Recorded 6 October 2021. Carlos Lousto of the Rochester Institute of Technology presents "From numerical simulations of binary black hole mergers to insights into astrophysics and gravitational waves" at IPAM's Workshop I: Computational Challenges in Multi-Messenger Astrophysics.
Abstract: The late orbital dynamics of spinning binary black holes remains a fascinating area of research. Among the notable spin effects observed in supercomputer simulations are the hangup effect which prompts or delays the merger of binary black holes depending on the sign of the spin-orbit coupling, the flip-flop of black hole spins in a binary, passing from aligned to antialigned periods with respect to the orbital angular momentum, the alignment instability (a case of imaginary flip-flop frequencies), and the total flip of the orbital angular momentum, leading to beaconing patterns of gravitational radiation.
Through numerical simulations it was found the large recoils of the final black hole remnant, reaching up to 5000km/s. Accurate modeling of those recoil velocities allows, for instance, to use observational measurements of recoiling supermassive quasars, like 3C 186, to infer the masses and spins of the progenitor binary.
Fitting formulas relating initial binary parameters (individual masses and spins) to the final merger properties (peak amplitudes and frequency, and final remnant mass and spin) are of interest for applications to astrophysical and gravitational wave observations.
Finally, we demonstrate how catalogs of black hole merger waveforms can be used to accurately determine the binary's parameters, directly from the observed gravitational waves by directly applying them to O1/O2 LIGO/Virgo observations.
This simulations shows the accretion patterns around two merging black holes. This is to show the smoothness of the transition between IllinoisGRMHD to harm3d, which are two different magnetohydrodynamics codes.
Speaker: Eduardo Mario Gutiérrez (CCRG, Rochester Institute of Technology)
Title: Electromagnetic signatures from supermassive black hole binaries approaching merger
Theoretical models predict that when two galaxies merge, the supermassive black holes at their nuclei might end up forming close binary systems of sub-parsec scales. The gravitational waves emitted by these systems are targets of current Pulsar Timing Arrays and of future interferometers as LISA (Laser Interferometer Space Antenna). Unlike most stellar-mass black hole mergers, supermassive black hole binaries (SMBHBs) live and die in gas-rich environments (the cores of galaxies) and they can present similar phenomenology to single AGNs; namely, accretion disks, jets and the subsequent multi-wavelength emission. A detailed knowledge of the main radiation signatures from these systems is crucial to differentiate them from normal AGNs and to identify potential targets for multi-messenger observations. In this talk, I will present new theoretical predictions of the electromagnetic emission from close SMBBHs. Using data from GRMHD simulations of these systems, we produce realistic ray traced images, spectra, and lightcurves at different wavelengths. We explore the influence of the black hole spin, accretion rate, and line-of-sight inclination on these products and identify specific features that may discriminate SMBHBs from normal AGNs.
Speaker: Luciano Combi (Instituto Argentina de Radioastronomia, Rochester Institute of TechnologyI
Title: Accretion onto spinning supermassive black hole binaries
Massive binary black holes (MBBH) are expected to be in the gas-rich environment of galaxies and emit electromagnetic waves through accretion. At close separations, the dynamical spacetime and the non-linear behavior of the plasma make the system fairly complex. For this reason, numerical simulations are key tools to make accurate predictions of Its multi-messenger emission.
In this talk, we present an overview of recent results on general relativistic magnetohydrodynamical simulations of accretion disks around supermassive black hole binaries. First, we introduce a new approximate metric representing two spinning black holes approaching merger. We use this metric to perform long-term simulations of circumbinary disks and mini-disks. We analyze the periodic behavior and orbital motion of the mini-disks, their interaction with the circumbinary disk, and the electromagnetic outflows produced by the black holes. These simulations constitute the first steps to modeling realistic lightcurves and spectra from MBBH with equal masses.
Manuela Campanelli, astrophysicist and Professor of Mathematical Sciences at Rochester Institute of Technology, simulates compact objects in the universe, like black holes and neutron stars. Frontera allows her team of researchers to simulate these complex systems twice as fast as previous systems.