Star-burst regions in the LMC

Aims. Filamentary structures of early type stars are found to be a common feature of the Magellanic Clouds formed at an age of about 0.9-2*10^8 yr. As we go to younger ages these large structures appear fragmented and sooner or later form young clusters an

Astronomy&Astrophysicsmanuscriptno.LMC˙starbursts(DOI:willbeinsertedbyhandlater)

February5,2008

Star-burstregionsintheLMC

E.Livanou1,M.Kontizas1,I.Gonidakis1,E.Kontizas2,F.Maragoudaki1,S.Oliver3,A.Efstathiou4,andU.Klein5

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arXiv:astro-ph/0512193v3 24 Feb 2006

345

DepartmentofAstrophysicsAstronomy&Mechanics,FacultyofPhysics,UniversityofAthens,GR-15783Athens,GreeceInstituteforAstronomyandAstrophysics,NationalObservatoryofAthens,P.O.Box20048,GR-11810Athens,GreeceAstronomyCentre,DepartmentofPhysics&Astronomy,UniversityofSussex,Brighton,BN19QJ,UKDepartmentofComputerScienceandEngineering,CyprusCollege,6DiogenesStr,1516Nicosia,CyprusRadioastronomischesInstitutderUniversitat,Bonn,AufdemHugel71,53121,Bonn,Germany

Receiveddate/accepted

Abstract.Aims.FilamentarystructuresofearlytypestarsarefoundtobeacommonfeatureoftheMagellanicCloudsformed

atanageofabout0.9 2×108yr.Aswegotoyoungeragestheselargestructuresappearfragmentedandsoonerorlaterformyoungclustersandassociations.Intheopticaldomainwehavedetected56suchlargestructuresofyoungobjects,knownasstellarcomplexesintheLMCforwhichwegivecoordinatesanddimensions.Wealsoinvestigatestarformationactivityandevolutionofthesestellarcomplexesandde netheterm“starburstregion”.Methods.IRpropertiesoftheseregionshavebeeninvestigatedusingIRASdata.Acolour-magnitudediagram(CMD)andatwo-colourdiagramfromIRASdataoftheseregionswarecomparedwithobservationsofstarburstgalaxiesandcross-matchingwithHIIregionsandSNRswasmade.Radioemissionmapsat8.6-GHzandtheCO(1→0)linewerealsocrosscorrelatedwiththemapofthestellarcomplexes.Results.Ithasbeenfoundthatnearly1/3ofthestellarcomplexesareextremelyactiveresemblingtheIRbehaviourofstarburstgalaxiesandHIIregions.Thesestellarcomplexesillustratingsuchpropertiesarecalledhere“starburstregions”.TheyhostanincreasednumberofHIIregionsandSNRs.ThemainstarbursttracersaretheirIRluminosity(F60wellabove5.4Jy)andthe8.6-GHzradioemission.FinallytheevolutionofallstellarcomplexesisdiscussedbasedontheCOemission.

Keywords.LMC–starformingregions–stellarcomplexes

1.Introduction

DuetoitsproximitytoourGalaxyandtheSMC,theLMCof-ferstwoimportantadvantages:i)thepossibilitytostudyitsstellarcontentdowntolowstellarmassesandii)thepos-sibilitytofollowtheconsequencesofthecloseinteraction,about2 4×108yrago(Gardiner&Noguchi1996;Kunkel,Demers&Irwin2000),withtheSMC.Stellarcomplexesarede nedaslargestructures(clumplike)ingalaxiesdominatedbyrecentlyformedstellarcomponentmixedwithveryyoungclusters,stellarassociationsandgas(Martinetal.1976;vandenBergh1981;Elmegreen&Elmegreen1983;Feitzinger&Braunsfurth1984;Elmegreen&Elmegreen1987;Ivanov1987;Larsonetal.1988;Efremov1989;Larsonetal.1992;Efremov&Chernin1994;Elmegreenetal.1994;Kontizasetal.1994;Efremov1995;Battinelli,Efremov&Magnier1996;Elmegreen&Efremov1996;Kontizasetal.1996).Sofartheyhavebeendetectedasregionswithyoungstellarcom-ponentandenhancedstellarnumberdensity,comparedtothesurroundingregion.IntheLMCstellarcomplexeshavebeendetectedusingUKSchmidtplates(Maragoudakietal.1998).Intheopticaldomainwehavedetected56large

structures

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