Evidence for primordial black holes in LIGO/Virgo gravitational-wave data. (arXiv:2105.03349v1 [gr-qc])
<a href="http://arxiv.org/find/gr-qc/1/au:+Franciolini_G/0/1/0/all/0/1">Gabriele Franciolini</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Baibhav_V/0/1/0/all/0/1">Vishal Baibhav</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Luca_V/0/1/0/all/0/1">Valerio De Luca</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Ng_K/0/1/0/all/0/1">Ken K. Y. Ng</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Wong_K/0/1/0/all/0/1">Kaze W. K. Wong</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Berti_E/0/1/0/all/0/1">Emanuele Berti</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Pani_P/0/1/0/all/0/1">Paolo Pani</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Riotto_A/0/1/0/all/0/1">Antonio Riotto</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Vitale_S/0/1/0/all/0/1">Salvatore Vitale</a>
With approximately $50$ binary black hole events detected by LIGO/Virgo to
date and many more expected in the next few years, gravitational-wave astronomy
is shifting from individual-event analyses to population studies aimed at
understanding the formation scenarios of these sources. There is strong
evidence that the black hole mergers detected so far belong to multiple
formation channels. We perform a hierarchical Bayesian analysis on the GWTC-2
catalog using a combination of ab-initio astrophysical formation models
(including common envelope, globular clusters, and nuclear star clusters) as
well as a realistic population of primordial black holes formed in the early
universe. The evidence for a primordial population is decisively favored
compared to the null hypothesis and the inferred fraction of primordial black
holes in the current data is estimated at $0.27^{+0.28}_{-0.24}$ ($90%$
credible interval), a figure which is robust against different assumptions on
the astrophysical populations. The primordial formation channel can explain
events in the upper mass gap such as GW190521, which are in tension with
astrophysical formation scenarios. Our results suggest the tantalizing
possibility that LIGO/Virgo may have already detected black holes formed after
inflation. This conclusion can ultimately be confirmed in the era of
third-generation interferometers.
With approximately $50$ binary black hole events detected by LIGO/Virgo to
date and many more expected in the next few years, gravitational-wave astronomy
is shifting from individual-event analyses to population studies aimed at
understanding the formation scenarios of these sources. There is strong
evidence that the black hole mergers detected so far belong to multiple
formation channels. We perform a hierarchical Bayesian analysis on the GWTC-2
catalog using a combination of ab-initio astrophysical formation models
(including common envelope, globular clusters, and nuclear star clusters) as
well as a realistic population of primordial black holes formed in the early
universe. The evidence for a primordial population is decisively favored
compared to the null hypothesis and the inferred fraction of primordial black
holes in the current data is estimated at $0.27^{+0.28}_{-0.24}$ ($90%$
credible interval), a figure which is robust against different assumptions on
the astrophysical populations. The primordial formation channel can explain
events in the upper mass gap such as GW190521, which are in tension with
astrophysical formation scenarios. Our results suggest the tantalizing
possibility that LIGO/Virgo may have already detected black holes formed after
inflation. This conclusion can ultimately be confirmed in the era of
third-generation interferometers.
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