How SFRIs vary with methods of sampling the IMF and duplicity

TL;DR

This paper uses the BPASS code to study how binary stars and sampling methods of the initial mass function affect galaxy spectra, finding that binaries reduce stochastic effects and complicate maximum stellar mass determination.

Contribution

It introduces a new analysis of binary populations' impact on galaxy spectra and their interaction with IMF sampling methods using the BPASS code.

Findings

Observations favor stochastic IMF sampling but with limited significance.

Binary populations reduce stochastic effects in stellar populations.

Harder to determine variable maximum stellar mass with binaries.

Abstract

Using our new Binary Population and Spectral Synthesis (BPASS) code we explore the affect of binary populations on the integrated spectra of galaxies. We also explore the interplay of binary populations and a varying maximum stellar mass. We compare our synthetic populations to observations of H$\alpha$ emission from isolated clusters and H$\alpha$ and FUV observations of galaxies. We find that observations tend to favour a pure stochastic sampling of the initial mass function although the evidence is not significant. We also find that binaries make a stellar population less susceptible to the stochastic effects of filling the IMF. Therefore making it more difficult to determine if there is a variable maximum stellar mass.