Star formation history of resolved galaxies. I. The Method

TL;DR

This paper introduces a novel maximum likelihood method using genetic algorithms to accurately determine the star formation and metallicity histories of resolved stellar systems from color-magnitude diagrams, validated with synthetic and real data.

Contribution

The paper presents a new, robust method for deriving star formation and chemical enrichment histories from resolved stellar populations, improving accuracy over previous techniques.

Findings

Successfully recovers parameters for star clusters consistent with literature

Accurately reconstructs complex star formation histories

Provides reliable results for the Carina dwarf galaxy

Abstract

We present a new method to determine the star formation and metal enrichment histories of any resolved stellar system. This method is based on the fact that any observed star in a colour-magnitude diagram will have a certain probability of being associated with an isochrone characterised by an age t and metallicity [Fe/H] (i.e. to have formed at the time and with the metallicity of that isochrone). We formulate this as a maximum likelihood problem that is then solved with a genetic algorithm. We test the method with synthetic simple and complex stellar populations. We also present tests using real data for open and globular clusters. We are able to determine parameters for the clusters (t, [Fe/H]) that agree well with results found in the literature. Our tests on complex stellar populations show that we can recover the star formation history and age-metallicity relation very accurately. Finally, we look at the history of the Carina dwarf galaxy using deep BVI data. Our results compare well with what we know about the history of Carina.