标题： 星系团合并的流体动力学模拟：由引力驱动的巨大暗物质粒子对撞机 显示英文标题

标题： Hydrodynamical simulations of merging galaxy clusters: giant dark matter particle colliders, powered by gravity

摘要： 地面上的粒子加速器会撞击带电粒子，然后观察出射碎片的轨迹——但它们无法操控暗物质。幸运的是，暗物质是星系团的主要成分，而星系团则持续受到引力的作用聚集在一起。我们表明，星系团合并可以被利用作为巨大的天然暗物质对撞机。我们分析了一个包含自相互作用暗物质（SIDM）的宇宙的流体力学模拟，在这个模拟中所有粒子都通过引力相互作用，而且暗物质粒子也可以通过一个大质量媒介彼此散射。在星系团碰撞期间，SIDM会扩散开来并且落后于星团成员星系。单个系统可能具有难以解释的独特动力学行为。然而，统计上，我们发现许多碰撞中暗物质空间偏移的平均值或中位数可以被稳健建模，并且与我们的观测角度和晕质量无关，即使是在质量不相等的系统之间的碰撞中也是如此。如果SIDM的截面为sigma/m = 0.1cm^2/g = 0.18barn/GeV，“子弹性”滞后将是气体的约5%，并且可以在约100个精心挑选的星系团的弱透镜观测中以95%的置信度被检测到。 显示英文摘要

摘要： Terrestrial particle accelerators collide charged particles, then watch the trajectory of outgoing debris - but they cannot manipulate dark matter. Fortunately, dark matter is the main component of galaxy clusters, which are continuously pulled together by gravity. We show that galaxy cluster mergers can be exploited as enormous, natural dark matter colliders. We analyse hydrodynamical simulations of a universe containing self-interacting dark matter (SIDM) in which all particles interact via gravity, and dark matter particles can also scatter off each other via a massive mediator. During cluster collisions, SIDM spreads out and lags behind cluster member galaxies. Individual systems can have quirky dynamics that makes them difficult to interpret. Statistically, however, we find that the mean or median of dark matter's spatial offset in many collisions can be robustly modelled, and is independent of our viewing angle and halo mass even in collisions between unequal-mass systems. If the SIDM cross-section were sigma/m = 0.1cm^2/g = 0.18 barn/GeV, the 'bulleticity' lag would be ~5 percent that of gas due to ram pressure, and could be detected at 95 percent confidence in weak lensing observations of ~100 well-chosen clusters.