Formation of the off‐centre bar in the Large Magellanic Cloud: a collision with a dark satellite?
Formation of the off‐centre bar in the Large Magellanic Cloud: a collision with a dark satellite?
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大麦哲伦云中偏心条的形成：与暗卫星的碰撞？
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发表时间：
2008
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通讯作者：
K. Bekki
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作者：
K. Bekki
最近基于深近红外南天巡天和2微米全天巡天对大麦哲伦星云（LMC）结构特性的观测表明，即使在较老的恒星群体中，LMC也有一个偏离中心的棒。以前的动力学模型包括大麦哲伦星云、小麦哲伦星云（SMC）和银河系之间的潮汐相互作用，但是，并没有很好地再现较老的偏心棒。在这里，我们表明，如果已经存在棒的LMC可以与质量为105 × 108 M <$的低质量银河系次晕（大致相当于LMC质量的百分之几）碰撞，则可以形成偏离中心的棒。碰撞后的模拟恒星分布似乎显示出“偏离中心的酒吧”，不是因为酒吧的中心显着偏离LMC的动力学中心，而是因为盘的基本恒星分布相对于酒吧的中心显着不对称。我们讨论是否偏离中心的酒吧中观察到的麦哲伦型矮星系可以形成的结果，潮汐相互作用与低质量的晕没有或很少可见的物质。
Recent observations of the structural properties of the Large Magellanic Cloud (LMC) based on the Deep Near-Infrared Southern Sky Survey and Two Micron All-Sky Survey have revealed that the LMC has an off-centre bar even in the older stellar populations. Previous dynamical models including tidal interaction between the LMC, the Small Magellanic Cloud (SMC) and the Galaxy, however, did not reproduce the older off-centre bar so well. Here, we show that the off-centre bar can be formed if the LMC with an already-existing bar can collide with a low-mass Galactic subhalo as massive as ∼5 × 108 M⊙ (roughly corresponding to a few per cent of the LMC mass). The simulated stellar distribution after the collision appears to show an ‘off-centre bar’, not because the centre of the bar significantly deviates from the dynamical centre of the LMC, but because the underlying stellar distribution of the disc is significantly asymmetric with respect to the centre of the bar. We discuss whether off-centre bars observed in Magellanic-type dwarf galaxies can be formed as a result of tidal interaction with low-mass haloes with no or little visible matter.