1996AJ 112.2398H 2 3 Cerro TololoInter-AmericanObservatory, NationalOpticalAstronomy technique employedinoursurveywasdescribeddetailby Cátedra PresidencialdeCiencias(Chile), 1996-1997. Astronomy, Inc.,(AURA),undercooperative agreementwiththeNational Observatories, operatedbytheAssociation ofUniversitiesforResearchin this projectledtothediscoveryof50SNe(—1/3all Hamuy etal.(1993a)(PaperI).Inthecourseof1990-93 pemovae withtheaimofproducingamoderatelydistant THE ASTRONOMICALJOURNAL 2398 Astron.J.112 (6),December1996 0004-6256/96/112(6)/2398/10/$ 10.00 Chile atCerroCaláninitiatedaphotographicsearchforsu- Inter-American Observatory(CTIO)andtheUniversityof Science Foundation. SNe discoveredthroughouttheworldinsameperiod). (O.Ol^z^O.l) samplesuitableforcosmologicalstudies.The University ofArizona,StewardObservatory,Tucson,AZ85721. In mid-1990,agroupofastronomerstheCerroTololo © American Astronomical Society • Provided by theNASA Astrophysics Data System -1_ _1 :m 2 Society. We findacosmicrecessionvelocityforVirgoof1223±115kmsandFornax1342±70, have evaluatedtherecessionvelocitiesofthesetwoclustersbasedonCalán/TololoHubblediagrams. magnitude-decline relationistakenintoaccount.UsingtheinertialreferenceframeofdistantSNela, kmsMpc. Thisvalueis—10%-15%largerthantheobtainedbyassumingthatSNelaare BV(I) datafortheseobjectsandnearbySNela,wehaveshownthatthereexistsasignificantdispersion la HubblediagramcaneasilybiastheresultstowardluminousSNela,unlessabsolute luminous SNela.Hence,theuseofPopIobjectssuchasCepheidstocalibratezeropoint younger stellarpopulation(spiralsandirregulars)appeartohosttheslowestdeclining,thereforemost perfect standardcandles.AswehaveshowninPaperV,thereisnowstrongevidencethatgalaxieswith where tisthetimeofBmaximum,peakBVImagnitudecorrectedforluminosityvariations,and The Calán/Tololosupernovasurveyhasdiscovered—30typelasupemovaeatredshiftsouttoz~0.1.Using and arelativedistancemodulusofAyLt(Fornax-Virgo)=0.19±0.23©1996AmericanAstronomical and the“corrected”apparentmagnitudesofbest-observedSNelainVirgoFornaxclusters,we distances recentlymeasuredwiththeHubbleSpaceTelescopetofournearbySNela(1937C,1972E, Ara(Z?), SNelaprovetobehighprecisiondistanceindicators,yieldingrelativedistanceswitherrors in theintrinsicluminositiesoftheseobjects.WehavedevisedarobustYminimizationtechnique Am(B) isasingleparameterdescribingthewholelightcurvemorphology.Whenproperlycorrectedfor simultaneously fittingtheBVIlightcurvestoparametrizeSNeventasafunctionof[t.nii,Am(i?)], —7%-10%. ThecorrectedpeakmagnitudesareusedtoconstructBVIHubblediagrams,andwithCepheid 1981B, and1990N)wederiveavalueoftheHubbleconstant/7=63.1±4(internal)±2.9(external) KC B 15 15 B15 0 2 2 National OpticalAstronomyObservatories,CerroTololoInter-AmericanObservatory,Casilla603,LaSerena,Chile National OpticalAstronomyObservatories,CerroTololoInter-AmericanObservatory,Casilla603,LaSerena,Chile 1 Mario Hamuy,M.Phillips,NicholasB.Suntzeff,andRobertA.Schommer Electronic mail:[email protected],[email protected],[email protected],[email protected] THE HUBBLEDIAGRAMOFCALÁN/TOLOLOTYPElaSUPERNOVAE 1. INTRODUCTION Departamento deAstronomía,UniversidadChile,Casilla36-D,Santiago,Chile Received 1996June17;revisedSeptember5 Electronic mail:[email protected] AND THEVALUEOF 0 VOLUME 112,NUMBER6 3 ABSTRACT José Maza R. Aviles BV{RI) CCDphotometryfor27oftheseCalán/Tololo younger stellarpopulationappear tohostthemostluminous lips (1993)thattheabsoluteB and VmagnitudesofSNela lished inPaperI,H(Mazaetal.1994),andHI tronomers andCTIOstaffmembers,wewereabletogather these objectsweremembersofthetypelaclass,majority curve. Inaddition,wefoundevidence thatgalaxieshavinga latter studyconfirmed,ingeneralterms,thefindingbyPhil- of whichwerefoundnearmaximumlight. Followup spectroscopicobservationsrevealedthat32of are correlatedwiththeinitial decline rateoftheBlight SNe la.Preliminarylightcurvesandspectroscopywerepub- (Hamuy etal.1994)forsixevents.Basedonphotometry 1995) wediscussedtheHubblediagramsinBandV.The 13 oftheCalán/TololoSNela,inPaperIV(Hamuyetal. kc Thanks tothegenerouscollaborationofmanyvisitingas- © 1996Am.Astron. Soc.2398 DECEMBER 1996 1996AJ 112.2398H -1 follow-up photometry.Hence, the totalsampleofdistant though notfoundbyus,were included inourprogramof we haveaddedtwoSNela—19900 and1992al—which,al- curves wereobtainedforatotal of27events.Tothissample Hubble diagrams.InSec.4wediscussourresults,andin our sample(Sec.2),wepresentinSec.3theresultingBVI Hubble diagramintheIband.Afterabriefdescriptionof for thefullsetofCalán/TololoSNela,aswellfirst galaxies. Thepurposeofthecurrentpaperistopresentand between SNelaluminositiesandthemorphologyofhost the absolutemagnitude-declineraterelation,and(2)link major conclusionsofPaperIVconcerning(1)thereality ties ofthisfullset29SNela.Thesedataconfirmthe to asPaperV),wehavereexaminedtheabsoluteluminosi- complete sampleof27Calán/TololoSNela,andalsofortwo the zeropointofHubblerelation. Cepheid distancetothehostgalaxyofSN1972Ederive in therangeH=62-67kmsMpcwasfoundusing peak luminosity-declineraterelation,andaHubbleconstant nificant decreaseinthescatterofBandVHubbledia- nificant biasintodeterminationsofbothHandg-Asig- SNe laconsideredinthispaper is29. Calán/Tololo survey,adequately sampledBV(I)light discuss thefinalversionsofHubblediagraminBandV accompanying paper(Hamuyetal.1996a,hereafterreferred grams whichweincludedinourfollowupprogram.Inan additional SNelafoundinthecourseofothersurveypro- grams wasobtainedwhenthedatawerecorrectedfor Sec. 5wesummarizeourconclusions. SNe la,andpointedoutthatthiseffectcouldintroducesig- 2399 HAMUYETAL:TYPElaSNe 0 0 KC We havenowproduceddefinitivelightcurvesforthe Of the32SNeladiscoveredduringcourseof 93 ah 93 ag 930 93H 93B 92bs 92br 92bp 92bo 92bl 92bk 92bh 92bg 92bc 92 au 92aq 92 al 92ag 92ae 92P 92K 92 J 9 lag 91U 91S 90Y 90T 900 90af (i) © American Astronomical Society • Provided by theNASA Astrophysics Data System 4.030(25) 3.523(92) 4.351(12) 3.897(35) 3.616(63) 3.992(28) 4.223(16) 4.066(22) 4.080(22) 3.958(28) 4.193(17) 3.872(37) 4.420(10) 4.374(11) 3.736(46) 4.110(20) 4.240(15) 4.131(20) 3.774(44) 4.260(14) 4.481(09) 3.627(60) 3.891(36) 4.137(20) 4.178(17) 3.935(29) 4.177(18) 4.326(13) 4.279(14) log(cz) CMB (2) 2. THECALÁN/TOLOLODATABASE 17.72(08) 16.84(08) 18.37(09) 19.38(17) 18.41(07) 15.86(07) 18.11(10) 17.70(08) 16.72(08) 15.16(07) 18.21(21) 19.45(09) 14.60(07) 15.83(21) 16.40(21) 17.81(21) 17.87(07) 17.16(21) 16.32(10) 16.33(21) 17.67(07) 18.53(11) 17.36(08) 16.41(08) 18.62(12) 16.08(07) 17.70(21) 14.62(14) 17.70(21) (3) ' 17.82(06) 18.46(06) 15.85(06) 17.62(06) 17.69(06) 17.76(06) 16.61(06) 18.30(07) 19.34(10) 17.36(07) 18.11(07) 16.76(07) 15.24(06) 18.16(16) 19.35(07) 14.65(06) 15.09(16) 16.34(16) 17.77(16) 17.37(16) 17.12(16) 16.31(08) 16.37(16) 18.41(09) 16.28(07) 18.51(08) 16.11(06) 17.58(16) 14.54(15) VmAX (4) Table 1.ColorsandmagnitudesoftheCalán/TololoSupernovaela. 16.55(06) 18.78(06) 15.97(05) 18.31(06) 17.04(06) 14.94(06) 16.68(15) 18.01(06) 17.99(06) 18.70(10) 17.64(06) 17.80(06) 15.58(05) 18.41(15) 19.77(09) 16.41(06) 16.39(06) 14.94(15) 14.86(19) 16.52(15) 18.07(15) 17.61(15) 17.35(15) 16.70(09) 17.84(15) Ima (5) V BmAX“MAX -0.05(05) -0.04(05) -0.09(03) -0.08(03) -0.05(03) -0.03(03) -0.04(10) 0.00(05) 0.08(05) 0.23(05) 0.04(05) 0.01(03) 0.00(05) 0.05(10) 0.10(05) 0.06(10) 0.33(10) 0.04(10) 0.01(05) 0.03(05) 0.12(05) 0.07(05) 0.13(05) 0.11(05) 0.74(10) 0.12(10) 0.08(05) 0.04(10) 0.05(03) (6) r -1 +51og(H/65) mation totheCMBframewas performedbyaddingthe microwave background(CMB) frame.Theheliocentricred- maximum andthepeakmagnitudesB,V/max• this series.Thesetemplateswerefittotheobservedphotom- robust ^-minimizingfittingproceduresimilartothatde- rate parameterAra(Z?)(Phillips1993)arealsoprovided. tic CartesianCoordinates).The formeristhemotionof vectors (-30,297,-27)and(7,-542,302) kms(inGalac- vation ofthenucleiparent galaxiesandthetransfor- velocity (cz)oftheparentgalaxycorrectedtocosmic for the29SNeinfollowingformat: etry ofeachSNsolvingsimultaneouslyforthetimeB plates arethesubjectofPaperVIII(Hamuyetal.1996c)in light curvetemplateswereemployed.Thisnewsetoftem- the /-banddata,anupdatedandexpandedsetofBV(I) maximum light,thepeakmagnitudeswereestimatedusinga followup photometricobservationsdidnotbeginuntilafter around maximumlight.Fortheremaining18objectswhose curve), byfittingalow-order(3-4)polynomialtothedata later thanday+1(countedsincethepeakofBlight which thetimeoffirstphotometricobservationwasno We wereabletoperformthismeasurementfor11SNe measured directlyfromtheobservationswheneverpossible. As discussedinPaperVII,maximum-lightmagnitudeswere magnitudes intheB,V,andIbandsinitialdecline photometric reductions.Estimatesofthemaximumlight light curvesforthissetof29SNelaalongwithdetailsthe referred toasPaperVII),wegivetheindividualBV(RI) shifts wereallmeasuredfromour ownspectroscopicobser- scribed inPaperIV.Note,however,thatordertoinclude (See PaperVIIforfurtherdetailsofthisfittingprocedure.) 0 MAXMAX 15 KC KC -18.89(13) -18.96(11) -19.40(09) -19.03(12) -19.36(15) -19.64(23) -19.03(22) -18.89(10) -19.47(32) -19.07(13) -19.34(18) -17.72(44) -19.49(25) -19.24(22) -19.17(24) -19.40(17) m -19.28(26) -19.10(12) -19.23(11) -18.45(19) -19.04(13) -18.66(18) -18.76(25) -19.13(13) -18.98(19) -18.92(23) -19.40(35) -18.95(11) -18.56(24) max Column (2):decimallogarithmoftheheliocentricradial Column (1):SNname. In Table1welisttherelevantinformationforthisstudy In anaccompanyingpaper(Hamuyetal.1996b;hereafter (7) +51og(H/65) 0 -18.97(11) -19.41(16) -18.70(11) -19.35(08) -19.13(12) -19.03(10) -19.32(14) -19.56(23) -19.08(18) -18.99(08) -19.42(31) -19.31(18) -18.46(42) -19.48(35) -19.55(21) -19.28(18) -19.00(11) -18.89(20) -19.21(19) -19.13(11) -19.14(10) -18.68(19) -19.16(11) -19.03(10) -18.77(25) -19.11(18) -19.18(10) -19.04(19) lvi -19.24(22) MAX (8) +51og(H/65) 0 -18.79(11) -18.83(10) -19.04(14) -18.57(10) -18.61(42) -19.16(37) -19.02(17) 1V1 -18.81(11) -18.91(10) -18.74(19) -18.87(12) -19.03(08) -18.65(24) -18.85(12) -19.22(22) -18.83(17) -19.13(31) -18.98(18) -19.03(18) -18.78(18) -19.37(20) -18.98(17) -18.65(19) -18.98(19) -18.93(21) MAX (9) 0.87(05) 0.87(10) 0.87(10) 0.96(10) Ami(B) 1.32(10) 1.69(05) 1.05(10) 1.15(10) 1.11(05) 1.04(10) 1.56(05) (10) 1.22(05) 1.69(10) 1.69(10) 1.51(10) 1.57(10) 1.49(10) 1.46(10) 1.19(10) 1.28(10) 1.93(10) 1.06(10) 1.13(10) 1.15(10) 1.30(10) 1.32(10) 1.04(10) 1.13(10) 1.56(10) 5 0.0 0.8 EW(NalD) [A] <4.0 <1.1 <0.2 <0.5 <0.4 <0.5 <0.3 <0.2 <1.3 <1.1 <0.05 <0.5 <0.2 <0.4 1.0 <0.2 <0.1 1.2 <0.5 <3.1 1.1 1.2 <0.2 <0.2 <4.0 (H) 2399 1996AJ 112.2398H 4 = 4 -1 _1 1- B lightcurvedecaysinthefirst15daysaftermaximumlight. respect totheCMBasmeasuredwithCOBE(Smootetal tions ofSNelagatheredatCTIO,following thesamepreceptsdescribedby Since theKtermsforSNelain/band arenotavailableintheliterature This wouldrequirethatthegalaxiespossesspeculiarmotions Paper IV,thispropertywouldbeexpectedifthescatterwere Note thatthequoteddispersionissimplermsdeviation ^max 5logcz—2.948(±0.029)o-=0.19n=25.(3) £max~5 logcz—3.151(±0.029)ct=0.38n=29,(1) yield thefollowingzeropointsanddispersions: ridge lines,whichcorrespondto(weighted)least-squaresfits based onthesignal-to-noiseratioofspectra. lent widthofNaIDinterstellarabsorptionduetothehost III andIV. the templatefittingprocedurepreviouslydescribedinPapers In mostcases(24SNe)thisparameterwasestimatedthrough Hubble diagramofSNelawithitszeropointdulycalibrated tude, theredshiftofhostgalaxy(inCMBframe),and magnitudes oftheSNcalculatedfromapparentmagni- calculated byHamuyetal.(1993b).Note,however,thatno host galaxy(Burstein&Heiles1982),andfortheKterms magnitudes oftheSNasdeterminedfromlightcurves, 2400 HAMUYETAL.:TYPElaSNe Hamuy etal.(1993b). we calculatedthesecorrectionsbased on ourownspectroscopicobserva- of thevalue600kmsassumed inthehorizontalerror with respecttothepureHubble flowconsiderablyinexcess due primarilytothepeculiarmotionsofhostgalaxies. dispersion isgreatestforthenearestSNe.Aspointedoutin of thepointsaboutfit. of thedatatotheoreticallinesconstantluminosity, only abletoplaceanupperlimittheequivalentwidth galaxy fromthespectraofSNe.Inmostcaseswewere fined byPhillips(1993)astheamountinmagnitudesthat with CepheiddistancestonearbySNela. discussed inSec.4thisvaluecorrespondscloselytothe host galaxy(seeSec.3). correction hasbeenappliedforpossibleobscurationinthe corrected forforegroundextinctioninthedirectionof units ofmdex. of ±600kmstoeachgalaxywhichisgiveninbrackets and IfortheCalán/TololoSNeladatagiveninTable1.The an assumedHubbleconstantofH=65kms“Mpc.As sun withrespecttotheLocalGroup(Lynden-Bell&Lahav ^max=5 logez-3.175(±0.025)cr=0.26n=29,(2) 1992). Weassignedapossiblepeculiarvelocitycomponent 1988) whilethelatterismotionofLocalGroupwith 0 The mostobviouspropertyofthesediagramsisthatthe Figure 1showstheresultingHubblediagramsinB,V, Column (11):anestimate(inAngstroms)oftheequiva- Column (10):thedeclinerateparameterAm(5),de- Columns (7),(8),and(9):theabsoluteB,V,Ipeak Column (6):the“color”ofSN,^max- Columns (3),(4),and(5):theapparentB,V,Ipeak 15 © American Astronomical Society • Provided by theNASA Astrophysics Data System 3. THEHUBBLEDIAGRAMSINB,V,ANDI _1 -1 _1 -1 21/2= reddening vectors(withslopesof4.1ini?,3.1V,and1.85 Table 1),andso itsredcolormaybeevidence ofsignificant is aSN1991bg-likeeventwhose veryredcolorandlow tered on#-V~0.Of thethreeoutliers,SN1992K Plotted forcomparisoninthesamefigureareGalactic the spectraofafewSNe.Inordertoexaminethis Table 1showsthatNaIDinterstellarlinesweredetectedin the observeddispersioninHubblediagrams.Indeed, motions. between 299±99and540±180kms;thelargervaluesare from theCfA2andSouthernSkyRedshiftSurveyranging Marzke etal(1995)measurepairwisevelocitydifferences km s.Thesevaluesareconsiderablyinexcessofmeasure- redshift; however,ifwerestrictthesampleto11galaxies bars plottedinFig.1.Ifweinterprettheentirescatter luminosity isalmostcertainly intrinsic (seePaperIII).The in I)correspondingtoacolorexcessofE(5—V)=0.2.We Calán/Tololo SNeasafunctionofthe#—VWxcolor. alternative, weplotinFig.2theabsolutemagnitudesof dominant portionoftheobservedscatterarisesfrompeculiar values forpairwisevelocities,itisextremelyunlikelythata gram derivedabovearestill3crinexcessoftheselarger avoid richAbellclustersandthescatterinHubbledia- analysis. SincetheSNfoundinCalán/Tololosample derived whendensevirializedsystemsareincludedinthe ments ofthecosmicvelocitydispersion.Forexample, within 10000kms,thermsresidualvelocityisstill1050 km s.Thisvalueisdominatedbylargeresidualsathigher velocity scatterwouldbe((ucMB-^Hubbieflow))1420 Fig. 1.TheHubblediagramsinB,V,andIforthe29Calán/TololoSNela. spectrum ofSN1993Hshowed weakNaIDabsorption(see see that26ofthe29SNeliein awell-definedclumpcen- V datainthisfigureasduetopeculiarvelocities,therms MAXMAX MAX Dust intheparentgalaxiesprobablyalsocontributesto Raw HubbleDiagrams Calan/Tololo SNela 2400 1996AJ 112.2398H -= m m m cors ^max^max0.3, withanrmsdispersionofonly0.06 the dispersioninBHubblediagram,0.19V,and tion. Themeancoloroftheremaining26SNeis the redcolorofthisSNwasintrinsicorduetodustextinc- that observedinthefast-decliningSN1986G(Phillipsetal. this objectalsoshowedTiIIabsorption,similarinstrengthto reddening vectors(withslopesof4.1inB,3.1V,and1.85I)corre- peak luminositiesofSNela.Fortunately, asshownbyPhil- in theHubblediagramsFig. 1 isanintrinsicspreadinthe Hubble diagrams. 0.1 linI.However,itislikelythatatleastpartofthe the hostgalaxies,itcouldaccountforasmuch0.25of mag. Ifthisdispersionwereentirelyduetodustextinctionin tion duetothehostgalaxy.Hence,wecannotsaywhether limit of4Âontheequivalentwidthanypossibleabsorp- of SN1990Y,theonespectrumavailabletousissuchlow dust extinction.However,themaximum-lightspectrumof Fig. 2.TheabsoluteB,V,andImagnitudesoftheCalán/Tololosample lips (1993)and confirmed inPaperV(andalso inaprelimi- and cannotexplainallofthe observed dispersioninthe that dustextinctionintheparentgalaxiesisgenerallysmall, effects theydisplayinadiagramlikeFig.2,weconclude an intrinsiccolorspread—ismadedifficultbythesimilar out thesetwodifferentpossibilities—dustreddeningversus observed dispersionincolorisintrinsic(e.g.,SNe1992bcvs signal-to-noise thatwecanonlyplaceanuninterestingupper at leastpartlyintrinsic(seeNugentetal.1995).Inthecase sponding toE(2?—V)=0.2areindicated. 29 SNela,plottedasafunctionoftheir#-Vmaxl°TheGalactic 2401 HAMUYETAL.:TYPElaSNe same directionasthereddeningvectors.Althoughsorting 1992bc; PaperII)which,coincidentally,appearstoruninthe 1987), whichmayindicatethattheredcolorofthisSNwas max As showninPaperV,themajor sourceofthedispersion © American Astronomical Society • Provided by theNASA Astrophysics Data System -1 -/> peared tobesteeper thantheslopederivedfor theGalán/ brighter thanthenearbysample,althoughitisclearthat rameter Am(5).Excludingthethreeevents(SNe1990Y, tions, orplanetarynebulaluminosity functiondistancesap- In PaperVwefoundthatthe slope obtainedforanearby fect theslopeofabsolutemagnitude-decline raterelation. the distantSNe).ThemajoreffectseeninFig.3islarger faintest ofthenearbySNearenotfoundindistant magnitudes oftheCalán/TololoSNeasafunctionred- order tostudythiseffect,weplotinFig.3theabsoluteBVI Lower luminosityeventswillbeincreasinglydifficulttofind correct theHubblediagramsforthiseffect. yield slopesof0.784±0.182inB,0.707±0.150V,and linear least-squarefitstothedatafor26remainingSNe Fig. 1ofPaperV,theabsolutemagnitudesGalán/ most luminousSNeladisplaytheslowestdeclinerates.In the Blightcurve.Thesenseofthiscorrelationisthat light arestronglycorrelatedwiththeinitialdeclinerateof km s)illustratestheseparationofsampleintotwogroups. plotted asafunctionofredshift.Theverticallinelogez=4(10000 Fig. 3.TheabsoluteB,V,andImagnitudesoftheCalán/TololoSNela 0.575±0.178 inI.WeshallusetheserelationsSec.4to Tololo SNeareplottedasafunctionofthedeclineratepa- nary wayinPaperIV),theabsolutemagnitudesatmaximum sample ofSNelawithCepheid, surfacebrightnessfluctua- slightly brighterthanthedistantsampleof18(M^x sample. Indeed,themeanvaluesfornearest11SNeare shift. ThemostdistantSNe(logcz>4)arenotsignificantly at largerredshifts,leadingtoclassicalMalmquistbias.In scatter atlowerredshifts.Malmquist biasmay,however,af- survey issusceptibletovarietyofpossibleselectioneffects. = -19.08±0.17forthenearbysamplevs-19.04±0.06 1992K, and1993H)inthesamplewith^max^max0.2, 15 A magnitudelimitedSNesearchsuchastheCalán/Tololo 3 3.S 44.5 l0CZ g()cMB 5 2401 1996AJ 112.2398H There mayalsohavebeena bias inthesurveytoavoid clusters mightnot havebeenavoided,thusgiving theob- nearby clusters(e.g.,Virgoor Fornax)thuspreferentially their discoveryatlargerredshifts inaphotographicsearch. galaxies ornearspiralarms,posing increasingdifficultiesto galaxies occurpreferentiallynearthecentralpartsofhost diagram fornearbySNe. overall effectistoproducealargescatterintheHubble nearby sample,representingthebrightestSNe.Thus we alsofindthefoursmallestvaluesofAra(Z?)inthis from aMalmquisteffect,sincethesearethefainterSNe.But the fourlargestvaluesofAm(Æ),asmightbeexpected more distantgroup(logcz>4).InthelowerhalfofFig.4we nificantly higherinthenearbysample(logcz<4)than tion ofredshift.Clearlytheratiospirals/nonspiralsissig- basic categoriesofspiralsandnonspirals)plottedasafunc- sampling thespiral-richfieldnearby; atlargerdistancesrich the hostgalaxiesofCalán/TololoSNela(separatedinto upper halfofFig.4whichshowsthemorphologicaltypes sible causesforthiseffect.ItcouldbethattheSNeinspiral Ara(Æ) vsredshift.Inthenearbysamplewefindthreeof ent selectioneffectcanbeappreciatedmoreclearlyinthe V), arepreferentiallyfoundinthenearersample.Thisappar- which arethemostluminouseventsofoursample(seePaper panel. show anotherrepresentationofthiseffectinaplot over mostofthevolumesurveyedbyCalán/Tololo Tololo sample.Wenotethatthefourintrinsically-faintest plotted vsredshift.Notethewidespreadindeclineratesnearby the moredistantgroup(logc£>4).(bottom)Thedeclinerate[Am(ß)] nonspirals issignificantlyhigherinthenearbysample(logcz<4)than Tololo SNelaplottedasafunctionofredshift.Notethattheratiospirals/ scatter inthisfigureisthatSNehostedbyspiralgalaxies, Fig. 4.(top)ThemorphologicaltypesofthehostgalaxiesGalán/ sample couldbebiasedtoflattervalues. search, andthustheslopesobtainedforCalán/Tololo SNe inthenearbysamplewouldnothavebeendiscovered sample, indicativeofthefullrangemorphologicaltypesseenintop 2402 HAMUYETAL.:TYPElaSNe 15 15 15 15 As brieflydiscussedinPaperIV,thereareseveralpos- A puzzlingaspectofthesamplewhichcontributesto NonSpirals Spirals © American Astronomical Society • Provided by theNASA Astrophysics Data System ra' 1.5 0.5 2 3 3.544.55 -1 I O ©000(000ooo o logiez)^ c oo o cP° I 1 OCB ODOO 5 2 = m m -5 = by Vaughanetal.(1995). heavily reddenedorintrinsicallylow-luminosity eventshasbeenproposed /max-0.575(±0.178)[A«2(B)-1.] A colorcutoff(at5—V<0.25) asanobjectivecriteriatoexclude the peakmagnitude-declineraterelationhasreduced Fig. 5showsthecorrectedVHubblediagram.Applicationof tudes ofaneventwith=1.1mag.Thelowerhalf of thereducedYindicates,is now entirelyconsistentwith observed magnitudesofeachSNtotheequivalentmagni- The secondtermontheleftoftheseequationscorrects 5max-0.784(±0.182)[A«z(5)-1.] 4iax5 logcz-2.958(±0.030)a=0A9«=22.(6) scatter inthisdiagramtoalevel of0.14which,asthevalue from thesamesampleof26Calán/TololoSNela,weobtain: helped todecreasethedispersion[cf.Eqs.(l)-(3)],espe- decline raterelation.AdoptingtheslopesderivedinPaperV diagrams isobtainedbycorrectingforthepeakluminosity- effect in/,ontheotherhand,isnegligible. cially intheBband(0.24vs0.38forfullsample).The The upperhalfofFig.5showstheVHubblediagramforthis ^MAX=51og CZ-3.177(±0.029)cr=0.24n=26,(4) parent galaxiesofthissubsample26events.Linearregres- the followingzeropointsanddispersions: ment theabsolutemagnitude-declineratedependence)give to the26eventswith#max^max^0.20.Asmentionedin subsample of26SNe.Excludingthethreereddesteventshas diagrams. InkeepingwithPaperV,weshalllimitthesample Calán/Tololo SNeandreanalyzethecorrespondingHubble lation allowsustocorrecttheapparentmagnitudesof ^max-0.707(±0.150)[A«2(5)-1.] sion fitstothedataforthissubsample(ignoringmo- Sec. 3thereislittleroomforsignificantextinctioninthe correct forthedependenceofabsolutemagnitudeon that thederivationofHubbleconstantwillnotbegreatly planations, thedefinitivecauseofthisratherunusualsample sideration. affected, andtheselectioneffectswarrentmorecarefulcon- SNe laluminosityfunctionfromthesedataclearlywouldbe Am(i5). Wecaution,however,thatattemptstoderivethe affected bythissomewhatbizarresampleeffectbecausewe effect isstillunclear.Whatevertheexactcause,itappears Vmax5 logcz=3.188(±0.026)cr=0.22n—26,(5) served morphologicalsignal.Whiletheseareplausibleex- 15 MAXMAX 15 15 15 A moredramaticdecreaseinthedispersionofHubble The existenceoftheabsolutemagnitude-dechneratere- = 5logcz—3.057(±0.035)(7=0.13«=22.(9) = 5logcz—3.329(±0.031)o-=0.14«=26,(8) = 5logcz—3.318(±0.035)í7=0.17«=26,(7) 4.1 TheCorrectedHubbleDiagrams 4. DISCUSSION 2402 1996AJ 112.2398H _1 ity fieldbasedonthesedatawillbegiveninaseparatepaper peculiar velocities,the11nearestobjectsimplyanrmsve- rate dependence. Tololo samplewithT^0.20.(bottompanel)TheHubbledia- Fig. 5.(toppanel)TheHubblediagraminVfortheSNelaGalán/ E(/5 —V)^0.1.Forthe15SNemeetingthiscondition(900, lines ^0.5Â.Forgastypicalofthatfoundinthediskour upper limittotheequivalentwidthofNaIDinterstellar ther tothoseobjectsforwhichwehavebeenableplacean tion inthehostgalaxiesbyrestrictingsampleevenfur- locity of550kms.Amoredetailedanalysistheveloc- If we,again,interpretthisscatterasbeingentirelydueto indicators (withprecisionsinrelativedistances~7%-10%). factor of1.5allowsSNelatobeusedasexcellentdistance the assumederrors.Thereductionofabyapproximately gram forthesame26eventsaftercorrectionpeakluminosity-decline 2403 HAMUYETAL.:TYPElaSNe 90af, 9IS,9lag,92J,92ae,92al,92bc,92bg,92bh,92bk, own Galaxy,suchalimitcorrespondstocolorexcesses 92bl, 92bo,93B,930),thezeropointsofcorrected (Suntzeff etal.1996a). MAX 12 34 612 “References.- Sahaetal.(1994);ahaai (1995);Sahaetal.(1996);andage(1996). References.- Pierce&Jacoby(1995);Phillips &Eggen(1996); We cantestthesensitivityoftheseresultstodustextinc- mMPhot 1990N NGC4639Sb32.00(23) 4 12.74(03)12.72(03)12.95(05)1.07(05)0.00(02)-19.26(25) -19.28(24)-19.05(24)6 1981B NGC4536Sc31.10(13) 3 12.03(03)11.93(03)—1.10(05)0.00(02)-19.07(16) -19.17(15)3,4,5 1937C IC4182S/Irr28.36(09) 1 8.80(09)8.82(11)—0.87(10)0.00(02)-19.56(15) -19.54(16)1 1972E NGC5253Irr27.97(07) 2 8.49(14)8.49(15)8.80(19)0.87(10)0.05(02)-19.69(18) -19.64(18)-19.26(21)2 SN HostMorph.DistanceModulusBVmax*MAX Am(B)E(B-V)maxMAXMAX (1) (2)(3)(4)(5)(6)(7) (8) (9)(10)(11)(12)(13)(14) © American Astronomical Society • Provided by theNASA Astrophysics Data System MAX 15 6 Galaxy TypeModulusRef“ Ref Distance 34 56 Table 2.NearbySNesample. Buta &Turner(1983);arbonetal.(1982); Tsvetkov(1982);Lira(1995). -1 1_ — kmsMpc (Sandageetal.1996).Sincethesevalues heid distancestothehostgalaxiesofsixnearbySNela(SN proach wewishtomakethenearbysamplereflectprop- be directlymeasuredfromthefightcurves.Toconvertthese remainder ofthisdiscussion.Althoughadequatephotometry in order. Hubble constantbasedontheCalán/TololoSNewouldseem luminosity-decline raterelation,areexaminationofthe were calculatedwithoutincludingcorrectionsforthepeak tained H{B)=56±4kms~Mpcand7/(V=58±4 cantly differentthanthezeropointsobtainedfrom26 Hubble diagramsprovetobe—3.318±0.046inÆ,—3.324 tances arefistedinTable2thefollowingformat: Table 2),whichisveryclosetothemeanobservedcolorof to correctforpossibleobscurationinthehostgalaxies.Note values intoabsolutemagnitudes,weassumedthetrueCeph- mum fightsothatthepeakmagnitudesanddeclineratescan template-fitting techniqueemployedfortheCalán/Tololo is availableforSNe1937Cand1972E,neitherwasobserved derive apreciseestimateofthedeclinerateparameter Sandage etal.1996).FromtheseSNe,authorsob- diagram ofthedistantSNela(Sahaetal.1994,1995,1996; SNe. 0.03±0.06 ofthesubsample26Calán/Tololoevents. extinction, ofthefourcalibratingSNeis0.01±0.07(see that themean#max^maxcolor,correctedforforeground erties ofthedistantsampleforwhichwehavenotattempted and thecolorexcessesE(5—V)fromBurstein&Heiles eid distancemodulimeasuredbySandageandcollaborators SNe 198IBand1990N,ontheotherhand,havewell- SNe toestimatetheirpeakmagnitudesanddeclinerates. at maximumlight,sowemustusethesame^-minimizing Am(B). Hence,thesetwoeventsarenotconsideredinthe sampled fightcurveswithcoveragebeginningbeforemaxi- (1984) forinterstellardustinourowngalaxy.Withthisap- 1990N inNGC4639)withtheaimtocalibrateHubble 1981B inNGC4536,SN1960F4496,and 1895B and1960F(Schaefer1995,1996),weareunableto 1937C inIC4182,SNe1895Band1972ENGC5253,SN ±0.041 inV,and-3.039±0.046/,whichareinsignifi- ()0 15 Recently, SandageandcollaboratorshavemeasuredCep- The relevantdataforthesefourSNewithCepheiddis- Owing tothepoorqualityoflightcurvesSNe 4.2 TheHubbleConstant 2403 1996AJ 112.2398H / fi / wm m m rected Hubblerelations[Eqs.(7)-(9)]wehave, ties fromtheapparentmagnitude,distancemodulus,andred- by Pierce&Jacoby(1995).Thisdifferenceisascribedtothe brators. Incolumns(2)-(4)we give theabsolute2?,V,and/ logtfo(') =0.2{M'-0.707(±0.150)[Am(ßl] log //(S)=0.2{M-0.784(±0.182)[A/nB1.1] the correctedHubblediagramsofCalán/TololoSNe the 2?,V,andIbands.Theerrorestimatesincludeuncertain- magnitudes, thedistancemodulusofhostgalaxy,and peak magnitudesoftheSNcalculatedfromapparent Note thatthepeakmagnitudeswederivedforSN1937C Table 3summarizesourcalculations fortheindividualcali- dening. was assumedtoconvertthecolorexcessextinctionin Heiles (1984)forinterstellardustinourowngalaxy. data. magnitudes oftheSNasdeterminedfromlightcurves. column (4). 2404 HAMUYETAL.:TYPElaSNe log //o(/)=0.2{M-0.575(±0.178)[Am (S)- 1.1] SNe, suitablycorrectedfortheirdeclinerates.Fromthecor- along withtheabsolutemagnitudesoffourcalibrating assumed colorexcess.AstandardGalacticreddeninglaw different techniquesoffittingthelightcurvetemplatesto are brighterby0.14inBand0.18Vthanthosefound scheme intheHubbleAtlasofGalaxies(Sandage1961). MAX15 0MAX15 MAX 15 Mi^corr =M^-0.575[Anns1.1] MLuccorr =max'0-707[Am-1.1] max ,C0ITMmax"0-784[Amis-1-1] Notes: ax 15 Weighted Average -19.28(10)-19.31(09)-19.08(16)63.3(3.8)63.3(3.4)62.2(5.4) The valueoftheHubbleconstantcanbedeterminedfrom Column (14):referencestotheSNphotometry. Columns (11),(12),and(13):theabsoluteB,V,I Column (10):thecolorexcessE(5—V)fromBurstein& Column (9):thedeclinerateparameterÀm(Æ). Columns (6),(7),and(8):theapparentB,V,Ipeak Column (5):referencestothedistancemodulusgivenin Column (3):thehostgalaxymorphologyfollowing Column (2):thenameofhostgalaxy. Column (4):thetruedistancemodulusofhostgalaxy. Column (1):SNname. 1990N -19.24(25)-19.26(24)-19.03(24)65.5(9.2)65.2(8.5)63.8(8.1) 1981B -19.07(16)-19.17(15)—70.7(7.7)67.9(6.5) 1972E -19.50(20)-19.47(19)-19.13(22)57.9(7.0)59.1(6.6)61.0(7.2) 1937C -19.38(18)-19.38(17)—61.3(7.0)61.7(6.4) 15 SN MgI< (1) (2)(3)(4)(5)(6)(7) © American Astronomical Society • Provided by theNASA Astrophysics Data System AXiCorrAXirarr Table 3.CorrectedabsolutemagnitudesandvaluesofHq. cr=0.20 cr=0.14(7=0.07cr=5.6a=4.0cr=2.0 + 28.057(±0.035)}. (12) + 28.329(±0.031)}, (11) + 28.318(±0.035)},(10) ^1mAX,coit Ho(B)Ho(V)Ho(I) m 1r_- m -1 peak luminosity-declineraterelation,wheretheerroresti- bration (assumedtobe±0.10).Theresultingdispersionof Hq includeuncertaintiesinthe(corrected)absolutemagni- therefore fallat theextremeendofpeak luminosity- Fig. 4,or2ofPaperV).SNe 1937Cand1972E,onthe ployed becauseitis“typical” for typelaeventslikethose km s“Mpc"and//(V)=63±8sMpc. Hubble constantobtainedfromEqs.(10)-(12).Theerrorsin the slopeofabsolutemagnitude-declineraterelationship. peak magnitudesoftheindividualSNecorrectedfor other hand,wereslow-declining events[Am(2?)~0.9],and discovered intheCalán/Tololo survey (seethelowerhalfof important, SNe198IBand1990Nbothhaddeclineratesof light magnitudesof198IBand1990Nweredirectlyob- with thepreliminaryresultspublishedinPaperIVfrom three determinationsoftheHubbleconstant. error istheuncertaintyinzeropointofCepheidcali- colors gives Weighted averagesin5,V,and2oftheabsolutemagnitudes tudes, thezeropointofHubblediagram,andob- In columns(5)-(7)wegivethecorrespondingvaluesof foreground reddening,distancemodulus,declinerate,and mates includeuncertaintiesfromtheapparentmagnitude, Ara(2?)~l.l, whichisthereference valuewehaveem- and 1972Eforseveralreasons.Firstofall,themaximum and 1990NshouldbegivenmoreweightthanSNe1937C ably smallerthanthisconservativeestimate.Theexternal which isthesmallestofuncertaintiesindividual and Iarenotallindependent,weadoptanerrorforthemean and thevaluesofHubbleconstantforfourcalibrating Hubble constantintheVfilterforanindividualSN(1972E). we summarizetheerrorbudgetofourcalculations diagram (0.17inB,0.14V,and0.13I).InTable4 served, whereaswehadtoestimatethoseof1937Cand Since theerrorsinindividualvaluesof27fromB,V, single-color determinations.Thetrueinternalerrorisprob- SNe aregiveninthebottomfineofTable3. served scatteroftheindividualSNeincorrectedHubble cr=0.5 kmsMpcshowsthegoodagreementamongall 1972E throughtemplatefitting.Secondly,andprobablymore 13 Calán/TololoSNe,namely,Hq(B)=62±U 0 15 15 0 1- m m m m m m 27= 63.1±3.4(internal)±2.9(external)kms~Mpc. Note thatthesevaluesof72areinexcellentagreement Of thefourcalibrators,itcouldbearguedthatSNe198IB Averaging thevaluesofHubbleconstantforthree 0 0 4 AbsoluteVMagnitude(=(l)-|-(2)-|-(3))0.18™ 2 Reddening{=3.1*a_)0.06 9 ScatterofHubbleDiagram0.14 8 ZeroPointofHubbleDiagram0.031 7 CorrectedAbsoluteVMagnitude(=(4)+(5)+(6))0.19 6 Amis(=0.10*0.707)0.07™ 5 MmaxvsAmisslope(=0.15*[Amis-l.l])0.03™ 3 DistanceModulus0.07™ 1 ApparentVMagnitude0.15 E(Bv) Table 4.ErrorbudgetinthecalculationofHq(V). Total (=(7)+(8)+(9))0.24™ Error Source(mag) 1-1 =6.6 kmsMpc SN 1972E 2404 1996AJ 112.2398H -1 1- 1 6 6 1- ; paper andthatofTammann&Sandage(1995).Aswehave 2405 HAMUYETAL.:TYPElaSNe H(I)=51.l±5.5 kmsMpc,whichareincloseagree- relations. Aweightedaverageoftheabsolutemagnitudes biases intheslopesofabsolutemagnitude-declinerate reasons giveninthepreviousparagraph,thesevaluesin- tions andtheHubblediagramtheyuse(Tammann& ity isnotsurprisingsinceweareusingtheirCepheidcalibra- ment withtheresultsofSandageetal.(1996).Thissimilar- km s“Mpc,H(V)=56A±3.1sand four calibratingSNelagiveH(B)=5.9±3 constant: Table 3forSNe198IBand1990NaloneyieldsaHubble and 1990Nthereforeminimizestheeffectofuncertaintiesor decline raterelation(seeFig.2ofPaperV).Use198IB are includedintheHubblediagramsofbothpresent and 1990Naremuchmorerepresentative(intermsofboth magnitude-decline relationship.ThisisbecauseSNe1981B Note thatthelattervaluesarenowveryclosetoHubble crease toH(B)=63.8±6.5kms“Mpc“,V)=623 distant Calán/TololoSNefromPaperIV.If,however,weuse nous SNela.Hence,theuseofPopIobjectssuchasCeph- pear tohosttheslowest-declining,andthereforemostlumi- decline rateandluminosity)ofthe'‘average”SNelawhich constant thatwederivewhencorrectfortheabsolute only SNe198IBand1990Nasthecalibratorsforsame Sandage 1995)isheavilyweightedbytheinclusionofseven eids tocalibratethezeropointofSNelaHubblediagram with youngerstellarpopulation(spiralsandirregulars)ap- count. can easilybiastheresultstowardluminousSNela,unless A recentreanalysisofthesedataby the samegroupgivesadistanceof heid distancetoM100of17.1±2 Mpc(^=31.16±0.20). the absolutemagnitude-declinerelationistakenintoac- shown inPaperV,thereisnowstrongevidencethatgalaxies ±5.9 kms“Mpc“,and7i(/)=60.5±8.5kmsMpc. 0 16.1 ±1.3Mpc,ort¿ =31.4±0.17 (Ferrareseetal.1996). 0 0 0 0 / 8910u 4567 _1- Leibundgut etal.(1993);Smith(1996);Hamuy(1991);Suntzeff(1996b). Barbon etal.(1989);Kimeridze&;Tsvetkov(1986);Lira(1995);Filippenko(1992); # =66.9±5.2(intemal)±3.1(extemal)kmsMpc. If weignorethepeakluminosity-dechneraterelation, Freedman etal.(1994)haveused HSTtomeasureaCep- 4.3 TheRecessionVelocitiesoftheVirgoandFornax 0 123 © American Astronomical Society • Provided by theNASA Astrophysics Data System References.- Buta&Turner(1983);Barbonetal.(1982);Tsvetkov Table 5.SNeinVirgoandFornaxwithmodemphotometry. 1991bg NGC437414.76(10)13.97(05)13.51(05)1.93(10)7,8 1994D NGC452611.86(03)11.90(03)12.11(03)1.32(05)9 1990N NGC463912.74(03)12.72(03)12.95(05)1.07(05)6 1984A NGC441912.50(10)12.30(10)—4,5 1991T NGC452711.69(03)11.51(03)11.62(03)0.94(05)6 1981B NGC453612.03(03)11.93(03)—1.10(05)1,2,3 92A NGC138012.57(03)12.55(03)12.80(03)1.47(05)11 80N NGC131612.49(03)12.44(03)12.70(04)1.28(04)10 SN HostBotsVob,lobiAm(B)Photometry (1) (2)(3)(4)(5)(6)(7) 15 Galaxy References Clusters Fornax Virgo -1 -1 -1 m m m //=82±17 kmsMpc.WhethertheFreedmanetal. problem sincethepeculiarmotionsofCalán/TololoSNe locity of1404±80kms,thisgroupfoundavalue Based onthisdistanceandanassumedcosmicrecessionve- peak magnitude-declineraterelationindicatethatarediscus- Leibundgut &Pinto(1992);morerecentphotometryandthe manner wasmadebyLeibundgut&Tammann(1990)and tances. AnearlierattempttoderivetheVirgodistanceinthis historical observationsoftheSNelainVirgoandFornax velocity oftheclusteranddepth.Onotherhand, the extragalacticdistancescalebasedonVirgocluster corrections forthepeculiarvelocityofVirgo.Estimates choice of1404kmsiscorrectornotrestsontheadopted in thephotographiclightcurvesforSN1984Alimitsour Virgo andFornaxSNewithmodemphotometry.Thescatter clusters topredicttheirrecessionvelocitiesandrelativedis- are asmallfractionoftheirredshifts. our methodofusingdistantSNelaisnotaffectedbythis the quotederrorsforindividual correctedmagnitudesin- magnitude-decline raterelation areshowninTable6.Here value of1.10(±0.10). we shallassumethatthisSNhasthefiducialdechnerate suffer fromlargeuncertaintiesduetothepossiblepeculiar magnitude-dechne raterelation, andtheuncertaintyin clude thephotometricanddechne rateerrorsgiveninTable correcting thepeakmagnitudes of theindividualSNefor (B)— 12.16±0.20,(V)=12.07and(/)=12.23 ability tomeasureaprecisevalueofAm(Z?)forthisevent; sion ofthisissueisworthwhile.InTable5wesummarizethe 5, theerrorsinslopesthatwe havefittedtotheabsolute 0 ±0.05, and(/)=12.75±0.5forFornax.Theresultsof ±0.39 forVirgoand<£}=12.53±0.4,(V)=12.50 15 Vcorr =Vobs-0.707[Am1.1] Notes: lcorr =lobs-0.575[Anns1.1] Bcorr =-0.784[Am1.1] 15 15 Velo city(CMB) Velocity(CMB) We canuseourobservedHubblediagram,combinedwith Excluding thepeculiareventSN1991bg,wefind Table 6.CorrectedmagnitudesforSNeinVirgoandFornax. Average Average Fornax: Virgo: 1994D 1990N 1984A 1981B 1991T 92A 80N SN Bçorrl (1) (2)(3)(4) corr 1 1 1,246(119) kms“ 1,339(83) kms’ 12.35(18) 12.31(03) 12.28(19) 12.16(20) 11.69(18) 11.82(18) 12.76(18) 12.50(21) 12.03(18) <7=0.05 cr=:0.46 1 1 1,200(114) kms“ 1,337(69) kms“ 12.29(16) 12.31(15) 12.30(01) 12.07(20) 11.74(15) 11.62(15) 12.74(15) 11.93(15) 12.30(19) a=0.46 £7=0.02 1 1 1,137(200) kms“ 1,348(68) kms“ 12.59(01) 12.59(15) 12.60(14) 12.22(38) 11.98(14) 11.71(14) 12.97(14) £7=0.01 £7=0.66 2405 1996AJ 112.2398H 7 m m m -1 m -1 _17 1 magnitudes ofthetwoSNemustbeafortuitousconsequence than theerrorsinindividualmagnitudes.Alikelysource tion ofthecorrectedmagnitudesforVirgoSNeisgreater maps ofBurstein&Heiles(1982).Regardingpossibleob- not correctedforforegroundreddeningsincethe make thecorrectedmagnitudessomewhatbrighter.Wehave the meancorrectedmagnitudes(alsoshowninTable6)are The errorsintheindividualrecession velocities derivedfromBandVare the observedheliocentriccluster velocityof1050±35 here wecanderiveourinfallvelocityintoVirgo.Adopting The situationforVirgoismorecomplex,sincetherea colors. cosmic recessionvelocitiesshowninTable6.Restricting in I. in themeancorrectedmagnitudesforFornax,adopting0.13 errors inthecorrectedmagnitudestoestimaterealistic the cluster,extremelycloseagreementincorrected effects forFornaxwillbesmallduetothecompactnatureof the individualmagnitudes.Althoughweexpectthatdepth nitudes ofthetwoFornaxSNeismuchlessthanerrorsin the otherhand,standarddeviationofcorrectedmag- cluster galaxiesobtainedtodate(Sandageetal.1996).On cluster, estimatedbyFreedmanetal(1994)tobe±0.35 for thisadditionaldispersionisthesignificantdepthof cantly differentthanthatinthedistantsample. galaxy reddeningintheFornaxandVirgoSNeisnotsignifi- events intheCalán/TololoSNe.Hence,webelievethathost use asanobjectivecriteriatoexcludeheavilyreddened ered herehaveß—V^0.20whichisthecolorcutoffthatwe mean coloroftheCalán/TololoSNe[(ß-V)=0.03 nax SNe[(5-V)=0.03±0.02(rms)]areveryclosetothe values arezeroforbothVirgoandFornax,basedonthe while thefasterdeclineratesoftwoFornaxSNeactto very similartothemeanobservedmagnitudesgivenabove, grams (0.17inB,0.14V,and0.13/).Notethatthe observed scatteroftheindividualSNeinHubbledia- 2406 HAMUYETAL:TYPElaSNe less thanthisestimate. individual single-colordeterminations. The trueerrorisprobablysomewhat we adoptanerrorforthemeanwhich is typicaloftheuncertaintiesin at leastpartiallycorrelated(e.g.,dueto theeffectofclusterdepth),andso cosmic recessionvelocityofVirgo1223kmsestimated wide rangeofestimatesforthecorrectvelocity.Basedon value forFornaxagreeswellwiththemeasuredvelocities. values withrecentresultsfromtheliterature.Thepredicted data forallfiveSNe,theresultingmeanvelocityVirgois ourselves totheBandVresultsforVirgo,whichthereis of smallnumberstatistics.Hence,weshallusetheindividual and alsoapparentinthefewCepheiddistancesofVirgo five VirgoSNe[(#-V)=0.09±0.10(rms)]andthetwoFor- average Am(Æ)fortheVirgoSNeis—1.10andtherefore scuration inthehostgalaxies,notethatmeancolorof (0.19/V2) in5,0.1l(0.16/v^)V,and0.10(0.15/vT) 1342±70 kms,wherewehaveusedtheresultsinallthree 1223 kms,towhichweconservativelyassignanerrorof ±0.06(rms)]. Also,alloftheVirgoandFornaxSNeconsid- ±115 kms“.ThecorrespondingvalueforFornaxis 15 Table 6showsthat,inallthreecolors,thestandarddevia- In Table7weshowacomparisonofthesepredictedv If wenowapplyEqs.(7),(8),and(9),derivethe CMB © American Astronomical Society • Provided by theNASA Astrophysics Data System 1 m 1 m m 1- m m -1 -1 m m km s’fromBingellietai(1993)andacorrectionof—107 being perfectstandardcandles. Nevertheless,therelatively relative distancemoduli.WefindA/¿(5)=0.15±0.24 improve thesignificanceofresult.Notealsothatthereis km s"totheLocalGroupcenterderivedfromGalactic tween ~0.4inBand—0.2 /.Thus,SNelaarefarfrom la arecharacterizedbysignificant dispersionsthatrangebe- Tololo databasehasshownthat theHubblediagramsofSNe initiated in1990wastoaddress thequestionofhowreliable has amuchsmallerdepth(<0.15).Arecentdetermination the Fornaxclustersincethisisrelativelynearbyand Hence, theeasiestpredictiontotestis,infact,distance will beneededbeforethefirstpredictioncanverified. tance modulus),Cepheiddistancesforanumberofspirals of 1150±51kms",aninfallvelocity180±126sis velocity ofVirgo;ifweuseHuchra’s(1988)preferredvalue terminations (e.g.,Jerjen&Tammann1993;Bureauetal given byLynden-Bell&Lahav(1988),weinferaninfallof coordinates (/=284°,¿>=74°)andthetransformationvector are typelaSNeasextragalactic standardcandles.TheCalán/ distance modulusof31.30±0.23(Freedman1996),inrea- of theCepheiddistancetoNGC1365inFornax,yieldsa cluster (assumedbyFreedmanetaltobe±0.35indis- of thecluster. fore, M100(/x=31.04±0.17)ismostlikelyonthenearside can makethefollowingpredictions: four nearbycalibratorsgivenatthebottomofTable3,we corrected forthepeakluminosity-declineraterelationof ered ineithercluster. tion willimproveconsiderablywhenmoreSNearediscov- from the/-bandTully-FisherrelationofA/¿=—0.06±0.15 implied. et al.(1982)resultof331±41kmsandmorerecentde- 280± 120kms.ThisvalueisconsistentwiththeAaronson • ThedistancemodulusoftheFornaxclusteris31.60±0.15. • ThetruedistancemodulusofVirgois31.41±0.22.There- A/z=0.19±0.23 Thisliesaboutl-crfromarecentresult and Ayu,(V)=0.23±foracombinedestimateof still disagreementoverthecorrectvalueofheliocentric sonable agreementwiththeabovedetermination. (Bureau etal1996).Again,theaccuracyofdetermina- 1996), althoughclearlyalargersampleofSNeareneededto Due totheproblemofintrinsicdepthVirgo Finally, ifweassumetheaverageabsolutemagnitudes From thesecorrectedmeanmagnitudeswecanalsoderive (1) ThemaingoaloftheCalán/Tololosurveywhichwe Table 7.RecessionalvelocitiesoftheVirgoandFornaxclusters. Cluster PredictedPreviousReference Fornax 1,342±70 Virgo 1,223±115 -1 vcMB Values [km s] 1,354 HeldfeMould1994 1,338 Jerjen&Tammann1993 1,404 Huchra1988 1,179 Jerjen&Tammann1993 5. CONCLUSIONS 2406 1996AJ 112.2398H _1- m -1 Jerjén, H.,&Tammann,G.A.1993,A&A, 276,1 kmsMpc. Theimplicationofignoringthepeak Leibundgut, B.,etal.1993,AJ,105,301 Leibundgut, B.,&Pinto,P.A.1992,ApJ, 401,49 Leibundgut, B.,&Tammann,G.A.1990, A&A,230,81 Held, E.V.,&Mould,J.R.1994,AJ,107,1307 Hamuy, M.,Phillips,M.Schommer,R.A.,Suntzeff,N.B.,Maza,J.,& Hamuy, M.,etal1994,AJ,108,2226(PaperHI) Hamuy, M.,Phillips,M.Wells,L.A.,&Maza,J.1993b,PASP,105, Hamuy, M.,etal.1993a,AJ,106,2392(PaperI) Freedman, W.L.1996,inProceedingsofTheExtragalacticDistanceScale, Freedman, W.L.,etal.1994,Nature,371,757 Filippenko, A.V.,etal.1992,AJ,104,1543 Ferrarese, L.,etal1996,ApJ,464,568 Buta, R.J.,&Turner,A.1983,PASP,95,72 Burstein, D.,&Heiles,C.1984,ApJS,54,33 Burstein, D.,&Heiles,C.1982,AJ,87,1165 Bureau, M.,Mould,J.R.,&Stavely-Smith,L.1996,ApJ,463,60 Bingelli, B.,Popescu,C.C,&Tammann,G.A.1993,A&AS,98,275 Barbon, R.,lijima,T,&Rosino,L.1989,A&A,220,83 Barbon, R.,Ciatti,F.,&Rosino,L.1982,A&A,116,35 Fornax cluster,wepredicttheHubbleflowatVirgoof1223 that futureworkshouldmakemoreuseofthisband. Kimeridze, G.N.,&Tsvetkov,D.Y.1986, Afz,25,513 Huchra, J.P.1988,inTheExtragalacticDistanceScale,ASPConf.Ser.4, Hamuy, M.,etal.1996c,AJ,112,2438(PaperVIU) Hamuy, M.,etal1996b,AJ,112,2408(PaperVII) Hamuy, M.,Phillips,M.Maza,J.,Suntzeff,N.B.,Schommer,R.A.,& Hamuy, M.,Phillips,M.Maza,J.,Wischnjewsky,Uomoto,A., Aaronson, M.,Huchra,J.,Mould,Schechter,P.L.,&Tully,R.B.1982, la, andthe“corrected”apparentmagnitudesoffivebest- Hubble constantbyafactor~10%-15%. luminosity-decline raterelationistounderestimatethe Hubble constantof#=63.1±3.4(internal)±2.9(external) distances withprecisions~7%-10%. for thedeclinerates,SNelacanbeusedtoderiverelative 0.17-0.13 Thus,aftercorrectingtheapparentmagnitudes decrease inthescatterBV1Hubblediagramstolevels luminosity-dechne raterelationshipresultsinasignificant effect seemstobelesspronouncedthanintheoriginal decline ratesoftheirlightcurves(seePaperV),althoughthis luminosities oftheseeventsarecorrelatedwiththeinitial of Phillips(1993)fromagroupnearbySNelathatthe observed SNelaintheVirgoclusterandtwo 2407 HAMUYETAL.:TYPElaSNe sample studiedbyPhillips.Applicationofthepeak small dispersionobservedin/isencouraging,andsuggests ±115 kmsand1342±70forFornax.The“cor- “corrected” BVIHubblediagramsweobtainavalueforthe 1972E, 198IB,and1990Ntocalibratethezeropointof 0 Aviles, R.1996a,AJ,112,2391(PaperV) Landolt, A.U.,&Khatwani,R.1991,AJ,102,208 Print Services,Provo),p.257 edited byS.vandenBerghandC.J.Pritchet(BrighamYoungUniversity Aviles, R.1995,AJ,109,1(PaperIV) 787 ApJ, 258,64 STScI Springmeeting,editedbyM.Livio,inpreparation (4) UsingtheinertialreferenceframeofdistantSNe (2) TheCalán/Tololodatabasehasconfirmedthefinding (3) UsingpublishedCepheiddistancestoSNe1937C, © American Astronomical Society • Provided by theNASA Astrophysics Data System REFERENCES m1 With acollectiveeffort,however,suchgoalappears Tammann, G.A.,&Sandage,A.1995, ApJ,452,16 Phihips, M.1993,ApJ,413,L105 Nugent, P.,Phillips,M.,Baron,E.,Branch,D.,&Hauschildt,P.1995,ApJ, Marzke, R.O.,Geller,M.J.,daCostaL.N.,&Huchra,J.P.1995,AJ,110, Lynden-Bell, D.,&Lahav,O.1988,inLarge-ScaleMotionstheUni- under NSFCooperativeAgreementNo.AST-8947990and knowledges supportprovidedforthisworkbytheNational possible thankstoGrantNo.92/0312fromFondoNacional the declinerateofsuchobjectswillrequirelargetelescopes. task sincealargenumberofeventsatredshifts0.3-0.5 unique toolformeasuringthedistancestoverydistantgal- rected” magnitudesalsoimplyarelativedistancemodulus Vaughan, T.E.,Branch,D.,Miller,D. 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