论文标题
通过漂移引起的溅射在活性银河核中的粉尘破坏
Dust Destruction by Drift-Induced Sputtering in Active Galactic Nuclei
论文作者
论文摘要
最近的中红外高空间分辨率观察结果表明,活跃的银河核(AGNS)可以容纳具有几个PC大小的极性灰尘区域,并且可以通过中央发动机的辐射来携带这种灰尘。极性灰尘发射通常表现出非常弱或缺乏硅酸盐10- $ $ $ M排放功能。一个可能的解释是,极性灰尘以微米大小的大晶粒为主,因为这些谷物没有显示硅酸盐特征,而尚不清楚如何优先提供给极性区域的大谷物。我们在这里提出了一个新的情况,描述了极地地区大晶粒的流行。我们表明,晶粒通过AGN的辐射压力加速到高血压漂移速度,高超音速漂移导致通过动力学溅射破坏尘埃。溅射比大谷物更快地破坏小谷物,因此,更大的谷物将优先吹入更长的距离。尽管高超音速漂移或动力学溅射往往会因较小的谷物而受到抑制,但由于库仑的阻力很小,但它们也可能因库仑爆炸而破坏。去除小谷物和/或大晶粒的存活可能会解释出极性灰尘发射中缺乏10- $ $ $ M的排放特征。
Recent mid-infrared high spatial resolution observations have revealed that active galactic nuclei (AGNs) may host a polar dust region with the size of several pc, and such dust may be carried by radiation from the central engine. The polar dust emission often exhibits very weak or absence of the silicate 10-$μ$m emission feature. A possible explanation is that the polar dust is dominated by micron-sized large grains because these grains do not show the silicate feature, while it remains unclear how large grains are preferentially supplied to the polar region. We here propose a new scenario describing the prevalence of large grains at the polar region. We show that grains are accelerated to the hypersonic drift velocity by the radiation pressure from AGN, and the hypersonic drift results in dust destruction via kinetic sputtering. Sputtering destroys small grains faster than the large ones, and thus larger grains will be preferentially blown over longer distance. Although the hypersonic drift, or kinetic sputtering, tends to be suppressed for very small grains due to the Coulomb drag, they might also be disrupted by Coulomb explosion. Removal of small grains and/or survival of large grains may explain the lack of a silicate 10-$μ$m emission feature in polar dust emission.