Swift coalescence of supermassive black holes in cosmological mergers of massive galaxies

Journal Article · Sat Sep 10 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/828/2/73· OSTI ID:22868713

Khan, Fazeel Mahmood ^[1]; Fiacconi, Davide; Mayer, Lucio ^[2]; Berczik, Peter ^[3]; Just, Andreas ^[4]

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1. Department of Space Science, Institute of Space Technology, P.O. Box 2750 Islamabad (Pakistan)
2. Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, CH-8057 Zürich (Switzerland)
3. National Astronomical Observatories and Key Laboratory of Computational Astrophysics, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, 100012, Beijing (China)
4. Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstrasse 12-14, D-69120, Heidelberg (Germany)

Supermassive black holes (SMBHs) are ubiquitous in galaxies with a sizable mass. It is expected that a pair of SMBHs originally in the nuclei of two merging galaxies would form a binary and eventually coalesce via a burst of gravitational waves. So far, theoretical models and simulations, focusing only on limited phases of the orbital decay of SMBHs under idealized conditions of the galaxy hosts, have been unable to directly predict the SMBH merger timescale from ab-initio galaxy formation theory. The predicted SMBH merger timescales are long, of order Gyrs, which could be problematic for future gravitational wave (GW) searches. Here, we present the first multi-scale ΛCDM cosmological simulation that follows the orbital decay of a pair of SMBHs in a merger of two typical massive galaxies at z∼3, all the way to the final coalescence driven by GW emission. The two SMBHs, with masses ∼10{sup 8} M{sub ⊙}, settle quickly in the nucleus of the merger remnant. The remnant is triaxial and extremely dense due to the dissipative nature of the merger and the intrinsic compactness of galaxies at high redshift. Such properties naturally allow a very efficient hardening of the SMBH binary. The SMBH merger occurs in only ∼10 Myr after the galactic cores have merged, which is two orders of magnitude smaller than the Hubble time.

• OSTI ID: 22868713
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 828; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BLACK HOLES
COALESCENCE
COMPUTERIZED SIMULATION
COSMOLOGICAL MODELS
DECAY
GALAXIES
GALAXY NUCLEI
GRAVITATIONAL WAVES
INTERACTIONS
MASS
RED SHIFT