Can we distinguish astrophysical from primordial black holes via the stochastic gravitational wave background?

Abstract

One of the crucial windows for distinguishing astrophysical black holes from primordial black holes is through the redshift evolution of their respective merger rates. The low redshift population of black holes of astrophysical origin is expected to follow the star formation rate. The corresponding peak in their merger rate is going to peak at a redshift smaller than that of the star formation rate peak (z p ≈ 2), depending on the time delay between the formation and mergers of black holes. Black holes of primordial origin are going to be present before the formation of the stars, and the merger rate of these sources at high redshift is going to be large. We propose joint estimation of a hybrid merger rate from the stochastic gravitational wave background, which can use the cosmic history of merger rates to distinguish between the two populations of black holes. Using the latest bounds on the amplitude of the stochastic gravitational wave background amplitude from the third observation run of LIGO/Virgo, we obtain weak constraints at 68% C.L. on the primordial black hole merger rate index 2.56 +1.64 −1.76 and astrophysical black hole time delay 6.7 +4.22 −4.74 Gyr. We should be able to distinguish between the different populations of black holes with the forthcoming O5 and A+ detector sensitivities.

GW200105 and GW200115 are compatible with a scenario of primordial black hole binary coalescences

“…Meanwhile, the required abundance of PBHs were found to be compatible with the existing upper limits from other observations. The inferred upper limits were shown to be close to the existing upper limits, implying that such scenarios can be further tested by observations of stochastic gravitational-wave background (SGWB) in the near future [25][26][27][28][29]. In addition, we found that the mass function of PBHs with m * = 5.4M and σ = 0.54 almost simultaneously explains the observed merger rates of GW200105 and GW200115, including the center values and error bars.…”

The redshift dependence of black hole mass distribution: Is it reliable for standard sirens cosmology?

“…An independent way to infer the PISN mass distribution is using the cross-correlation technique after marginalizing over the GW bias parameters (Mukherjee & Wandelt 2018;Mukherjee et al , 2021bDiaz & Mukherjee 2021). A proper inference of the mass distribution of the BBHs will also be useful for the analysis of the stochastic GW background (Mukherjee & Silk 2020; Callister et al 2020;Mukherjee & Silk 2021;Mukherjee et al 2021a) and lensing event rates (Oguri 2018;Mukherjee et al 2021e). The amplitude of the stochastic GW background and also the lensing event rates strongly depend on the mass distribution of the BBHs.…”

Prospects of discovering sub-solar primordial black holes using the stochastic gravitational wave background from third-generation detectors

“…In this paper, we estimate the SGWB signal from subsolar mass compact objects, and the possibility of detection via upcoming gravitational wave detectors. By exploring the evolution of the merger rate of the subsolar sources and their mass distribution, we will be able to distinguish between sources of primordial origin and astrophysical origin as proposed by [43]. Along with the SGWB, individual events can also shed light on the existence of subsolar PBHs [38][39][40]44].…”