Star Formation Histories of Local Group Dwarf Galaxies

TL;DR

This study analyzes star formation histories of Local Group dwarf galaxies using archival data, revealing correlations between galaxy luminosity, type, and recent star formation activity, with implications for galaxy classification.

Contribution

It provides a homogeneous measurement of star formation histories across many dwarf galaxies, highlighting the link between galaxy type and recent star formation.

Findings

Luminous dwarf spheroidals show extended star formation.

Less luminous systems formed most stars over ten Gyr ago.

Irregulars show no clear trend in star formation history.

Abstract

We report preliminary results of a project to homogeneously measure star formation histories for the majority of Local Group dwarf galaxies, based on archival WFPC2 observations. For the dwarf spheroidal and elliptical galaxies, we find that the more luminous systems all show extended star formation episodes, while the less luminous systems typically formed most of their stars over ten Gyr ago. Irregular galaxies show no comparable trend. We find that a galaxy's classification as an irregular or spheroidal is entirely explained by its star formation within the past Gyr or less. Several elliptical/spheroidal systems actively formed stars within the past two Gyr, and would have been indistinguishable from present-day irregulars if observed two Gyr ago.