Following massive black hole binaries and triplets to coalescence in live galaxy simulations: gravitational wave source predictions with RAMCOAL

Tuesday 8 Sept 2026, 14:00 → 15:00 Asia/Shanghai

Tsung-Dao Lee Institute/S4F-SW - Open Area (Tsung-Dao Lee Institute)

Kunyang（坤阳） Li（李）

Host: Yosuke Mizuno
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Abstract:
Low-frequency gravitational-wave surveys need not just how often massive black holes (MBHs) merge, but the parameters carried to coalescence: masses, mass ratio, spins, eccentricity, and the delay since galaxy assembly. These depend on dynamical regimes that cosmological galaxy simulations cannot resolve. We extend RAMCOAL, a subgrid model in the RAMSES hydrodynamical code, to follow MBH binaries and now triplets — from galactic scales down to coalescence during the simulation. Black holes evolve from sink particles through a dynamical-friction phase into bound binaries hardened by stellar scattering, gas torques, circumbinary-disc coupling, and gravitational-wave emission, all within the live, evolving galaxy. When a later merger delivers a third MBH that drives the system chaotic, the model maps the interaction onto a library of three-body outcomes and updates the surviving binary, allowing exchanges, recoils, and ejections. Using isolated-galaxy tests, we show that the encounter geometry alone can change which pair finally coalesces, the eccentricity carried into the gravitational-wave band, and the merger delay (~0.3 to ~3.5 Gyr in our two configurations). By keeping coalescence, accretion, spin, and recoil coupled to the host galaxy, RAMCOAL aims to provide pre-coalescence source properties and electromagnetic context for multimessenger predictions.

Biography:
Kunyang Li （李坤阳）joined the Center for Computational Astrophysics (CCA) as a Flatiron Research Fellow in 2025. Her work focuses on modelling the evolution and realistic coalescence processes of massive black holes "on-the-fly" in cosmological simulations and on developing optimal strategies for detecting GW counterparts through EM searches.