Magnetic field amplification and star bursts induced by mergers of disk galaxies

我们计划通过数值模拟来探索盘状星系合并过程中的磁场演化、星星形成活动和分子气体。理论和观测研究都表明，合并在星系演化中起着重要作用，并有迹象表明合并期间的磁场放大。基于初步的数值模拟绝热气体盘没有暗物质晕，我们提出了一个更现实的模型，通过引入暗物质晕建模粒子，更详细的处理化学反应，特别是形成分子氢，亚网格物理学包括湍流，星星的形成，和反馈的星系合并。我们将采用磁流体动力学自适应网格细化代码恩佐，包括一个新的亚网格尺度模型磁流体动力学湍流和天体化学包KROME模拟分子气体的形成比以前的星系模拟更详细。此外，我们将应用一个动力学模型的星星的形成，是不是基于一个固定的效率参数对应于所观察到的Kennicutt-Schmidt关系孤立星系。这种方法被成功地应用于模拟孤立的盘星系没有磁场，正确的效率是由模型再现。在这个项目中，我们将扩展该模型的磁流体动力学的情况下，测试它在孤立的磁盘模拟，然后将其应用到合并。概述的方法将使我们能够解开不同渠道的湍流生产磁场放大的影响（基本上是不稳定性与反馈），合并参数，如磁盘的方向和影响参数的依赖，以及合并系统中的星星形成和分子气体含量之间的关系。

We plan to explore the evolution of the magnetic field, the star formation activity, and the molecular gas during mergers of disk galaxies by means of numerical simulations. Both theoretical and observational studies showed that mergers play a significant role in the evolution of galaxies and there are indications of magnetic field amplification during mergers. Based on preliminary numerical simulations of adiabatic gaseous disks without dark matter halos, we propose a substantially more realistic model of galaxy mergers by introducing dark-matter halos modelled be particles, a more detailed treatment of chemical reactions, particularly the formation of molecular hydrogen, and subgrid physics encompassing turbulence, star formation, and feedback. We will employ the magnetohydrodynamical adaptive mesh refinement code Enzo, including a novel subgrid-scale model for magnetohydrodynamical turbulence and the astrochemistry package KROME to model the formation of molecular gas in greater detail than in previous galaxy simulations. Moreover, we will apply a dynamical model of star formation that is not based on a fixed efficiency parameter corresponding to the observed Kennicutt-Schmidt relation for isolated galaxies. This approach was successfully applied in simulations of isolated disk galaxies without magnetic fields, for which the correct efficiency is reproduced by the model. In this project, we will extend the model to the magnetohydrodynamical case, test it in isolated disk simulations and then apply it to mergers. The outlined methodology will allow us to unravel the impact of different channels of turbulence production on magnetic field amplification (basically instabilities vs feedback), the dependence on merger parameters such as disk orientation and impact parameter, and the relation between star formation and molecular gas content in merging systems.