超新星遗迹IC 443和HB 21中激波H2气体的正对对位比研究
Ortho-to-Para Ratio Studies of Shocked H2 Gas in the Two Supernova Remnants IC 443 and HB 21
摘要：
我们对两颗超新星遗迹IC 443和HB 21中的冲击氢气体进行了近红外（2.5-5.0 μm）光谱研究，这两颗超新星遗迹因与附近分子云的相互作用而闻名。观测是用AKARI卫星上的红外照相机进行的。在7000 K <= E（v，J）<= 20000 K的能量范围内，IC 443中的冲击H2气体显示出2.4+0.3-0.2的邻对比（OPR），这明显低于平衡值3，表明存在非平衡OPR。HB 21中的冲击气体也表明潜在的非平衡OPR在1.8-2.0的范围内。能级布居可用具有单一OPR的幂律热混合模型来描述，温度积分范围为1000-4000 K。我们得出的结论是，所获得的非平衡OPR可能来源于解离J-冲击的重整H2气体，考虑到几个因素，如冲击组合的要求，线比，和的可能性，H2气体可以形成与非平衡OPR的晶粒。我们还研究了C-冲击和部分解离J-冲击的起源的非平衡OPR。然而，我们发现，它们是不相容的，所观察到的离子发射线的解离J-冲击需要解释。如果解离J冲击是H2发射的原因，那么H原子在晶粒表面上的碰撞能的差异将导致IC 443和HB 21的OPR之间观察到的差异。我们的研究表明，解离J冲击可以使冲击H2气体具有非平衡OPR。
英文摘要：
We present near-infrared (2.5-5.0 μm) spectral studies of shocked H2 gas in the two supernova remnants IC 443 and HB 21, which are well known for their interactions with nearby molecular clouds. The observations were performed with Infrared Camera (IRC) aboard the AKARI satellite. At the energy range 7000 K <= E(v,J) <= 20000 K, the shocked H2 gas in IC 443 shows an ortho-to-para ratio (OPR) of 2.4+0.3-0.2, which is significantly lower than the equilibrium value 3, suggesting the existence of non-equilibrium OPR. The shocked gas in HB 21 also indicates a potential non-equilibrium OPR in the range of 1.8-2.0. The level populations are well described by the power-law thermal admixture model with a single OPR, where the temperature integration range is 1000-4000 K. We conclude that the obtained non-equilibrium OPR probably originates from the reformed H2 gas of dissociative J-shocks, considering several factors such as the shock combination requirement, the line ratios, and the possibility that H2 gas can form on grains with a non-equilibrium OPR. We also investigate C-shocks and partially-dissociative J-shocks for the origin of the non-equilibrium OPR. However, we find that they are incompatible with the observed ionic emission lines for which dissociative J-shocks are required to explain. The difference in the collision energy of H atoms on grain surfaces would make the observed difference between the OPRs of IC 443 and HB 21, if dissociative J-shocks are responsible for the H2 emission. Our study suggests that dissociative J-shocks can make shocked H2 gas with a non-equilibrium OPR.
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