Conservative limits on primordial black holes from the LIGO-Virgo-KAGRA observations

TL;DR

This paper uses LIGO-Virgo-KAGRA data to set conservative upper limits on the contribution of primordial black holes to dark matter, considering binary formation and evolution within dark matter halos.

Contribution

It introduces a method to derive the most conservative upper limits on PBH merger rates using gravitational wave data, accounting for binary formation and interactions inside halos.

Findings

Limits on PBH dark matter fraction range from 10^-4 to 2×10^-2.

For PBH masses 5-80 M_sun, the fraction is 10^-3 to 10^-2.

Provides competitive constraints in the 5-50 M_sun mass range.

Abstract

Primordial black holes (PBH) may constitute a considerable fraction of dark matter. In this work we use the recent observations by the LIGO-Virgo-KAGRA (LVK) collaborations to set direct limits on stellar-mass range PBHs. We evaluate the merger rates of PBH binaries by accounting for the binaries formed by two-body captures inside dark matter halos and by studying the evolution of PBH binaries inside such halos through binary-single interactions. Those type of interactions contribute to what is a minimum of PBH merger rates at low redshifts detectable by LVK. Thus, they allow us to derive what is the most conservative upper limits on the presence of merging PBH binaries in the gravitational-wave observations. We study both the case where PBHs have a monochromatic mass-distribution and the case where that distribution is described by a log-normal function. Our derived limits on the mass fraction of dark matter composed of PBHs is in the range of $10^{-4}$ to $2\times 10^{-2}$, depending on the exact assumptions relating to the PBH binaries properties. For reasonable assumptions on those PBH binaries' properties before their evolution inside dark matter halos, we get that fraction to be in the range of $10^{-3} - 10^{-2}$, for PBH masses of 5-80 $M_{\odot}$. Our work provide some of the most competitive limits in the mass range of 5-50 $M_{\odot}$. [abridged]