MOCCA code for star cluster simulations II: comparison with n-body simulations
MOCCA code for star cluster simulations II: comparison with n-body simulations
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DOI：
10.1093/mnras/stt307
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发表时间：
2011-12
影响因子：
4.8
通讯作者：
M. Giersz;D. Heggie;J. Hurley;Arkadiusz Hypki Nicolaus Copernicus Astronomical Centre-Arkadiusz-Hypki-Nicolaus-Copernicus-Astronomical-102815779;P. Sciences;U. Edinburgh-U.-Edi
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作者：
M. Giersz;D. Heggie;J. Hurley;Arkadiusz Hypki Nicolaus Copernicus Astronomical Centre-Arkadiusz-Hypki-Nicolaus-Copernicus-Astronomical-102815779;P. Sciences;U. Edinburgh-U.-Edi
我们描述了蒙特卡罗代码的重大升级，该代码之前已用于密集星团的许多研究。我们概述了根据大型 N 系统（最高 N = 200000）的 N 体模拟校准新蒙特卡罗代码的结果所需的步骤。除了旧版本之外，新版本的蒙特卡罗代码（称为 MOCCA）还包含用于三体和四体相互作用的直接 FewBody 积分器，以及基于 Fokushige 和 Heggie (2000) 的逃逸过程的新处理。现在，满足逃逸标准的恒星不会立即被移除，而是可以在系统中停留一段时间，这取决于恒星能量超过临界能量的程度。他们被称为潜在的逃亡者。 FewBody 积分器允许遵循所有相互作用通道，这对于星团中观察到的各种类型物体的创建速率非常重要，并确保以类似于 N 体模型的方式处理双星的能量生成。对于大 N 的 N 体模拟，最多需要调整三个参数。两个（或一个，取决于所选择的方法）与逃逸过程相关，一个负责确定相互作用概率。采用的自由参数与 N 无关。它们允许 MOCCA 代码以合理的精度重现 N 体结果，不仅可以重现簇演化速率和簇质量分布，还可以重现质量和双星结合能的详细分布。此外，该代码还可以跟踪蓝离散星和黑洞黑洞双星的形成速率。该代码计算双星和单星之间的相互作用直至最大分离rpmmax，并且发现MOCCA代码需要相当大的rpmmax值才能与N体模拟一致。 MOCCA代码是目前最先进的真实星团模拟代码。与 N 体代码相比，它可以详细地跟踪集群演化，但速度要快几个数量级。
We describe a major upgrade of a Monte Carlo code which has previously been used for many studies of dense star clusters. We outline the steps needed in order to calibrate the results of the new Monte Carlo code against N -body simulations for large N systems, up to N = 200000. The new version of the Monte Carlo code (called MOCCA), in addition to the old version, incorporates direct FewBody integrator for three- and four-body interactions, and new treatment of the escape process based on Fokushige & Heggie (2000). Now stars which fulfil the escape criterion are not removed immediately, but can stay in the system for a certain time which depends on the excess of the energy of a star above the critical energy. They are called potential escapers. FewBody integrator allows to follow all interaction channels, which are important for the rate of creation of various types of obj ects observed in star clusters, and assures that the energy generation by binaries is treated in a meaner similar to the N-body model. There are at most three parameters which have to be adjusted against N-body simulations for large N . Two (or one, depends on the chosen approach) connected with the escape process and one responsible for determination of the interaction probabilities. The adopted free parameters are independent on N . They allow MOCCA code to reproduce N-body results, in a reasonably precision, not only for the rate of clu ster evolution and the cluster mass distribution, but also for the detailed distributions of ma ss and binding energy of binaries. Additionally, the code can follow the rate of formation of blue stragglers and black hole black hole binaries. The code computes interactions between binaries and single stars up to a maximum separationrpmax, and it is found that the MOCCA code needs rather large value of rpmax to get agreement with the N-body simulations. The MOCCA code is at present the most advanced code for simulations of real star clusters. It can follow the cluster evolution in details compara ble to N-body code, but orders of magnitude faster.