Search for Black Hole Merger Families

TL;DR

This paper searches for evidence of hierarchical triple black hole mergers in gravitational wave data, aiming to understand black hole binary origins and evolution, and highlights the importance of mass distribution properties in constraining merger scenarios.

Contribution

It introduces an improved statistical method to identify hierarchical black hole merger families in gravitational wave data, considering black hole spins and various mass bounds.

Findings

Identification of candidate black hole merger pairs.

Hints of hierarchical merger family presence.

Emphasis on mass distribution's role in merger scenarios.

Abstract

The origin, environment, and evolution of stellar-mass black hole binaries are still a mystery. One of the proposed binary formation mechanisms is manifest in dynamical interactions between multiple black holes. A resulting framework of these dynamical interactions is the so-called hierarchical triple merger scenario, which happens when three black holes become gravitationally bound, causing two successive black hole mergers to occur. In such successive mergers, the black holes involved are directly related to each other, and hence this channel can be directly tested from the properties of the detected binary black hole mergers. Here we present a search for hierarchical triple mergers among events within the GWTC-1 and GWTC-2 catalogs of LIGO/Virgo, the eccentric localization of GW190521 and those found by the IAS-Princeton group. The search includes improved statistical quantification that also accounts for black hole spins. We perform our analysis for different upper bounds on the mass distribution of first generation BHs. Our results demonstrate the importance of the mass distributions' properties for constraining the hierarchical merger scenario. We present the individually significant merger pairs. The search yields interesting candidate families and hints of its future impact.