Dwarf galaxies in the Local Group the VLT perspective

Recent results on the evolution of Local Group dwarf galaxies obtained from VLT imaging and spectroscopy are briefly reviewed, and prospects for dwarf galaxy research at the VLT are discussed in the light of the current and forthcoming instrumentation. Som

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aDwarfgalaxiesintheLocalGroup:theVLTperspectiveEnricoV.HeldOsservatorioAstronomicodiPadova,vicolodell’Osservatorio5,35122Padova,ItalyAbstract.RecentresultsontheevolutionofLocalGroupdwarfgalaxiesobtainedfromVLTimagingandspectroscopyarebrie yreviewed,andprospectsfordwarfgalaxyresearchattheVLTarediscussedinthelightofthecurrentandforthcominginstrumentation.Someaspectsoffutureinstrumentdevelopments,suchasdeepwide- eldimagingatbothopticalandnear-infraredwavelengths,thatmaybeofadvantageforresearchontheevolutionofdwarfgalaxies,arebrie ydiscussed.1IntroductionUnderstandingtheoriginandevolutionofdwarfgalaxiesandtheirluminosityandmassdistributionsmayhaveimportantconsequencesinmodernobserva-tionalcosmology.Whiledwarfgalaxiesaredi culttostudyevenatmoderateredshifts,especiallythosewithoutactivestarformation,bothstar-formingandquiescentdwarfscanbestudiedwithconsiderabledetailintheLocalGroup(LG).DwarfgalaxiesintheLGarecloseenoughthattheprocessofstarforma-tion,theirdynamicalevolutionandtheinterplaybetweenstarsandinterstellarmediumcanbestudiedindetail.Byanalyzingtheircolor-magnitudediagramsonecanderivestarformationhistoriesandreconstructtheirevolutionatlook-backtimescomparabletotheageoftheuniverse.However,soundknowledgeoftheage-metallicityrelationisrequiredtoobtainreliabledeterminationofthestarformationhistory.Spectroscopyisthereforeneededtoaddessentialinfor-mationtoconstrainthechemicalenrichmenthistories.ThiscontributionwillfocusonstudiesofstellarpopulationsandkinematicsofresolvedLocalGroupgalaxies.Ibrie yreviewtheworkdonesofarattheVLT,anddiscusstheprospectfordwarfgalaxyresearchattheVLTinthelight

oftheexistingandforthcominginstrumentation.SomeideasforfutureVLTinstrumentsarealsopresented.

2DwarfgalaxyevolutionwiththeVLT

2.1Opticalimaging

Studiesofresolveddwarfgalaxiesinthelastdecade,usingbothHSTandgroundbasedinstrumentation,haveprovidedacomplexpictureoftheirstarformationhistories.Starformationcanproceedeitherindistinctepisodes,asinthecase

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