盘状星系中超气泡的演化。用解析模型研究井喷
Superbubble evolution in disk galaxies, I. Study of blow-out by analytical models
摘要：
星系风是本宇宙中星暴星系和高红移星系中的一种常见现象。它们的来源是由恒星形成区域连续的超新星爆炸驱动的超级气泡，在星际介质中挖出大洞，将热的富含金属的气体喷射到晕和银河系附近。我们研究了指数分层圆盘中超气泡的演化。我们提出了先进的分析模型，这种泡沫的膨胀，并计算其在空间和时间的演变。有了这些模型，人们可以得到的能量输入，需要吹出的超级气泡进入晕，并得出破碎的壳，因为瑞利-泰勒不稳定性发展后不久，气泡开始加速进入晕。为了解析地计算气泡的速度和加速度，对Kompaneets近似进行了修正。我们的新模型不同于以前的模型，因为它第一次提出了一个分析计算的指数密度分布驱动的随时间变化的能量输入率的超级气泡的膨胀。利用主序寿命和初始质量函数模拟了OB星超新星爆发的时间序列。我们计算了由三种不同的能量输入提供动力的超气泡的形态和运动学，并推导出吹出所需的能量输入作为周围星际介质的密度和尺度高度的函数。计算壳体中的瑞利-泰勒不稳定性时间尺度，以估计壳体何时开始碎裂并最终破裂。分析模型是一种非常有效的工具，可以与观测结果进行比较，例如本文讨论的局部气泡和W 4气泡，并且还可以深入了解超级气泡演化的动力学。
英文摘要：
Galactic winds are a common phenomenon in starburst galaxies in the local universe as well as at higher redshifts. Their sources are superbubbles driven by sequential supernova explosions in star forming regions, which carve out large holes in the interstellar medium and eject hot, metal enriched gas into the halo and to the galactic neighborhood. We investigate the evolution of superbubbles in exponentially stratified disks. We present advanced analytical models for the expansion of such bubbles and calculate their evolution in space and time. With these models one can derive the energy input that is needed for blow-out of superbubbles into the halo and derive the break-up of the shell, since Rayleigh-Taylor instabilities develop soon after a bubble starts to accelerate into the halo. The approximation of Kompaneets is modified in order to calculate velocity and acceleration of a bubble analytically. Our new model differs from earlier ones, because it presents for the first time an analytical calculation for the expansion of superbubbles in an exponential density distribution driven by a time-dependent energy input rate. The time-sequence of supernova explosions of OB-stars is modeled using their main sequence lifetime and an initial mass function. We calculate the morphology and kinematics of superbubbles powered by three different kinds of energy input and we derive the energy input required for blow-out as a function of the density and the scale height of the ambient interstellar medium. The Rayleigh-Taylor instability timescale in the shell is calculated in order to estimate when the shell starts to fragment and finally breaks up. Analytical models are a very efficient tool for comparison to observations, like e.g. the Local Bubble and the W4 bubble discussed in this paper, and also give insight into the dynamics of superbubble evolution.
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