A Quantitative Link Between Globular Clusters and the Stellar Halos in Elliptical Galaxies

TL;DR

This study establishes a quantitative relationship between globular clusters and the stellar halos of elliptical galaxies, revealing how globular cluster populations correlate with galaxy stellar mass and metallicity distributions.

Contribution

It introduces a new Monte Carlo modeling approach that links globular clusters with diffuse stellar populations without relying on parametric fits, using a novel colour-metallicity relation.

Findings

Globular cluster numbers increase as metallicity decreases.

A successful model links globular clusters to galaxy stellar halos.

Detection of a blue tilt in globular cluster subpopulations.

Abstract

This paper explores the quantitative connection between globular clusters and the diffuse stellar population of the galaxies they are associated with. Both NGC 1399 and NGC 4486 (M87) are well suited for this kind of analysis due to their large globular cluster populations. The main assumption of our Monte Carlo based models is that each globular cluster is formed along with a given diffuse stellar mass that shares the same spatial distribution, chemical composition and age. The main globular clusters subpopulations, that determine the observed bimodal colour distribution, are decomposed avoiding a priori parametric (e.g. Gaussian) fits and using a new colour (C-T1)-metallicity relation. The eventual detectability of a blue tilt in the colour magnitude diagrams of the blue globulars subpopulation is also addressed. A successful link between globular clusters and the stellar galaxy halo is established by assuming that the number of globular clusters per associated diffuse stellar mass t is a function of total abundance [Z/H] and behaves as t=gamma*exp(delta[Z/H]) (i.e. increases when abundance decreases).