Evolution of Galaxy Star Formation and Metallicity: Impact on Double Compact Objects Mergers

TL;DR

This paper examines how different galaxy statistics and metallicity relations influence the rates and properties of merging compact object binaries across cosmic time.

Contribution

It compares the effects of using star formation rate versus stellar mass functions and the Fundamental Metallicity Relation versus Mass Metallicity Relation on binary merger predictions.

Findings

Higher metallicity star formation at high redshift with FMR

Metallicity decreases with redshift using MZR

Impacts on merger rates and binary properties

Abstract

We study the impact of different galaxy statistics and empirical metallicity scaling relations on the merging rates and on the properties of compact objects binaries. First, we analyze the similarities and differences of using the star formation rate functions or the stellar mass functions as galaxy statistics for the computation of the cosmic star formation rate density. Then we investigate the effects of adopting the Fundamental Metallicity Relation or a classic Mass Metallicity Relation to assign metallicity to galaxies with given properties. We find that when the Fundamental Metallicity Relation is exploited, the bulk of the star formation occurs at relatively high metallicities even at high redshift; the opposite holds when the Mass Metallicity Relation is employed, since in this case the metallicity at which most of the star formation takes place strongly decreases with redshift. We discuss the various reasons and possible biases originating this discrepancy. Finally, we show the impact that these different astrophysical prescriptions have on the merging rates and on the properties of compact objects binaries; specifically, we present results for the redshift dependent merging rates and for the chirp mass and time delay distributions of the merging binaries.