We study the dynamics of massive black hole pairs in clumpy gaseous circumnuclear disks. We track the orbital decay of the light, secondary black hole $M_{\bullet2}$ orbiting around the more massive primary at the center of the disk, using $N$-body/smoothed particle hydrodynamic simulations. We find that the gravitational interaction of $M_{\bullet2}$ with massive clumps $M_{\rm cl}$ erratically perturbs the otherwise smooth orbital decay. In close encounters with massive clumps, gravitational slingshots can kick the secondary black hole out of the disk plane. The black hole moving on an inclined orbit then experiences the weaker dynamical friction of the stellar background, resulting in a longer orbital decay timescale. Interactions between clumps can also favor orbital decay when the black hole is captured by a massive clump which is segregating toward the center of the disk. The stochastic behavior of the black hole orbit emerges mainly when the ratio $M_{\bullet2}/M_{\rm cl}$ falls below unity, with decay timescales ranging from $\sim1$ to $\sim50$ Myr. This suggests that describing the cold clumpy phase of the inter-stellar medium in self-consistent simulations of galaxy mergers, albeit so far neglected, is important to predict the black hole dynamics in galaxy merger remnants.
翻译:我们研究了大黑洞在冷却气体环核磁盘中的动态。 我们跟踪光的轨道衰变, 二级黑洞 $M ⁇ bullet2} $M ⁇ bullet2} 美元在磁盘中心围绕更大规模初级轨道运行, 使用 $N$- 身体/ moose 粒子流体动力模拟。 我们发现, $M ⁇ bulllet2} 美元与大块堆积的重力相互作用, 恒星体的大规模残渣不固定地侵扰着本来很平滑的轨道衰变。 在接近大规模悬浮时, 重力弹弓可以踢出磁盘平面平面平面上的二级黑洞。 在倾斜轨道上移动的黑洞会经历较弱的动态摩擦, 从而导致一个更长的轨道衰减时间级。 当黑洞被一个巨大的悬浮块捕获到磁盘中心时, 黑洞轨道的冷凝度行为将主要出现在 $M ⁇ bullet2 /M\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\