激波后分子云的加热和冷却  

COOLING AND HEATING OF MOLECULAR CLOUDS BEHIND A SHOCK WAVES

作　　者：张国金[1] 李守中[2] 孙锦[3] 

机构地区：[1]中国科学院空间科学与应用研究中心,北京100080 [2]北京大学地球物理系,北京100871 [3]北京师范大学天文系,北京100875

出　　处：《天文学报》1993年第3期255-265,共11页Acta Astronomica Sinica

摘　　要：本文从激波模型出发,考虑到在激波速度V_s≥100Kms^(-1)的情况下,波阵面后的氢分子将被离解,且进一步所有的氢将被电离的事实,研究了几种典型的加热冷却机制对分子云温度的影响,通过解定态下的动力学方程,得到了V_s=100Kms^(-1)的致密分子云从温度为4×10~5K降到80K左右的过程以及各种粒子数密度和各种冷却率随温度的变化曲线.比较分子云初始数密度n。不同时的结果,发现n_0不同时,分子云冷却到80K时的尺度将不同,n_0越大冷却尺度越小.但是,不论n_0为多大,在T<4000K时,起主要作用的冷却机制均是H_2振——转辐射,总冷却速率极大值恒在T=20000K处,与n_0的大小无关.计算还表明,激波通过分子云后,金斯质量判据M_(J2)远小于激波通过前的M_(J1).Based on the skock mode, molecular Hydrogens are dissociated and all atomic Hydrogens are ionized behind a shock front when shock velocity is more than 100 km^s. Considering several typical heating and cooling mechanisms to the molecular clouds, solving the time-inde-pendence hydrodynamic equations, we have got the cooling and heating processes between 4×10~5k and 80 k and the evolving curves of several kinds of number densities, n_H^+, n_H, n_(H_2) and cooling rates with temperature. Comparing the distribution curves with distance from shock front under different initial number densities (n_0) of clouds, we have found that the higher the number density is, the smaller the cooling scale of molecular cloud is. However, in spite of different no, the main cooling mechanism is the radiation of Vib.-Rot of molecular hydrogens when the temperature is below 4000 K. Our calculation show that M_(J_2) is much more smaller than M_(J_1) where M_(J_2) and M_(J_1) are ean's mass criterions when a cloud is behind and ahead of a shock respectively, that the shock can help the protostar formation from a molecular clouds.

关 键 词：激波 分子云 加热 冷却 

分 类 号：P155.22[天文地球—天文学]