State of the field: Binary black hole natal kicks and prospects for isolated field formation after GWTC-2. (arXiv:2011.09570v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Callister_T/0/1/0/all/0/1">T. A. Callister</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Farr_W/0/1/0/all/0/1">W. M. Farr</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Renzo_M/0/1/0/all/0/1">M. Renzo</a>
Advanced LIGO and Advanced Virgo’s newly-released GWTC-2 catalog of
gravitational-wave detections offers unprecedented information about the spin
magnitudes and orientations of merging binary black holes (BBHs). Notably,
analysis of the BBH population suggests the presence of binaries whose
component spins are significantly misaligned with respect to their orbital
angular momenta. Significantly misaligned spins are typically predicted to be
at odds with isolated field formation via standard common envelope (CE)
evolution, and hence a “smoking gun” signature of dynamical binary formation
inside dense stellar clusters. Here, we explore whether the LIGO/Virgo
observation of spin-orbit misalignment indeed rules out the possibility that
BBHs are formed entirely in the field via standard CE evolution. In particular,
we seek to understand whether, by varying the natal kicks black holes receive
upon formation, we can invoke the CE scenario to self-consistently explain both
the observed spin distribution and merger rate of BBHs. We find that it remains
possible, although likely implausible, to explain the observed BBH population
only if black holes receive extreme natal kicks, with a velocity dispersion
$sigma = 9.7^{+26.7}_{-5.9}times10^2,mathrm{km},mathrm{s}^{-1}$ and
$sigma>260,mathrm{km},mathrm{s}^{-1}$ at 99% credibility. To avoid this
condition, we argue that it is necessary to assume that isolated black holes
are born with non-vanishing natal spins, that one or more alternative channels
contribute to the observed BBH population, and/or that other unforeseen
mechanisms serve to yield large spin-orbit misalignment in the field.
Advanced LIGO and Advanced Virgo’s newly-released GWTC-2 catalog of
gravitational-wave detections offers unprecedented information about the spin
magnitudes and orientations of merging binary black holes (BBHs). Notably,
analysis of the BBH population suggests the presence of binaries whose
component spins are significantly misaligned with respect to their orbital
angular momenta. Significantly misaligned spins are typically predicted to be
at odds with isolated field formation via standard common envelope (CE)
evolution, and hence a “smoking gun” signature of dynamical binary formation
inside dense stellar clusters. Here, we explore whether the LIGO/Virgo
observation of spin-orbit misalignment indeed rules out the possibility that
BBHs are formed entirely in the field via standard CE evolution. In particular,
we seek to understand whether, by varying the natal kicks black holes receive
upon formation, we can invoke the CE scenario to self-consistently explain both
the observed spin distribution and merger rate of BBHs. We find that it remains
possible, although likely implausible, to explain the observed BBH population
only if black holes receive extreme natal kicks, with a velocity dispersion
$sigma = 9.7^{+26.7}_{-5.9}times10^2,mathrm{km},mathrm{s}^{-1}$ and
$sigma>260,mathrm{km},mathrm{s}^{-1}$ at 99% credibility. To avoid this
condition, we argue that it is necessary to assume that isolated black holes
are born with non-vanishing natal spins, that one or more alternative channels
contribute to the observed BBH population, and/or that other unforeseen
mechanisms serve to yield large spin-orbit misalignment in the field.
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