# Progenitors of binary black hole mergers detected by LIGO

## TL;DR

This paper reviews possible formation channels for binary black hole mergers detected by LIGO, analyzing their characteristics and discussing how future observations can distinguish between these origins.

## Contribution

It provides a comparative analysis of formation mechanisms and presents population synthesis predictions for spins and masses across different metallicities.

## Key findings

- Low black hole spins are consistent with LIGO observations.
- Different formation channels produce distinguishable mass and spin distributions.
- Future gravitational wave data can help identify the dominant formation pathways.

## Abstract

Possible formation mechanisms of massive close binary black holes that can merge in the Hubble time to produce powerful gravitational wave bursts detected during advanced LIGO O1 science run are briefly discussed. The pathways include the evolution from field low-metallicity massive binaries, the dynamical formation in globular clusters and primordial black holes. Low effective black hole spins inferred for LIGO GW150914 and LTV151012 events are discussed. Population synthesis calculations of the expected spin and chirp mass distributions from the standard field massive binary formation channel are presented for different metallicities (from zero-metal Population III stars up to solar metal abundance). We conclude that that merging binary black holes can contain systems from different formation channels, discrimination between which can be made with increasing statistics of mass and spin measurements from ongoing and future gravitational wave observations.