论文标题
大规模遗前核的氘化学动力学
Deuterium Chemodynamics of Massive Pre-Stellar Cores
论文作者
论文摘要
High levels of deuterium fractionation of $\rm N_2H^+$ (i.e., $\rm D_{frac}^{N_2H^+} \gtrsim 0.1$) are often observed in pre-stellar cores (PSCs) and detection of $\rm N_2D^+$ is a promising method to identify elusive massive PSCs.但是，达到这种高水平申请所需的物理和化学状况仍然不确定，$ \ rm n_2h^+$和$ \ rm n_2d^+$ $ $ $观察的诊断效用也是如此。我们对大规模，湍流，磁性PSC进行3D磁水动力学模拟，并与复杂的脱水天体化学网络相结合。尽管核心具有一定的磁性/湍流支撑，但它在大约一个自由落体的时间内在重力下崩溃，这标志着模拟的末端。我们的基金模型在此期间实现了相对较低的$ \ rm d_ {frac}^{n_2h^+} \ sim 0.002 $。然后，我们研究$ \ rm H_2 $（$ \ rm opr^{H_2} $）的初始ORTHO-PARA比率的影响，温度，宇宙射线（CR）电离速率，CO和N种体耗竭因子和先前的PSC化学进化。我们发现，高CR电离率和高耗竭因子允许模拟的$ \ rm d_ {frac}^{n_2h^+} $和绝对丰度，以在一个自由落体时间内匹配观察值。对于$ \ rm opr^{h_2} $，较低的初始值有助于$ \ rm d_ {frac}^{n_2h^+} $的增长，而与观察到的系统相比，剥离的空间结构太广泛了。对于具有升高Cr离子化速率和显着重元素耗竭的示例模型，我们随后研究了核心的运动学和动态性能，以其$ \ rm n_2d^+$发射所追踪。经历相当快速崩溃的核心在其平均速度图中表现出干扰的运动学。尽管如此，由于磁支持，核心通常会根据其$ \ rm n_2d^+$速度分散在运动次运动中出现。
High levels of deuterium fractionation of $\rm N_2H^+$ (i.e., $\rm D_{frac}^{N_2H^+} \gtrsim 0.1$) are often observed in pre-stellar cores (PSCs) and detection of $\rm N_2D^+$ is a promising method to identify elusive massive PSCs. However, the physical and chemical conditions required to reach such high levels of deuteration are still uncertain, as is the diagnostic utility of $\rm N_2H^+$ and $\rm N_2D^+$ observations of PSCs. We perform 3D magnetohydrodynamics simulations of a massive, turbulent, magnetised PSC, coupled with a sophisticated deuteration astrochemical network. Although the core has some magnetic/turbulent support, it collapses under gravity in about one freefall time, which marks the end of the simulations. Our fiducial model achieves relatively low $\rm D_{frac}^{N_2H^+} \sim 0.002$ during this time. We then investigate effects of initial ortho-para ratio of $\rm H_2$ ($\rm OPR^{H_2}$), temperature, cosmic ray (CR) ionization rate, CO and N-species depletion factors and prior PSC chemical evolution. We find that high CR ionization rates and high depletion factors allow the simulated $\rm D_{frac}^{N_2H^+}$ and absolute abundances to match observational values within one freefall time. For $\rm OPR^{H_2}$, while a lower initial value helps the growth of $\rm D_{frac}^{N_2H^+}$, the spatial structure of deuteration is too widespread compared to observed systems. For an example model with elevated CR ionization rates and significant heavy element depletion, we then study the kinematic and dynamic properties of the core as traced by its $\rm N_2D^+$ emission. The core, undergoing quite rapid collapse, exhibits disturbed kinematics in its average velocity map. Still, because of magnetic support, the core often appears kinematically sub-virial based on its $\rm N_2D^+$ velocity dispersion.
