On the Interpretation of the Globular Cluster Luminosity Function

TL;DR

This paper investigates how the variable mass-to-light ratio in globular clusters affects the conversion from luminosity to mass functions, revealing that accounting for M/L variability alters the inferred initial mass distribution.

Contribution

It introduces a model that incorporates luminosity-dependent M/L ratios to better interpret the globular cluster mass function from observed luminosity data.

Findings

The observed GCLF aligns with a power-law or Schechter initial mass function.

Accounting for M/L variability shifts the peak mass lower by 0.1-0.3 dex.

The GCMF slope below the peak is shallower than the GCLF slope.

Abstract

The conversion of the globular cluster luminosity function (GCLF, dN/dlogL) to the globular cluster mass function (GCMF, dN/dlogM) is addressed. Dissolving globular clusters (GCs) become preferentially depleted in low-mass stars, which have a high mass-to-light ratio. This has been shown to result in a mass-to-light ratio (M/L) that increases with GC luminosity or mass, because more massive GCs have lost a smaller fraction of their stars than low-mass GCs. Using GC models, we study the influence of the luminosity dependency of M/L on the inferred GCMF. The observed GCLF is consistent with a powerlaw or Schechter type GC initial mass function in combination with a cluster mass-dependent mass loss rate. Below the peak, the logarithmic slope of the GCMF is shallower than that of the GCLF (0.7 versus 1.0), whereas the peak mass is 0.1-0.3 dex lower when accounting for the variability of M/L than in the case where a constant M/L is adopted.