Gravitational-Wave Research Seminar

The LIGO detections of gravitational waves from ~ 30 solar mass black holes suggests progenitor stars of low metallicity ([Z/Z⊙] ≲ 0.3). In this talk I will provide constrains on where the progenitors of GW150914 and GW170104 may have formed, based on models of galaxy formation and evolution combined with binary population synthesis models. First I will combine estimates of galaxy properties (star-forming gas metallicity, star formation rate and merger rate) across cosmic time to predict the low redshift BBH merger rate as a function of present day host galaxy mass, formation redshift of the progenitor system and different progenitor metallicities. I will show that the signal is dominated by binaries formed at the peak of star formation in massive galaxies and binaries formed recently in dwarf galaxies. Then, I will present a prediction of the distribution merged and  binary black hoes in the MW, based on a combination of a very high resolution hydrodynamic simulation and a binary evolution model. A handful of these systems may be detectable by LISA, but also SKA and/or microlensing surveys.