We extend the random-walk model of Vitvitska et al. for predicting the spins of dark matter halos from their merger histories. Using updated merger rates, orbital parameter distributions, and N-body constraints we show that this model can accurately reproduce the distribution of spin parameters measured in N-body simulations when we include a weak correlation between the spins of halos and the angular momenta of infalling subhalos. We further show that this model is in approximate agreement with the correlation of the spin magnitude over time as determined from N-body simulations, while it slightly underpredicts the correlation in the direction of the spin vector measured from the same simulations. This model is useful for predicting spins from merger histories derived from non-N-body sources, thereby circumventing the need for very high resolution simulations to permit accurate measurements of spins. It may be particularly relevant to modeling systems which accumulate angular momentum from halos over time (such as galactic discs) - we show that this model makes small but significant changes in the distribution of galactic disc sizes computed using the Galacticus semi-analytic galaxy formation model.

中文翻译：

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暗物质晕自旋的随机游走模型

我们扩展了 Vitvitska 等人的随机游走模型。用于从它们的合并历史中预测暗物质晕的自旋。使用更新的合并率、轨道参数分布和 N 体约束，我们表明该模型可以准确地再现在 N 体模拟中测量的自旋参数的分布，当我们包括晕的自旋和入射角动量之间的弱相关性时亚晕。我们进一步表明，该模型与从 N 体模拟确定的自旋幅度随时间的相关性近似一致，而它略微低估了从相同模拟测量的自旋矢量方向上的相关性。该模型可用于根据源自非 N 体源的合并历史预测自旋，从而避免了对非常高分辨率模拟的需要，以允许精确测量自旋。它可能与随着时间的推移从晕圈（例如星系盘）积累角动量的建模系统特别相关——我们表明，该模型对使用 Galacticus 半解析星系形成模型计算的星系盘大小分布产生了微小但显着的变化.