Speaker
Description
Traditional numerical simulations employing gravitational softening are unable to resolve the small-scale dynamics and gravitational wave emission from supermassive black hole binaries. Instead, the parsec-scale dynamics is typically modelled by postprocessing the simulations using either semi-analytic methods based on orbit-averaged equations or by resimulating the core regions of the merged galaxies using an altogether separate N-body code.
An alternative is to use a hybrid approach, such as the KETJU code, recently developed in our group. The KETJU code includes algorithmically regularised regions around every supermassive black hole (SMBH). This allows for simultaneously following global galactic-scale dynamical and astrophysical processes, while solving accurately the dynamics of SMBHs at sub-parsec scales. In addition, the KETJU code also includes post-Newtonian terms in the equations of motions of the SMBHs, which allows us to directly calculate the expected gravitational wave signal from the motion of the resolved SMBH binary in mergers of massive galaxies. We demonstrate here how KETJU can be used to model the dynamics of SMBHs in a full cosmological setting and thus provide more accurate predictions for the upcoming LISA gravitational wave observatory. Finally, we also present a new public version of the KETJU supermassive black hole (SMBH) dynamics module, as implemented into the GADGET-4 code.
