Merger rate of a subdominant population of primordial black holes

Abstract

The formation of astrophysical and primordial black holes influences the distribution of dark matter surrounding them. Black holes are thus expected to carry a dark matter 'dress' whose properties depend on their formation mechanism and on the properties of the environment. Here we carry out a numerical and analytical study of the merger of dressed black holes, and show that the distribution of dark matter around them dramatically affects the dynamical evolution of the binaries. Although the final impact on the merger rate of primordial black holes is rather small with respect to the case of 'naked' black holes, we argue that our analysis places the calculation of this rate on more solid ground, with LIGO-Virgo observations ruling out a dark matter fraction of 10 −3 for primordial black holes of 100 solar masses, and it paves the way to more detailed analyses of environmental effects induced by dark matter on the gravitational wave emission of binary black holes.

Early structure formation in primordial black hole cosmologies

“…Ref. [91] studied the interaction of pairs of PBH initially clothed by PDM. They find that as the PBH orbit, they lose their PDM halos and dynamical friction effects tend to circularize and shrink the orbit.…”

Merger history of primordial black-hole binaries

“…The progenitors of these BBHs are still unknown and under intensively investigation (see e.g. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]). These LIGO/Virgo BBHs present a much heavier mass distribution (in particular the sourceframe primary mass of GW170729 event can be as heavy as 50.2 +16.2 −10.2 M [7]) than that inferred from X-ray observations [28][29][30][31], which would challenge the formation and evolution mechanisms of astrophysical black holes.…”

Constraining the primordial black hole abundance with 21-cm cosmology

“…Black holes (BHs) produced prior to big bang nucleosynthesis (BBN), i.e., primordial black holes (PBHs), represent such an alternative -remarkably, this solution is as old as particle dark matter [5]. In particular, this scenario has recently attracted much attention [6][7][8][9][10][11][12] in the context of the LIGO and VIRGO discoveries of several binary BH mergers [13][14][15][16][17].The idea that PBHs could be formed by strong accretion during the radiation-dominated epoch was first introduced five decades ago [18]. It was later suggested that initial fluctuations in the early Universe could give rise to a large number of gravitationally collapsed objects with masses above the Planck mass [19], that however, would not grow substantially by accretion [20].…”