Polar Ring Galaxies and the Tully-Fisher relation

We have investigated the Tully-Fisher relation for Polar Ring Galaxies (PRGs), based on near infrared, optical and HI data available for a sample of these peculiar objects. Many PRGs show larger HI line-widths than expected for the observed K band luminosi

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a**TITLE**ASPConferenceSeries,Vol.**VOLUME***,**YEAROFPUBLICATION****NAMESOFEDITORS**PolarimplicationsRingGalaxiesforthedarkandthehaloTully-Fishershaperelation:MagdaArnaboldiINAF,AstronomicalObservatoryofTurinEnricaIodiceINAF,AstronomicalObservatoryofCapodimonteFrederickBournaud&FrancoiseCombesLERMA,ObservatoryofParisLindaS.SparkeDept.ofAstronomy,UniversityofWisconsinWimvanDrielGEPI,ObservatoryofParisMassimoCapaccioliINAF,ObservatoryofCapodimonteAbstract.WehaveinvestigatedtheTully-FisherrelationforPolarRingGalaxies(PRGs),basedonnearinfrared,opticalandHidataavailableforasampleofthesepeculiarobjects.ThetotalK-bandluminosity,whichmainlycomesfromthecentralhostgalaxy,andthemeasuredHilinewidthat20%ofthepeakline uxdensity,whichtracesthepoten-tialinthepolarplane,placemostpolarringsofthesamplefarfromthe

Tully-Fisherrelationde nedforspiralgalaxies,withmanyPRGsshowinglargerHiline-widthsthanexpectedfortheobservedKbandluminosity.Thisresultiscon rmedbyalargersampleofobjects,basedonB-banddata.Thisobservationalevidencemayberelatedtothedarkhaloshapeandorientationinthesesystems,whichwestudybynumericalmodelingofPRGformationanddynamics:thelargerrotationvelocitiesobservedinPRGscanbeexplainedbya attenedpolarhalo,alignedwiththepolarring.

1.Introduction

PolarRingGalaxies(PRGs)arepeculiarobjectscomposedofacentralspheroidalcomponent,thehostgalaxy,surroundedbyanouterring,madeupofgas,stars

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We have investigated the Tully-Fisher relation for Polar Ring Galaxies (PRGs), based on near infrared, optical and HI data available for a sample of these peculiar objects. Many PRGs show larger HI line-widths than expected for the observed K band luminosi

2M.Arnaboldi,E.Iodiceetal.

anddust,whichorbitsnearlyperpendiculartotheplaneofthegas-poorcentralgalaxy(PRGC;Whitmoreetal.1990).Previouspapers(Arnaboldietal.1995,1997;Iodiceetal.2002a,2002b,2002c)foundthatevenwherethemorphologyofthehostgalaxyresemblesthatofanearly-typesystem,PRGsshowmanysim-ilaritieswithlate-typegalaxies.ThePRGsarecharacterizedbyalargeamountofneutralhydrogen(Hi),alwaysassociatedwiththepolarstructure(Schechteretal.1984;vanGorkometal.1987;Arnaboldietal.1997),andbyagas-to-totalluminosityratiointheB-bandtypicaloflate-typegalaxies.

ByexploringthepropertiesofthehostgalaxyandringintheopticalandNIR,forasampleofPRGs,Iodiceetal.(2002a,2002b,2002c)foundthattheconnectionwithspiralsistighter.TheTully-Fisherrelation(TF)isthemostimportantscalingrelationfordisks(Tully&Fisher,1977):thisisanempiricalrelationshipbetweenthediskrotationalvelocity(Vrot)anditsabsoluteluminos-4,approximately.Inthepastfewyears,severalstudiesity(L),whereL∝VrothaveassertedthevalidityoftheTFrelationforsomeclassesofdiskgalaxieswhichshowdi erentphotometricandkinematicalpropertieswithrespectto‘classical’,high-surface-brightnessspiralgalaxies(Matthews,vanDriel&Gal-lagher1998a,1998b;McGaughetal.2000;Chungetal.2002).TheselatestdevelopmentsindicatethattheTFrelationisprobingaverycloseliaisonbe-tweenthedarkhaloparametersandthetotalquantityofbaryonsingalaxies:thedarkhalo,whichisresponsiblefortheHilinewidthandthe atrotationcurveintheouterregionsofadisk,istunedtothetotalamountofbaryonsintheluminouscomponent.

InPRGs,theHilinewidth( V)measuresthedynamicsalongthemeridianplane,whichisdominatedbythedarkmatter,whilethebaryonsarenearlyequallydistributedbetweenthehostgalaxyandthepolarring.WewishtoinvestigatethepositionofthePRGsinthelog( V) Lplane,andstudyviaN-bodysimulationsof3-Dsystemswhetherthedarkhaloshapemayin uencetheirpositioninthelog( V) Lplane,withrespecttotheTFrelationofbrightdisks.Thequestionofthedarkhaloshapeisimportanti)toconstraindarkmattermodels,throughcosmologicalsimulations(Navarro,Frenk&White1996,1997;Bullocketal.2001)whichpredictthedistributionofthehaloshapesandtheuniversalradialdependenceofthedarkmatterdistribution;ii)togivehintsonthenatureofdarkmatter(seeCombes2003asareview);andfurthermoreiii)thedarkhalopropertiesinPRGscangiveimportantconstraintsontheformationscenariosforthesepeculiarobjects,whichisstillanopenissue(seeIodiceetal.2002a,2002c,andreferencestherein).

2.Observations

Newnear-infraredJ,HandKnimagesareavailableforasampleofPRGs(Iodiceetal.2002a,2002b,2002c),whichareselectedfromthePRGC,andforESO235-G58.TheBbandmagnitudeisknownformanyPRGs(VanDrieletal.2002,2003;Gallagheretal.2002),andtheHiintegratedlinepro ledatawereobtainedfromseveralpublishedhydrogenobservationsofPRGs,carriedoutbye.g.Richteretal.(1994),vanGorkometal.(1987),vanDrielandcollaborators(2000,2002,2003),withseveralradiotelescopes.

We have investigated the Tully-Fisher relation for Polar Ring Galaxies (PRGs), based on near infrared, optical and HI data available for a sample of these peculiar objects. Many PRGs show larger HI line-widths than expected for the observed K band luminosi

PRGsandtheTF-relation3

ToderivetheTFrelationfornormaldiskgalaxies,wewillusetheverylargeanddetaileddatasetavailableintheI-bandfromGiovanellietal.(1997)http://doc.guandang.netingtheobservationalrelationbetweenmorphologicaltypeindexandtheB Icolors(deJong

1996).

LeftPanel AbsolutemagnitudeintheKbandvs.themea-suredHilinewidthat20%ofthepeakline uxdensity( V20),forPRGsoftheselectedsample,comparedwithasampleofspiralgalaxiesfromVerheijen(2001),andwiththeresultsfrom3-Dsimulationsand2-Dmodels(formass-lessringsandringsthatareasmassiveasthehostgalaxy),seealsoBournaud&Combes(2003).Thelong-dashedlineisalinearinterpolationoftheTFrelationfo …… 此处隐藏：11160字，全部文档内容请下载后查看。喜欢就下载吧 ……