【摘要】 本文详细考虑了Ortho-H₂O在分子云能量平衡过程中所起的作用,并将Ortho-H₂O分子加热率Γ_ortho-H2O与尘埃-气体碰撞加热率Γ_dust-gas以及气体总冷却率Λ_gas进行了比较。发现,对于T_K=20K的云,当尘埃温度为35K时,Γ_ortho-H2O在n（H₂）≥10⁴cm^-3时已经达到甚至超过Λ_gas;当尘埃温度为40 K时,即使密度低到10²—10³ cm^-3,Γ_ortho-H2O也几乎可以与Λ_gas相当,水分子确实加强了气体与尘埃之间的耦合。本文还详细比较了不同碰撞截面、尘埃发射率、速度梯度以及水的丰度对于计算结果的影响。更多还原

【Abstract】 The role of water molecules in energy equilibrium of the molecular clouds has been considered. When there are IR sources embedded in the molecular elouds the action of water molecules is rather complicated. It has been shown that the rate of the net energy gain P produced by water molecules through the photon-trapped and collision deexcitation processes is a function of the gas density n（H₂）, the gas temperature T_k, the dust temperature T_d, the water abundance X（H₂O） and the distances r from the central IR sources. Water molecules heat the gas in the regions which are not far from the IR sources, but they become coolants in the regions farther from them. At the same dust temperature T_d, the water molecule changes its role from a coolant into a heating agent while T_k changes from greater than T_d to less than it. For each value of the dust temperature there is a balance temperature T_K^c, at which the water molecule neither heats the gas nor cools it, and a peak temperature T_o at which the heating rate by the water molecule reaches its maximum. Moreover, T_L^e pproaches T_d as the water abundance increases. We have compared the heating rate Γ_ortho-H2O by ortho-H₂O molecules with the heating rate Γ_dust-gas by the inelastic collision between the dust and gas and the total cooling rate of the gas Λ_gas. It is found that for a cloud of the gas temperature T_K=20K, when n（H₂）≥10⁴cm^-3 and T_d=35K, Γ_ortho-H2O has reached and even exceeded Λ_gas, when T_d=40K, Γ_ortho-H2O has almost become comparable with Λ_gas even though the gas density drops to lower than 10³ cm^-3. At the same time it is shown that water molecules actually strengthen the coupling between the gas and dust. It has also discussed how the various collision cross-sections, the dust emission rates, the velocity gradients, and the water abundance affect the results of our calculations.更多还原