The evolution of primordial black holes and their final observable spins

Abstract

Primordial black holes in the mass range of ground-based gravitational-wave detectors can comprise a significant fraction of the dark matter. Mass and spin measurements from coalescences can be used to distinguish between an astrophysical or a primordial origin of the binary black holes. In standard scenarios the spin of primordial black holes is very small at formation. However, the mass and spin can evolve through the cosmic history due to accretion. We show that the mass and spin of primordial black holes are correlated in a redshift-dependent fashion, in particular primordial black holes with masses below O(30)M are likely non-spinning at any redshift, whereas heavier black holes can be nearly extremal up to redshift z ∼ 10. The dependence of the mass and spin distributions on the redshift can be probed with future detectors such as the Einstein Telescope. The mass and spin evolution affect the gravitational waveform parameters, in particular the distribution of the final mass and spin of the merger remnant, and that of the effective spin of the binary. We argue that, compared to the astrophysical-formation scenario, a primordial origin of black hole binaries might better explain the spin distribution of merger events detected by LIGO-Virgo, in which the effective spin parameter of the binary is compatible to zero except possibly for few high-mass events. Upcoming results from LIGO-Virgo third observation run might reinforce or weaken these predictions.

Bayesian analysis of LIGO-Virgo mergers: Primordial versus astrophysical black hole populations

“…So called second generation mergers, i.e. those involving one or more BHs which have already undergone a previous merger, are expected to be very rare compared with primary mergers [19,41] (although also see Ref. [56]).…”

Mapping the asymptotic inspiral of precessing binary black holes to their merger remnants

“…[25]), and primordial (e.g. [61]) BHs. Our analysis highlights potential caveats and provides a stepping stone to take those ideas to completion.…”

Distinguishing double neutron star from neutron star-black hole binary populations with gravitational wave observations

“…We assume an isotropic source position and orientation in the sky. We neglect the spins of both NSs (in which case the dimensionless spin parameter is expected to be ≲0.3 [117]) and BHs (see e.g., [118,119]). Although BHs, in principle, can have large spin, this should not significantly affect our results, because tidal deformability effects are expected to be dominant over spin effects at the relevant post-Newtonian order [120].…”

“…Moreover, we are focusing on black hole masses up to 2 M ⊙ . These may involve BHs of primordial origin or dark matter cores (see Appendix A), and theoretical calculation in these scenarios suggest that BH spins should be negligible [119,121,122].…”