RUI: Star Formation and Interstellar Gas in Extragalactic Tails and Bridges

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AST-0205761SmithCollisions and close encounters between galaxies can cause major changes in the galaxies, dramatically altering both the morphology and star formation rate. A frequent consequenceof such an interaction is the production of extended tails and bridges, which often contain massive young stars. These structures may fragment and/or disperse, forming new dwarf galaxies and/or enriching the intergalactic medium. At present, there are still many outstanding questions about the properties of the interstellar gas and star formation in these features. What are the rates and efficiencies of star formation in these features, and how do these depend on the interaction parameters and timescales? What are the properties of the interstellar gas in these structures? Are the properties of these features consistent with them being the precursors of dwarf galaxies? Is star formation in these features subject to a `threshold' effect, only occurring above a `critical' gas surface density?To address these questions, Dr. Beverly Smith, at East Tennessee State University, will carry out a comprehensive multi-wavelength study of a sample of two dozen tails and bridges and a similar size comparison sample of dwarf galaxies. Using multi-wavelength data, Dr. Smith will measure the atomic to molecular hydrogen ratios, metallicities, star formation rates, and efficiencies in these tails and bridges, and will determine how these depend upon the parameters of the interaction. She will determine how the properties of these tails and bridges compare with those of dwarf galaxies. These observations will be done in conjunction with hydrodynamical modeling of the systems in the sample, which will better define the interaction parameters and help determine the conditions needed to trigger star formation in tails and bridges. Using these results, Dr. Smith will search for a star formation `threshold' in tails and bridges analogous to that found for galactic disks, and will investigate whether the efficiency of star formation is higher in tidal features than in features caused by ram pressure stripping, as predicted by theoretical models. This award is made under the auspices of the Research in Undergraduate Institutions program at NSF.***