Constraints on Dark Energy Models Including Gamma Ray Bursts

In this paper we analyze the constraints on the property of dark energy from cosmological observations. Together with SNe Ia Gold sample, WMAP, SDSS and 2dFGRS data, we include 69 long Gamma-Ray Bursts (GRBs) data in our study and perform global fitting us

ConstraintsonDarkEnergyModelsIncludingGammaRayBursts

DepartmentofAstronomy,SchoolofPhysics,PekingUniversity,Beijing,100871,P.R.China

2

DepartmentofAstronomy,NanjingUniversity,Nanjing210093,P.R.Chinaand

3

InstituteofHighEnergyPhysics,ChineseAcademyofScience,P.O.Box918-4,Beijing100049,P.R.China

Inthispaperweanalyzetheconstraintsonthepropertyofdarkenergyfromcosmologicalob-servations.TogetherwithSNeIaGoldsample,WMAP,SDSSand2dFGRSdata,weinclude69longGamma-RayBursts(GRBs)datainourstudyandperformglobal ttingusingMarkovChainMonteCarlo(MCMC)technique.Darkenergyperturbationsareexplicitlyconsidered.WepayparticularattentiontothetimeevolutionoftheequationofstateofdarkenergyparameterizedaswDE=w0+wa(1 a)withathescalefactoroftheuniverse,emphasizingthecomplementarityofhighredshiftGRBstoothercosmologicalprobes.ItisfoundthattheconstraintsondarkenergybecomestringentbytakingintoaccounthighredshiftGRBs,especiallyforwa,whichdelineatestheevolutionofdarkenergy.

1

HongLi1,MengSu1,ZuhuiFan1,ZigaoDai2andXinminZhang3

arXiv:astro-ph/0612060v3 12 Nov 2007

I.INTRODUCTION

Cosmologicalobservations,includingTypeIasupernovae(SNeCosmicMicrowaveBackgroundradiationLarge-ScaleStructuresandsoon,haveprovidedstrongevidenceforaspatially atuniversebeinginastageofacceleratingexpansion.InthecontextofFriedmann-Robertson-Walkercosmology,thisaccelerationisattributedtoanewformofenergywithnegativepressure,dubbeddarkenergy(DE),whosenatureremainsabigpuzzle.ThesimplestcandidateforDEisthecosmologicalconstant.However,itsu ersfromthe netuningand[8,9].ManydynamicalmodelsonDE,suchasquintessence[10,11,12,13],phantomk-essence[15,16]andquintom,havebeenproposedtoavoidabovedi culties.Amongthem,thequintommodelallowstheequationofstate(EOS)crossing-1duringevolution[17].Extensivestudiesonthismodelhasbeencarriedonboththeoreticallyandphenomenologically28,29,30,31,34,36,37,38].

Di erentDEmodelspredictdi erentglobalevolutionsaswellasdi erentstructureformationsoftheuniverse.ThereforecosmologicalobservationscanprovideimportantconstraintsonthenatureofDE.However,degeneraciesofcosmologicalparametersexistinalmostallcosmologicalobservations,i.e.,theyaresensitivenottosingleparametersbuttosomespeci ccombinationsofthem.Itisthereforehighlynecessarytocombinedi erentprobestobreakparameterdegeneraciessoastoachievetightcosmologicalconstraints.Furthermore,di erentobservationsarea ectedbydi erentsystematicerrors,anditisthushelpfultoreducepotentialbiasesbycombiningdi erentprobes.Toperformjointanalyzes,global ttingisthemostsecurestudy,becauseitavoidsusingstrong,andsometimeseveninappropriatepriorsobtainedfromotherobservations.

ObservationsonSNeIahaveplayedimportantrolesinDE3,4].However,duetothedi cultiesofdetectinghigh-redshiftSNeIa,suchageometricalmeasurementislimited.ThefutureSNAP/JDEMisplanedtoprobeuptoredshiftaroundz～2.Ontheotherhand,the3-yearWMAPdata(WMAP3),whichissofarthemostprecisemeasurementoftheCMB,revealstheinformationoboutouruniverseatredshiftaroundz～1100.Inbetween,therehavenotbeenmanyprobesaccessibletous.Inthisregard,GRBsarethemostpromisingtracersoftheevolutionoftheuniverseatredshiftaroundafewtoevenafewtensbecausetheyarethemostpowerfuleventsintheuniverse.ThecurrentlyoperatingSwiftsatelliteisabletodetectabout100longdurationGRBeventswithinoneyear,andweexpectthatitwillopenupapotentiallynewwindowforGRBcosmographicstudies.Atpresent,themeasuredredshiftsofGRBshaveextendedtoz=6.29[39].EventhoughthephysicaloriginofthelongGRBisnotveryclear,manyextensivediscussionsabouttherelationsbetweenthespectralandtemporalparametersshowthepotentialforusinglongGRBsascosmiccandlesforcosmography.

Recently,headwayhasbeenmadeinconsideringhowtomakeGRBsstandardcandles.IntheliteraturetherearemanystudiesabouttheintrinsiccorrelationsbetweentemporalorspectralpropertiesofGRBsandtheirisotropicenergiesandluminositiy,forexample,thespectrallag theluminositycorrelation(τ Liso)[40],theluminosity variablitycorrelation(V-Liso)[41],thespectralpeakenergy isotropicenergycorrelation(Epeak-Eiso)[42],thepeakspectralenergy isotropicluminositycorrelation(Epeak-Lisoandtheisotropicluminosity peakenergy highsignaltimescalecorrelation(Liso-Epeak-T0.45)[44]andsoon.ThesecorrelationshelpGRBsnearlytobe”knowncandles”Shaeferobtainedthe rstGRBHubblediagramof9GRBswithknownredshiftbyusingthespectrallagandthevariabilityindicators,andfromtheGRBhubblediagramheconstrained m<0.35within1σcon dencethat,manyinvestigationsbeentriggeredonusingGRBsascosmologicalprobes[47,50,51,52,53,54,55].Veryrecently,Shaefer[56]hasconstructedaGRBHubbleDiagramwith69GRBs

In this paper we analyze the constraints on the property of dark energy from cosmological observations. Together with SNe Ia Gold sample, WMAP, SDSS and 2dFGRS data, we include 69 long Gamma-Ray Bursts (GRBs) data in our study and perform global fitting us

overaredshiftrangeof0.17to>6,with39GRBshavingredshiftsz>1.5.ItisthelargestGRBsamplesofar.TheaimofthispaperistopresentamoregeneralanalysisontheEOSofDEbyincludingGRBdatainadditiontoCMB,LSSandSNeIainglobal tting.Wemainlyconsiderthedynamicaldarkenergyparameterizationforthereisnocompellingreasontoneglecttheevolutionofdarkenergyfactitiously.WeemployMCMCtechniquesfortheanalysis.TheMCMCmethodistheglobal ttingonthecosmologicalparametersandweusetheoriginalCMBandLSSdataratherthanusetheCMBshiftparameter,thelineargrowthfactorortheBaryonAcousticOscillation(BAO)measuredfromtheLargescalestructuresurvey.Theglobal ttingisthemostsecurewayforprocessingdatabecauseitisajointanalysisanditcanavoidusingsomestrongoreveninappropriatepriorsfromothers.Thee ectsofdarkenergyperturbationsarecarefullytakenintoaccountwithgreatattentionpaidtotheperturbationswhentheequationofstategetsacross …… 此处隐藏：18380字，全部文档内容请下载后查看。喜欢就下载吧 ……