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Do Tidal Interactions Trigger Starbursts in Dwarf Galaxies?

Abstract

Starburst dwarf galaxies are galaxies experiencing a period of intense star formation. These are extensively studied systems, though the mechanism that triggers the starbursts is poorly understood. Tidal interactions and gas accretion are thought to be potential starburst trigger mechanisms, although internal, secular drivers have not been ruled out. If starbursts are a result of external perturbations, then one would expect to see signatures of interaction in the gaseous disk of the galaxy. To examine this hypothesis, we study newly-obtained deep, wide-field HI maps from the Green Bank Telescope (GBT) of a sample of nine well-studied nearby starburst dwarf galaxies to search for signs of interactions, such as diffuse gas emission and potential companions. Our sample is unique in that we have multiwavelength data for all sources, including previously derived the star formation histories from Hubble Space Telescope imaging of the resolved stellar populations. In this work we first focus on NGC 784 and NGC 672 as a prototype system for evaluating methods to determine the presence and properties of low surface-brightness neutral gas in the outer disk region and then apply these methods to the rest of the sample. We found that three out of the nine GBT sources showed possible tidal interaction signatures, suggesting that tidal interactions may trigger starbursts in some systems but are not a universal cause.

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