The link between mass distribution and starbursts in dwarf galaxies

TL;DR

This study links the starburst activity in dwarf irregular galaxies to their central mass distribution, showing that steep inner rotation curves correlate with recent intense star formation.

Contribution

It provides observational evidence connecting the inner mass distribution of dwarf irregulars to their starburst activity, using HST data and star formation history analysis.

Findings

Starburst dwarfs have steep inner rotation curves.

Starburst activity correlates with centrally concentrated mass.

Quiescent irregulars have slowly rising rotation curves.

Abstract

Recent studies have shown that starburst dwarf galaxies have steeply rising rotation curves in their inner parts, pointing to a close link between the intense star formation and a centrally concentrated mass distribution (baryons and dark matter). More quiescent dwarf irregulars typically have slowly rising rotation curves, although some "compact" irregulars with steep, inner rotation curves exist. We analyze archival Hubble Space Telescope images of two nearby "compact" irregular galaxies (NGC 4190 and NGC 5204), which were selected solely on the basis of their dynamical properties and their proximity. We derive their recent star-formation histories by fitting color-magnitude diagrams of resolved stellar populations, and find that the star-formation properties of both galaxies are consistent with those of known starburst dwarfs. Despite the small sample, this strongly reinforces the notion that the starburst activity is closely related to the inner shape of the potential well.