Building dwarf galaxies out of merged young star clusters

Young star clusters in interacting galaxies are often found in groups or clusters of star clusters containing up to 100 single clusters. In our project we study the future fate of these clusters of star clusters. We find that the star clusters merge on tim

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aBuildingdwarfgalaxiesoutofmergedyoungstarclustersMichaelFellhauerInst.f¨urTheor.Phys.&Astrophys.Univ.Kiel,Leibnizstr.15,24098Kiel,GermanyAbstractYoungstarclustersininteractinggalaxiesareoftenfoundingroupsorclustersofstarclusterscontainingupto100singleclusters.Inourprojectwestudythefuturefateoftheseclustersofstarclusters.We ndthatthestarclustersmergeontimescalesofafewdynamicalcrossingtimesofthesuper-cluster.Theresultingmergerobjecthassimilaritieswithobserveddwarfellipticals(dE).Furthermore,ifde-structiveprocessesliketidalheating,dynamicalfrictionorinteractionwithdiscorbulgeoftheparentgalaxyaretakenintoaccountourmergerobjectsmayevolveintoobjectsresemblingdwarfspheroidalgalaxies(dSph),withouttheneedofahighdarkmattercontent.1IntroductionSystemsofinteractinggalaxies(likeTheAntennaeorStephan’sQuintet)showintensestarformation.Inthetidaltailsone ndsespeciallyyoungmassivestarclusters(Re ≈2 10pc;M≈104 107M⊙;seee.g.Whitmore

etal.(1999)).Thesestarclustersarenotdistributeduniformlybutareclusteredintogroups,somecontainingmorethanahundredclusters.Withthisprojectweinvestigatethefuturefateoftheseclustersofstarclusters(whatwecall“super-cluster”).FollowingtheargumentsofKroupa(1998)thesesuper-clustersmaybeboundentities,meaningthatthestarclustersinthesuper-clusterarenotonlyboundtothetidal eldoftheparentgalaxybutalsoboundtoeachother.Therefore,thestarclustersareverylikelytomergewitheachotheronafewdynamicaltimesofthesuper-cluster.Thismergingprocessandtheresultingmergerobjectarethemajortopicofthisproject.

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