The triggering of starbursts in low-mass galaxies
Federico Lelli (1, 2), Marc Verheijen (2), Filippo Fraternali (3, and 2) ((1) Dept. of Astronomy, Case Western Reserve University, (2) Kapteyn, Astronomical Institute, University of Groningen, (3) Dept. of Physics and, Astronomy, University of Bologna)

TL;DR
This study analyzes the HI gas distribution and kinematics in 18 nearby starburst dwarf galaxies, revealing external interactions or gas infall as triggers for starbursts, with morphological evidence supporting these mechanisms.
Contribution
It provides the first detailed comparison of HI morphology in starburst and typical dwarf galaxies, linking asymmetries to external triggering mechanisms.
Findings
Starburst dwarfs show more asymmetric HI morphologies than typical irregulars.
Older starbursts have more symmetric HI distributions, indicating relaxation over time.
Most starburst dwarfs have potential external perturbers within 200 kpc.
Abstract
Strong bursts of star formation in galaxies may be triggered either by internal or external mechanisms. We study the distribution and kinematics of the HI gas in the outer regions of 18 nearby starburst dwarf galaxies, that have accurate star-formation histories from HST observations of resolved stellar populations. We find that starburst dwarfs show a variety of HI morphologies, ranging from heavily disturbed HI distributions with major asymmetries, long filaments, and/or HI-stellar offsets, to lopsided HI distributions with minor asymmetries. We quantify the outer HI asymmetry for both our sample and a control sample of typical dwarf irregulars. Starburst dwarfs have more asymmetric outer HI morphologies than typical irregulars, suggesting that some external mechanism triggered the starburst. Moreover, galaxies hosting an old burst (>100 Myr) have more symmetric HI morphologies than…
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