The impact of binaries on the dynamical mass estimate of dwarf galaxies

TL;DR

This paper investigates how binary stars influence the measurement of velocity dispersion and dynamical mass estimates in dwarf galaxies, revealing that binaries can significantly affect dark matter inferences.

Contribution

Developed a tool to assess binary star effects on velocity dispersion estimates, applied it to dwarf galaxies, showing binaries can bias mass calculations especially in low-mass systems.

Findings

Binary stars significantly affect velocity dispersion measurements.

Impact is more pronounced in low-mass, low-density dwarf galaxies.

Results suggest re-evaluating dark matter content in such systems.

Abstract

Binary stars are recognized to be important in driving the dynamical evolution of stellar systems and also in determining some of their observational features. In this study, we explore the role that binary stars have in modulating the estimates of the velocity dispersion of stellar systems. To this aim, we developed a tool which allows to investigate the dependence of synthetic velocity dispersion on a number of crucial quantities characterizing the binary content: binary fraction and the distributions of their mass ratio, eccentricity and semi-major axis. As an application, we evaluate the impact that binary stars have on the estimation of the dynamical mass of dwarf spheroidal and ultra-faint dwarf galaxies, finding that it can be particularly relevant, especially for low mass and low density systems. These results bear profound implications for the interpretation of the measured velocity dispersion in such systems, since it weakens or relieves the claim for the need of large amounts of dark matter.