论文标题
星形分子云中的磁场与密度关系
The Magnetic Field versus Density relation in Star-Forming Molecular Clouds
论文作者
论文摘要
我们使用非理想的三维磁性水力动力学模拟研究了具有动态重要的磁场的湍流分子云中的磁场到密度（$ b-ρ$）的关系。我们的模拟表明，在相对平坦的低密度制度和较高密度下的幂律制度之间，有一个可区分的断裂密度$ρ_ {\ rm t} $。我们根据磁场，湍流和重力的相互作用提出了$ρ_ {\ rm t} $的分析理论。断裂密度$ρ_ {\ rm t} $以初始alfvén马赫的强度缩放，用于sub-alfvénic（$ \ Mathcal {M {m} _ {m} _ {m} _ {m} _ {\ rm a} _ {\ rm A0} _ {\ rm a0} _ {\ rm a0} <1 $ $）和trans-alfvénicnic和trans-alfvénicnic （$ \ MATHCAL {M} _ {\ rm A0} \ SIM 1 $）云。我们适合模型云的$ρ_{\ rm t} $作为$ \ Mathcal {M} _ {\ rm a0} $的函数，由不同的初始音量马赫数$ \ Mathcal {m _ {m _ {\ rm 0}} $的初始音量$ \ MATHCAL {\ MATHCAL {\ rm 0}} $ and pas $β$β的初始值{\ rm 0}} $。这意味着$ρ_ {\ rm t} $表示从亚临界质量到超临界状态的质量到频率比的过渡是由分子云的初始湍流压缩设置的。
We study the magnetic field to density ($B-ρ$) relation in turbulent molecular clouds with dynamically important magnetic fields using nonideal three-dimensional magnetohydrodynamic simulations. Our simulations show that there is a distinguishable break density $ρ_{\rm T}$ between the relatively flat low density regime and a power-law regime at higher densities. We present an analytic theory for $ρ_{\rm T}$ based on the interplay of the magnetic field, turbulence, and gravity. The break density $ρ_{\rm T}$ scales with the strength of the initial Alfvén Mach number $\mathcal{M}_{\rm A0}$ for sub-Alfvénic ( $\mathcal{M}_{\rm A0}<1$) and trans-Alfvénic ($\mathcal{M}_{\rm A0} \sim 1$) clouds. We fit the variation of $ρ_{\rm T}$ for model clouds as a function of $\mathcal{M}_{\rm A0}$, set by different values of initial sonic Mach number $\mathcal{M_{\rm 0}}$ and the initial ratio of gas pressure to magnetic pressure $β_{\rm 0}$. This implies that $ρ_{\rm T}$, which denotes the transition in mass-to-flux ratio from the subcritical to supercritical regime, is set by the initial turbulent compression of the molecular cloud.
