On the efficiency of jet production in FR II radio galaxies and quasars
On the efficiency of jet production in FR II radio galaxies and quasars
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DOI：
10.1093/mnras/stw3330
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发表时间：
2016-12
影响因子：
4.8
通讯作者：
Katarzyna Rusinek;M. Sikora;D. Kozieł-Wierzbowska;L. Godfrey
中科院分区：
文献类型：
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作者：
Katarzyna Rusinek;M. Sikora;D. Kozieł-Wierzbowska;L. Godfrey
在许多具有扩展射电结构的射电星系中，喷流的能量似乎超过了它们的吸积光度。在吸积率非常低的系统中，这可能是由于辐射效率低下的吸积流导致的非常低的吸积光度。在具有高吸积率的系统中，吸积流预计是辐射有效的，并且这种强大的射流的产生可能需要涉及磁制动盘（MAD）的吸积场景。然而，MAD方案的数值模拟表明，喷流产生效率仅在几何厚吸积流中较大，并且大致与$（H/R）^2 $成比例，其中$H$是圆盘高度，$R$是到BH的距离。利用FRII射电星系和类星体的样本吸积在中等吸积率，我们表明，他们的喷气机是更强大的比预测的MAD方案。我们讨论了这种差异的可能起源，这表明它可以与近似采用MHD模拟治疗光学厚吸积流内的MAD区，或可能表明，吸积盘的几何厚度比标准理论预测。
Jet powers in many radio galaxies with extended radio structures appear to exceed their associated accretion luminosities. In systems with very low accretion rates, this is likely due to the very low accretion luminosities resulting from radiatively inefficient accretion flows. In systems with high accretion rates, the accretion flows are expected to be radiatively efficient, and the production of such powerful jets may require an accretion scenario which involves magnetically arrested discs (MADs). However, numerical simulations of the MAD scenario indicate that jet production efficiency is large only for geometrically thick accretion flows and scales roughly with $(H/R)^2$, where $H$ is the disc height and $R$ is the distance from the BH. Using samples of FRII radio galaxies and quasars accreting at moderate accretion rates we show that their jets are much more powerful than predicted by the MAD scenario. We discuss possible origins of this discrepancy, suggesting that it can be related to approximations adopted in MHD simulations to treat optically thick accretion flow within the MAD-zone, or may indicate that accretion disks are geometrically thicker than the standard theory predicts.