We present the catalogue of a wide-field CFHT/WHT spectroscopic survey of the lensing cluster Cl0024+1654 at z=0.395. This catalogue contains 618 new spectra, of which 581 have identified redshifts. Adding redshifts available from the literature, the final

2O.Czoskeetal.:SpectroscopicsurveyofCl0024:I.Thecatalogue

iesistakingplace.Theadventofnewwide- eldCCDmosaiccamerasavailableonanumberoflargetelescopes(e.g.CFHT,CTIO,Subaru,ESO2.2m)makesitpossi-bletoobtainphotometricandmorphologicalinformationon1-10Mpcscalesaroundtheclustercentres.However,wide- eldinvestigationofclustersdemandsbothimag-ingandspectroscopicobservations.Individualspectraofgalaxiesdescribetheirspectralenergydistributionandprovidetheirredshift,whichisindispensabletoproduceacatalogueofclustermemberswithradialvelocityandinformationregardingtheirstellarcontentandstarfor-mationhistory.Atpresentthereisonlyalimitednumberofclusterswithmorethan～200spectroscopicallyiden-ti edmembergalaxies(e.g.Abrahametal.1996),andespeciallyathighredshift(z>～0.2)spectroscopicallywell-studiedclustersbecomeveryrare,mostlyduetothefactthatcontaminationby eldgalaxiesincreasesrapidlywithredshift.

Thefactthatclustersarenotisolatedsystemsalsoraisesquestionsconcerningthetraditionalwaysofesti-matingmassesofclustersofgalaxiesthroughdi erentmassestimators:gravitationallensinganalyses,kinemati-calanalysesfromredshiftsofclustermembergalaxiesandX-rayobservations.

Gravitationallensingissensitivetothetotalintegratedmassalongtheline-of-sightfromtheobservertothelensedsources,weightedbytheappropriatecombinationofangu-larsizedistancesbetweenobserver,lensandsource(e.g.Schneider,Ehlers&Falco1992,Bartelmann&Schneider2001).Inthepresenceofmassivestructuresotherthantheclusteralongthelineofsight,rgespectroscopicsurveysprovideadditionalinformationneededtocorrectlyinterpretthelensinganal-ysisinthiscase.Metzleretal.(2000)investigatethein u-enceofthepresenceof lamentsandgroupsofgalaxiesinthevicinityofaclusteronweaklensingestimatesoftheclustermassand ndthatsigni cantoverestimates(uptoafactor1.5to2)arepossibleandevenlikely.SimilarinvestigationswithcomparableresultswereconductedbyCenetal.(1997)andReblinskyetal.(1999).

Asimilarbiasshouldbeexpectedtoa ectmeasure-mentsofvelocitydispersions:ifforegroundorbackgroundgroupsofgalaxiesintheimmediateneighbourhoodoftheclusterareaddedintotheredshifthistogram,butarenotresolvedandrecognizedasseparateentities,theveloc-itydispersionoftheclusteritselfwillbeoverestimated.Generallyonly30to50membergalaxiesareusedtoestimatetheline-of-sightvelocitydispersion(andvirialclustermass;seee.g.thelargecompilationsofGirardietal.1998andGirardi&Mezzetti2000).Furthermore,themeasuredredshiftsaregenerallyconcentratedwithinarelativelysmallregionwithinaprojectedradiusof～500h 1kpcoftheclustercentre.Whereasonecanarguethatthesenumbersmightbesu cientforrelaxedclusterswithregularspatialandvelocitydistributions,thevari-ousderivedestimateswillcontainlargesystematicerrorsifunresolvedsubstructuresarepresent.Whatcanbeob-

tainedfromredshiftsurveysisagalaxynumberdensityweightedline-of-sightvelocitydispersionaveragedalongtheline-of-sight.Withasu cientlylargenumberofclus-termemberredshiftsitispossibletomeasurethevariationoftheline-of-sightvelocitydispersionwithprojecteddis-tancefromtheclustercentre(Carlbergetal.1997),butdeterminationofevenmoredetailedinformationonthedynamicalstatus(e.g.velocityanisotropypro le)ofaclusterrequiresaforbiddinglylargenumberofredshifts(e.g.Merritt1987).

Clearly,combininginformationcomingfromgravita-tionallensing(weakandstrong),theX-rayemissionfromthehotintra-clustergas,theSunyaev-Zeldoviche ectandthegalaxyvelocitydistributionisthebestwaytoarriveatsecuremassestimatesforclustersofgalaxies(seee.g.Castanderetal.2000).Thisisnowpossibleforseveralcases.Ofparticularinterestareclustersforwhichasig-ni cantdiscrepancybetweendi erentmassestimatesisfound.Onesuchclusteristhewell-knownlensingclus-terCl0024+16541.About100redshiftsofgalaxiesinthisclusterwereobtainedbyDressler&Gunn(1992)andDressleretal.(1999),resultinginavelocitydispersionofσ 1300kms 1,whichisconsistentwithmassestimatesderivedfromthespectaculararcsystemintheclustercentre(Kassiola,Kovner&Fort1992,Smailetal.1996,Tysonetal.1998,Broadhurstetal.2000).Cl0024+1654wasamongthe rstclustersinwhichacoherentshearsig-nalduetoweaklensingwasfound(Bonnetetal.1994).Acrudemassestimatefromthisanalysiswasconsistentwiththestronglensingandkinematicalestimates.Inaddi-tiontothesignalduetoCl0024+1654itself,Bonnetetal.(1994)alsofoundacoherentsignaltothenorth-eastoftheclustercentreinanareawherenoobviousgalaxyoverden-sitycouldbeseen.TheX-rayluminosityofCl0024+1654ontheotherhandisunusuallylowforaclusterofthisvelocitydispersion,andmassestimatesfromtheX-rayobservationsareafactoroftwotothreelowerthanthelensingandkinematicalestimates(Soucailetal.2000).

InordertobetterunderstandthedynamicsofCl0024+1654andhowitisembeddedinthesurroundinglarge-scalestructure,wehaveconductedawide- eldspec-troscopicsurveyattheCanada-France-HawaiiTelescope(CFHT)andtheWilliamHerschelTelescope(WHT)from1992to1996.Inthispaperwepresentthecatalogueofthegalaxiesobservedforthissurvey.Section2summa-rizesthephotometricandspectroscopicobservations.ThedatareductionandanalysisarepresentedinSection3.Section4discussessomeinterestingglobalresultsofthesurveyanddescribessomestructuresfoundintheredshiftdistributionthatarenotdirectlyrelatedtotheclusterCl0024+1654.AsummaryisgiveninSection5.Ade-tailedanalysisofthedynamicsoftheclusteritselfandits