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The properties of Low Surface Brightness galaxies

The properties of Low Surface Brightness galaxies

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aThepropertiesofLowSurfaceBrightnessgalaxiesD.MonnierRagaigne(delphine.ragaigne@obspm.fr),W.vanDrielandC.BalkowskiObservatoiredeParis,GEPI,Meudon,FranceS.BoissierInstituteofAstronomy,UniversityofCambridge,UKN.PrantzosInstitutd’AstrophysiquedeParis,Paris,FranceAbstract.AdescriptionisgivenofthesamplesofLowSurfaceBrightnessgalaxies(LSBs)usedforcomparisonwithmodelsoftheirchemicalandspectro-photometricevolution(Boissieretal.,thisVolume).ThesesamplesshowthelargevariationandscatterinobservedglobalpropertiesofLSBs,someofwhichcannotbemodeledwithoutaddingstarburstsortruncationstotheirstarformationhistory.Keywords:Galaxies:fundamentalparameters,Galaxies:general,Galaxies:pho-tometry,Infrared:galaxies,Radiolines:galaxies1.IntroductionInthepastfewdecades,theexistencehasbeenshownofgalaxieswithabluecentraldiscsurfacebrightnesswellbelowtheFreemanvalueofµB,0=21.65magarcsec 2),whichistypicaloftheaveragepreviouslycatalogued“classical”HighSurfaceBrightnessspirals(HSBs).Partic-ularilyinthelastdecadeaconsiderablebodyofobservationaldatahasbeencollectedonthisclassofLowSurfaceBrightnessgalaxies(LSBs),whichmayturnouttobecrucialtostudiesofgalaxyformationandevolutionandofthe‘cosmic’chemicalevolution,if(assuggestedbyO’Neil&Bothun2000)theyrepresentthemajorityofgalaxies.Althoughthereisnounambiguousde nitionofanLSBgalaxy,weadoptedasthelimitbetweenHSBsandLSBsabluecentraldiscsurface

brightnessvalueofµB,0=22magarcsec 2,acommonlyusedcriterion.ThoughLSBsshowalargevarietyofobservedproperties(seebe-low),theirobviousinteresthasmotivatedvarioustheoreticalstudiestowardsanunderstandingoftheirnature.Inarecentseriesofpapers,thechemicalandspectro-photometricevolutionof“classical”HSBspi-ralgalaxieswascomputed(forvariousgalacticmassesandangularmomentum)andcomparedquitesuccessfullytovarioustypesofob-servationalquantitieslikecolours,spectrum,starformatione ciencyandgasfractionaswellastotheirTully-Fisherrelationship(Boissier&Prantzos1999,2000;Boissieretal.2001;seealsoPrantzosetal.,this c2008KluwerAcademicPublishers.PrintedintheNetherlands.

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