Letters of Intent received in 2019

LoI 2021-2066
Astrophysical Black Holes as Gravitational Wave Sources

Topics

Black Holes of various mass scales
Galactic Nuclei, dynamics and evolution
Galactic and Extragalactic Star Clusters
Formation of black hole binaries
Compact galaxies
Multi-messenger astronomy
Gravitational Wave Instruments
Evolution of massive stars

Rationale

Recent observations of stellar-mass black holes via gravitational waves (GW) and direct imaging of a supermassive black hole gave us much more confidence in the existence of various types of black holes in the universe. We were able to probe the physical parameters of black holes in greater detail through GW observations. The detection of a merger event between two neutron stars further advanced our knowledge on the nature of gamma-ray bursts by coincidence observation of electromagnetic waves.
In spite of these progresses the astrophysical origin of the observed GW events is still unknown. Are the merging black holes due to isolated binaries in the galactic field, or have they undergone dynamical encounters in star clusters? The relatively high black hole masses observed from the LIGO/Virgo events have puzzled stellar evolution theorists; an origin from star clusters has difficulty to explain observed event rates. Other more exotic formation processes have been proposed, such as interactions of star clusters with AGN disks, triples, primordial black holes. Next generation ground based detectors and multi-messenger observations will provide better limits on astrophysical parameters of GW sources, such as orbital data and spins.
In the future space based GW detectors and pulsar timing will provide data on supermassive black hole binaries in galactic nuclei, on extreme mass ratio inspirals and on the earlier dynamical phases of LIGO/Virgo sources. Computer models of black holes, nuclear star clusters and active galactic nuclei as well as their electromagnetic observations (e.g. of tidal disruptions, quasars, optical/IR and radio astronomy) should be used to determine appropriate gravitational waveforms and discriminate the origin of sources observed with future gravitational wave instruments.
The combination of gravitational wave and electromagnetic wave observations and of observations across different parts of the spectrum (both for GW and EM) will enrich our understanding of the universe significantly. This symposium is intended to discuss the astrophysical origin of LIGO/Virgo sources as well as the sources for future low-frequency GW observations. The topics include the dynamical phenomena related to the black holes, stellar populations, stellar dynamics, modeling GW sources, and multi-messenger astronomy; hence it will enhance our astrophysical understanding of black holes and their dynamics in galaxies, galactic nuclei, and star clusters and enables us to better probe the universe with data from current and next generation GW detectors.