标题： 恒星团形成建模：合并 显示英文标题

标题： Modelling Star Cluster Formation: Mergers

摘要： 星团在巨大分子云中的形成涉及云的局部坍缩成小而富含气体的子云团，这些子云团随后可以碰撞并合并以形成最终的星团。 在本文中，我们模拟了这些子云团之间的碰撞，使用耦合的平滑粒子流体动力学来处理气体，使用N体动力学来处理恒星。 我们受到之前分子云坍缩的辐射流体动力学模拟的指导，这些模拟提供了碰撞星团的全局特性，如它们的恒星和气体质量，以及它们的初始位置和速度。 原始模拟中的子云团被处理为汇粒子，在碰撞后立即合并成一个单一实体。 我们表明，更详细的处理提供了更复杂的图景。 在碰撞速度高于约10 km/s的情况下，星团的恒星成分在3 Myr内不会形成一个整体的星团，尽管气体可能会这样做。 在较低的速度下，星团最终会合并，但所需的时间尺度可能比后续碰撞的时间更长。 结果星团的结构无法用任何标准密度分布很好地拟合，而且星团并不处于平衡状态，而在我们的模拟时间内继续膨胀。 我们得出结论，大规模巨大分子云模拟中对子云团合并的简单汇粒子处理提供了最终星团特性的上限。 显示英文摘要

摘要： Star cluster formation in giant molecular clouds involves the local collapse of the cloud into small gas-rich subclusters, which can then subsequently collide and merge to build up the final star cluster(s). In this paper, we simulate collisions between these subclusters, using coupled smooth particle hydrodynamics for the gas and N-body dynamics for the stars. We are guided by previous radiation hydrodynamics simulations of molecular cloud collapse which provide the global properties of the colliding clusters, such as their stellar and gas masses, and their initial positions and velocities. The subclusters in the original simulation were treated as sink particles which immediately merged into a single entity after the collision. We show that the more detailed treatment provides a more complex picture. At collisional velocities above ~ 10 km/s, the stellar components of the cluster do not form a monolithic cluster within 3 Myr, although the gas may do so. At lower velocities, the clusters do eventually merge but over timescales that may be longer than the time for a subsequent collision. The structure of the resultant cluster is not well-fit by any standard density distribution, and the clusters are not in equilibrium but continue to expand over our simulation time. We conclude that the simple sink particle treatment of subcluster mergers in large-scale giant molecular cloud simulations provides an upper limit on the final cluster properties.