Bridging the Bondi and Event Horizon Scales: 3D GRMHD Simulations Reveal X-shaped Radio Galaxy Morphology
Bridging the Bondi and Event Horizon Scales: 3D GRMHD Simulations Reveal X-shaped Radio Galaxy Morphology
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DOI：
10.3847/2041-8213/ac7bed
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发表时间：
2022-02
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通讯作者：
A. Lalakos;O. Gottlieb;N. Kaaz;K. Chatterjee;M. Liska;I. Christie;A. Tchekhovskoy;I. Zhuravleva-I.-Zhuravle
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作者：
A. Lalakos;O. Gottlieb;N. Kaaz;K. Chatterjee;M. Liska;I. Christie;A. Tchekhovskoy;I. Zhuravleva-I.-Zhuravle
X 形射电星系 (XRG) 产生不对齐的 X 形射流对，占射电星系的 10%。 XRG被认为出现在具有双超大质量黑洞（SMBH）、SMBH合并或大规模环境介质不对称性的星系中。我们证明 XRG 形态可以在没有这种特殊的、预先存在的条件的情况下自然形成。我们的 3D 广义相对论磁流体动力学 (GRMHD) 模拟首次跟踪磁化旋转气体从半径为 R B 的 SMBH 影响范围外到引力半径为 R g 的 SMBH 的最大尺度分离，迄今为止，R B/R g = 103。最初，我们的等密度热气体轴对称系统包含弱垂直磁场，并在快速旋转的超大黑洞的赤道平面内旋转。我们用小规模 2% 水平的压力扰动来播种气体。落入的气体形成吸积盘，SMBH 发射出相对论磁化的准直射流，到达 R B 之外。在落入气体的压力下，射流间歇性地打开和关闭，不规则地摆动，并向不同方向膨胀成对的空腔，类似于 X 形射流形态。合成 X 射线图像显示了多对喷气动力冲击和空腔。大规模磁通量在SMBH上积聚，变得动态重要，并导致磁滞盘状态。 SMBH 以 2% 的 Bondi 速率吸积（M87* 为 Ṁ≃2.4×10−3M⊙yr−1），并以 η = 150% 的效率发射双喷流。这些喷流足够强大（P jets ≃ 2 × 1044 erg s−1），可以沿着SMBH自旋轴逃逸并结束短暂的间歇喷流状态，其瞬态性质可以解释XRG的稀有性。
X-shaped radio galaxies (XRGs) produce misaligned X-shaped jet pairs and make up ≲10% of radio galaxies. XRGs are thought to emerge in galaxies featuring a binary supermassive black hole (SMBH), SMBH merger, or large-scale ambient medium asymmetry. We demonstrate that XRG morphology can naturally form without such special, preexisting conditions. Our 3D general-relativistic magnetohydrodynamic (GRMHD) simulation for the first time follows magnetized rotating gas from outside the SMBH sphere of influence of radius R B to the SMBH of gravitational radius R g at the largest scale separation, R B/R g = 103, to date. Initially, our axisymmetric system of constant-density hot gas contains a weak vertical magnetic field and rotates in the equatorial plane of a rapidly spinning SMBH. We seed the gas with small-scale 2% level pressure perturbations. Infalling gas forms an accretion disk, and the SMBH launches relativistically magnetized collimated jets reaching well outside R B. Under the pressure of the infalling gas, the jets intermittently turn on and off, erratically wobble, and inflate pairs of cavities in different directions, resembling an X-shaped jet morphology. Synthetic X-ray images reveal multiple pairs of jet-powered shocks and cavities. Large-scale magnetic flux accumulates on the SMBH, becomes dynamically important, and leads to a magnetically arrested disk state. The SMBH accretes at 2% of the Bondi rate ( Ṁ≃2.4×10−3M⊙yr−1 for M87*) and launches twin jets at η = 150% efficiency. These jets are powerful enough (P jets ≃ 2 × 1044 erg s−1) to escape along the SMBH spin axis and end the short-lived intermittent jet state, whose transient nature can account for the rarity of XRGs.