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Free keywords:
General Relativity and Quantum Cosmology, gr-qc,Astrophysics, Cosmology and Extragalactic Astrophysics, astro-ph.CO, Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE
Abstract:
Some analyses of the third gravitational wave catalogue released by the
LIGO-Virgo-KAGRA collaboration (LVK) suggest an excess of black holes around
$15-20 M_{\odot}$. In order to investigate this feature, we introduce two
flexible population models, a semi-parametric one and a non-parametric one.
Both make use of reversible jump Markov chain Monte-Carlo to optimise their
complexity. We also illustrate how the latter can be used to efficiently
perform model selection. Our parametric model broadly agrees with the fiducial
analysis of the LVK, but finds a peak of events at slightly larger masses. Our
non-parametric model shows this same displacement. Moreover, it also suggests
the existence of an excess of black holes around $20 M_{\odot}$. We assess the
robustness of this prediction by performing mock injections and running
hierarchical analyses on those. We find that such a feature might be due to
statistical fluctuations, given the small number of events observed so far,
with a $5\%$ probability. We estimate that with a few hundreds of observations,
as expected for O4, our non-parametric model will, be able to robustly
determine the presence of this excess. It will then allow for an efficient
agnostic inference of the properties of black holes.
