Formation of Our Galaxy Studied with Super-High Resolution Next-Generation Simulator

1.我们完成了（1）名为ASURA的并行N体加SPH水力代码和（2）由16台PC组成的PC集群，每台PC与特定的自重力硬件（GRAPE）连接。由于这些使我们能够研究银河系的形成过程，我们称之为银河系模拟器（MWS）。(1)我们使用MWS进行高分辨率模拟，其中一个星系用10^7个粒子表示，这比以前的类似模拟大得多。从它们中，我们可以追踪到星际气体形成恒星的凝聚过程，其密度高达10^2cm-3，这与我们银河系中分子云的密度相吻合。(2)我们假定了一个唯象参数C_<eff>，用它来表示单位体积的星星形成率为C^<eff>_<eff>×ρ_<gas>/t_<ff>，其中，&gt;_<gas>as和t_<ff>分别代表气体的局部密度和自由壁时标。我们的高分辨率模拟结果表明，星星的形成速率可以用密度为10^0cm ~ 2的气体的辐射冷却时间来表示，<-3>而与C_无关<eff>。(3)因此，我们得到了一个处方，如何管理星星形成在低分辨率模拟。(4)我们模拟了星系-星系碰撞。我们发现星星形成爆发预计在碰撞的早期阶段，远远早于星系合并。基于有限差分格式，开发了自引力磁流体动力学模拟的自适应网格加密程序。计算了原恒星相的碎裂过程，证实了该程序的计算结果与以前的嵌套网格程序的计算结果一致。这使我们能够扩展主题。3.为了将模拟结果与观测结果进行比较，我们开发了一个基于Monte Carlo方法的分子转动跃迁辐射转移程序。我们已将其应用于星暴星系和形成分子云的星星。

1. We completed (1) a parallelized N-body plus SPH hydro code called ASURA and (2) a PC cluster composed of 16 PC's each connected with a specific hardware for self-gravity (GRAPE). Since these enable us to study the formation process of our Galaxy, we call them Milky Way Simulator (MWS).(1) We perform high resolution simulations with MWS, in which one galaxy is expressed with 10^7 particles, which is much larger than previous similar simulations. From them, we can trace the condensation process of interstellar gas to form stars up to〜10^2cm-3, which coincides with the density of molecular clouds in our Galaxy.(2) A phenomenological parameter, C_<eff>, has been assumed, with which the star formation rate per unit volume is assumed as C^<eff>_<eff>×ρ_<gas>/t_<ff>, where>_<gas> as and t_<ff> represent, respectively, the local gas density and free-wall timescale of the gas. Our high resolution simulations indicate us that the star formation rate is well expressed with a radiative cooling time of a gas with a density of 10^0cm_<-3>, irrespective of C_<eff>.(3) Thus, we obtained a prescription how to manage the star formation in low resolution simulations.(4) We performed simulations of galaxy-galaxy collision. We found that a star formation burst is expected in the early phase of the collision far before making a galaxy merger.2. We developed an adaptive mesh refinement (AMR) code for self-gravitating magnetohydrodynamical simulation based on the finite-difference scheme. Calculating the fragmentation process in the protostellar phase, we have confirmed that this code gives the consistent result obtained with previous nested grid code. This enables us to extend the subjects.3. To compare the simulation result with observation, we have developed a radiative transfer code for molecular rotational transitions based on Monte Carlo method. We have applied this to starburst galaxy and star forming molecular cloud.