We simulated binary supermassive black holes moving in an ultralight dark matter soliton. The simulations ran longer and at higher resolution than earlier efforts.
For black hole and soliton parameters consistent with very large galaxies the orbit decayed faster than predicted by simple semi-analytic approximations or previous simulations. This is apparently due to the soliton being “pinched” by the black holes near their centres, increasing the density of dark matter and the resulting drag. As a consequence these systems may move more quickly through the pulsar timing band than expected from gravitational wave emission alone, providing a new mechanism for constraining the presence of ultralight dark matter in galaxies.
Abstract
Ultralight (or fuzzy) dark matter (ULDM) is an alternative to cold dark matter. A key feature of ULDM is the presence of solitonic cores at the centers of collapsed halos. These would potentially increase the drag experienced by supermassive black hole (SMBH) binaries, changing their merger dynamics and the resulting gravitational wave background. We perform detailed simulations of high-mass SMBH binaries in the soliton of a massive halo. We find more rapid decay than previous simulations and semi-analytic approximations. We confirm expectations that the drag depends strongly on the ULDM particle mass, finding masses greater than 10−21 eV could potentially alleviate the final parsec problem and that ULDM may even suppress gravitational wave production at lower frequencies in the pulsar timing band.
- Boey, Wang, Kendall and Easther
- Supermassive Binaries in Ultralight Dark Matter Solitons
- Phys. Rev. D 112, 023510 or ArXiV:2504.16348
Black holes in a “pinched” soliton.