数值模拟对星系团中大质量次晕丰度预测的挑战：Abell 2142事例
Numerical simulations challenged on the prediction of massive subhalo abundance in galaxy clusters: the case of Abell 2142
摘要：
在这封信中，我们比较了丰富的，附近的（$z=0.09$）星系团，阿贝尔2142，成员星系的丰度与从国家的最先进的数值模拟，无论是碰撞在不同的分辨率和包含重子物理学的冷却，恒星形成和反馈的形式提取可比维里质量的晕。我们还使用两个半解析模型来解释孤儿星系的存在。从斯隆数字巡天数据发布12（SDSS DR 12）数据库中获取的光度和光谱信息，使我们能够估计Abell 2142成员星系的恒星速度色散。这个量被用作安全集群成员的总质量的代理，并适当地与模拟中的subhalos进行比较。我们发现，模拟晕有一个统计上显着的（$\gtrsim 7$西格玛置信水平）更少量的大规模（圆速度以上$200\,{\rm km\, s^{-1}}$）subhalos，即使在考虑可能的不完整的意见。这些结果证实了最近对哈勃前沿场星系团MACS J0416 \citep{grillo2015}的强透镜研究的发现，并表明观察到的差异已经存在于暗物质（DM）的暗晕水平，并且不能通过引入重子物理来解决。更深入地了解观测和模拟之间的这种差异，将为DM粒子的物理性质和重子对宇宙结构形成和演化的影响提供有价值的见解。
英文摘要：
In this Letter we compare the abundance of member galaxies of a rich, nearby ($z=0.09$) galaxy cluster, Abell 2142, with that of halos of comparable virial mass extracted from sets of state-of-the-art numerical simulations, both collisionless at different resolutions and with the inclusion of baryonic physics in the form of cooling, star formation, and feedback by active galactic nuclei. We also use two semi-analytical models to account for the presence of orphan galaxies. The photometric and spectroscopic information, taken from the Sloan Digital Sky Survey Data Release 12 (SDSS DR12) database, allows us to estimate the stellar velocity dispersion of member galaxies of Abell 2142. This quantity is used as proxy for the total mass of secure cluster members and is properly compared with that of subhalos in simulations. We find that simulated halos have a statistically significant ($\gtrsim 7$ sigma confidence level) smaller amount of massive (circular velocity above $200\,{\rm km\, s^{-1}}$) subhalos, even before accounting for the possible incompleteness of observations. These results corroborate the findings from a recent strong lensing study of the Hubble Frontier Fields galaxy cluster MACS J0416 \citep{grillo2015} and suggest that the observed difference is already present at the level of dark matter (DM) subhalos and is not solved by introducing baryonic physics. A deeper understanding of this discrepancy between observations and simulations will provide valuable insights into the impact of the physical properties of DM particles and the effect of baryons on the formation and evolution of cosmological structures.
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