论文标题
通过辐射扭矩和活性银核的灭绝来建模晶粒旋转破坏
Modelling Grain Rotational Disruption by Radiative Torques and Extinction of Active Galactic Nuclei
论文作者
论文摘要
观察到单个活性银河核（AGN）的灭绝曲线通常显示出朝向遥远的波长陡峭上升，可以用小的麦哲伦云（SMC）类似的灰尘模型来描述。该功能表明，在AGN的本地环境中，小型$ a \ leq0.1μm$的小防尘粒的主导地位，但是这种小谷物的起源尚不清楚。在本文中，我们旨在通过应用辐射扭矩破坏（RATD）来解释这一观察到的特征，以建模AGN辐射从FUV到中红外（MIR）波长的灭绝。我们发现，在AGN的强烈辐射场中，大小$ a \ geq0.1μm$的大型复合晶粒大小将ratd的尺寸大大中断为较小的尺寸，最多可在极性方向上$ d _ {\ rm ramd}> 100 $ pc，$ d _ {\ d _ {\ rm cantd} \ rm can sim 10 $ 10 $ PC。因此，光学灭绝会减少，而fuv-near-ultraviolet（NUV）消光增加，产生陡峭的远紫外线灭绝曲线。因此，由于小晶粒的增强，最终的总视觉灭绝率显着下降至$ r _ {\ rm V} <3.1 $，距离AGN中心的距离降低。 $ r _ {\ rm v} $与Ratd效率的依赖性将帮助我们通过光度观测来研究AGN环境中的灰尘特性。此外，我们建议，RATD与其他尘埃破坏机制之间的强度结合，这些机制负责破坏$ a \ leq0.05μm$的非常小的晶粒，这是解释观察到的二分法的“ SMC”和“灰色”灭绝曲线的关键。
Extinction curves observed toward individual Active Galactic Nuclei (AGN) usually show a steep rise toward far-ultraviolet (FUV) wavelengths and can be described by the Small Magellanic Cloud (SMC)-like dust model. This feature suggests the dominance of small dust grains of size $a \leq 0.1 μm$ in the local environment of AGN, but the origin of such small grains is unclear. In this paper, we aim to explain this observed feature by applying the RAdiative Torque Disruption (RATD) to model the extinction of AGN radiation from FUV to mid-infrared (MIR) wavelengths. We find that in the intense radiation field of AGN, large composite grains of size $a \geq 0.1 μm$ are significantly disrupted to smaller sizes by RATD up to $d_{\rm RATD} > 100$ pc in the polar direction and $d_{\rm RATD} \sim 10$ pc in the torus region. Consequently, optical-MIR extinction decreases, whereas FUV-near-ultraviolet (NUV) extinction increases, producing a steep far-UV rise extinction curve. The resulting total-to-selective visual extinction ratio thus significantly drops to $R_{\rm V} < 3.1$ with decreasing distances to AGN center due to the enhancement of small grains. The dependence of $R_{\rm V}$ with the efficiency of RATD will help us to study the dust properties in the AGN environment via photometric observations. In addition, we suggest that the combination of the strength between RATD and other dust destruction mechanisms which are responsible for destroying very small grains of $a \leq 0.05 μm$ is the key for explaining the dichotomy observed 'SMC' and 'gray' extinction curve toward many AGN.
