒星的反馈,以遵循四个盘状星系的相互作用和合并。星系模型的总质量跨越23倍,旨在代表本地宇宙中的典型星系。我们发现,合并驱动的恒星形成是一个强大的合并质量比的函数,很少,如果有的话,诱导恒星形成大质量比合并。我们定义了一个爆发的效率,这是有用的合并驱动的恒星形成的特点和测试,它是不敏感的反馈参数化的不确定性。与以往的工作一致,我们发现爆发效率依赖于原星系的结构。特别是,存在一个巨大的恒星隆起稳定磁盘和抑制合并驱动的恒星形成大质量比合并。直接的共面合并轨道产生最大的潮汐扰动,并产生最强烈的恒星形成爆发。与天真的预期相反,更紧凑的气体分布或增加的气体分数都降低了爆破效率。由于有效的反馈模型和新版本的SPH在这里采用,这里提出的合并的爆发效率小于在以前的研究。

英文摘要:

We employ numerical simulations of galaxy mergers to explore the effect of galaxy mass ratio on merger--driven starbursts. Our numerical simulations include radiative cooling of gas, star formation, and stellar feedback to follow the interaction and merger of four disk galaxies. The galaxy models span a factor of 23 in total mass and are designed to be representative of typical galaxies in the local Universe. We find that the merger--driven star formation is a strong function of merger mass ratio, with very little, if any, induced star formation for large mass ratio mergers. We define a burst efficiency that is useful to characterize the merger--driven star formation and test that it is insensitive to uncertainties in the feedback parameterization. In accord with previous work we find that the burst efficiency depends on the structure of the primary galaxy. In particular, the presence of a massive stellar bulge stabilizes the disk and suppresses merger--driven star formation for large mass ratio mergers. Direct, co--planar merging orbits produce the largest tidal disturbance and yield that most intense burst of star formation. Contrary to naive expectations, a more compact distribution of gas or an increased gas fraction both decrease the burst efficiency. Owing to the efficient feedback model and the newer version of SPH employed here, the burst efficiencies of the mergers presented here are smaller than in previous studies.

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