Collapse of a Supermassive Star
to a Supermassive Black Hole


There is compelling evidence that supermassive black holes (SMBH's) exist. Yet the origin of these objects or their seeds is unknown. SMBH's with 109 solar masses must have formed by z > 6, or within 109 years after the Big Bang, to power quasars. It may be difficult for gas accretion to build up such a SMBH by this time unless the initial seed black hole already has a substantial mass. One plausible progenitor of a massive seed black hole is a supermassive star (SMS).

In the following two simulations, we follow the collapse of a SMS in both a 3D post-Newtonian simulation and an axisymmetric simulation in full general relativity. The initial SMS of arbitrary mass M in these simulations rotates uniformly at the mass-shedding limit and is marginally unstable to radial collapse. The final black hole mass and spin have been determined to be Mh = 0.9 and Jh/Mh2 = 0.75. The remaining mass goes into a disk of mass Mdisk/M = 0.1. This disk arises even though the total spin of the progenitor star, J/M2 = 0.97, is safely below the Kerr limit. The calculations performed here apply to any marginally unstable n = 3 polytrope uniformly rotating at the break-up speed, independent of stellar mass or the source of internal pressure.

We experiment with various visualization techniques in the animations that follow. Some movies follow 2D plots of density in either the equatorial or meridional planes. We also show some animations in which we watch about 100,000 Lagrangian tracers that follow fluid elements. The initial distribution of these tracers is proportional to the initial mass density. Their trajectories at later times are computed using the fluid velocities.

For a comprehensive review of simulations of SMBH formation in general relativity, see Shapiro 2003 in Carnegie Observatories Astrophysics Series, Vol. I. Coevolution of Black Holes and Galaxies, ed. L. C. Ho (Cambridge Univ. Press: Cambridge) 2003 astro-ph/0304202.

Initial Configuration

Post-Newtonian Simulation

We first present the results of a (3+1) hydrodynamic simulation in the post-Newtonian approximation of general relativity. We follow the collapse until the PN approximation breaks down, i.e. the spacetime metric begins to deviate appreciably from flat space at the stellar center.

General Relativistic Simulation

Next, we show the results of an axisymmetric hydrodynamical simulation in full general relativity. We follow the collapse to the formation of a Kerr-like black hole surrounded by a disk.

last updated 1 jul 03 by rlc

Center for Theoretical Astrophysics---University of Illinois at Urbana-Champaign

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