Revising natal kick prescriptions in population synthesis simulations. (arXiv:1909.06385v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Giacobbo_N/0/1/0/all/0/1">Nicola Giacobbo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mapelli_M/0/1/0/all/0/1">Michela Mapelli</a>
Natal kicks are matter of debate and significantly affect the merger rate
density of compact objects. Here, we present a new simple formalism for natal
kicks of neutron stars (NSs) and black holes (BHs). We describe the magnitude
of the kick as $v_{rm kick}propto{}f_{rm H05},{},{}m_{rm
ej},{},{}m_{rm rem}^{-1}$, where $f_{rm H05}$ is a normalization factor,
drawn from a Maxwellian distribution with one-dimensional root-mean-square
velocity $sigma{}=265$~km~s$^{-1}$, $m_{rm ej}$ is the mass of the supernova
(SN) ejecta and $m_{rm rem}$ is the mass of the compact object. This formalism
matches the proper motions of young Galactic pulsars and can naturally account
for the differences between core-collapse SNe of single stars, electron-capture
SNe and ultra-stripped SNe occurring in interacting binaries. Finally, we use
our new kick formalism to estimate the local merger rate density of binary NSs
($R_{rm BNS}$), BH–NS binaries ($R_{rm BHNS}$) and binary BHs ($R_{rm
BBH}$), based on the cosmic star formation rate density and metallicity
evolution. In our fiducial model, we find $R_{rm
BNS}sim{}600$~Gpc$^{-3}$~yr$^{-1}$, $R_{rm
BHNS}sim{}10$~Gpc$^{-3}$~yr$^{-1}$ and $R_{rm
BBH}sim{}50$~Gpc$^{-3}$~yr$^{-1}$, fairly consistent with the numbers inferred
from the LIGO-Virgo collaboration.
Natal kicks are matter of debate and significantly affect the merger rate
density of compact objects. Here, we present a new simple formalism for natal
kicks of neutron stars (NSs) and black holes (BHs). We describe the magnitude
of the kick as $v_{rm kick}propto{}f_{rm H05},{},{}m_{rm
ej},{},{}m_{rm rem}^{-1}$, where $f_{rm H05}$ is a normalization factor,
drawn from a Maxwellian distribution with one-dimensional root-mean-square
velocity $sigma{}=265$~km~s$^{-1}$, $m_{rm ej}$ is the mass of the supernova
(SN) ejecta and $m_{rm rem}$ is the mass of the compact object. This formalism
matches the proper motions of young Galactic pulsars and can naturally account
for the differences between core-collapse SNe of single stars, electron-capture
SNe and ultra-stripped SNe occurring in interacting binaries. Finally, we use
our new kick formalism to estimate the local merger rate density of binary NSs
($R_{rm BNS}$), BH–NS binaries ($R_{rm BHNS}$) and binary BHs ($R_{rm
BBH}$), based on the cosmic star formation rate density and metallicity
evolution. In our fiducial model, we find $R_{rm
BNS}sim{}600$~Gpc$^{-3}$~yr$^{-1}$, $R_{rm
BHNS}sim{}10$~Gpc$^{-3}$~yr$^{-1}$ and $R_{rm
BBH}sim{}50$~Gpc$^{-3}$~yr$^{-1}$, fairly consistent with the numbers inferred
from the LIGO-Virgo collaboration.
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