Rapid Formation of Supermassive Black Hole Binaries in Galaxy Mergers with Gas
L. Mayer,1,2*
S. Kazantzidis,3*
P. Madau,4,5
M. Colpi,6
T. Quinn,7
J. Wadsley8
Supermassive black holes (SMBHs) are a ubiquitous component
of the nuclei of galaxies. It is normally assumed that after
the merger of two massive galaxies, a SMBH binary will form,
shrink because of stellar or gas dynamical processes, and ultimately
coalesce by emitting a burst of gravitational waves. However,
so far it has not been possible to show how two SMBHs bind during
a galaxy merger with gas because of the difficulty of modeling
a wide range of spatial scales. Here we report hydrodynamical
simulations that track the formation of a SMBH binary down to
scales of a few light years after the collision between two
spiral galaxies. A massive, turbulent, nuclear gaseous disk
arises as a result of the galaxy merger. The black holes form
an eccentric binary in the disk in less than 1 million years
as a result of the gravitational drag from the gas rather than
from the stars.
2 Institut für Astronomie, ETH Zürich, Wolfgang-Pauli-Strasse 16, CH-8093 Zürich, Switzerland.
3 Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics, Stanford University, Post Office Box 20450, MS 29, Stanford, CA 94309, USA.
4 Department of Astronomy, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA.
5 Max Planck Institute für Astrophysik, Karl-Schwarzschild Strasse 1, 85740 Garching bei Muenchen, Germany.
6 Dipartimento di Fisica, Università di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano, Italy.
7 Department of Astronomy, University of Washington, Stevens Way, Seattle, WA 98195, USA.
8 Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada.
* To whom correspondence should be addressed. E-mail: lucio{at}phys.ethz.ch (L.M.); stelios{at}slac.stanford.edu (S.K.)
