The merger rate of primordial-black-hole binaries
read the original abstract
Primordial black holes (PBHs) have long been a candidate for the elusive dark matter (DM), and remain poorly constrained in the ~20-100 Msun mass range. PBH binaries were recently suggested as the possible source of LIGO's first detections. In this paper, we thoroughly revisit existing estimates of the merger rate of PBH binaries. We compute the probability distribution of orbital parameters for PBH binaries formed in the early Universe, accounting for tidal torquing by all other PBHs, as well as standard large-scale adiabatic perturbations. We then check whether the orbital parameters of PBH binaries formed in the early Universe can be significantly affected between formation and merger. Our analytic estimates indicate that the tidal field of halos and interactions with other PBHs, as well as dynamical friction by unbound standard DM particles, do not do significant work on nor torque PBH binaries. We estimate the torque due to baryon accretion to be much weaker than previous calculations, albeit possibly large enough to significantly affect the eccentricity of typical PBH binaries. We also revisit the PBH-binary merger rate resulting from gravitational capture in present-day halos, accounting for Poisson fluctuations. If binaries formed in the early Universe survive to the present time, as suggested by our analytic estimates, they dominate the total PBH merger rate. Moreover, this merger rate would be orders of magnitude larger than LIGO's current upper limits if PBHs make a significant fraction of the dark matter. As a consequence, LIGO would constrain ~10-300 Msun PBHs to constitute no more than ~1% of the dark matter. To make this conclusion fully robust, though, numerical study of several complex astrophysical processes - such as the formation of the first PBH halos and how they may affect PBH binaries, as well as the accretion of gas onto an extremely eccentric binary - is needed.
This paper has not been read by Pith yet.
Forward citations
Cited by 10 Pith papers
-
Microscopic primordial black holes as macroscopic dark matter from large extra dimensions
In the ADD extra-dimension model, microscopic primordial black holes undergo runaway accretion and grow to macroscopic scales, allowing them to comprise all dark matter with initial abundances as low as 10^{-44}.
-
Smoluchowski Coagulation Equation and the Evolution of Primordial Black Hole Clusters
Monte Carlo solutions to the Smoluchowski coagulation equation yield runaway timescales and mass evolution for primordial black hole clusters at different redshifts based on cluster properties.
-
GW231123: A Possible Primordial Black Hole Origin
GW231123's masses and high spins are consistent with primordial black holes that accreted mass and angular momentum in the early universe within the standard PBH framework.
-
Merger rate of initially clustered primordial black holes for the two-body channel
Weak initial clustering of primordial black holes reduces the PBH fraction needed to explain LIGO-Virgo-KAGRA mergers in the two-body channel, while strong clustering suppresses the rate via three-body formation.
-
CMB constraints on ultra-light primordial black holes with extended mass distributions
For ultra-light PBHs with extended mass distributions, new CMB-derived 95% exclusion bounds on f_PBH are obtained by jointly varying ΛCDM parameters, yielding f_PBH < 1.6 × 10^{-5} for a uniform distribution between 1...
-
Effects of formation channels and gravitational lensing on stochastic gravitational wave background
Using HBI on GWTC-4 data the authors compute lensed SGWBs for ABHs and PBHs and conclude that LIGO and ET can distinguish the two formation channels in specific frequency ranges, with ET offering broader coverage.
-
In-depth analysis of the clustering of dark matter particles around primordial black holes. Part III: CMB constraints
CMB data limits the s-wave annihilation cross section of thermal dark matter particles to ≲ 10^{-30} cm³/s scaled by PBH fraction and mass for PBHs heavier than ~10^{-10} solar masses.
-
Machine Learning for Multi-messenger Probes of New Physics and Cosmology: A Review and Perspective
A review summarizing machine learning methods for multi-messenger probes of dark matter and new physics, with a proposed plan for future integrated analyses.
-
Science with the Einstein Telescope: a comparison of different designs
The paper evaluates how triangular versus two-L-shaped geometries, arm lengths, and presence of low-frequency instruments affect the science reach of the Einstein Telescope for compact binaries, multi-messenger events...
-
Primordial Black Holes as Dark Matter: Recent Developments
Primordial black holes in specific mass ranges could account for some or all dark matter while resolving structure-formation and seed problems in standard cosmology.
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.