Galaxy Clustering Around Nearby Luminous Quasars
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We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
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aGALAXYCLUSTERINGAROUNDNEARBYLUMINOUSQUASARS1KarlB.Fisher,JohnN.Bahcall,So aKirhakosInstituteforAdvancedStudy,SchoolofNaturalSciences,Princeton,NJ08540andDonaldP.SchneiderDepartmentofAstronomyandAstrophysics,ThePennsylvaniaStateUniversity,UniversityPark,PA16802Received
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
ABSTRACT
Weexaminetheclusteringofgalaxiesaroundasampleof20luminous
<0.30)quasarsobservedwiththeWideFieldCamera-2onlowredshift(z~
theHubbleSpaceTelescope.TheHSTresolutionmakespossiblegalaxy
identi cationbrighterthanV=23.5andascloseas2′′tothequasar.We
ndasigni cantenhancementofgalaxieswithinaprojectedseparationof
1<~100hkpcofthequasars.Ifwemodeltheqso/galaxycorrelationfunction
asapowerlawwithaslopegivenbythegalaxy/galaxycorrelationfunction,
we ndthattheratiooftheqso/galaxytogalaxy/galaxycorrelationfunctions
is3.8±0.8.Thegalaxycountswithinr<15h 1kpcofthequasarsaretoo
>100h 1kpc).highforthedensitypro letohaveanappreciablecoreradius(~
Ourresultsreinforcetheideathatlowredshiftquasarsarelocatedpreferentiallyingroupsof10–20galaxiesratherthaninrichclusters.Weseenosigni cant
di erenceintheclusteringamplitudesderivedfromradio-loudandradio-quiet
subsamples.
Subjectheadings:quasars;galaxyclustering
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
1.INTRODUCTION
Overthelasttwodecades,ithasbeenwellestablishedthatquasarsareassociatedwithenhancementsinthegalaxydistribution.Historically,thisprovidedthe rstdirectobservationalevidencethatquasarswereindeedcosmologicalinorigin(Bahcall,Schmidt,&Gunn1969;Bahcall&Bahcall1970;Gunn1971;Stockton1978).Overtheyears,
<0.4,quasarsresideinsmallconsiderableevidencehasaccumulatedthatlowredshift,z~
tomoderategroupsofgalaxiesratherthaninrichclusters(cf.Hartwick&Schade1990,Bahcall&Chokshi1991,andreferencestherein).Athigherredshifts,thereisamarkeddi erenceintheenvironmentsofradio-loudandradio-quietquasars(Yee&Green1987).
>0.6,radio-loudquasarsareoftenfoundinassociationwithrichclustersAtredshiftsz~
(AbellrichnessR≥1)whileradio-quietquasarsappeartoremaininsmallergroups,orperhapsintheouterregionsofclusters(Boyleetal.1988;Yee1990).
Thegalaxyenvironmentaroundquasarsprovidesmanyimportantcluesastowhattriggersandsustainstheircentralengines.As rstsuggestedbyToomre&Toomre(1972),mergersandinteractionsofgalaxiescanprovideane cientmechanismfortransportinggasintotheinnerregionsofagalaxyorquasar.Therehavebeenattemptstomodeltheinteraction/mergerratesofordinarygalaxiesinordertoexplaintheluminosityfunctionofquasars(DeRobertis1985;Roos1985;Carlberg1990)andtherapidevolutionofthemerger/interactionrateinclusterswithredshiftmayprovideanaturalexplanationofthestrongevolutionofclusteringobservedaroundradio-loudquasars(Stocke&Perrenod1981;Roos1981).Knowledgeofthegalaxyenvironmentaroundquasarsisalsoimportantforunderstandingthelargescaledistributionofquasarsandhowitrelatestothestructureseeningalaxysurveys(Bahcall&Chokshi1991).
<0.3)InthisLetter,weexaminethegalaxyenvironmentaroundtwentynearby(z~
brightquasarsobservedwiththeWideFieldandPlanetaryCamera-2(WFPC2)ofthe
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
HubbleSpaceTelescope(HST).These eldswereimagedaspartofanongoinginvestigationintothenatureofthehostenvironmentofquasars(Bahcall,Kirhakos,&Schneider1994,1995a,1995b,1996a).TheexceptionalresolutionoftheHSTimagesallowscompaniongalaxiestobedetectedatverycloseprojectedseparations,insomecasesr~3h 1kpc<2′′),andgalaxy/starseparationtobeperformeddowntoV~23.5.Thegoalofthe(~
workpresentedhereistoquantifytheexcessofgalaxiesassociatedwiththesequasars.TheoutlineoftheLetterisasfollows.Abriefdescriptionofthequasarsampleusedinouranalysisisgivenin§2.In§3.1wearguethatgalaxycountsareinconsistentwithbeingdrawnfromauniformbackground.In§3.2,westrengthenthisconclusionbycorrectingthecountsforthebackgroundcontamination.Wealsopresenttheexcessgalaxycountsabovethebackgroundinannuliofprojectedseparation.Fromthesecounts,wequantifytheamplitudeofthegalaxyclusteringaroundthequasarsin§3.3intermsofaquasar-galaxyspatialcrosscorrelationamplitude.Wediscussourresultsandtheirrelationtopreviousworkin§4.
2.DATA
ThesampleofobjectsanalyzedinthisLetterconsistsof20oftheintrinsicallymostluminous(MV< 22.9,forH0=100kms 1Mpc 1, 0=1)nearby(z<0.30)radio-quietandradio-loudquasarsselectedfromtheV´eron-Cetty&V´eron(1993)catalog.Table1liststheindividualquasarsandtheirredshifts.Thequasarsspantheredshiftrange0.086≤z≤0.29withamedianredshiftofzmed=0.18.Detailsoftheobservationsandtheresultingimagesforelevenofthetwenty eldshavebeenpresentedinBahcall,Kirhakos,&Schneider(1994,1995a,1995b);theremainingobservationswillbepresentedinBahcalletal.(1996b,inpreparation).Sixofthequasars(denotedwithanasteriskinTable1)areradio-loud,whiletheremainderareradio-quiet(Kellermann1989).
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
Eachquasar eldwasimagedwiththeWFPC2throughtheF606W lter,whichissimilar,butslightlyredderthantheVbandpass(λ=5940 A, λ=1500 A).Thequasarswerepositionedwithin4′′±1.2′′ofthecenterofWideFieldCameraCCD3(WF3).SimultaneousimageswereobtainedintheadjacentCCDchips2and4(WF2andWF4respectively)whichtogetherwithWF3forma“L”shapedimage(see gure1).Eachchiphas800×800pixelsandanimagescaleof0.0996′′pixel 1atthechip’scenter;thiscorrespondstospatialresolutionof2.1h 1kpc/arcsecataredshiftz=0.20( 0=1).Thee ectiveareas(areasnotcoveredbypyramidshadows)ofWF2,WF3,andWF4are1.59,
1.60,and1.59sqarcminrespectively.MoredetailedinformationontheWFPC2anditsphotometricsystemcanbefoundinBurrows(1994),Traugeretal.(1994),andHoltzmanetal.(1995a,b).Therelativelylongexposures(1100or1400seconds),combinedwiththeexcellentspatialresolution,allowedgalaxiestobeidenti edintheimagesdowntolimiting
<2′′fromthecentralquasar.Weperformedmagnitudem(F606W)≤24.5andcloseas~
aperturephotometryonthe eldgalaxies;circularapertureswithradiiof0.3′′to10′′wereusedasappropriate.
3.GALAXYCOUNTSAROUNDQUASARS
3.1.RawCounts:EvidenceforaStrongEnhancement
Ifgalaxiesaredistributedaroundlowredshiftquasarswithapowerlawdistribution,ξ(r)~(r/10h 1Mpc) 1.77(assuggestedby,e.g.,Yee&Green1987),thentherewillbeaverystrongenhancementofthecountswithin30′′(r~60h 1kpcatz=0.2)ofthequasar.Moreover,becausethecentersofWF2andWF4areo setfromthequasar,therewillbeanenhancementofgalaxiesinWF3relativetoWF2andWF4.Thebackgroundgalaxycounts
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
risesteeplywithmagnitudeandthiswilldiluteanysignalofexcessgalaxies.Muchofthebackgroundcontaminationcanberemovedsimplybycountingonlythosegalaxieswithapparentmagnitudesintherangethatislikelytobephysicallyassociatedwiththequasars.Agoodcompromisebetweeneliminatingtoomanyassociatedgalaxiesandminimizingthee ectofforeground/backgroundinterlopers,istocountgalaxiesineach eld,i,whichareinthemagnituderangem (zi) 1tom (zi)+2,wherem (zi)istheapparentmagnitudeofanL galaxyattheredshiftofthequasar,zi.Themean(median)valueofm (zi)foroursampleis18.2(18.1);thetotalrangeofm (zi)is16.4≤m (zi)≤19.2.Incomputingm (z),wehavetakenanL galaxytocorrespondtoanabsolutemagnitudeM (F606W)= 20.75andhaveusedtheK-correctionsbetweenabsoluteandapparentmagnitudesgiveninFukugita,Shimasaku,&Ichikawa(1995).
Figure1showsthepositionsofallgalaxiesinourtwenty eldswith
m (zi) 1≤m≤m (zi)+2;geometriccorrectionswereappliedaccordingto
Holtzmanetal.(1995a).Inthepanelcontainingthequasar(WF3,lowerleft),thereisaclearexcessofgalaxies(50galaxies)relativetoWF2(upperleft)andWF4(18and17galaxiesrespectively).ThehypothesisthatthecountsinallthreechipsaredrawnfromanunderlyingPoissondistributionwithacommonmeanleadstoamaximumlikelihoodmeanperchipof28.4andachi-squaredofχ2=24.5;theprobabilitythatχ2foronedegreeoffreedomisthislargebychanceisonlyP=7×10 7.Thus,withoutanydetailedmodeling,wecanruleoutthepossibilitythatthecountsarerandom uctuationsinthebackgrounddistribution.Inthefollowingsections,weattempttomakethisconclusionprogressivelymorequantitativeby rstmodelingthebackgroundgalaxydistributionandthenintroducingamodelforthespatialdistributionofgalaxiesaroundthequasars.
3.2.CorrectingfortheBackgroundGalaxies
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
Inordertofurtherquantifytheexcessofgalaxycountsaroundthequasars,weneedanestimateofthecontributionfrombackgroundgalaxies.In gure2,weshowthegalaxycounts(d2N/dmd ,persquarearcsec)versusmagnitudeforthe“o quasar”chipsWF2andWF4,inbins m(F606W)=0.5.Thecountsatm(F606W)>21.5magarewellapproximatedbyapowerlaw,log10d2N/dmd = 10.8+0.33m(F606W);thecountsatbrightermagnitudesareinexcessofthoseobtainedbyextrapolatingthefaintpowerlaw t.Becausetheseparationofthecentersofchips2and4isnotlarge(101′′correspondsto213h 1kpcatz=0.2),thecountsinthesechipsareacombinationofbothbackgroundgalaxiesandthe(relativelybright)galaxiesphysicallyassociatedwiththequasars,andhenceyieldanoverestimateofthetruebackground.Wehavecomparedthepower-law twiththecountsderivedfromtheHSTMediumDeepSurvey(MDS)(Gri thsetal.1994;S.Casertano,privatecommunication)whichcoversamuchlargerareaofthesky.Theagreementisgood,andintheremainderofthisLetter,wewilladoptthepowerlawin gure2asourestimateofd2N/dmd .TheagreementwiththeMDSisalsoausefulconsistencycheckforsystematicerrorsinourderivedmagnitudes.
Inthetwenty elds,thereare11galaxiesintherangem (zi) 1≤m≤m (zi)+2withinaprojectedseparationlessthan25h 1kpcofthequasar;thetotalnumberexpectedfromthed2N/dmd powerlawrelationisonly0.99.TheprobabilityoftheobservedcountsbeingaPoissonrealizationofthebackgroundisextremelysmall,P=8×10 9,twoorderofmagnitudessmallerthanourpreviousestimateobtainedbyneglectingthebackground.ThisisalsoamuchstrongerconstraintthantheupperlimitgiveninBahcall,Kirhakos,&Schneider(1995a),P=2×10 2,basedoneight eldsandan(over)estimateofthebackgroundobtainedfromthecountsinWF2andWF4.
Wehavealsocomputedcountswithinprojectedseparationsof5and10h 1kpc.Inthetwenty elds,we nd2/0.039and5/.16(number/numberexpectedinthebackground)
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
withr<5h 1kpcandr<10h 1kpcrespectively;thecorrespondingrandomprobabilitiesareP=7×10 4andP=7×10 7.Thereisasuggestivedi erenceinthecounts
derivedfromtheradio-loudandradio-quietsubsamples.Theradio-quietquasars(14 elds)had0/.027(P=0.97)and2/.11(P=5×10 3)forthe5and10h 1kpccounts;thecorrespondingnumbersfortheradio-loudsample(6 elds)were2/.012(P=8×10 5)and3/.05(P=2×10 5).
In gure3,weshowthefractionalexcessofgalaxiesabovethebackground,
δN/N(r) = Ni(r)/Nb,i(r) 1,obtainedbyaveragingthecountsinthetwenty eldsinbinsof15h 1kpcprojectedseparation.HereNi(r)istheactualcountofgalaxieswithprojectedseparationsbetweenr r/2andr+ r/2intheith eldandNb,i(r)istheexpectedbackgroundcontribution.Again,wehaveonlyconsideredthosegalaxiesintheapparentmagnituderangem (zi) 1tom (zi)+2.
From gure3,wecanimmediatelydrawtwoconclusions.First,thereisasigni cantexcessofgalaxieswithinprojectedseparationsofr<h 1kpcfromthequasars.Second,thereappearstobenosigni cantdi erenceinthegalaxycountsfortheradio-loudandradio-quietsubsamplesfor10h 1kpc<r<100h 1kpc.Inthenextsection,wequantifytheobservedclusteringintermsofthespatialquasar/galaxycross-correlationfunction.
3.3.EstimatingtheSpatialClusteringAmplitude
Adetailedderivationoftherelationbetweenangularcountsandaspatialdistributionofgalaxiesintermsofacross-correlationfunctionisgiveninLongair&Seldner(1979).Brie y,oneassumesthatthegalaxydistribution(abovethebackground)aroundthequasarisspeci edbyaquasar/galaxycross-correlationfunction,ξqg(r,z).Theobservedexcessinprojectedseparationintheith eldisthenobtainedbyintegratingξqg(r,z)
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
overtheredshiftdistributionofgalaxies(dN/dz)iintheapparentmagnituderange
[m (zi) 1≤m≤m (zi)+2],
Ni(r)/Nb,i(r) 1= dθdz(dN/dz)iξqg(s,z)
dzdV,(2)
whereφ(zi)istheintegraloftheluminosityfunctionovertheabsolutemagnitudes
[M (zi) 1≤M≤M (zi)+2]correspondingthetheapparentmagnituderange
[m (zi) 1≤m≤m (zi)+2],
φ(zi)≡ M (zi)+2
M (zi) 1dMΦ(M).(3)
Thecosmologicalmodel( 0,Λ,H0)entersintheaboveequationsimplicitlyinthevolumeelement,angulardistance,andluminositydistance.Weadoptacanonicalmodelwith 0=1,H0=100kms 1Mpc 1,andΛ=0.Thebasicresultsofourstudyarelargelyindependentofthischoice.Theredshiftdistributioniscomputedusinganon-evolvingSchechter(1976)luminosityfunctionwithafaintendslopeofα=0.97(Lovedayetal.1992).TheK-correctionsnecessaryforcomputingtherelationbetweenabsoluteandapparentmagnitudeshavebeentakenfromFukugita,Shimasaku,&Ichikawa(1995).In
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
theresultsthatfollow,theH0dependenceisexplicitlyindicated.Thederivedclusteringamplitudesremainwithinthestatederrorsas 0isvariedfrom0.1to1.0.
Thecross-correlationfunction,ξqg(r,z),isusuallyassumedtoevolvewithredshift.Aconvenientmodelforthisevolutionistoassumethatonsmallscalestheclusteringisconstantinphysicalcoordinates,i.e.thenumberofexcessgalaxiesaroundthequasar,n(z)ξqg(r,z),isaconstant(n(z)isaveragenumberdensityattheepochz).Thusforanyassumedshapeofthecorrelationfunction,F(r),ξqg(r,z)evolvesas
ξqg(r,z)=1
1+z .(4)
Thefactorof(1+z)3compensatesforthechangeinthemeannumberdensity,whiletheredshiftfactorintheargumentofF(r)issimplyamatterofconvention;oneusuallyspeci estheshapeintermsofphysicalseparationswhilein(1),wehavespeci edξqg(r,z)intermsofcomovingseparation.
Weconsiderthreedi erentmodelsforF(r).The rstmodelisapowerlaw,F(r)=Bqgr 1.77,withaslopeequaltothatofthegalaxy/galaxycorrelationfunction(Davis&Peebles1983)andtheamplitudetakenasafreeparameter.Thesecondmodelisanexponentialsurfacedensityofgalaxies,µ(r)=µ0exp( r/rc)which,afterdeprojectionbyastandardAbelinversion,correspondstoF(r)=µ0/πrcK0(r/rc)(K0(x)beingthemodi edBesselfunction).ThismodelwasproposedbyMerri eld&Kent(1989)asatypicalgalaxypro learoundcentrallydominantclustergalaxies.Weadopttheirbestestimateofacoreradiusofrc=100h 1kpc,andvarytheamplitudeµst,weconsideramodi edHubblepro leF(r)=A[1+(r/rc)2] 3/2(Binney&Tremaine1987,eqn.2-37)withrc=100h 1kpcandAafreeparameter.Thesethreemodelshavedi erentbehavioratsmallr.Boththepowerlawandexponentialmodelsdivergeasr→0(althoughthelaterdoessoonlyweakly,K0(x)~ ln(x)),whilethemodi edHubblemodelasymptoticallyapproachesaconstant.
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
Wevariedtheamplitudeofthemodelstoachieveamaximumlikelihood ttotheexcessgalaxycountsinbinsofprojectedseparationof15h 1kpc.Thelimitednumberof eldspreventedusfromvaryingmorethanoneparameterpermodel.Figure3showstheresultingbest- tmodels;theamplitudesofthepower-lawmodelaregiveninTable2.At
>30h 1kpc,theexcesscountsarerelatively atandallthreemodelsfortheseparationsr~
correlationfunction tthedata.However,thecountsintheinnermostbinr<15h 1kpcliesigni cantlyabovethecountsatlargerseparations;theriseinthecountsatsmallradiiisparticularlystrikinginthe veradioloud elds.Thepower-lawistheonlymodelforξqg(r)consideredwhichrisessteeplyenoughtoaccountforthisexcess.
4.DISCUSSION
Ifthequasarsweredistributedliketypicalgalaxies,thenthederivedvalueof Bqg wouldbeequaltotheamplitudeofthegalaxy/galaxycorrelationfunction, Bgg ~20(Davis&Peebles1983).Ahighervalueof Bqg suggeststhatthequasarsliepreferentiallyinregionsofaboveaveragegalaxydensity.FollowingBahcall&Chokshi(1991),wecanconvertourvaluesofBqgintoanestimateofthetypicalrichnessofquasargalaxyenvironment.Here,wede nerichnessasthenumberofL galaxiesassociatedwiththequasar;thisisgivenbyasimpleintegraloverthecorrelationfunction,N=4πn ξqg(r)r2dr,wherethelimitsofintegrationarer=0to1.5h 1Mpc(thetraditionalAbellradius),andn ≈1.5×10 2h3Mpc 3isthenumberdensityofL ingthevaluesof Bqg inTable2,we ndthequasarstypicallyresideingroupsof16–25galaxies.ThesenumbersshouldbecomparedtothetypicalrichnessofAbellclusterswhichhave30–49and50–79membersforrichnessclassesR=0andR=1respectively.Moreover,thisestimateismostlikelyanupperlimitsincethereisevidencethatthegalaxypro learoundquasarsfallso
>0.25h 1Mpc(Ellingson,Yee,&Green1991).Inordertomoresteeplythanr 1.77forr~
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
testtherobustnessofourresultstoasteepeningofthegalaxypro le,we ttedadoublepowerlawmodelwithslopeof 1.77forr≤0.25h 1Mpcand 3forr>0.25h 1Mpc.Thebest tamplitudes,Bqg,forthismodelincreasedbyabout10%(stillwellwithinthequoted1 σerrors),yet,thenumberofinferedbrightgalaxiesassociatedwiththequasarsdecreasedto8duetothesteeperpro leatlargeseparations.
Thederivedamplitudes, Bqg ,inthepurepowerlawcasearesomewhatlargerthantheestimatesbyYee&Green(1987).Theyexaminedtheclusteringof9radio-loudand16radio-quietquasarsintheredshiftrange0.15<z<0.30.Onscalesof~20–500h 1kpc,theyestimated Bqg ≈60±20and Bqg ≈42±14forradio-loudandradio-quietquasarsrespectively.Hayman(1990)derivedgalaxycountsaroundlowredshift(z<0.3)quasarsfromthePalomarSkySurveyprints.Hefoundthattheratioofthequasar/galaxyandgalaxy/galaxyangularcorrelationfunctionswas3.1±0.6;ifthequasarsandgalaxieshavesimilarselectionfunctions,thistranslatestoanestimatesimilartoYee&Greenof Bqg ~61±12.French&Gunn(1983)analysedasample25low-redshiftquasars<0.35)selectedfrom1.2-mPalomarSchmidtplatesandconcluded B =25±12;(z~qg
theyalsoanalysedthedatasetofStockton(1978,27quasarswithredshiftsz≤0.45selectedfromtheredSkySurveyprints)andderived,viathesameanalysis,Bqg=79±40.Ourmeasurementsare,withtheexceptionofYee&Green’svalueforradio-quietquasars,consistentwithinthequotederrors.Theslightlyhigherclusteringamplitudewederivefortheradio-quietsubsamplemaybearesultofoursamplebeingthesubsetofthemostluminousquasars.
Yee&Green(1987)foundthattheclusteringamplitudeofgalaxiesaroundradio-loudquasarsincreasedbyafactor~3betweenz~0.4–0.6andatz~0.6radio-loudquasarsarefoundinenvironmentsasrichasAbellclassR=1.Opticalquasarsdonotevolveasrapidly(Boyleetal.1988),perhapsindicatingadi erentformationscenario.Ithas
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
beensuggestedthequasarsandactivegalacticnucleimaybetriggeredbyinteractions(e.g.,Toomre&Toomre1972;Stocke&Perrenod1981;Roos1981,Yee1987).Thiso ersasimpleexplanationforwhythequasarsaretypicallynotfoundinrichclustersatlowredshifts;thehighvelocitydispersionofsuchclustersleadstoalowinteractionrate.
TheHSTWFPC2isanexcellentinstrumentforextendingthepresentanalysistofainter,low-redshift,quasars.Thisextensionwouldimprovethecountingstatisticswhilealsoprovidinginformationregardingpossiblecorrelationsofthequasarenvironmentwith
<0.6)couldbeaccomplishedluminosity.Theimagingofofmoderateredshiftquasars(z~
byHSTwithsingleorbitexposures.Thisimagingwouldprovideamoredirectcomparisonwithpreviousgroundbasedworkandwouldincreaseourknowledgeoftheevolutionaryhistoryofthequasarenvironment.Anincreasedknowledgeofthequasarenvironmentwouldbeusefulinusingquasarobservationstoprobelargescalestructureathigherredshifts.
WewouldespeciallyliketothankStefanoCasertanoandthemembersoftheMediumDeepSurveyforusefulcommentsandforallowingustocompareournumbercountsandmagnitudeswiththeirmeasurements.Wehavealsobene tedfromdiscussionswithNetaBahcall,MichaelStrauss,OferLahav.Wethanktheanonymousrefereeforhelpfulsuggestions.ThisworkwassupportedinpartbyNASAcontractNAG5-1618,NASAgrantnumberNAGW-4452,andgrantnumberGO-5343fromtheSpaceTelescopeScienceInstitute,whichisoperatedbytheAssociationofUniversitiesforResearchinAstronomy,Incorporated,underNASAcontractNAS5-26555.KBFacknowledgesthesupportoftheNSF.
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
REFERENCES
Bahcall,J.N.,Kirhakos,S.,&Schneider,D.P.1996a,ApJ,inpress
Bahcall,J.N.,Kirhakos,S.,&Schneider,D.P.1996b,inpreparation
Bahcall,J.N.,&Bahcall,N.A.1970,PASP,82,721
Bahcall,J.N.,Kirhakos,S.,&Schneider,D.P.1994,ApJ,435,L11
Bahcall,J.N.,Kirhakos,S.,&Schneider,D.P.1995a,ApJ,450,486
Bahcall,J.N.,Kirhakos,S.,&Schneider,D.P.1995b,ApJ,454,L175
Bahcall,J.N.,Schmidt,M.,&Gunn,J.E.1969,ApJ,157,L77
Bahcall,N.A.&Chokshi,A.1991,ApJ,380,L9
Binney,J.,&Tremaine,S.1987,GalacticDynamics(Princeton:PrincetonUniversity
Press),p.39
Boyle,B.J.,Shanks,T.&Yee,H.K.C.1988,inLargeScaleStructuresoftheUniverse,
IAUSymp.No.130,ed.J.Audouze,M.-C.Pelletan,andA.Szalay,p.576.Dordrecht:Kluwer
Burrows,C.J.1994,HubbleSpaceTelescopeandPlanetaryCamera2Instrument
Handbook,Version2.0(Baltimore:SpaceTelescopeScienceInstitute)
Carlberg,R.G.1990,ApJ,350,505
Davis,M.&Peebles,P.J.E.1983,ApJ,267,465
DeRobertis,M.M.1985,AJ,90,998
Efstathiou,G.,Ellis,R.S.,&Peterson,B.A.1988,MNRAS,232,431
Ellingson,E.Green,R.F.&Yee,H.K.C.1991,ApJ,371,49
French,H.B.&Gunn,J.E.1983,ApJ,269,29
Fukugita,M.,Shimasaku,K.,&Ichikawa,T.1995,PASP,107,945
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
Gri ths,R.E.,etal.1994,ApJ,437,67
Gunn,J.E.1971,ApJ,164,L113
Hartwick,F.D.A.&Schade,D.1990,ARAA,28,437
Holtzman,J.A.etal.1995a,PASP,107,156
Holtzman,J.A.etal.1995b,PASP,inpress
Kellermann,K.I.,Sramek,R.,Schmidt,M.,Sha er,D.B.,&Green,R.1989,AJ,98,1195Longair,M.S.&Seldner,M.1979,MNRAS,189,433
Loveday,J.,Peterson,B.A.,Efstathiou,G.,&Maddox,S.1992,ApJ,390,338
Merri eld,M.R.&Kent,S.M.1989,AJ,98,351
Peebles,P.J.E.1980,TheLarge-ScaleStructureoftheUniverse,(Princeton:Princeton
UniversityPress)
Roos,N.1985,A&A,104,218
Schechter,P.L.1976,ApJ,203,297
Stocke,J.T.&Perrenod,S.C.1985,ApJ,245,375
Stockton,A.1978,ApJ,223,747
Toomre,A.&ToomreJ.1972,ApJ,178,623
Trauger,J.T.etal.1994,ApJ,435,L3
V´eron-Cetty,M.P.,&V´eron,P.1993,ACatalogueofQuasarsandActiveNuclei(Sixth
Edition),ESOScienti cReport,No.13
V´eron-Cetty,M.P.,&Woltjer,L.1990,A&A,236,69
Yee,H.K.C.1987,AJ,94,1461
Yee,H.K.C.1990EvolutionoftheUniverseofGalaxies,ASPConferenceSeries,Vol.10,
p.322(SanFrancisco:BookCrafters,Inc.)
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
Yee,H.K.C.,&Green,R.F.1984,ApJ,280,79
Yee,H.K.C.,&Green,R.F.1987,ApJ,319,28
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
TABLE1
quasarsample
NameDateExp.(sec)MVz
Radioloud
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
TABLE2
ClusteringAmplitudes
Sample Bqg 1 σRange Bqg / Bgg
inunitsof[h 1Mpc]1.77
Bgg =19.8(h 1Mpc)1.77
We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as clos
FIGURECAPTIONS
Fig.1.—MosaicofthegalaxycountsinWF2,WF3,andWF4(upperleft,lowerleft,andrightpanelsrespectively)foralltwenty elds.Inagiven eldi,wecountonlythosegalaxiesinthemagnituderangem (zi) 1tom (zi)+2wherem (zi)istheapparentmagnitudeofanL galaxyattheredshiftofthequasar,zi.
Fig.2.—Numbercounts,d2N/dmd ,versusm(F606W).The lledcirclesrepresentthecountsdetermineddirectlyfromtheo chipsineachQSO eld.Poissonerrorsareshown.Thelineisaleastsquares ttothefaintcountswithm(F606W)>21.5.
Fig.3.—Averagegalaxycounts δN/N(r) ofthefullquasarsampleandradioandradio-quietsubsets.Thesolidpointsarethecountscomputedusingapowerlaw ttothefaintcountsofchips2and4forthebackground(cf. gure2);theopensymbols(shifted.025inthelog)showthecountsderivedusingthebackgroundcountsfromtheMediumDeepSurvey.Theerrorbarsshowthescatterbetweenthedi erent elds.Thecurvesarethepredictedcorrelationfunctionsifthegalaxy/quasarcrosscorrelationfunctionisapowerlawwithindexγ=1.77(solid),anexponentialsurfacedensity(dashed),oramodi edHubblepro le(dotted).Allcalculationsassume 0=1andΛ=0.
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