Massive black hole merger rates: the effect of kpc separation wandering and supernova feedback. (arXiv:2006.03065v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Barausse_E/0/1/0/all/0/1">Enrico Barausse</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dvorkin_I/0/1/0/all/0/1">Irina Dvorkin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tremmel_M/0/1/0/all/0/1">Michael Tremmel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Volonteri_M/0/1/0/all/0/1">Marta Volonteri</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonetti_M/0/1/0/all/0/1">Matteo Bonetti</a>
We revisit the predictions for the merger rate of massive black hole binaries
detectable by the Laser Interferometer Space Antenna (LISA) and their
background signal for pulsar-timing arrays. We focus on the effect of the
delays between the merger of galaxies and the final coalescence of black hole
binaries, and on the effect of supernova feedback on the growth of black holes.
By utilizing a semi-analytic galaxy formation model, not only do we account for
the processes that drive the evolution of binaries at separations $lesssim 1$
pc (gas-driven migration, stellar hardening and triple/quadruple massive black
hole systems), but we also improve on previous studies by accounting for the
time spent by massive black hole pairs from kpc down to a few pc separation. We
also include the effect of supernova feedback, which may eject a substantial
amount of gas from the nuclear region of low-mass galaxies, thus hampering the
growth of black holes via accretion and suppressing their orbital migration in
circumbinary disks. In spite of the inclusion of these novel physical effects,
we predict that the LISA detection rate should still be in excess of $sim 2
mbox{yr}^{-1}$, irrespective of the model for the seeds of the black hole
population at high redshifts. However, scenarios in which black holes form from
$sim100 M_odot$ seeds are more significantly impacted by the feedback from
supernovae. We also present predictions for the mass ratio distribution of the
merger population, and find that binaries typically have mass ratios between
$sim 0.1$ and $1$. Predictions for the stochastic background in the band of
pulsar-timing array experiments are instead rather robust, and show only a mild
dependence on the model.
We revisit the predictions for the merger rate of massive black hole binaries
detectable by the Laser Interferometer Space Antenna (LISA) and their
background signal for pulsar-timing arrays. We focus on the effect of the
delays between the merger of galaxies and the final coalescence of black hole
binaries, and on the effect of supernova feedback on the growth of black holes.
By utilizing a semi-analytic galaxy formation model, not only do we account for
the processes that drive the evolution of binaries at separations $lesssim 1$
pc (gas-driven migration, stellar hardening and triple/quadruple massive black
hole systems), but we also improve on previous studies by accounting for the
time spent by massive black hole pairs from kpc down to a few pc separation. We
also include the effect of supernova feedback, which may eject a substantial
amount of gas from the nuclear region of low-mass galaxies, thus hampering the
growth of black holes via accretion and suppressing their orbital migration in
circumbinary disks. In spite of the inclusion of these novel physical effects,
we predict that the LISA detection rate should still be in excess of $sim 2
mbox{yr}^{-1}$, irrespective of the model for the seeds of the black hole
population at high redshifts. However, scenarios in which black holes form from
$sim100 M_odot$ seeds are more significantly impacted by the feedback from
supernovae. We also present predictions for the mass ratio distribution of the
merger population, and find that binaries typically have mass ratios between
$sim 0.1$ and $1$. Predictions for the stochastic background in the band of
pulsar-timing array experiments are instead rather robust, and show only a mild
dependence on the model.
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