Effects of a non-universal IMF and binary parameter correlations on compact binary mergers

TL;DR

This paper investigates how non-universal initial mass functions and correlated binary parameters, varying with metallicity and redshift, influence the predicted rates and properties of compact binary mergers using population synthesis models.

Contribution

It introduces a model incorporating metallicity- and redshift-dependent IMFs and correlated binary parameters into population synthesis simulations.

Findings

Variation in merger rates with metallicity and redshift.

Differences in binary population properties due to non-universal IMF.

Impact of parameter correlations on merger predictions.

Abstract

Binary population synthesis provides a direct way of studying the effects of different choices of binary evolution models and initial parameter distributions on present-day binary compact merger populations, which can then be compared to empirical properties such as observed merger rates. Samples of zero-age main sequence binaries to be evolved by such codes are typically generated from an universal IMF and simple, uniform, distributions for orbital period $P$, mass ratio $q$ and eccentricity $e$. More recently, however, mounting observational evidence has suggested the non-universality of the IMF and the existence of correlations between binary parameters. In this study, we implement a metallicity- and redshift-dependent IMF alongside correlated distributions for $P$, $q$ and $e$ in order to generate representative populations of binaries at varying redshifts, which are then evolved with the COMPAS code in order to study the variations in merger rates and overall population properties.