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Orbital Evolution of Binary Black Holes in Active Galactic Nucleus Disks: A Disk Channel for Binary Black Hole Mergers?
- Source :
- The Astrophysical Journal. 911:124
- Publication Year :
- 2021
- Publisher :
- American Astronomical Society, 2021.
-
Abstract
- We perform a series of high-resolution 2D hydrodynamical simulations of equal-mass binary black holes (BBHs) embedded in active galactic nucleus (AGN) accretion disks to study whether these binaries can be driven to merger by the surrounding gas. We find that the gravitational softening adopted for the BBH has a profound impact on this result. When the softening is less than ten percent of the binary separation, we show that, in agreement with recent simulations of isolated equal-mass binaries, prograde BBHs expand in time rather than contract. Eventually, however, the binary separation becomes large enough that the tidal force of the central AGN disrupts them. Only when the softening is relatively large do we find that prograde BBHs harden. We determine through detailed analysis of the binary torque, that this dichotomy is due to a loss of spiral structure in the circum-single disks orbiting each BH when the softening is a significant fraction of the binary separation. Properly resolving these spirals -- both with high resolution and small softening -- results in a significant source of binary angular momentum. Only for retrograde BBHs do we find consistent hardening, regardless of softening, as these BBHs lack the important spiral structure in their circum-single disks. This suggests that the gas-driven inspiral of retrograde binaries can produce a population of compact BBHs in the gravitational-wave-emitting regime in AGN disks, which may contribute a large fraction to the observed BBH mergers.<br />accepted by ApJ, a new Table 2 is added
- Subjects :
- Angular momentum
Active galactic nucleus
010504 meteorology & atmospheric sciences
Astrophysics::High Energy Astrophysical Phenomena
Population
FOS: Physical sciences
Binary number
Astrophysics::Cosmology and Extragalactic Astrophysics
Astrophysics
01 natural sciences
Gravitation
Binary black hole
0103 physical sciences
Tidal force
education
010303 astronomy & astrophysics
Softening
Astrophysics::Galaxy Astrophysics
0105 earth and related environmental sciences
High Energy Astrophysical Phenomena (astro-ph.HE)
Physics
education.field_of_study
Astronomy and Astrophysics
Space and Planetary Science
Astrophysics::Earth and Planetary Astrophysics
Astrophysics - High Energy Astrophysical Phenomena
Subjects
Details
- ISSN :
- 15384357 and 0004637X
- Volume :
- 911
- Database :
- OpenAIRE
- Journal :
- The Astrophysical Journal
- Accession number :
- edsair.doi.dedup.....2e929c99de6025c245394256c9df2262