Thermal instabilities in radiatively driven winds - Application to emission line clouds of quasars and active galactic nuclei
Thermal instabilities in radiatively driven winds - Application to emission line clouds of quasars and active galactic nuclei
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DOI：
10.1086/159344
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发表时间：
1981-11
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影响因子：
--
通讯作者：
M. Beltrametti
中科院分区：
文献类型：
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作者：
M. Beltrametti
结果表明，在质量损失率不小于约50%的情况下，来自活动星系核的辐射驱动的光学薄风是热不稳定的M/sub / sun/ yr/sup -1/。云形成的距离为或接近于。=10/sup / 8/ cm/sup -3/，温度为100℃左右。=10/sup 4/ K，半径在3.10/sup 14/和10/sup 15/ cm之间，这些值与观测值一致。由于云是在高速风中形成的，这个模型（和Eilek和Caroff的模型一样）避免了利用辐射压力将云从静止加速到0.1c的固有干扰问题，这需要解释发射线的宽度。讨论了气体的热平衡，给出了热不稳定性判据，并进行了微扰分析。这种分析仅限于热光度<或接近热光度的物体。=2 × 10/sup 46/ ergs /sup -1/。对于更明亮的物体，只有稍微光学厚的风对电子散射可能是不稳定的，前提是可以将此分析扩展到光学厚的情况。
It is shown that radiatively driven optically thin winds from active galactic nuclei are thermally unstable provided that the mass loss rates are not smaller than approx.50 M/sub sun/ yr/sup -1/. Clouds form at distances of or approx. =10/sup 8/ cm/sup -3/, temperatures of > or approx. =10/sup 4/ K, and radii between 3.10/sup 14/ and 10/sup 15/ cm. These values agree with the values deduced from observations. Since the clouds are formed in a high velocity wind, this model (as does the model by Eilek and Caroff) avoids problems of disruption inherent in using radiation pressure to accelerate clouds from rest to velocities up to 0.1c needed to explain the emission line widths. The thermal balance of the gas is discussed, the criteria for thermal instability are given, and a perturbation analysis is made. This analysis is restricted to objects with bolometric luminosities < or approx. =2 x 10/sup 46/ ergs s/sup -1/. For more luminous objects, only winds slightly optically thick to electron scattering can be unstable, provided one can extend this analysis to the optically thick case.