What Are The Effects Of The Kicked Black Hole Onto The Torus? (Planetary Science)

Summary:

  • Donmez and colleagues in their recent paper carried out the study on the effects of the kicked black holes onto the accreted torus by using the general relativistic hydrodynamical code.
  • They have found Papaloizou-Pringle Instability (PPI) produced on the torus due to kicked black hole.
  • The higher the perturbation velocity produced by the kicked black hole, the longer time the torus takes to reach the saturation point.
  • When black hole got kicked, that kicked triggers the radial nonaxisymmetric oscillation on the accretion disk which they call “funnel walls” or “spiral shock waves”.
  • These funnel walls are responsible for accreting matter towards the black hole.
  • At the later time of evolution, the accretion through the funnel is stopped and PPI is developed on the torus around the black hole. It would cause either an increase or an decrease in the black hole kick velocity.

In recent years, number of numerical simulations and astronomical observations have revealed the kicked black hole at the center of the black hole X-ray binaries and the Active Galactic Nuclei (AGN). This has occurred due to the asymmetric momentum loss of the black hole, either in a case of black hole mergers or in the release of the gravitation radiation during this process. One of the new observations was made in a distant galaxy which is known as quasar 3C 186. It is the most massive black hole which is kicked out of its central home. The merging two black holes produces gravitational waves which carry energy and angular momentum of the system. Finally, when they merge in a violent collision, and the released energy is enough, the newly formed black hole would be kicked away from the center of the galaxy or even out of the entire galaxy in the opposite side of the location with the highest gravitational waves. The range of the kick can vary depending on the properties of these two colliding black holes, their separation, and inclination angles. The kick velocities range from the smallest possible value up to 2000km/s. Many studies suggested that, kick velocity drives a perturbation on a newly accreted torus around the black hole. Now, Donmez and colleagues studied the effects of the kicked black holes onto the accreted torus by using the general relativistic hydrodynamical code, focusing on changing the dynamics of the accretion disk during the accretion disk-black hole interaction.

High energetic astrophysical sources such as X-ray binaries, gamma ray bursts, and AGNs are powered by the accretion mechanism onto the black holes. A high accretion rate could be presented during the development of the instability. One of those instabilities is called the PPI, which is prone the development of the non-axisymmetric instability. The time dependent rest-mass density distribution is generated by PPI and it may lead to emission of radiation. During the development of PPI, some vigorous dynamics of the torus would be observed. The vigorous phenomena happening on the torus dynamics around the kicked black hole would cause the conversion of the gravitational binding energy into thermal and kinetic energies during the process of losing the angular momentum.

In the recent paper, Donmez and colleagues have observed Papaloizou-Pringle Instability (PPI) instability in their models which have developed due to the kick that the center of black hole-torus system receives.

In order to understand the dynamical feature of the torus with respect to the perturbation amplitude produced by the kicked black hole, they have varied the parameter χ, which is a free parameter to control the perturbation on the torus radial velocity, and it is found that different values of χ produce pretty much same behavior for given black hole-torus system. Only some time delays when the PPI instability was reached the saturation point and types of shock waves created during the time evolution were observed. It is clearly found that the PPI seen for m = 1 in the exponential growth mode is developed around the rotating and non-rotating black holes. The non-axisymmetric growing mode m = 1 causes the formation of the spiral shock wave appeared in the rotating matter around the black holes.

Fig. 1.— The logarithmic rest-mass density of the torus on equatorial plane with linearly spaced isocountours around the rotating black hole for the model K09C. The spiral structure seen in snapshot is a mechanism to have a PPI m = 1 mode. The domain is [Xmin, Ymin] → [Xmax, Ymax)] = [[40M, ;40M)] → [40M, 40M].

They also observed that the mass accretion rates, which appear around rotating black hole is almost 2 times bigger than the one around the non-rotating black hole and showed that the accretion associated with the saturation of PPI growth mode occurs much earlier in case of the rotating black holes. Additionally, the location of the maximum density of the perturbed torus around the rotating black hole gets closer with the non-rotating case after they reach the saturation point, even though they are initially operated with a distance of 4.95M.

Fig 2. The logarithmic rest-mass density of the torus on equatorial plane with linearly spaced isocountours around the non-rotating black hole for the model K00C. The domain is [Xmin, Ymin] → [Xmax, Ymax)] = [[ 60M, ;60M)] → [60M, 60M]. © Donmez et al.

Furthermore, they have observed the PPI instability in their models which have developed due to the kick that the center of black hole-torus system receives. The kicked black hole triggers the radial nonaxisymmetric oscillation on the disk. And these oscillations on the equilibrium stage of the torus lead to the PPI. When the growing PPI azimuthal mode occurs just before or after reaching of the saturation point could trigger it not only in the torus, but also in the black hole. It would cause either an increase or an decrease in the black hole kick velocity.

Fig. 3.— The locations of the maximum rest-mass density for models K09A, K09B, and K09C.
It gives the position of the maximum rest-mass density at the radial distance as a function of time. © Donmez et al.

Finally, they concluded that the rest-mass density oscillation, the spiral shock waves and the resulting PPI that they have found in their numerical simulations during the time evolution could play an important role in explaining the vigorous X-rays phenomena observed from the galactic nuclei and the quasars.

Featured image: This not-to-scale cartoon shows a supermassive black hole along with its retinue of gaseous disk, clouds, and jets, altogether known as an active galactic nucleus (AGN). The torus is key to explaining how the same object can appear differently from different angles. A quasar that appears brilliant when viewed face-on turns faint when viewed through its torus of dusty gas. © C.M. Urry and P. Padovani


Reference: Orhan Donmez, Anwar Al-Kandari, Ahlam Abu Seedo, “On the dynamics of the torus around the kicked black hole”, ArXiv, pp. 1-18, 2021. https://arxiv.org/abs/2104.01150


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