O I lambda8446 emission in Seyfert 1 galaxies
O I lambda8446 emission in Seyfert 1 galaxies
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Seyfert 1 星系中的 O I lambda8446 发射
DOI：
10.1086/157952
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
S. Grandi
中科院分区：
文献类型：
--
作者：
S. Grandi
在16个观测到的Seyfert 1星系中，有13个发射出了Board O I lambda8446，其强度与H. cap . alpha.相比。取值范围为0.01 ~ 0.07。lambda8446没有窄分量，但在形状和宽度上与H的宽分量相似。由于缺乏观测到的O I λ da7774，很容易排除重组和碰撞激发是λ da8446的激发机制。连续荧光更难排除，但在情况B条件下，lambda7990/lambda8446的预测值明显低于观察到的上限。因此，激发机制一定是L..在波温荧光过程中泵送。为了使这一机制可行，气体中必须存在大量的O I，这是L的来源…光子，和大的光学深度在H. cap α…一个简单的均匀板模型和一个稍微复杂的宽线云的分层模型都不能再现观测到的λ 8446/H。比率。然而，最近以更精确的方式处理辐射传输的计算表明，在云的深处，氢和氧基本上是中性的，被L…光子将填充到H的n=2能级（导致tau/sub Halpha/的较大值），并且Balmer连续电离和碰撞激发，结合He漫射辐射引起的基态电离，可以产生L.. β ..光子。简单计算表明，观测值为λ 8446/H。可以以这种方式复制的；然而，布满灰尘的模型似乎被排除在外。因此，这些新的宽线云模式是为了报告观测到的Ly.. /H.. .活核中的比值似乎是重现观测到的λ 8446/H所必需的。还有比率。«少
Board O I lambda8446 emission is seen in 13 out of 16 observed Seyfert 1 galaxies with strengths compared to H..cap alpha.. ranging from 0.01 to 0.07. lambda8446 has no narrow component but is similar in shape and width to the broad component of H..cap alpha... Recombination and collisional excitation are easily ruled out as the excitation mechanisms of lambda8446 by the lack of observed O I lambda7774. Continuum fluorescence is harder to rule out, but assuming case B conditions, the predicted value of lambda7990/lambda8446 falls significantly above the observed upper limits. Therefore, the excitation mechanism must be L..beta.. pumping in a Bowen fluorescence process. For this mechanism to be operable, gas must be present with a large population of O I, a source of L..beta.. photons, and a large optical depth in H..cap alpha... A simple uniform-slab model and a somewhat more sophisticated stratified model of a broad-line cloud fail to reproduce the observed lambda8446/H..cap alpha.. ratio. However, recent calculations which treat radiative transfer in the lines in a more accurate manner show that deep within the cloud, where H and O are largely neutral, trapped L..cap alpha.. photons will populate the n=2 levels of H (causing large valuesmore » of tau/sub Halpha/), and Balmer continuum ionization and collisional excitation, combined with ground state ionization due to He diffuse radiation, can produce L..beta.. photons. Simple calculations show that observed values of lambda8446/H..cap alpha.. can be reproduced in this manner; dusty models seem to be ruled out, however. Therefore, these new models of broad-line clouds which were calculated in order to reporduce the observed Ly..cap alpha../H..cap alpha.. ratios in active nuclei seem to be necessary to reproduce the observed lambda8446/H..cap alpha.. ratio as well.« less