Global simulations of accreting black holes
Phil Armitage and Chris Reynolds
Effect of the disk inclination on observed emission

The movie shows a turbulent accretion disk surrounding a non-rotating (Schwarzschild) black hole, as seen by a distant observer. During the sequence, the camera moves from a face-on (i=1 degree) view of the disk to an almost edge-on angle (i=80 degrees). The relativistic effects of beaming and light bending become increasingly apparent at higher inclinations.

View high (7.0 Mb) medium (4.6 Mb), or low quality mpeg versions (2.4 Mb) of the animation, or an animation of the influence of inclination on the lightcurve.

Line profile variability at i=80 degrees

Animation showing the predicted appearance of a turbulent disk around a Schwarzschild black hole as viewed by a distant observer at an inclination angle of 80 degrees - ie almost edge-on. The plot in the lower right shows the profile of line emission from the disk, assuming that the line is excited locally by the predicted disk emission.

View high quality (8.0 Mb) or lower quality (2.4 Mb) mpeg versions of the animation.

Line profile variability at i=30 degrees

As above, except that the disk is viewed at the less extreme inclination of 30 degrees.

View high quality (9.6 Mb) or lower quality (3.6 Mb) mpeg versions of the animation.

Mean azimuthal magnetic field in r-z plane

Movie of azimuthally averaged toroidal field (1.3 Mb, mpeg)

Technical details
The animations are derived from global magnetohydrodynamic simulations of disk accretion in a pseudo-Newtonian potential (Paczynski and Wiita 1980). The main goal of the simulations is to investigate the predicted variability of accreting black holes. The models are three-dimensional but vertically unstratified and isothermal, and are computed in cylindrical co-ordinates using the ZEUS MHD code at a resolution of 288 (phi) x 192 (r) x 48 (z) mesh points. We compute the "emission" in the disk rest frame using several slightly different prescriptions, but in all cases the basic assumption is that the local magnetic stress traces regions of high dissipation.

To make the images and compute the lightcurve, we calculate the mapping between the rest frame emission and that seen by a distant observer (the "transfer function"), using a ray tracing method that models the relevant relativistic effects. Because of the high Doppler shift near the marginally stable orbit, there is a strong K-correction which alters the detailed appearance of the images depending upon the assumed spectrum of the source. We have assumed a power-law spectrum with an index of -1 in constructing the movies shown above.

The movies show about half of the simulation data analyzed in the paper, and do not take account of the differing time of flight of photons from different regions of the accretion disk, though this effect is included in our calculations of light curves and power spectra. Nor have we attempted to visualize the redshift of different part of the disk - our attempts to do this haven't looked very good.

The variability of accretion onto Schwarzschild black holes from turbulent magnetized disks, Philip J. Armitage and Christopher S. Reynolds, MNRAS, 341, 1041 (2003).