回溯麦哲伦星云
Tracing the Magellanic Clouds Back in Time
摘要：
在一些简化的假设下，给出了麦哲伦云、银河系和M31的过去运动的解，并拟合到云和M31的实测速度。星系被建模为孤立的物体，红移约为10，当它们的速度相对于宇宙的一般膨胀很小时，与结构增长的引力不稳定性相一致。本星系群外的质量被模拟为第三个大质量动力学因素，它负责云的角动量。在这些假设下，一个合理的解要求银河系的圆速度v_c在200 ~ 230 km/s之间。在v_c和外部质量位置的选择所允许的适度变化范围内，该解似乎是唯一的。在这个解中，高红移的原麦哲伦云位于银河系的南极附近（以现在的方向），距离银河系约200 kpc，并以约200 km/s的速度移动。
英文摘要：
A solution is presented for the past motions of the Magellanic Clouds, the Milky Way galaxy, and M31, fitted to the measured velocities of the Clouds and M31, under some simplifying assumptions. The galaxies are modeled as isolated bodies back to redshift about 10, when their velocities relative to the general expansion of the universe were small, consistent with the gravitational instability picture for the growth of structure. Mass outside the Local Group is modeled as a third massive dynamical actor that is responsible for the angular momentum of the Clouds. A plausible solution under these assumptions requires that the circular velocity v_c of the Milky Way is in the range 200 to 230 km/s. The solution seems to be unique up to the modest variations allowed by the choices of v_c and the position of the exterior mass. In this solution the proto-Magellanic Clouds at high redshift were near the South pole of the Milky Way (in its present orientation), at physical distance about 200 kpc from the Milky Way and moving away at about 200 km/s.
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