of 75
Population of Merging Compact Binaries Inferred Using Gravitational
Waves through GWTC-3
R. Abbott
etal.
*
(LIGO Scientific Collaboration, Virgo Collaboration, and KAGRA Collaboration)
(Received 4 February 2022; revised 28 October 2022; accepted 19 December 2022; published 29 March 2023)
We report on the population properties of compact binary mergers inferred from gravitational-wave
observations of these systems during the first three LIGO-Virgo observing runs. The Gravitational-Wave
Transient Catalog 3 (GWTC-3) contains signals consistent with three classes of binary mergers: binary
black hole, binary neutron star, and neutron star
black hole mergers. We infer the binary neutron star
merger rate to be between 10 and
1700
Gpc
3
yr
1
and the neutron star
black hole merger rate to be
between 7.8 and
140
Gpc
3
yr
1
, assuming a constant rate density in the comoving frame and taking the
union of 90% credible intervals for methods used in this work. We infer the binary black hole merger rate,
allowing for evolution with redshift, to be between 17.9 and
44
Gpc
3
yr
1
at a fiducial redshift (
z
¼
0
.
2
).
The rate of binary black hole mergers is observed to increase with redshift at a rate proportional to
ð
1
þ
z
Þ
κ
with
κ
¼
2
.
9
þ
1
.
7
1
.
8
for
z
1
. Using both binary neutron star and neutron star
black hole binaries, we obtain a
broad, relatively flat neutron star mass distribution extending from
1
.
2
þ
0
.
1
0
.
2
to
2
.
0
þ
0
.
3
0
.
3
M
. We confidently
determine that the merger rate as a function of mass sharply declines after the expected maximum neutron
star mass, but cannot yet confirm or rule out the existence of a lower mass gap between neutron stars and
black holes. We also find the binary black hole mass distribution has localized over- and underdensities
relative to a power-law distribution, with peaks emerging at chirp masses of
8
.
3
þ
0
.
3
0
.
5
and
27
.
9
þ
1
.
9
1
.
8
M
. While
we continue to find that the mass distribution of a binary
s more massive component strongly decreases as a
function of primary mass, we observe no evidence of a strongly suppressed merger rate above
approximately
60
M
, which would indicate the presence of a upper mass gap. Observed black hole
spins are small, with half of spin magnitudes below
χ
i
0
.
25
. While the majority of spins are preferentially
aligned with the orbital angular momentum, we infer evidence of antialigned spins among the binary
population. We observe an increase in spin magnitude for systems with more unequal-mass ratio. We also
observe evidence of misalignment of spins relative to the orbital angular momentum.
DOI:
10.1103/PhysRevX.13.011048
Subject Areas: Astrophysics, Gravitation
I. INTRODUCTION
The first three observing runs of the Advanced LIGO
[1]
and Advanced Virgo
[2]
gravitational-wave observatories
were undertaken between September 2015 and March
2020. During that time, gravitational-wave (GW) signals
from 90 mergers of binaries comprised of black holes
(BHs) and neutron stars (NSs) were observed. The
Gravitational-Wave Transient Catalog 3 (GWTC-3)
[3]
combines observations from the first three observing runs
(O1, O2
[4]
, and O3
[3,5,6]
). In this paper, we use those
observations to infer the populations of NS and BH binaries
in the Universe. To reduce contamination from events of
nonastrophysical origin, we restrict our attention to 76
events which have a false alarm rate (FAR) of less than one
per year, presented in Table
I
. Sixty-nine events are
identified as binary black holes (BBHs), four events are
neutron star
black holes (NSBHs), two events are binary
neutron stars (BNSs), and one event, GW190814, is either a
NSBH or BBH
[7]
. With this expanded catalog, we can
start to probe the detailed characteristics of the populations,
such as the distributions of component masses and spins, as
well as investigate possible correlations between source
properties.
The results presented here expand our understanding of
the Universe relative to our previous merger census
[20]
,
which was based upon events observed in O1, O2, and the
first half of O3 (O3a) as summarized in the Gravitational-
Wave Transient Catalog 2 (GWTC-2)
[5]
. In addition to an
increased total number of events, our census now contains
an entirely new class of events. The first GW observation
was a BBH merger
[8]
, and the first BNS observation,
*
Full author list given at the end of the article.
Published by the American Physical Society under the terms of
the
Creative Commons Attribution 4.0 International
license.
Further distribution of this work must maintain attribution to
the author(s) and the published article
s title, journal citation,
and DOI.
PHYSICAL REVIEW X
13,
011048 (2023)
2160-3308
=
23
=
13(1)
=
011048(75)
011048-1
Published by the American Physical Society