Abstract We present a method for customizing the root grid of zoom-in initial conditions used for simulations of galaxy formation. Starting from the white noise used to seed the structures of an existing initial condition, we cut out a smaller region of interest and use this trimmed white noise cube to create a new root grid. This new root grid contains similar structures as the original, but allows for a smaller box volume and different grid resolution that can be tuned to best suit a given simulation code. To minimally disturb the zoom region, the dark matter particles and gas cells from the original zoom region are placed within the new root grid, with no modification other than a bulk velocity offset to match the systemic velocity of the corresponding region in the new root grid. We validate this method using a zoom-in initial condition containing a Local Group analog. We run collisionless simulations using the original and modified initial conditions, finding good agreement. The dark matter halo masses of the two most massive galaxies at z = 0 match the original to within 15%. The times and masses of major mergers are reproduced well, as are the full dark matter accretion histories. While we do not reproduce specific satellite galaxies found in the original simulation, we obtain qualitative agreement in the distributions of the maximum circular velocity and the distance from the central galaxy. We also examine the runtime speedup provided by this method for full hydrodynamic simulations with the ART code. We find that reducing the root grid cell size improves performance, but the increased particle and cell numbers can negate some of the gain. We test several realizations, with our best runs achieving a speedup of nearly a factor of two.

中文翻译：

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使用自定义网格的初始条件提高放大宇宙学模拟的性能

摘要 我们提出了一种自定义用于模拟星系形成的放大初始条件根网格的方法。从用于为现有初始条件的结构播种的白噪声开始，我们切出一个较小的感兴趣区域，并使用这个修剪过的白噪声立方体来创建一个新的根网格。这个新的根网格包含与原始网格相似的结构，但允许更小的盒子体积和不同的网格分辨率，可以调整以最适合给定的模拟代码。为了最小化缩放区域的干扰，来自原始缩放区域的暗物质粒子和气室被放置在新的根网格内，除了体积速度偏移以匹配新根网格中相应区域的系统速度外，没有任何修改. 我们使用包含本地组模拟的放大初始条件来验证此方法。我们使用原始和修改后的初始条件运行无碰撞模拟，找到了很好的一致性。z = 0 时两个最大质量星系的暗物质晕质量与原始星系的匹配度在 15% 以内。重大合并的时间和质量都得到了很好的再现，完整的暗物质吸积历史也是如此。虽然我们没有重现在原始模拟中发现的特定卫星星系，但我们在最大圆周速度的分布和与中央星系的距离方面获得了定性的一致性。我们还检查了此方法为使用 ART 代码进行完整流体动力学模拟所提供的运行时加速。我们发现减少根网格单元大小可以提高性能，但是增加的粒子和细胞数量可以抵消一些增益。我们测试了几个实现，我们最好的运行实现了近两倍的加速。