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

使用超高分辨率下一代模拟器研究银河系的形成

基本信息

批准号：
17340059
负责人：
TOMISAKA Kohji
金额：
$ 8.54万
依托单位：
National Astronomical Observatory of Japan
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

项目摘要

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.

1. 我们完成了 (1) 一个名为 ASURA 的并行 N 体加 SPH 水力代码，以及 (2) 由 16 台 PC 组成的 PC 集群，每台 PC 都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，我们将其称为银河系模拟器（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要大得多。由此，我们可以追踪星际气体凝结形成恒星的过程，最高可达〜10^2cm-3，这与我们银河系分子云的密度相吻合。（2）假设了唯象参数C_<eff>，单位体积的恒星形成速率假设为C^<eff>_<eff>×ρ_<gas>/t_<ff>，其中>_<gas> as 和t_<ff> 分别表示气体的局部气体密度和自由壁时间尺度。我们的高分辨率模拟表明，无论C_<eff>如何，恒星形成速率都可以用密度为10^0cm_<-3>的气体的辐射冷却时间来很好地表达。（3）因此，我们获得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，在碰撞的早期阶段，预计会在星系合并之前发生恒星形成爆发。2．我们开发了一种基于有限差分格式的自重力磁流体动力学模拟的自适应网格细化（AMR）代码。通过计算原恒星阶段的碎片过程，我们已经确认该代码给出了与之前的嵌套网格代码获得的一致结果。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，我们开发了基于蒙特卡罗方法的分子旋转跃迁的辐射传递代码。我们已将其应用于星爆星系和恒星形成分子云。