High redshift FRII radio sources large-scale X-ray

arXiv:0709.3635v1[astro-ph]23Sep2007Mon.Not.R.Astron.Soc.000,000–000(0000)Printed2February2008(MNLATEXstylefilev2.2)HighredshiftFRIIradiosources:large-scaleX-rayenvironmentE.Belsole1,2⋆,D.M.Worrall2,M.J.Hardcastle3,&J.H.Croston31InstituteofAstronomy,UniversityofCambridge,MadingleyRoad,Cambridge,CB30HA,U.K.2DepartmentofPhysics,UniversityofBristol,TyndallAvenue,BristolBS81TL,U.K.3SchoolofPhysics,AstronomyandMathematics,UniversityofHertfordshire,CollegeLane,Hatfield,HertfordshireAL109AB,U.K.Accepted2007July27.Received2007July27;inoriginalform2007May19ABSTRACTWeinvestigatethepropertiesoftheenvironmentaround20powerfulradiogalaxiesandquasarsatredshiftsbetween0.45and1.UsingXMM-NewtonandChandraobservationsweprobethespatialdistributionandthetemperatureoftheclustergas.Wefindthatmorethan60percentofpowerfulradiosourcesintheredshiftrangeofoursamplelieinaclusterofX-rayluminositygreaterthan1044ergs−1,andallbutoneofthenarrow-lineradiogalaxies,forwhichtheemissionfromthenucleusisobscuredbyatorus,lieinaclusterenvironment.Forbroad-linequasarstheX-rayemissionfromthecoredominatesanditismoredifficulttomeasuretheclusterenvironment.However,withinthestatisticaluncertaintieswefindnosignificantdifferenceinthepropertiesoftheenvironmentasafunctionoftheorientationtothelineofsightoftheradiojet.Thisisinagreementwithunificationschemes.Ourresultshaveimportantimplicationsforclustersurveys,asclustersaroundpowerfulradiosourcestendtobeexcludedfromX-rayandSunyaev-Zeldovichsurveysofgalaxyclusters,andthuscanintroduceanimportantbiasintheclusterluminosityfunction.Mostoftheradiosourcesarefoundclosetopressurebalancewiththeenvironmentinwhichtheylie,butthetwolow-excitationradiogalaxiesofthesampleareobservedtobeunder-pressured.Thismaybethefirstobservationalindicationforthepresenceofnon-radiativeparticlesinthelobesofsomepowerfulradiogalaxies.Wefindthattheclustersaroundradiosourcesintheredshiftrangeofoursamplehaveasteeperentropy-temperaturerelationthanlocalclusters,andtheslopeisinagreementwiththepredictionsofself-similargravitationalheatingmodelsforclustergasinfall.ThissuggeststhatselectionbyAGNfindssystemslessaffectedbyAGNfeedbackthanthelocalaverage.WespeculatethatthisisbecausetheAGNinoursamplearesufficientlyluminousandrarethattheirAGNactivityistoorecenttohavecausedtheonsetofmeasurablefeedbackandincreasedentropyintheclusters,especiallyinthecooleroneswherelocallytheeffectoffeedbackareexpectedtobemostevident.IfthisisconfirmedbyforthcomingX-raymissionsitwillimproveourunderstandingoftheheatingandcoolingprocessesinhigh-redshiftgalaxyclusters.Keywords:galaxies:active–galaxies:highredshift–quasars:general–radiocontinuum:galaxies–X-rays:galaxies:clusters1INTRODUCTIONMuchevidencesupportstheexistenceofagaseousenvironmentaroundpowerfulradiogalaxiesandquasars.Theoretically,mod-elsofjetconfinementimplythatanexternalmediumwithpres-suresimilartothepressurefoundatthecentreofgalaxyclustersisrequiredtokeepthejetcollimated(Begelman,Blandford,&Rees1984).Observationally,twoofthemostpowerfulradiogalax-ies,CygnusA(Arnaudetal.1984;Reynolds&Fabian1996)and3C295(e.g.Henry&Henriksen1986;Allenetal.2001),arelo-catedinthecentreofrichclustersofgalaxies.Studiesbasedonopticalobservationsfindthat,atredshift∼0.2−0.3,power-⋆E-mail:[e-mail]-RileytypeII(FRII)sourcesarefoundinrelativelymodestenvironments(groupscale,e.g.,Hill&Lilly1991;Zirbel1997;Woldetal.2000;Best2004,andreferencestherein),whileathigherredshiftstheenvironmentsofFRIIsmayagainberichclusterswithrichnesscomparabletoAbellclassIorhigher(e.g.,Hall&Green1998).Thisevidenceisprovidedmainlybystud-iesbasedongalaxyover-densities,gravitationalarcs(Deltornetal.1997;Woldetal.2002)andlensingshearofsurroundingfieldgalaxies(Bower&Smail1997).Henceithasbeenapparentformanyyearsthatpowerfulradiogalaxiesandquasarsshouldactassign-postsofmassivegalaxyclustersathighredshift.TheclearestobservationalevidencefortheexistenceofaclusteraroundaradiosourceisthedetectionofanX-rayemit-ting,thermal,large-scalemediumsurroundingit.UsingROSAT2E.Belsoleetal.Table1.ThesampleSourceRA(J2000)Dec(J2000)redshiftscaletypeNHLiterature(hms)(◦′′′)(kpc/arcsec)(×1020cm−2)3C6.1001630.99+791650.880.8407.63NLRG14.80thiswork3C184073924.31+702310.740.9948.00NLRG3.45B043C200082725.44+291846.510.4585.82LERG3.74thiswork3C207084047.58+131223.370.6847.08LDQ4.12Br02/G033C220.1093239.65+790631.530.6106.73NLRG1.87W013C228095010.70+142000.070.5526.42NLRG3.18thiswork3C254111438.71+403720.290.7347.28LDQ1.90CF03/D033C263113957.03+654749.470.6466.90LDQ1.18CF03/H023C265114528.99+313349.430.8117.54NLRG1.90thiswork3C275.1124357.67+162253.220.5576.40LDQ1.99CF033C280125657.85+472020.300.9968.00NLRG1.13D033C292135041.95+642935.400.7136.90NLRG2.17B043C295141120.65+521209.040.4615.530NLRG1.32A013C309.1145907.60+714019.890.9047.80GPS-Q2.30thiswork3C330160934.71+655637.400.5496.41NLRG2.81H023C334162021.85+173623.120.5556.38LDQ4.24thiswork3C345164258.80+394836.850.5946.66CDQ1.13G033C380182931.78+484446.450.6917.11CDQ5.67thiswork3C427.1210406.38+763311.590.5726.49LERG10.90thiswork3C454.3225357.76+160853.