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-Body+SPH HELHO代码和(2)由16台PC组成的PC集群，每台PC都连接着一个特定的自重硬件(GRPE)。(1)我们用银河系模拟器进行了高分辨率的模拟，其中一个星系用10^7个粒子表示，比以前的类似模拟要大得多。(2)假定了一个唯象参数C_&lt；ff&gt；，单位体积的恒星形成率假定为C^&lt；eff&gt；_&lt；eff&gt；×ρ_&lt；gas&gt；/t_&lt；ff&gt；，，其中&gt；_t；分别表示局部气体密度和气体的自由壁时间标度。我们的高分辨率模拟表明，恒星形成率可以很好地用密度为10 cm~(-3)的气体的辐射冷却时间来表示，而与C_&lt；ef&gt；无关。(3)因此，我们得到了如何在低分辨率模拟中管理恒星形成的处方。(4)我们进行了星系-星系碰撞的模拟。我们发现，在星系合并之前，恒星形成早在碰撞的早期阶段就被预料到了。开发了一种基于有限差分格式的自适应网格加密(AMR)程序，用于自引力磁流体力学模拟。计算了原恒星阶段的碎裂过程，证实了该程序与以前的嵌套网格程序得到的结果是一致的。这使我们能够扩展主题。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蒙特卡罗方法的分子转动跃迁辐射转移程序。我们已经将其应用于恒星爆发星系和恒星形成的分子云。

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.