The rise and fall of a challenger: the Bullet Cluster in Lambda Cold Dark Matter simulations
The rise and fall of a challenger: the Bullet Cluster in Lambda Cold Dark Matter simulations
复制标题
挑战者的兴衰：Lambda 冷暗物质模拟中的子弹团
DOI：
10.1093/mnras/stv1433
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
K.
中科院分区：
文献类型：
--
作者：
Thompson;R.;Dave;R.;Nagamine;K.
子弹星系团通过直接的经验证据证明了无碰撞暗物质的存在，为Λ冷暗物质（ΛCDM）模型提供了一些最好的证据，同时由于其祖先星系团的成对速度异常高，因此构成了一个严重的挑战。在这里，我们调查的概率找到这样一个高速度对大volumeN-体模拟，特别是专注于晕之间的差异，发现算法。我们发现，算法，不占运动学的下降组产生巨大不同的统计数据和概率。当采用therockstarhalo发现器，考虑粒子的速度，我们发现许多子弹状对候选人，密切匹配不仅是高成对的速度，而且质量，质量比，分离距离和碰撞角的初始条件，已被证明产生子弹集群在非宇宙学流体动力学模拟。在Mhalo ≥ 1014 M的晕中找到高成对速度对的概率为4.6 × 10− 4，而使用基于朋友的朋友（FoF）方法的概率要低34倍。这是因为Bullet祖细胞的典型空间范围使得FoF倾向于将它们分组为单个晕，尽管运动学明显不同。进一步要求两个祖先之间有适当高的平均质量，我们发现潜在的子弹状候选者的共动数密度为100 - 10 Mpc-3。我们的研究结果表明，ΛCDM直接产生大量的，高相对速度的晕对类似于子弹星系团的祖先，因此子弹星系团并没有对ΛCDM模型提出挑战。
The Bullet Cluster has provided some of the best evidence for the Λ cold dark matter (ΛCDM) model via direct empirical proof of the existence of collisionless dark matter, while posing a serious challenge owing to the unusually high inferred pairwise velocities of its progenitor clusters. Here, we investigate the probability of finding such a high-velocity pair in large-volumeN-body simulations, particularly focusing on differences between halo-finding algorithms. We find that algorithms that do not account for the kinematics of infalling groups yield vastly different statistics and probabilities. When employing therockstarhalo finder that considers particle velocities, we find numerous Bullet-like pair candidates that closely match not only the high pairwise velocity, but also the mass, mass ratio, separation distance, and collision angle of the initial conditions that have been shown to produce the Bullet Cluster in non-cosmological hydrodynamic simulations. The probability of finding a high pairwise velocity pair among haloes withMhalo≥ 1014M⊙is 4.6 × 10−4usingrockstar, while it is ≈34 × lower using a friends-of-friends (FoF)-based approach as in previous studies. This is because the typical spatial extent of Bullet progenitors is such that FoF tends to group them into a single halo despite clearly distinct kinematics. Further requiring an appropriately high average mass among the two progenitors, we find the comoving number density of potential Bullet-like candidates to be of the order of ≈10−10Mpc−3. Our findings suggest that ΛCDM straightforwardly produces massive, high relative velocity halo pairs analogous to Bullet Cluster progenitors, and hence the Bullet Cluster does not present a challenge to the ΛCDM model.