The True Durations of Starbursts: HST Observations of Three Nearby Dwarf Starburst Galaxies

TL;DR

This study uses HST observations to measure the starburst durations in three nearby dwarf galaxies, finding they last hundreds of millions of years, which challenges shorter timescale models and suggests large, galaxy-wide star formation events.

Contribution

It provides the first consistent observational measurement of long starburst durations in dwarf galaxies, resolving previous discrepancies and highlighting the extensive, galaxy-wide nature of these events.

Findings

Starbursts last approximately 200-400 Myr.

Shorter 3-10 Myr timescales are due to flickering events.

Star formation occurs across large regions of the galaxy.

Abstract

The duration of a starburst is a fundamental parameter affecting the evolution of galaxies yet, to date, observational constraints on the durations of starbursts are not well established. Here we study the recent star formation histories (SFHs) of three nearby dwarf galaxies to rigorously quantify the duration of their starburst events using a uniform and consistent approach. We find that the bursts range from ~200 - ~400 Myr in duration resolving the tension between the shorter timescales often derived observationally with the longer timescales derived from dynamical arguments. If these three starbursts are typical of starbursts in dwarf galaxies, then the short timescales (3 - 10 Myr) associated with starbursts in previous studies are best understood as "flickering" events which are simply small components of the larger starburst. In this sample of three nearby dwarfs, the bursts are not localized events. All three systems show bursting levels of star formation in regions of both high and low stellar density. The enhanced star formation moves around the galaxy during the bursts and covers a large fraction of the area of the galaxy. These massive, long duration bursts can significantly affect the structure, dynamics, and chemical evolution of the host galaxy and can be the progenitors of "superwinds" that drive much of the recently chemically enriched material from the galaxy into the intergalactic medium.