The cosmological distribution of compact object mergers from dynamical interactions with SMBH binaries. (arXiv:1906.10142v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Wang_Y/0/1/0/all/0/1">Yi-Han Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Leigh_N/0/1/0/all/0/1">Nathan Leigh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sesana_A/0/1/0/all/0/1">Alberto Sesana</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Perna_R/0/1/0/all/0/1">Rosalba Perna</a>
We combine sophisticated high precision scattering experiments, together with
results from the Millenium-II simulation, to compute the cosmic merger rate of
bound compact object (CO) binaries dynamically interacting with supermassive
black hole binaries (SMBHBs). We consider binaries composed of white dwarfs
(WDs), neutron stars (NSs) and black holes (BHs). The overall merger rates for
WD-WD, NS-NS, BH-BH, BH-NS binaries and EBBH (eccentric binaries of black
holes) from redshift $sim 5$ are found to be $4.32times 10^3,{rm
yr}^{-1}$($5.93times10^2,{rm yr}^{-1}$ for Type Ia SNe), $82.7,{rm
yr}^{-1}$, $96.3,{rm yr}^{-1}$, $13.1,{rm yr}^{-1}$ and $148,{rm
yr}^{-1}$ , respectively, for a nominal CO binary fraction in the Galactic
centre of 0.1. We calculate the distance ($R$) distribution of the merger sites
with respect to the host galaxies of the binaries. The distribution shows a
wide range of distances up to $sim$Mpc; this tail is produced by escaped
hyper-velocity CO binaries. Due to the differences in the matter density of the
surrounding environment, merger events with different $R$ are expected to
display significantly different signatures in their EM counterparts. In
particular, merger events (and especially NS-NS) producing a relativistic jet
but occurring in the intergalactic medium will have very weak afterglow
radiation relative to their prompt emission. These events, which we call
‘off-center’, can only be produced from a close encounter between CO binaries
and SMBHBs; hence the detection of such merger events would indicate the
existence of nearby SMBHBs, and in particular with high mass ratio, produced in
the aftermath of a major galaxy merger.
We combine sophisticated high precision scattering experiments, together with
results from the Millenium-II simulation, to compute the cosmic merger rate of
bound compact object (CO) binaries dynamically interacting with supermassive
black hole binaries (SMBHBs). We consider binaries composed of white dwarfs
(WDs), neutron stars (NSs) and black holes (BHs). The overall merger rates for
WD-WD, NS-NS, BH-BH, BH-NS binaries and EBBH (eccentric binaries of black
holes) from redshift $sim 5$ are found to be $4.32times 10^3,{rm
yr}^{-1}$($5.93times10^2,{rm yr}^{-1}$ for Type Ia SNe), $82.7,{rm
yr}^{-1}$, $96.3,{rm yr}^{-1}$, $13.1,{rm yr}^{-1}$ and $148,{rm
yr}^{-1}$ , respectively, for a nominal CO binary fraction in the Galactic
centre of 0.1. We calculate the distance ($R$) distribution of the merger sites
with respect to the host galaxies of the binaries. The distribution shows a
wide range of distances up to $sim$Mpc; this tail is produced by escaped
hyper-velocity CO binaries. Due to the differences in the matter density of the
surrounding environment, merger events with different $R$ are expected to
display significantly different signatures in their EM counterparts. In
particular, merger events (and especially NS-NS) producing a relativistic jet
but occurring in the intergalactic medium will have very weak afterglow
radiation relative to their prompt emission. These events, which we call
‘off-center’, can only be produced from a close encounter between CO binaries
and SMBHBs; hence the detection of such merger events would indicate the
existence of nearby SMBHBs, and in particular with high mass ratio, produced in
the aftermath of a major galaxy merger.
http://arxiv.org/icons/sfx.gif
