Evolution of BH-Disk system
- Model A1: 00° initial tilt
- Model A2: 45° initial tilt
- Model A3: 90° initial tilt
- Model A4: 180° initial tilt
 Three-dimensional rendering of BHD model A2 at t = 0. |
Three-dimensional rendering of BHD model A2 at t = 0. |
We follow the evolution of the matter and spin of a gaseous disk. In the cavity of the disk, we have the black hole (BH) denoted by the black spheroidal region and the spin vector represented by the yellow arrow. The initial shrinkage of the BH and disk sizes are due to gauge effects arrising from differences between the initial data and the evolution gauge choices.
In this case, the BH preserves its spin orientiation and magnitude and the disk retains its broad characteristics. The one-arm instability fully develops, but the induced BH orbit remains bounded. The color bar denotes the rest-mass density in the disk normalized to the initial maximum disk density.
The gravitational field is evolved by solving the Einstein field equations via the BSSN formalism and the matter is evolved by solving the equations of GRMHD via a high-resolution shock capturing scheme using the Illinois GRMHD code.
 Fig. 1-1: Meridional cut for the initial state |
 Fig. 1-2: Meridional cut for the final state |
 Fig. 1-3: Full 3D rendering for the final state |
 Fig. 1-4: Zoom in to central cavity for the final state |
In this case we observe two plunging accretion streams in opposite directions entering the BH above and below its symmetry plane along with the disk warping around the BH. The precession of the BH spin is evident.
 Fig. 2-1: Meridional cut for the initial state |
 Fig. 2-2: Meridional cut for the final state |
 Fig. 2-3: Full 3D rendering for the final state |
 Fig. 2-4: Zoom in to central cavity for the final state |
In addition to all of the observations listed in Model A2, we observe an overall broad spatial and spin alignment of the disk with the BH spin. Note that the spin of the BH is not perpendicular to the plunging streams.
 Fig. 3-1: Meridional cut for the initial state |
 Fig. 3-2: Meridional cut for the final state |
 Fig. 3-3: Full 3D rendering for the final state |
 Fig. 3-4: Zoom in to central cavity for the final state |
In this case after a certain time the disk becomes largely unstable, losing its initial structure and exhibiting massive mass accretion. The BH acquires a kick velocity that may result in an unbound orbit i.e keeps drifting away until the end of our simulations (Note: The movie is centered on the BH). Although the BH spin orientiation is preserved, its magnitude is significantly reduced due to accretion.
 Fig. 4-1: Meridional cut for the initial state |
 Fig. 4-2: Meridional cut for the final state |
 Fig. 4-3: Full 3D rendering for the final state |
 Fig. 4-4: Zoom in to central cavity for the final state |
