AAS 195th Meeting, January 2000
Session 51. ISM: Theory and Modelling
Display, Thursday, January 13, 2000, 9:20am-6:30pm, Grand Hall

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[51.10] Formation and Evolution of Tidal Dwarf Galaxies

M. Iyer, C.E Simpson (Florida International University), S.T Gottesman (Univerity of Florida), B.K Malphrus (Morehead State University)

It has been suggested that gravitational encounters between galaxies could result in the formation of dwarf galaxies in tidal debris fields. The idea was first promulgated by Zwicky(1956, Ergeb. Exaten Naturwiss. 29, 344), who suggested that self gravitating objects in tails were formed from gravitational encounters. We present high sensitivity 21 cm observations taken with the D array configuration of the VLA as a part of a multi- wavelength study of interacting galaxies to look for evidence of dwarf galaxy formation in the interaction fields. Five Arp galaxies were observed for approximately five hours each. Preliminary analysis of four galaxies reveals the signatures of severe interactions in some galaxies and less severe in others. Arp 31 only shows very low levels of disturbance in the optical and HI, revealing primarily the characteristics of a spiral galaxy. Analysis of Arp 135,however,indicates highly disturbed HI regions and the presence of clumps and knots in its close proximity. Arp 158 also shows various levels of disturbed HI regions along with the presence of clumps at very low levels. Arp 78 reveals the presence of an HI tail in the South-East direction opposite to the optical arm.

We are performing gravitational and stability tests on these clumps and knots to see if they are self gravitating and are capable of withstanding tidal distruptions. If this is the case, then these objects are most likely to be tidal dwarfs created by the interactions. We also intend to use optical and spectroscopic analysis to examine their stellar properties and star formation levels. The results of these observations and analysis will enhance our understanding of interactions and mergers, how they affect the present day universe, and the possibility that these intercations play a dominant role in the formation of dwarf galaxies.

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