Star formation histories of resolved galaxies

TL;DR

This review discusses how synthetic colour-magnitude diagrams are used to reconstruct star formation histories in resolved galaxies, revealing continuous star formation across different types with early activity in all studied galaxies.

Contribution

It summarizes the methodology of deriving star formation histories from colour-magnitude diagrams and presents results across various galaxy types, highlighting early and ongoing star formation.

Findings

All studied galaxies had star formation at the earliest observed times.

Early-type galaxies mainly formed stars early, but not exclusively.

Other galaxy types show continuous star formation with variations.

Abstract

The colour-magnitude diagrams of resolved stellar populations are the best tool to study the star formation histories of the host galactic regions. In this review the method to derive star formation histories by means of synthetic colour-magnitude diagrams is briefly outlined, and the results of its application to resolved galaxies of various morphological types are summarized. It is shown that all the galaxies studied so far were already forming stars at the lookback time reached by the observational data, independently of morphological type and metallicity. Early-type galaxies have formed stars predominantly, but in several cases not exclusively, at the earliest epochs. All the other galaxies appear to have experienced rather continuous star formation activities throughout their lifetimes, although with significant rate variations and, sometimes, short quiescent phases.