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arXiv 1610.08652astro-ph.HE
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标度不变的射电喷流和变化的黑洞自旋

Scale-invariant radio jets and varying black hole spin

Monika Moscibrodzka, Heino Falcke, Scott Noble

摘要:

在活动星系核和X射线双星中都经常观测到与相对论喷流有关的致密射电核。它们的辐射性质遵循一些一般的标度律,主要取决于它们的质量和吸积率。然而,有人提出,黑洞的自旋也可以强烈影响这些粒子的功率和射电通量。在这里,我们试图通过数值模拟来估计吸积盘发射的稳定喷流的射电光度对黑洞质量、吸积率和自旋的依赖关系。我们利用3D GRMHD方法模拟了低光度黑洞周围的吸积盘,其中喷流射电辐射是由喷流鞘产生的。我们发现,无线电通量增加约6倍的背洞自旋从0增加到a=0.98。这与吸积功率随自旋的增加相当,这意味着射电喷流和吸积功率之间的比率几乎没有变化。虽然我们的喷流脊柱功率的比例,如预期的布兰德福德-Znajek过程,喷流射电光度的依赖性黑洞自旋有点弱。同样,弱旋转的黑洞也能产生可见的射电喷流。无线电发射与黑洞质量和吸积率的整体标度与用于解释黑洞活动的基本平面的标度不变的分析模型是一致的。自旋不会在此模型中引入显著的散射。喷鞘模型可以很好地描述吸积系统,如SgrA* 和M87,以及低光度黑洞的一般标度行为。因此,该模型应适用于广泛的无线电喷流在亚爱丁顿黑洞。黑洞自旋对可见射电喷流的产生有影响,但可能不是产生可见射电喷流的主要驱动力。将我们的发现扩展到强大的类星体仍然是推测性的。

英文摘要:

Compact radio cores associated with relativistic jets are often observed in both active galactic nuclei and X-ray binaries. Their radiative properties follow some general scaling laws which primarily depend on their masses and accretion rates. However, it has been suggested that the black hole spin can also strongly influence the power and radio flux of these. Here, we attempt to estimate the dependency of the radio luminosity of steady jets launched by accretion disks on black hole mass, accretion rate and spin using numerical simulations. We make use of 3D GRMHD simulations of accretion disks around low-luminosity black holes in which the jet radio emission is produced by the jet sheath. We find that the radio flux increases roughly by a factor of 6 as the back hole spin increases from a~0 to a=0.98. This is comparable to the increase in accretion power with spin, meaning that the ratio between radio jet and accretion power is hardly changing. Although our jet spine power scales as expected for the Blandford-Znajek process, the dependency of jet radio luminosity on the black hole spin is somewhat weaker. Also weakly rotating black holes can produce visible radio jets. The overall scaling of the radio emission with black hole mass and accretion rate is consistent with the scale-invariant analytical models used to explain the fundamental plane of black hole activity. Spin does not introduce a significant scatter in this model. The jet-sheath model can describe well resolved accreting systems, such as SgrA* and M87, as well as the general scaling behavior of low-luminosity black holes. Hence the model should be applicable to a wide range of radio jets in sub-Eddington black holes. The black hole spin has an effect on the production of visible radio jet, but it may not be the main driver to produce visible radio jets. An extension of our findings to powerful quasars remains speculative.

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