The Mass-to-Light Ratios of Galactic Globular Clusters

TL;DR

This study investigates why observed mass-to-light ratios of Galactic globular clusters are lower than theoretical predictions by modeling their dynamical evolution and stellar mass function changes.

Contribution

It introduces a detailed dynamical model that accounts for star ejection and mass function evolution to explain the lower observed M/L ratios.

Findings

Dynamical evolution reduces M/L ratios by ejecting low-mass stars.

Model explains the ~20% discrepancy between observations and SSP predictions.

Stellar mass function evolution is key to understanding M/L ratios.

Abstract

The observed mass-to-light (M/L) ratios of globular clusters (GCs) are on average ~20% lower than expected from Simple Stellar Population (SSP) models, which only account for the effects of stellar evolution. We study the M/L ratio evolution of a sample of 24 Galactic GCs using parameterised cluster models. The dynamical evolution of GCs is included by accounting for their dissolution and by using a detailed description of the evolution of the stellar mass function. The ejection of low-mass stars leads to a decrease of M/L, which is found to explain the discrepancy between the observations and SSP models.