Supernova-driven winds in simulated dwarf galaxies
Supernova-driven winds in simulated dwarf galaxies
复制标题
模拟矮星系中超新星驱动的风
DOI：
10.1093/mnras/sty3252
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发表时间：
2018
影响因子：
4.8
通讯作者：
Chia
中科院分区：
文献类型：
--
作者：
Chia
利用高分辨率（粒子质量m_{\rmGas} = 1{\rmM_\odot}$）流体动力学模拟研究了孤立矮星系中超新星爆发驱动的星系风，包括非平衡冷却和化学反应、单个星星形成、恒星反馈和金属富集.我们发现，系统达到一个准稳态的GYR时间尺度上，虽然有很强的时间波动。膨胀的SNe导致超级气泡的形成，这些超级气泡从圆盘中破裂并排出热气，从而引发风。在维里半径处，质量、动量和能量的时均加载因子分别为3、1和0.05，金属富集因子为1.5。逃离光环的风由两种不同的发射温度组成。热气体在发射时获得足够的动能逃逸，而暖气体则没有。然而，热气体可以通过随后发射的热气体的冲压压力进一步加速并最终逃逸。不同温度阶段之间的强烈相互作用突出了基于其局部条件（例如伯努利参数）将温暖气体的性质外推到大距离的警告。我们的收敛性研究发现，风的性质收敛在$m_{\rm gas}=5 {\rm M_\odot}$（注入质量为500 {\rm M_\odot}$），一旦单个SNe的冷却质量变得无法解决，风就会急剧减弱。我们证明，注入SNe的终端动量（忽略剩余热能），在文献中流行的子网格模型，未能捕捉到压力驱动的风。失败归因于其假设，即即使对于高度聚集的SNe，大部分热能也在注入后立即辐射出去。
We investigate galactic winds driven by supernova (SN) explosions in an isolated dwarf galaxy using high-resolution (particle mass $m_{\rm gas} = 1{\rm M_\odot}$) hydrodynamical simulations that include non-equilibrium cooling and chemistry, individual star formation, stellar feedback and metal enrichment. We find that the system reaches a quasi-steady state on a Gyr-timescale though with strong temporal fluctuations. Clustered SNe lead to the formation of superbubbles which break out of the disk and vent out hot gas, launching the winds. At the virial radius, the time-averaged loading factors of mass, momentum and energy are 3, 1 and 0.05, respectively, and the metal enrichment factor is 1.5. Winds that escape the halo consist of two populations that differ in their launching temperatures. Hot gas acquires enough kinetic energy to escape when launched while warm gas does not. However, warm gas can be further accelerated by the ram pressure of the subsequently launched hot gas and eventually escape. The strong interactions between different temperature phases highlight the caveat of extrapolating properties of warm gas to large distances based on its local conditions (e.g. the Bernoulli parameter). Our convergence study finds that wind properties converge at $m_{\rm gas}=5 {\rm M_\odot}$ (with an injection mass of $500 {\rm M_\odot}$), and the winds weaken dramatically once the cooling masses of individual SNe become unresolved. We demonstrate that injecting the terminal momentum of SNe (neglecting the residual thermal energy), a popular sub-grid model in the literature, fails to capture pressure-driven winds. The failure owes to its assumption that most thermal energy is radiated away right after injection even for highly clustered SNe.