Merging massive black holes: the right place and the right time
  The LIGO/Virgo detections of gravitational waves from merging black holes of
$\simeq$ 30 solar mass suggest progenitor stars of low metallicity
(Z/Z$_{\odot} \lesssim 0.3$). In this talk I will provide constrains on where
the progenitors of GW150914 and GW170104 may have formed, based on advanced
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 with and
binaries formed recently in dwarf galaxies. Then, I will present what very high
resolution hydrodynamic simulations of different galaxy types can learn us
about their black hole populations.
