Gravothermal collapse of isolated self-interacting dark matter haloes: N-body simulation versus the fluid model
Gravothermal collapse of isolated self-interacting dark matter haloes: N-body simulation versus the fluid model
复制标题
孤立的自相互作用暗物质晕的重力热塌陷：N 体模拟与流体模型
DOI：
10.1111/j.1365-2966.2011.18684.x
复制
发表时间：
2011
影响因子：
4.8
通讯作者：
P. Shapiro
中科院分区：
文献类型：
--
作者：
J. Koda;P. Shapiro
对于各种孤立的自相互作用暗物质(SIDM)晕，我们直接将蒙特卡罗N体模拟与传导流体(气体)模型的解析解和数值解进行了比较。两种方法在解决尖顶核问题的碰撞强度问题上存在分歧，但对于孤立晕，两种方法的一致性在20%以内。N体与Balberg等人提出的流体模型中重力热塌陷的解析自相似解非常吻合。(2002)，当选择一个自由参数--导热系数C为0.75时。密度分布是自相似演化的，中心密度和速度色散与解析解完全匹配，预测指数fi=2.19，这也是密度分布的渐近斜率。我们还用Plummer模型、Hernquist分布和NFW分布对导电流体模型进行了模拟和一维数值计算，表明该流体模型适用于更真实的密度分布。在长平均自由程区域内，核最大膨胀时的中心密度与崩塌时间在20%以内一致。当平均自由程变得与系统大小相当时，我们看到崩溃速率中的延迟如预测的那样。在此过渡区，如果将短平均自由程中的另一个热传导前因数b设置为0.25，则重力热塌陷模拟与流体模型一致。如果用N体模拟标定热传导的两个前置因子C和b，则蒙特卡罗N体模拟与导电流体模型是一致的。我们的结果验证了这两种方法在碰撞自引力系统中的应用。在整个论文中，假设碰撞是各向同性的，与速度无关。
We make direct comparisons between Monte Carlo N-body simulations and analytic and numerical solutions of a conduction fluid (gaseous) model, for various isolated selfinteracting dark matter (SIDM) haloes. There is a disagreement between two methods on the sucient strength of collisionality to solve cuspy core problem, but we show that the two agree within 20% for isolated haloes. The N-body agrees very well with the analytical self-similar solution of gravothermal collapse in the fluid model by Balberg et al. (2002) when one free parameter, the coecient of thermal conduction C, is chosen to be 0.75. The density profile evolves self-similarly and the central density and velocity dispersion match the analytical solution perfectly with the predicted exponent fi = 2.19, which is also an asymptotic slope of the density profile. We also initialize the simulation and the 1D numerical calculation of the conducting fluid model with the Plummer’s model, the Hernquist profile and the NFW profile to show that the fluid model is applicable to more realistic density profiles. The central density at maximum core expansion and the collapse time agree within 20% in the long mean free path regime. As the mean free path become comparable to the system size, we see the delay in collapse rate as predicted. In this transitional regime, gravothermal collapse simulation agree with the fluid model if another prefactor of thermal conduction, b, in the short mean free path is set to 0.25. Monte Carlo N-body simulation and conducting fluid model agree with each other if two prefactors of thermal conduction C and b are calibrated by the N-body simulation. Our results validate the use of these two methods for collisional self-gravitating systems. Throughout the paper, the collision is assumed to be isotropic and velocity independent.