Lunch talk on May. 24th, 2018

Supermassive Black Hole Binary Mergers within Axisymmetric Galaxies: An Orbital Perspective

Speaker:李百乐（上海天文台）/ Baile Li(SHAO)

Venue:Gewu 4410

Time:12:30 PM, Thursday, 24th May, 2018

Abstract:It is known that particular centrophilic orbital families in non-spherical galaxies can, in principle, drive a black hole binary to shrink its orbit through three-body scattering until the black holes are close enough to strongly emit gravitational waves. 1) Most of these studies rely on orbital analysis of a static SMBH-embedded galaxy potential to support this view. We explore the orbital content within an N-body model of a mildly flattened, non-rotating, SMBH-embedded elliptical galaxy. Using both frequency-mapping and angular momentum criteria, we identify a wealth of resonant orbits in the axisymmetric model, including saucers, that are absent from an otherwise identical spherical system and that can potentially interact with the binary. We quantified the set of orbits that could be potentially scattered by the SMBH binary, and found that the axisymmetric model contained nearly six times the number of these potential loss cone orbits compared to our equivalent spherical model. 2) However, how these orbits transform as the second SMBH enters the center is not clear, so our understanding of which orbits actually interact with a SMBH binary is not ironclad. We also analyze flattened galaxy models with a SMBH binary, to determine which orbits actually do interact with the SMBH binary and how they compare with the set predicted in single SMBH-embedded models. We find close correspondence between the centrophilic orbits predicted to interact with the binary and those that are actually scattered by the binary, in terms of energy and Lz distribution, where Lz is the z component of a stellar particle's angular momentum. Because of the larger mass, the binary SMBH has a radius of influence ~ 4 times larger than in the single SMBH model, which allows the binary to draw from a larger reservoir of orbits to scatter. Of the prediction particles and scattered particles, nearly half have chaotic orbits, 40% have fx:fy=1:1 orbits, 10% have other resonant orbits.

Doodle:https://doodle.com/poll/547q6niupxifapaz