W44中非定常磁流体动力学激波的APEX观测
APEX observations of non-stationary magneto-hydrodynamical shocks in W44
摘要：
超新星遗迹被认为是银河系宇宙射线的来源。为了了解这些宇宙射线的起源、加速和组成，需要对当地星际介质的物理条件有详细的了解。SNR与分子云的冲击相互作用引起在远红外和亚毫米波长范围内的强分子发射，可以用作这些条件的非常有价值的示踪剂。应用MHD激波模型解释由此产生的谱线发射，可以获得有关超新星遗迹的能量和化学影响的信息。我们用APEX望远镜在${}^{12}$ CO（3-2）、（4-3）、（6-5）、（7-6）和${}^{13}$ CO（3-2）中绘制了超新星遗迹W 44中的两个区域。在五个不同的位置上，对应于CO排放的局部最大值的综合强度的提取，允许将这些强度与模型网格的输出进行比较，该模型将MHD冲击代码与基于“大速度梯度”近似的辐射转移模块相结合。我们发现，所观察到的CO线发射是兼容的非平稳冲击和预冲击密度的$10^4$厘米${}^{-3}$。我们的模型还允许约束冲击年龄，速度，冲击前的磁场强度组件垂直于视线，和完整的阶梯CO过渡。最后，我们的分析可以用来估计的贡献，如银河系的能量平衡和动量注入到周围的星际介质的SNR。
英文摘要：
Supernova remnants (SNRs) are considered as being the sources of galactic cosmic rays. In order to understand the origin, acceleration, and composition of these cosmic rays, detailed knowledge of the physical conditions in the local interstellar medium is needed. The shock interaction of SNRs with molecular clouds that gives rise to strong molecular emission in the far-IR and sub-mm wavelength regimes can be used as a highly valuable tracer of these conditions. The application of MHD shock models in the interpretation of the resulting line emission can yield information on the energetic and chemical impact of supernova remnants. We have mapped two regions in the supernova remnant W44 with the APEX telescope in ${}^{12}$CO (3-2), (4-3), (6-5), (7-6) and ${}^{13}$CO (3-2). The extraction of integrated intensities on five different positions, corresponding to local maxima of CO emission, allows to compare these intensities to the outputs of a grid of models, which combine an MHD shock code with a radiative transfer module based on the 'large velocity gradient' approximation. We find that the observed CO line emission is compatible with non-stationary shocks and a pre-shock density of $10^4$ cm${}^{-3}$. Our models furthermore allow to constrain shock ages, velocities, the pre-shock magnetic field strength components perpendicular to the line-of-sight, and the full ladder of CO transitions. Finally, our analysis can be used to estimate the contribution of such SNRs to, e.g. the galactic energy balance and the momentum-injection into the surrounding interstellar medium.
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