Scale-invariant radio jets and varying black hole spin
Scale-invariant radio jets and varying black hole spin
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DOI：
10.1051/0004-6361/201629157
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发表时间：
2016-10
影响因子：
6.5
通讯作者：
M. Mościbrodzka;H. Falcke;S. Noble
中科院分区：
文献类型：
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作者：
M. Mościbrodzka;H. Falcke;S. Noble
上下文在活动星系核和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，有人认为黑洞自旋也会强烈影响这些粒子的功率和射电通量。目标。我们试图用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性。方法.我们利用三维广义相对论磁流体动力学模拟吸积盘周围的低光度黑洞的喷流无线电发射产生的喷鞘。结果我们发现，随着黑洞自旋从1/10增加到1/10 = 0.98，射电通量大约增加6倍。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Blandford-Znajek过程，喷流射电光度对黑洞自旋的依赖性是有点弱。此外，弱旋转的黑洞可以产生可见的无线电喷流。射电辐射与黑洞质量和吸积率的整体比例与用于解释黑洞活动基本平面的标度不变分析模型一致。自旋不会在此模型中引入显著的散射。结论.喷鞘模型可以很好地描述吸积系统，如Sgr A* 和M 87，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射流在亚爱丁顿黑洞。黑洞旋转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。
Context. 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 that primarily depend on their masses and accretion rates. However, it has been suggested that black hole spin can also strongly influence the power and radio flux of these. Aims. 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. Methods. We make use of three-dimensional general relativistic magnetohydrodynamical simulations of accretion disks around low-luminosity black holes in which the jet radio emission is produced by the jet sheath. Results. We find that the radio flux increases roughly by a factor of 6 as the black 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 hardly changes. 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. Conclusions. The jet-sheath model can describe well-resolved accreting systems, such as Sgr A* and M 87, 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.