Constraining properties of dusty environments by infrared variability
Constraining properties of dusty environments by infrared variability
复制标题
通过红外变化限制多尘环境的特性
DOI：
10.1051/0004-6361/201117750
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发表时间：
2011
影响因子：
6.5
通讯作者：
Mpifr
中科院分区：
文献类型：
--
作者：
S. Hoenig;Makoto Kishimoto Ucsb;Mpifr
我们目前的模型模拟的时间可变的红外（IR）辐射从灰尘的入射辐射的变化的结果。为此，我们介绍了一个广义的处理温度变化的尘埃环境，这是不限于任何特定的天文来源。本文将这种处理方法应用于以径向亮度分布为主要参数的简化星团模型中，研究了第1型活动星系核（AGN）的红外辐射。我们表明，任何变化的信号在光学平滑更强，如果亮度分布是非常广泛的，这种平滑强烈依赖于波长。这也会影响光学和近/中红外发射之间的时间滞后，对于长波长和扩展的亮度分布，这可能高达10秒的升华半径。时滞对波长和分布的依赖性可以用来量化活动星系核环面的亮度分布，可以通过比较光学光变曲线与近红外和中红外光变曲线，或者直接比较近红外和中红外光变曲线。此外，我们的模型已被应用到附近的Seyfert 1星系NGC 4151的近红外数据。我们表明，简单的模型可以再现整体观察到的变异信号，并发现，约40%的能量在V波段的变异信号已被转换为K波段的变异。这一低数值可以用在环形内部边缘逐渐升华的云的“雪球”模型来解释。我们还注意到，我们的建模不支持在所观察到的光变曲线时期的时间滞后/升华半径的变化，尽管在V带发射的显着变化。
We present model simulations of time-variable infrared (IR) emission from dust as a consequence of variability of the incident radiation. For that we introduce a generalized treatment for temperature variations in a dusty environment, which is not limited to any specific astronomical source. The treatment has been incorporated into a simplified clumpy torus model, with the radial brightness distribution as the main parameter, to study the IR emission of type 1 active galactic nuclei (AGN). We show that any variability signal in the optical is smoothened stronger if the brightness distribution is very extended, and this smoothing strongly depends on wavelength. This also affects time lags between the optical and near-/mid-IR emission, which can be up to 10s of sublimation radii for long wavelengths and extended brightness distributions. The dependence of time lag on wavelength and distribution can be used to quantify the brightness distribution in an AGN torus, either by comparing optical light curves to near-IR and mid-IR light curves, or by directly comparing near-IR to mid-IR light curves. Moreover, our model has been applied to near-IR data of the nearby Seyfert 1 galaxy NGC 4151. We show that the simple model can reproduce the overall observed variability signal and found that about 40% of the energy in the variability signal in the V-band has been converted into K-band variability. This low value may be explained by a “snowball” model of gradually-sublimating clouds at the inner edge of the torus. We also note that our modeling does not support a change of time lag/sublimation radius over the observed light curve epoch in spite of a significant change in V-band emission.