论文标题
是否破碎：温度和金属性在热不稳定性演变中的作用
Shatter or not: role of temperature and metallicity in the evolution of thermal instability
论文作者
论文摘要
我们测试金属性变化（背景梯度和波动）如何使用分析计算和理想化的高分辨率1D流体动力学模拟影响局部热不稳定性的物理。尽管冷却功能（$λ[t，z] $）和冷却时间（$ t _ {\ rm -cool} $）取决于气体温度和金属性，但我们发现，热不稳定性的增长速率明确地仅取决于相对于温度的冷却功能（$ \ partiv ontiv and/partial pontial o p partiv and thep partiv and themit \ ln T $） （$ \ partial \lnλ/ \ partial \ ln z $）。对于$ 10^4〜 {\ rm k} \ lyssim t \ Lessim 10^7〜 {\ rm k} $的大部分，既是等速和等距模式（以较小和更大的长度出现在冷却时间中的声音长度和较大的声音长度[$ c_s t _ {$ c_s t _ { 10^7〜 {\ rm k} $）等速模式稳定。我们表明，即使是非线性进化也取决于等速模式是线性稳定还是不稳定的。对于稳定的等距模式，我们观察到小规模同质模式的生长，但这与密集冷却区域的非线性碎片不同。对于不稳定的等距扰动，我们不会在小尺度上观察到大密度扰动。虽然很小的云（$ \ sim {\ rm min} [c_st _ {\ rm cool}] $）以稳定的相位相位热不稳定性的非线性演化的瞬态状态形式，但大多数最终合并。
We test how metallicity variation (a background gradient and fluctuations) affects the physics of local thermal instability using analytical calculations and idealized, high-resolution 1D hydrodynamic simulations. Although the cooling function ($Λ[T,Z]$) and the cooling time ($t_{\rm cool}$) depend on gas temperature and metallicity, we find that the growth rate of thermal instability is explicitly dependent only on the derivative of the cooling function relative to temperature ($\partial \ln Λ/\partial \ln T$) and not on the metallicity derivative ($\partial \ln Λ/ \partial \ln Z$). For most of $10^4~{\rm K} \lesssim T \lesssim 10^7~{\rm K}$, both the isobaric and isochoric modes (occurring at scales smaller and larger than the sonic length covered in a cooling time [$c_s t_{\rm cool}$], respectively) grow linearly, and at higher temperatures ($\gtrsim 10^7~{\rm K}$) the isochoric modes are stable. We show that even the nonlinear evolution depends on whether the isochoric modes are linearly stable or unstable. For the stable isochoric modes, we observe the growth of small-scale isobaric modes but this is distinct from the nonlinear fragmentation of a dense cooling region. For unstable isochoric perturbations we do not observe large density perturbations at small scales. While very small clouds ($\sim {\rm min}[c_st_{\rm cool}]$) form in the transient state of nonlinear evolution of the stable isochoric thermal instability, most of them merge eventually.
