1994Aj 108. . 7 6 6B the Astronomical Journal

1994AJ 108. . 7 6 6B lr THE ASTRONOMICALJOURNAL 766 Astron.J.108 (3),September1994 0004-6256/94/108(3)/766/55/$0.90 ©1994Am.Astron. Soc. The NRAOisoperatedbyAssociated Universities, Inc.,undercooperativeagreementwiththeNationalScienceFoundation. © American Astronomical Society • Provided by the NASA Astrophysics Data System , Trinity University,SanAntonio,TexasandJetPropulsionLaboratory,CaliforniaInstituteofTechnology,Pasadena,78212 A representativesampleof12extendedquasarsfromthe3CRcataloghasbeenimagedat4.9GHzusing resolution (FWHM)of0'.34to0''38.Jetsaredetectedonatleastonesideeverysource.Thejetswell the VLA.Thesefullsynthesisobservationstypicallyachieveanrmsnoiseof20¡jJyperbeam,ata knots rangefrom<5%to—50%,butshownocommontrendwithdistancealongthejets.Inthatare feature isusuallythebrightest(untiljetnearsitshotspot).Thedegreesoflinearpolarizationat opening anglesofseveraljetsarenotconstant,butshowrecollimationafteraninitialregimerapid collimated comparedwiththoseinlesspowerfulsources,butspreadingisdetectedmostofthem.The the jets.Manyofjetsareinitiallystraighttowithinafewdegrees,butbendmoreinouterpart elongated indirectionsclosetothatofthejet,Evectorstendbeorthogonaljetaxis.The the source.Theprominenceofinner,straighterjetsegmentsrelativetoextendedlobescorrelates exceptions—misaligned knotswithmisalignedpolarizations—tendtobebrightfeaturesnearlargebendsin spreading. Manyofthejetscontainquasiperiodicstringsknots,whichknotclosesttocentral prominence ofthecounterjetsanticorrelateswiththatjets aspredictedbysimplerelativistic-beaming There isnoevidenceinthissamplethatcounterjetdetectabilitycorrelateswithsuchputativeinclination more bentjetsegmentsdoesnot.Candidatesforcounteijetemissionaredetectedinsevensources,butthere significantly withtheprominenceofmilliarcsecond-scalecentralfeatures,but between suchfeaturesand“jetknots.”Boththecompactnessof hotspotsandtheirpositioninthelobeare favor counterjetdetection,andtherearenocandidates oppositelong,uninterruptedstraight is nounambiguous,continuouscounterjetinanyofthem.Estimatesthefluxdensityratiosbetween prominent relativetootherextended emissionifthejetbendsthroughalargeangle,particularly ifalarge We offeranewempiricaldefinitionoftheterm“hotspot” that isintendedtoimprovethedistinction models forthejet/counterjetasymmetry.Thereis,however,strong evidencethatlargebendsinthemainjet indicators ascentralfeatureprominenceorprojectedlinear size. Thereisalsonoevidencethatthe straighter jetsegmentsandthecounterjetsbasedonthesetentativedetectionsrangefrom1.2:1to>175:1. bend occursabruptly.Thecounteijetted hotspotisalsolesswelldefinedifthejetmorebent. Thelobes from theouteredgeoftheirlobesthanarecounteijetted counterparts.Thejettedhotspotisless the morecompactoneisalwaysonjettedside.Jettedhotspots arealsomorelikelytoberecesseddeeply influenced byinteractionsbetweentheunderlyingbeamsandinhomogeneities inthesurroundingmaterial. inhomogeneity ofthejettedand counterjettedlobesifthehotspotsareexcluded.Thehave acommon of severalsourcesshowconsiderable inhomogeneity,includingfilamentation.Thereislittledifference inthe affected bywhethertheyarefedadetectablejet.Whenthehot spotsdiffersignificantlyincompactness, segments ofthemainjets.Thedetectabilitycounterjets in thesequasarsmaythereforebestrongly Department ofAstronomy,NewMexicoStateUniversity,LasCruces,88003 DEEP VLAIMAGINGOFTWELVEEXTENDED3CRQUASARS 1 National RadioAstronomyObservatory,Charlottesville,Virginia22903 Royal GreenwichObservatory,Cambridge,UnitedKingdom Haystack Observatory,Westford,Massachusetts01886 Received 1994January11;revisedApril18 Electronic mail:[email protected] Electronic mail:[email protected] Electronic mail:[email protected] Electronic mail:[email protected] Electronic mail:[email protected] VOLUME 108,NUMBER3 Colin J.Lonsdale Robert A.Laing David H.Hough Alan H.Bridle Jack O.Burns ABSTRACT SEPTEMBER 1994 766 1994AJ 108. . 7 6 6B 25-1 767 BRIDLEETAL.:TWELVE3CRQUASARS parently breakthebrightnesssymmetryoflobesso powers >10WHzat1.4GHzhavetwo-sidedlarge- one-sidedness ofthejetsinpowerfulsources.Thesecor- Bridle 1984).Itisimportanttounderstandwhythejetsap- dio jetsinthesesourcesareoverwhelminglyone-sided(e.g., view, thetwobeamsmaytransportsamepower,but respond tothree(notnecessarilymutuallyexclusive)views strongly inthepowerfulextendedsources. scale structures(the“classicaldouble”morphology),thera- beam onthedarksidemay(forexample)interactlesswith emission isdirectedawayfromusbybulkrelativisticmotion. identical tothebeamonbrightside,butitssynchrotron of theenergytransportprocesses: particles andfields. vironments ofthebeamsorintheircontentrelativistic powerful sourcesmaybeinducedbyasymmetriesintheen- chrotron emissivityislow,i.e.,theenergypipelinemore trapolation tolargerscalesofthepopularmodelsforone- mildly relativistictokiloparsecscales.Thisisasimpleex- sources impliesthatthebeamvelocitiesremainatleast On thisview,the“one-sidedness”ofjetsinpowerful side. Onthisview,thebrightness asymmetryofthesynchro- the other.Onthisview,brightnessasymmetriesofjetsin or adifferentmagneticfieldstrengthandconfiguration,than efficient onthedarksidethanbrightside.Onthis Rees 1978;Blandford&Königl1979;ScheuerReadhead surrounding gas,ormaycontainfewerrelativisticelectrons sidedness andsuperluminalmotioninparsec-scalejets(e.g., tron emissionfromthejetsresults fromarealasymmetryin 1979). power, orevennotothe “darkside.”Theengine the centralengine.Theengine intrinsicallysuppliesless the rateofenergytransportby beamsonthetwosidesof © American Astronomical Society • Provided by the NASA Astrophysics Data System Although manyextendedextragalacticradiosourceswith There areatleastthreeinterpretationsoftheapparent (1) Thereisabeamonthedarksidethatintrinsically (2) Thereisanactivebeamonthedarksidebutitssyn- (3) Muchlessishappeningon theapparentlyunjetted but otheraspectsofourdataalsosuggestthatanotherphenomenon,closelycoupledtojetbending,helps prominence correlationislessthanexpectedifthelarger-scalejetshavecharacteristicLorentzfactorsas prominence andasymmetriesofcentralfeatures,jets,counterjets,hotspots.Thecorrelationsbetween candidates areoftenS-symmetricrelativetothejetaxisandtheirhotspotsmoremisalignedthanin lobes isprovidedbypassivelyexpandingthefieldinjets.Thesourceswithpromisingcounterjet linear polarizationpattern,withlowatthecenterandhigh(oftenreaching40%to models inwhichtheaveragejetvelocitydecreaseswithincreasingdistancefromcentralobject.This to determinetheprominenceoffeaturesfarfromcentralregion.Overall,ourdatafavor“tiredjet” high asthoseinthemilliarcsecond-scalefeatures,however.Thisresultisfragilewithinoursmallsample, favor modelsinwhichthekiloparsec-scalejetsinitiallyhavebulkrelativisticvelocities.Theslopeof the prominenceandsidednessoflarge-scalestraightjetsegmentssmall-scalecentralfeatures sources withoutsuchcandidates.Counterjetsmaythereforebeeasiertodetectifthejetschangeorientation 60%) neartheedges.Thispatternmatchesexpectationsofmodelsinwhichmagneticfield compactness andplacementofjettedcounterjettedhotspots.Themodelsmayneedrefinementto makes itharderforthesimplestrelativistic-jetmodelstoaccountsystematicdifferencesin during thelifetimeofsource.Weoutlineimplicationsourresultsforvariousmodels include arangeofLorentzfactorsinthejetsatanygivendistancefromquasar. 1. INTRODUCTION must thereforereverseitspreference(“flip-flop”)occasion- Icke 1983;Rudnick&Edgar1984).Onthisview,theoppos- ally toformsourceswithtwosimilarlobes(Rudnick1982; We selectthesethreepossibilitiesfordiscussionnotbecause these interpretationsofone-sidednessinquasarjetsarein- they areeitherfullycomprehensiveorexclusive,butbecause ing beamswouldbeneitheridenticalnorsteadyintime. representative sampleoftwelvesuchsources. gies oflobesonthejettedandcounterjettedsides,ina the jetdetectionrateandprominencestatistics,(c)to compare ourdata.Manyargumentsfororagainsteachof they providethreeconvenientmodelextremeswithwhichto lined above.Section8summarizesourconclusionsandsug- models ofenergytransportinquasarradiosources.Section7 their mainfeatures.Section5derivesphysicalparametersfor sample ofextended3CRquasars.WeusedtheVLAat4.9 explore anysystematicdifferencesbetweenthemorpholo- and wecannotquantifytheone-sidedness.Wethereforetried conclusive becausethecounterjetsareusuallyundetected gests furtherwork. reviews theirimplicationsforthethreeclassesofmodelout- discusses andsummarizesourmainempiricalresults. the sourcesandexplorescorrelationsamongthem.Section6 introduces terminologythatweusetointerpretandquantify sample, andSec.3detailsourobservingstrategy,calibration GHz tomakesensitive,high-resolutionobservationsofa initial samplewasthe19strongest quasarswithlargestan- gular sizes>10"intherevised 3CRcatalog(Laingetal angular extentoftheirextended (lobe)radioemission.Our and datareduction.Section4presentsthenewimages (a) tofindevidenceofcounterjetemission,(b)quantify source structureswouldbereadily resolvedbythe~0"35 1983). Wechosetheangularsize limitsothatdetailsofthe The restofthepaperdiscusseshowourresultsaffect We selectedasampleofradioquasars bythestrengthand Section 2ofthispaperdescribeshowweselectedthe 2. THESAMPLE 767 1994AJ 108. . 7 6 6B jets werefound.Ifcounterjetsdetected,newconstraints powers aresimilartothesequasars hasalsobeenundertaken parallel VLAstudyofextendedradiogalaxieswhose to theavailableobservingtime, soweselectedasubsample posed ofquasars,itmay,however,bebiasedtowardsources ses. Thesamplesizethereforehad toberestrictedconform u,v plane,theobservationswere madeascontinuoussynthe- compensate thispossiblebiastowardend-onsources,buta concentration onsourcesoflargeangularsizeshouldpartly that areorientedtowardthelineofsightifopticalclas- sification dependsonorientation(e.g.,Barthel1989).Our could beplacedonthealternativemodelsforone-sided ful informationaboutthejets,orsystematicdiffer- appearance ofmostquasarjets.Becausethissampleiscom- ences betweenjettedandcounteijettedlobes,ifnocounter- tected morereadilyinquasarsthanradiogalaxies(Bridle 4.9 GHz.Weconcentratedonquasarsbecausejetsarede- (Fernini etal1993). & Perley1984).Thismaximizedourchancetoacquireuse- (19) Houghetal(1993) (18) Owen&Puschell(1984) (17) Owenetal(1978) (16) Laing,R.A.,inBridle&Perley(1984) (15) Eine&Scheuer(1980) (14) Leahyetal.(1989) (13) Wardle,J.F.C.,inCawthorneetal(1986) (12) Jenkinsetal(1977) (11) Burch(1979) (10) Bentleyetal(1975) (8) Swampetal(1984) (9) Burnsetal(1984) (7) Vermeulenetal(1993) (6) Feminietal(1991) (5) Swampetal.(1982) (FWHM) synthesizedbeamoftheVLA’sAconfigurationat (4) Pooley&Henbest(1974) (3) Miley&Hartsuijker(1978) (2) Laing(1981) (1) Kronberg,P.P.,inBridle&Perley(1984) 768 © American Astronomical Society • Provided by the NASA Astrophysics Data System To obtainbothhighsensitivity and densecoverageofthe BRIDLE ETAL.\TWELVE3CRQUASARS 1 (d) Projectedlargestlinearsizeinh'kpc(usingaFriedmanncosmology (c) Largestangularsizeinarcseconds. (a) RedshiftsàndvisualmagnitudesfromHewitt&Burbidge(1987); (b) Integrated5GHzfluxdensity(mJy)in1986/87onBaarsetal.(1977) 2120+168 3C4321.80517.9640715633,12,13,34,37 1137+660 3C2630.64616.3v1130511983,4,8,14,17,26,28-31 1100+772 3C249.10.31115.7v800531493,4,8,9,14-16,24-27 1704+608 3C3510.37115.3v1260752302,3,8,14,35,36 1622+238 3C3360.92717.5v830281183,4,8,34 1618+177 3C3340.55516.4v626582153,8,12,14,15,22,26,29,32,33 0903+169 3C2150.41118.3v427601963,4,8,2-2,23 0850+140 3C2081.1117.4v56014602,3,9,12,16,20,21 0833+654 3C2041.11218.21370371592-4,9,15-19 0710+118 3C1750.76816.6v690522123,12,14 0229+341 3C68.11.23819780532282,8,12-14 0133+207 3C470.42518.lv1390792623,4,6-11 0017+154 3C92.01218.2149014571-5 NAME 1 IAU 3C with H=10hkms’Mpc',q.5) larger. scale; fromourVLAdataorGregory&Condon(1991),whicheveris o "v" connotesaknownvariable. Table 1.Basicpropertiesoftheobservedquasars. a nv References toTable1 Notes toTable1 1 bCd (mJy) (■)(h'kpc) S LASLLSRefstootherradiodata 5 1- -1 rations. Thedetailedhourangle coveragesandintegration km s”Mpc,g=0.5)atradiowavelengths. projected linearsizesexceedlOOÄkpc(i/=10Ä particular sourcemorphology,orbywhetherajethadprevi- by anyintrinsicradioproperty.Inparticular,wedidnotse- single observingsessionswith the VLA’sAandBconfigu- of 13sourcesincludesall103CRquasarswhoselargest observed, andof3C47,forwhichweobtainedadeepVLA lect fororagainstprominenceofthecentralfeatures,any synthesis at4.9GHzfromFeminietal.(1991).Thissample ously beendetected. compatibility inrightascensionanddeclinationratherthan riods. Thefinalsubsamplewastherebychosenformutual of 12sourcesfromtheinitial19byconsideringhow sources fittedtogetherintothescheduled24hobservingpe- 0 0 The sourceswereobservedfor aslongpossiblein Table 1listsbasicpropertiesofthe12sourcesthatwe 3. THEOBSERVATIONSANDREDUCTIONS (36) Kronbergetal(1980) (35) Riley&Pooley(1975) (34) Feigelsonetal(1984) private communication (37) Swampetal(1986) (33) Houghetal(1992) (32) Wardle&Potash(1982) (31) Zensusetal(1987) (30) Shoneetal,inBrowne(1987) (29) Schilizzietal(1982) (26) Wardle,J.F.C.,privatecommunication (25) Lonsdale&Morison(1983) (24) Laing,R.A.,privatecommunication (28) Browne,I.W.A.,privatecommunication (27) Hough(1986) (23) Wardle,J.F.C.,Potash,R.I.&Roberts,D.H., (21) Menon(1976) (20) Cawthorneetal.(1986) (22) Hintzenetal.(1983) 3.1 Strategy 768 1994AJ 108. . 7 6 6B that of3C286duringeachobservingrun,assuming 3C286 hasfluxdensitiesof7.31and7.26Jyat4.835 and 3C345shouldbenoworsethan0''2. tures onourimagesrelativetothesemeanpositionsfor3C84 tion aresuchthaterrorsinthepositionsofindividualfea- calibration. Theuncertaintiesintheexternalphasecalibra- of 3C84and3C345(Table3)provideourprimaryposition baselines intheinnerthirdofw,i;plane. baselines intheAconfiguration.Theseambiguitieswerere- solved byrestrictingtheinitialantennaphasecalibrationto times ledtoambiguitiesinthephasewraponlonger In poorweather,thistwo-hourphasecalibrationcyclesome- secondary calibratorsnearthetargetsourceswereobserved. h ofonethestrongsources3C84and3C345,no calibration wasinterpolatedfromobservationsmadeevery2 in thehour-anglecoverage.Theprimaryamplitudeandphase determining baseline-basederrorsand(b)minimizinggaps calibration. Ourobservingstrategythereforeemphasized(a) structure (centralfeatures,hotspots,orboth)toallowself- exceeded 0.8ns. with 50MHzbandwidthintwofrequencychannels,centered each observingrunandwereresetifanyoffsetssignificantly fluctuations andalongintegrationtorestrictthesizesof integration toletself-calibrationtracktroposphericphase on 4.835and4.885GHz.Thevisibilitieswereaveragedfor data sets.Theantennadelaysettingswerecheckedbefore 20 s.Thisaveragingtimeisacompromisebetweenshort ing log.Tomaximizesensitivity,theobservationsweremade rived fromthehigh-elevationdata).Table2givesobserv- elevation datawerecalibratedseparatelyusingamodelde- down toanelevationof10°;forthissource,thelow- 20°. (Theoneexceptionwas3C432,whichobserved erally restrictingtheobservationstoelevationanglesabove times weredictatedbytheneedformutualscheduling,gen- 769 BRIDLEETAL.:TWELVE3CRQUASARS 3C432 3C351 3C336 3C334 3C263 3C249.1 3C215 3C208 3C204 3C175 3C 68.1 3C 9 Source Name 3C345 164117.608395410.82 3C263, 3C334,3C336,3C351 3C 84031629.569411951.94 3C9, 3C68.1,3C175,3C204 The fluxdensitiesof3C84and3C345werereferencedto © American Astronomical Society • Provided by the NASA Astrophysics Data System The assumedmeanpositionsoftheunresolvedstructure All sourcescontainedenoughfluxdensityincompact Table 3.Referenceframeforradiopositioncalibration. 29-Mar-86 12- Jul-87 29-Mar-86 29-Mar-86 11- Jul-87 ll-Jul-87 ll-Jul-87 ll-Jul-87 12-Jul-87 4- May-86 5- May-86 5-May-86 Config Date Position (B1950.0) A integ Table 2.VLAobservinglog. time (min) 478 390 403 442 431 448 403 450 390 419 436 327 3.2 Calibration 19-Jul-86 19-Jul-86 19-Jul-86 19-Jul-86 19-Jul-86 19-Jul-86 6-Dec-87 6-Dec-87 6-Dec-87 6-Dec-87 6-Dec-87 6-Dec-87 Config Date 3C432 3C208, 3C215,3C249.1, B integ time (min) 260 228 238 265 289 226 269 152 183 187 70 61 Used toCalibrate Calib Source 3C 84 3C345 3C 84 3C 84 3C 84 3C 84 3C 84 3C 84 3C345 3C345 3C345 3C 84 -14.4 -1.9 -4.1 -2.8 -3.7 -4.0 -5.1 -5.2 -4.4 -3.0 -4.4 min 1.5 (h) -7.1 max 4.7 4.0 7.8 3.8 2.0 2.8 2.9 4.6 4.1 6.1 1.6 (h) the primarybeam,high-resolution imageswerecon- low-resolution imagingshowed significantconfusionwithin the imagescouldbedeconvolved withanefficientFFT-based times theareaofskycontainingsignificantemission,sothat Cotton-Schwab ungridded-subtractionCLEAN algorithm structed inseveralpiecesusing themoreCPU-intensive CLEAN algorithm(Clark1980—the AIPStaskapcln).If sources werethenimagedathighresolutionoverleastfour sources orunexpectedlargescalestructure.Mostofthe mary beamatlowresolutiontolocatepossibleconfusing the delaytrackingcenterduringself-calibration. but manydeephigh-resolutionimagesofbrightextended baseline-based calibrationerrors.Theiroriginisuncertain, aging thephasedriftsofbrightfeatures(hotspots)farfrom software encountersuchlimits.Theymayresultfromaver- radio structuresmadeusingtheVLAandstandardAIPS time-dependent calibrationerrorsortotime-independent images. Theremainingimperfectionsinthedeconvolvedim- ages thereforecannotbeattributedeithertoantenna-based sponses tothestrongestcompactfeatures)remainedinsome limitations ondynamicrange(unremovablesidelobere- most imagestowhichtheywereapplied,buttheprincipal 3C84. Thesebaseline-basedcorrectionsnoticeablyimproved this occurred,weappliedfurtherbaseline-basedamplitude produce imageswhoseoff-sourcefluctuationswerewithin and phasecorrectionsderivedfromourobservationsof were producedfromthecombined(AplusBconfiguration) After thiscross-calibration,thefinalhigh-resolutionimages about 50%ofthoseexpectedfromthethermalnoise.When figuration databyreferencingthemintheouteru,vrangeto tion andtoadjusttherelativeamplitudecalibrationof data, sometimeswithfurtheriterationsofself-calibration. B configurationdatawerealignedinphasewiththeAcon- to theself-calibrationprocedurerefinephasecalibra- throughout laterself-calibrationcyclesusingtheSchwab antennas (withoutchangingthemeanamplitudescale).The hot spots.Thepositionsofthesefeatureswerepreserved These wereusuallythecentralfeaturesand/orpeaksof a wellcalibratedAconfigurationCLEANcomponentmodel. primary (external)calibrationwereusedtodeterminethepo- (1980) algorithm.CLEANcomponentmodelswerefedback sitions ofthebrightestcompactfeaturesineachsource. secondary (self)calibration.Preliminaryimagesbasedonthe polarization correctionsaregenerallyaccuratetobetterthan 0.1% and3°. mined fromtheobservationsof3C84;individualantenna The on-axisinstrumentalpolarizationpropertiesweredeter- tion angleis33°.Theaccuracyofthesecalibrations^2°. ing observationsof3C286,assumingthatitsEvectorposi- 3C286 shouldalwaysbeaccurateto^1%. scale oftheimagesrelativetotheseassumedvaluesfor 4.885 GHz,respectively.Thecalibrationoftheamplitude The datawereinitiallyimagedoverthewholeVLApri- For somesources,thisprocedureconvergedbutfailedto The NRAO’sAIPSsoftwarewasusedforallimagingand The polarizationpositionanglescaleswerecalibratedus- 3.3 Imaging 769 1994AJ 108. . 7 6 6B 2 well &Evans(1985—theAIPStasksVMandVTESS).For 770 BRIDLEETAL.:TWELVE3CRQUASARS beamwidth (e.g.,Cornwell&Evans1985). portant tointerpretingtheradiomorphologiesarepoorlyre- ing ofthemostintensecompactstructurefollowedbyMEM tures wascheckedbyalsomakingMaximumEntropy the MEMdeconvolutiontoextractmorphologicalinforma- of therestoringbeamsaremeanmajorandminor ments fromtheCLEANedimages.Thedeconvolved erwise noted,however,wemadeallquantitativemeasure- deconvolution oftheextendedemission.Exceptwhereoth- some sources,theoptimalprocessingprovedtobeCLEAN- Method (MEM)deconvolutions,usingthemethodofCorn- tion onscalessmallerthantheconventionalsynthesized solved byconventionalimageprocessing.Fortheseweused sions inthiscircularizationstepwere<5%;theworstcases data. Formostimages,thecorrectionstobeamdimen- synthesized beamderivedwithuniformweightingofthem,i; axes ofthebestGaussianfittocentralpeak“dirty” siduals fromtheCLEANcomponentsubtraction.Thewidths Gaussian convolvingbeamsandweresuperposedonthere- CLEAN componentmodelswererestoredwithcircular polarized intensitiesPwereadjustedfortheRiceanbias posed onselectedcontoursfromtheStokes/images.The tional tothedegreeoflinearpolarizationp=Vß+U/I The vectordisplaysshowvectorswhoselengthsarepropor- intensity contourmapsareoftheimagesmadeinStokesI. presented below.Intheaccompanyingfigures,total- are —10%. (Schwab 1984—theAIPStaskMX).Therealityoffaintfea- FWHM oftheGaussianrestoringbeam. within observationalerrorswith thebestavailablepositionformer,ifpresentinradiosources, wouldbeclassifiedasjet Bridle attheNationalRadioAstronomyObservatory. and whosepositionanglesarethoseoftheEvectors,super- & Fernini1989).Theresolutionquotedforeachimageisthe approximate correctionsintheAIPStaskCOMB(seeLeahy (e.g., Vinokur1965;Wardle&Kronberg1974)usingthe spot” areusedbelowinwaysthat requirecarefuldefinition.oblique,sothattheflowremains supersonicbeyondthem, 3C432 3C351 3C336 3C334 3C263 3C249. 3C215 3C208 3C204 3C175 3C 68. 3C 9 © American Astronomical Society • Provided by the NASA Astrophysics Data System For afewsources,somebrightsubstructuresthatareim- Table 4summarizesthemainparametersofimages A “centralfeature”isanunresolved featurecoincidingto FITS tapesoftheimagedataareavailablefromAlanH. The terms“centralfeature,” “jet,” “lobe,”and“hot FWHM 0.34 0.35 0.36 0.35 0.37 0.37 0.34 <") A+B configuration noise r.m.s.Figs. r.m.s. Peakto (kiJy) (I) 20 Table 4.VLAimagecatalog. 13900 7200 2700 7650 3850 3400 4300 1050 5900 1900 3800 5900 4.1 Terminology 4. THEIMAGES 27,28 25,26 22,23 20,21 34,35 32,33 16,17 12,13 10,11 8,9 5,6 1,2 FWHM 1.25 1.15 1.00 1.10 1.20 1.17 1.10 1.30 1.10 1.30 (") noise r.m.s. B configuration r.m.s. Peakto (M-Jy) (I) 52 3100 6900 5400 3800 9500 3000 4600 1190 3800 7600 3600 600 18,19 14,15 jet. jets containinternal,local,brightnessenhancementsthatwe for theopticalquasar.Althoughsuchfeaturesarefrequently for severalreasons.Itispoorlydefined,resolution- referred toas“cores,”weconsiderthistermbeprejudicial wide (afterdeconvolvingthesynthesizedbeam),(b)sepa- gines” ofthesources,ratherthanwithopaquebasea features wereconsideredtocoincidewiththe“centralen- pirical definitionoftheterm“hotspot”todistinguishalim- called, “hotspots,”butthereisnowellaccepteddefinition have localbrightnessenhancementsthatareconventionally duced bythesource.Manylobesinpowerfulradiosources generically describeas“jetknots.” the nucleusofparentobjectwhereitisclosesttoit.Many rable athighresolutionfromotherextendedstructure(ifany) Bridle (1986),i.e.,itis(a)atleastfourtimesaslong dependent, andisarelicofphysicalmodelinwhichthese brightest featureinthelobe,(b)haveasurfacebrightness hancements injetsandlobes.Weareattemptingtherebyto ited subsetofsuchfeaturesfromallotherbrightnessen- of thisterm(Perley1989;Laing1989).Weuseanewem- either spatiallyorbybrightnesscontrast,and(c)alignedwith ing thesynthesizedbeam)thatis<5%oflargestdiam- tinguish hotspotsfromthejetknotsthatmaybeonlyminor termination. Ourprime,butnotouronly,concernistodis- pearance, (d2)anabruptchangeofdirection(i.e.,byatleast than theendofjet,whichisdefinedby(dl)itsdisap- condition: (d)thehotspotmustbefurtherfromnucleus eter ofthesource.Ifajetisdetectedthenweaddfurther ing emissionand(c)havealinearFWHM(afterdeconvolv- that ismorethanfourtimesgreaterofthesurround- lows. Ifnojetisdetected,thenthehotspotmust:(a)be disturbances withinanongoing,continuousjet. apparent directionand/orcollimationofajet,oritsabrupt isolate aclassoffeaturethatmarksmajorchangesinthe than afactoroftwo(asmeasuredbythewidthsanyridge- 30° withinaknotdiameter),or(d3)decollimationbymore pression and/orparticleaccelerationinaflow,sotheymay properties willbedescribedasajet,althoughitislikelythat knots. Noemission“downstream”ofafeaturewiththese tinuing flow). like orknot-likefeaturesalongtheputativepathofanycon- pend onlyonsurfacebrightnessandangularorlinearsize, from majordisruptionsatnearly perpendicularshocks.The help todistinguishcaseswhere shocksinajetarehighly ten cannotseparatejetknotsand hotspots.Ouraddedingre- different physicalprocessesmaydominate.Bothjetknots such emissioncouldcontainongoingflows. dient ofcontinuityjetproperties throughafeaturemay independent ofrelationshipswithsurroundingstructure,of- share manyobservablecharacteristics.Definitionsthatde- and hotspotsarelikelytoberegionsofshock-drivencom- A “jet”isanarrowfeaturethatmeetsthecriteriausedby The “lobes”consistofalltheotherradioemissionpro- Our empiricaldefinitionofahotspotisthereforeasfol- We aretryingtodistinguishbetweenfeaturesinwhich Condition (d)isintendedtoseparatehotspotsfromjet 770 PQ UD r" 771 BRIDLE ETAL. : TWELVE 3CR QUASARS 771 ooo knots; the latter would be classified as hot spots. straight in PA 150° until the bright feature F 278 from the ^0 Note that by our definition there can be only one hot spot central feature. F is the most compact feature south of the per lobe. The features often described in the literature as central feature, as determined both by model-fitting to Fig. 1 “secondary hot spots” will here be regarded as fine structure and from an MEM deconvolution at 0712 resolution (not in the lobes, but will not be referred to as hot spots. shown). Feature F marks a significant change in the character We acknowledge that the results of applying the above of the jet, which brightens just before it. The average posi- criteria for jets, jet knots, and hot spots may depend on an- tion angle of the jet between F and I is also conspicuously gular resolution, at least until all but a few features of a radio different from that before F, but we do not resolve the struc- source are fully resolved. In particular, the criterion that a hot ture well enough to be sure where this realignment starts. spot should have a FWHM<5% of the largest angular diam- There is weak emission between the compact central fea- eter may be insufficiently stringent. We believe, however, ture D and the brightest part of the northwest lobe, with local that these criteria form a useful basis for classifying features peaks at C and B. These features could be part of a counterjet of quasar images at the relative resolution achieved in these leading into this lobe. A curved ridge extends northwest from observations. B and crosses the lobe before reaching the hot spot A. Some or all of this curved ridge may also be part of a bent coun- 4.2 3C9 teijet with a further peak near the first bend between B and A. The source has an overall S symmetry, but the jetted arm Figure 1 shows the total intensity image at 0736 resolution is about twice as long as the counterjetted arm in projection. from the combined A and B configuration data. This small Figure 2 shows the polarization data also at 0736 resolu- (14", 51h~x kpc) source has the highest red shift in the tion, superposed on contours from Fig. 1. The vector distri- sample [normally given as z=2.012 but see also Tytler & bution is locally confused, especially in the inner 4" (\6h~l Fan (1992) for a revised estimate of 2.0178]. Kronberg et al kpc) on the jetted side. Beyond 4", the E vectors tend to be (1991) suggested that the source is gravitationally imaged by perpendicular to the local jet axis, and to the outer edges of a galaxy about 10" away, but this suggestion has yet to be the lobes. The strong discontinuity in the E-vector directions confirmed by optical data (see also Yee et al. 1993). near feature F further suggests that this feature marks a point The compact feature D coincides with the optical identi- where either the jet or the surrounding medium, or both, fication. The jet is exceptionally knotty and its terminus in change character substantially. The trend for the E vectors to the southeast lobe is ill defined. Feature K meets our criteria be perpendicular to the jet axis and to the lobe edges further for the hot spot because of its brightness contrast and the from the central feature casts doubt on the likelihood that the abrupt change in direction of the ridge line in its vicinity. The major deflections of the jet result from gravitational imaging, jet therefore consists of features E through J. It is relatively as such imaging would not preserve these relationships (Kronberg et al. 1991). The degree of polarization in the jet reaches —30% near knot G. The degree of polarization in the 3C9 Total Intensity 4.9 GHz

Fig. 1. Distribution of total intensity (Stokes I) over 3C 9 with 0"36 (FWHM) resolution. D is the central feature and K is the jetted hot spot. C is the counteijet candidate, and parts of the ridge through B to the counterjetted hot spot A may be an extension of the counteijet. Contours are drawn at -1 (dotted), 1, 2, 3, 4, 6, 8, 10, 12,16, 20, 30, 40, 60, 80, 100, 200, 300, Fig. 2. Distribution of degree of linear polarization p and E-vector position 400, 600, 800, and 1000 times 60 /¿Jy per CLEAN beam area. The peak angle x over 3C 9 at 0'.'36 resolution, superposed on contours from Fig. 1. A intensity is 86.3 mJy per CLEAN beam area. vector of length 1" corresponds to /? = 1.

© American Astronomical Society • Provided by the NASA Astrophysics Data System PQ UD r" 772 BRIDLE ETAL. : TWELVE 3CR QUASARS 772 ooo lobes is greatest at their outer edges, where it reaches —40% elongated feature D, that appears to be a bright segment of a ^0 in the southeast (jetted) lobe and —30% in the northwest jet pointing toward a ridge in the north lobe. There is an (counteijetted) lobe. isolated, extended, bright knot (F) on the likely path of a counterjet, directly opposite the peak of feature D. At this 4.3 3C68.1 resolution, there are several subsidiary peaks (G,H,I) in the south lobe. Figure 3 shows the total intensity image at 1"1 resolution Figure 4 shows the polarization data at l .'l resolution su- from the B configuration data only. The source is a wide 1 perposed on contours from Fig. 3. In the lobes, the E vectors (53", 228h' kpc) double with symmetrically placed but are perpendicular to the adjacent boundary, and confused asymmetrically bright lobes (the integrated flux density of near the bright hot spots. At this resolution, the north jet is the northern lobe is 16 times that of the south lobe at 4.9 only weakly (9%) linearly polarized. GHz). The weak central feature E had not previously been Figure 5(a) shows the total intensity of the north lobe, jet, detected. Its radio position agrees well with that of the opti- and the central feature at 0"35 resolution from the combined cal identification. Between feature E and the north lobe is an A and B configuration data. Figure 5(b) shows the south lobe

3C68.1 Total Intensity 4.9 GHz Degr. of Polarization & Posn. Angle 34 11 00 3068.1 4.9 GHz

10 45

z< o_j QHI

02 29 27.8 27.4 27.0 26.6 RIGHT ASCENSION (B1950) Fig. 3. Distribution of total intensity (Stokes /) over 3C 68.1 with I'.'l 02 29 27.8 27.4 27.0 26.6 (FWHM) resolution. E is the central feature and B is the jetted hot spot. D, RIGHT ASCENSION (B1950) C, and the ridge joining them are the jet, and F is the counteijet candidate. Polarization scale: 1 arcsec = 0.40 Contours are drawn at -1 (dotted), 1, 2, 3, 4, 5, 6, 8, 10, 12, 14,16, 20, 30, 40, 60, 80, 100, 200, 300, 400, 500, 600, 800, 1000, 1200, and 1400 times Fig. 4. Distribution of degree of linear polarization p and E-vector position 150 jüüy per CLEAN beam area. The peak intensity is 311 mJy per CLEAN angle x over 3C 68.1 at T.'l resolution, superposed on contours from Fig. 3. beam area. A vector of length 1" corresponds to /?=0.4.

3C68.1 Total Intensity 4.9 GHz 3C68.1 Total Intensity 4.9 GHz

02 29 27.7 27.6 27.5 27.4 27.3 27.2 27.1 27.0 RIGHT ASCENSION (B1950) (b)

Fig. 5. Distribution of total intensity (Stokes I) over 3C 68.1 with 0'.'35 (FWHM) resolution, (a): North lobe, jet (D, C and the ridge joining them), and central feature (E). Contours are drawn at -1 (dotted), 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, 30, 40, 60, 80, 100, 120, 160, 200, 300, 400, 600, 800, 1000, and 1200 times 80 fúy per CLEAN beam area, (b): South lobe and counterjet candidate (Fl, F2). Contours are drawn at -1 (dotted), 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, and 16 times 60 /¿Jy per CLEAN beam area. The peak intensity is 124 mJy per CLEAN beam area. and the possible counterjet knot F at the same resolution. The feature D projected toward feature C is taken to be an exten- sensitivity of these images near the north lobe and jet knot D sion of the jet in what follows. There are also several reasons is limited by sidelobe responses to the northern hot spot. to believe that feature C is a jet knot. It cannot be the hot Both D and F are resolved along the major axis of the spot by our definition, as feature B has higher surface bright- source, but their morphologies are dissimilar. The jet seg- ness. It might be considered a secondary feature of the lobe ment D is well resolved and qualifies as a jet in its own right (not in the path of the jet), but there is evidence that a sinu- (Table 8) using the 4:1 axial ratio criterion for jethood. The ous ridge joins its west side to B and its east side to the counterjet candidate F contains a bright, compact knot FI extension of the jet into the north lobe. Feature C may there- and a faint extension F2 toward the southeast. We consider this combination a counterjet candidate rather than a con- fore mark the location of a large change in the direction and firmed counterjet, as it does not satisfy the 4:1 axial ratio the surface brightness of the jet. In what follows, we consider criterion. that B, which is the brightest feature in the lobe and lies on The bright emission complex in the north lobe is resolved the ridge emanating from C, is a hot spot marking the termi- into multiple features (A, B, C and extensions), as previously nus of a jet that deflects and brightens significantly at C. B documented by Swamp et al (1984). A narrow feature ex- itself shows evidence for compact substructure (see Table tending through the center of the north lobe along the axis of 12). An image with improved angular resolution and sensi-

3C68.1 4.9 GHz polarization increases from <20% to —50% toward the outer Degree of Polarization & Position Angle edges of the lobe. This resolution also shows that the counterjet candidate (not shown in Fig. 6) is about 5% linearly polarized at the peak FI, and about 15% polarized at the south and west edges of the more extended emission F2 near this peak.

4.4 3C175 Figure 7 shows the total intensity image at 1'.'3 resolution from the B configuration data only. The source is a wide (52", 2\2h~l kpc) double with asymmetrically placed lobes that have faint extensions toward the center of the source. A previously unknown jet links the central feature to the fainter, further southwest lobe. Although the contour at 100 ¿dy per CLEAN beam area apparently extends along a plausible counterjet path just to the east of the central feature, this detail is close to the level of the peak fluctuations far from the lobes. As there is no evidence for elongated emission here in our higher-resolution data (see Fig. 8), we conclude that there is no credible evidence for a counterjet. Figure 8 shows the total intensity image at 0'.'38 resolution from the combined A and B configuration data. The inner jet follows PA237!4±0!3 for the first 12" (49&-1 kpc) between the compact central feature M and knot I, but further out it curves southward toward feature D in the southwest lobe. It expands steadily between features L and H. Beyond H the transverse brightness profile is asymmetric, with sharper gradients to the northwest. Using our classification scheme, the compact feature C is the hot spot, based on the evidence for a large, abrupt change in the ridge line direction and dramatic decollimation beyond it. Note, however, that the less compact feature A protrudes through the wall of the lobe at its southwest edge and is close to the continuation of the original line of the jet. Although these are attributes of features that might be called hot spots in other sources, there is insufficient brightness contrast be- 02 29 27.5 27.4 27.3 27.2 27.1 27.0 26.9 26.8 tween A and the nearby lobe emission for A to meet our RIGHT ASCENSION (B1950) Polarization scale: 1 arcsec = 1.00 definition of a hot spot. (Feature A therefore fails to meet our definition in its own right as well as by comparison with C). The northeast lobe is strongly edge-brightened and has the compact hot spot (O) at its outermost edge. This hot spot is Fig. 6. Distribution of degree of linear polarization p and E-vector position 4 angle \ over the north lobe and jet of 3C 68.1 at 0'.'35 resolution, superposed at the vertex of a bright ‘U”-shaped region of emission that on contours from Fig. 5. A vector of length 1" corresponds to p = l. extends away from and behind it on both sides. Note that O is displaced from the axis of the inner jet projected into the northeast lobe, but this axis intersects the narrower northern tivity would be useful to check these interpretations of the arc of the U-shaped emission region near the hot spot. The northern jet and of the (A+B+C) emission complex. outer boundaries of both lobes are delineated by sharp The most compact feature of the south lobe at this reso- brightness gradients, to the south and west in the southwest lution is H, but this has insufficient brightness contrast with lobe and to the south and east in the northeast lobe. other features of the lobe to be considered a hot spot by our Figures 9(a) and 9(b) plot the polarization data for the definition. lobes on contours from Fig. 8. The degree of linear polariza- Figure 6 shows the high-resolution polarization data for tion of the jet varies from <14% at knot I to 31% at knot K, the north lobe and jet, superposed on contours from Fig. 5(a). but the signal is marginal except near the first knot and for There is no significant linearly polarized emission from the about 5" before feature D. The E vectors are within 10° of jet at this resolution. The increased resolution also reveals a perpendicular to the jet axis at knots L and K but become well organized pattern in the lobe’s polarization: the E vec- closer to parallel by feature D, where the degree of polariza- tors tend to be perpendicular to the adjacent lobe boundary, tion again rises to 29%. On the extended ridges within the and to the ridge line of the probable outer jet. The degree of lobes, the E vectors are generally perpendicular to the ridge

07 10 16.5 16.0 15.5 15.0 14.5 RIGHT ASCENSION (B1950) 14.0 13.5

Fig. 7. Distribution of total intensity (Stokes/) over 3C 175 with 1'.'3 (FWHM) resolution. Contours are drawn at —1 (dotted), 1, 2, 3, 4, 6, 8, 10, 12, 14, 16, 20, 24, 30, 40, 50, 60, 80, 100, 120, 140, 160, 200, 240, 300, 400, 500, 600, 800, and 1000 times 100 /Jy per CLEAN beam area. The peak intensity is 145 mjy per CLEAN beam area.

3C175 Total Intensity 4.9 GHz

07 10 16.5 16.0 15.5 15.0 14.5 14.0 13.5 RIGHT ASCENSION (B1950)

Fig. 8. Distribution of total intensity (Stokes /) over 3C 175 with 0'.'38 (FWHM) resolution. M is the central feature and C is the jetted hot spot. O is the counterjetted hot spot and there is no counteijet candidate. Contours are drawn at -1 (dotted), 1, 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, 30, 50, 70, 100, 120, 160, 200, 300, 500, 700, 1000, and 1200 times 50 /¿Jy per CLEAN beam area. The peak intensity is 65.0 mJy per CLEAN beam area.

© American Astronomical Society • Provided by the NASA Astrophysics Data System PQ UD r" 776 BRIDLE ETAL.: TWELVE 3CR QUASARS 776 ooo 3C175 Degree of Polarization & Position Angle 4.9 GHz A jet consisting of a string of bright knots (I to E) super- ^0 posed on fainter extended emission links the compact central feature J to a recessed bright feature (D) in the west lobe. The jet axis is roughly perpendicular to the extended optical line emission. The jet is straight for most of its length but deflects toward the north shortly before reaching D. There are further bright features (C and B) downstream before the extended edge-brightened region A. Feature B is noticeably elongated perpendicular to the direction to D and could be considered a candidate for the hot spot. Only D meets our definition, however, because (a) its surface brightness ex- ceeds that of B by a factor of 10 or more, (b) there is a large change in ridge line direction at its location, and (c) there is no evidence for jet emission beyond it that is as well collimated as the emission leading toward it. There is no evidence of a counteijet on the east side although there is a bright hot spot (L) at the eastern edge of the east lobe. Figures 11(a) and 11(b) plot the polarization data on contours from Fig. 10. The jet has —20% to —30% linear polarization at knots I, G, F, and E; the E vectors are nearly perpendicular to the jet axis at I and F but are misaligned 3C175 Degree of Polarization & Position Angle 4.9 GHz with it at G and E. On the extended ridges within the lobes, the E vectors are generally perpendicular to the ridge lines. Near the brighter features D to B, the distributions are more complex. The highest degrees of polarization (50% to 60%) occur near the edges of the lobes—north of knot B, west of knot A, and on the trailing northern and southern boundaries of the east lobe.

4.6 3C 208

Figure 12 shows the total intensity image at 037 resolution from the A and B configuration data. The source is 14" (60/i-1 kpc) in extent with symmetrically placed lobes. A jet consisting of several elongated knots (D,E,F) embedded in fainter emission links the compact feature G to a recessed hot spot (B) in the west lobe. B is the hot spot because it is (a) the brightest feature in the lobe (confirmed by an MEM image not shown here) and (b) the apparent terminus of the jet. The jet is straight for most of its length, but deflects toward Fig. 9. Distribution of degree of linear polarization p and E-vector position the south shortly before reaching B. There is no evidence of angle x over 3C 175 at 0'.'38 resolution, superposed on contours from Fig. 8. a narrow counterjet on the east side. It is unclear how the A vector of length 1" corresponds to p = l. (a): Southwest lobe, (b): North- elongated, diffuse feature (H) is related to the other emission east lobe. from the east lobe, but because it is resolved in all directions there is no strong reason to associate it with a counterjet. It lines. Near the hot spots, the distributions are more complex. might, however, prevent detection of a narrow counteijet if The highest degrees of polarization occur near the edges of one took a curved route between G and the hot spot J in the the lobes, 35% to 45% near knot A, and 40% to 55% north of east lobe. feature B. Figure 13 plots the polarization data superposed on contours from Fig. 12. The jet is strongly (40% to 45%) linearly 4.5 3C204 polarized at knots D and F. The detected E vectors are within 15° of perpendicular to the jet axis at knot E and beyond, but Figure 10 shows the total intensity image at 034 resolu- are misaligned by about 30° with this direction at knot F. On tion from the A and B configuration data. The source is about the extended ridges within the lobes, the E vectors tend to be 37" (159h-1 kpc) in extent with symmetrically placed lobes, perpendicular to the ridge lines. Near the hot spots B and J, both of which have faint extensions toward the south. the distributions are more complex. The highest degrees of Bremer et al. (1992) report [O n] emission extending ~8" polarization (25% to 40%) in the lobes occur near their south and ~4" north of the quasar. edges.

Fig. 10. Distribution of total intensity (Stokes /) over 3C 204 with 0734 (FWHM) resolution. J is the central feature and D is the jetted hot spot. L is the counteijetted hot spot and there is no counterjet candidate. Contours are drawn at —2 and —1 (dotted), 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, 30, 40, 60, 100, 200, 300, and 500 times 70 yuJy per CLEAN beam area. The peak intensity is 42.4 mJy per CLEAN beam area.

3C204 Degree of Polarization & Position Angle 4.9 GHz

08 33 21.0 20.5 20.0 19.5 19.0 18.5 RIGHT ASCENSION (B1950) Polarization scale: 1 arcsec = 1.25

Fig. 11. Distribution of degree of linear polarization p and E-vector position angle x over 3C 204 at 0734 resolution, superposed on contours from Fig. 10. A vector of length 1" corresponds to p = 125. (a): West lobe, jet and central feature, (b): East lobe and central feature.

Fig. 12. Distribution of total intensity (Stokes I) over 3C 208 with 0"37 (FWHM) resolution. G is the central feature and B is the jetted hot spot. J is the counterjetted hot spot and there is no counteijet candidate: the broad feature H is considered to be confusing lobe emission (see text). Contours are drawn at -1 (dotted), 1, 2, 3, 4, 5, 6, 8, 10,12, 16, 20, 30, 50, 70,100,120, 160, 200, 300, 500, 700,1000, and 1200 times 100 //Jy per CLEAN beam area. The peak intensity is 145 mJy per CLEAN beam area.

4.7 3C 215 be a counterjet, linking the weak feature B to the region near the peak of feature A. [The ridge line of this counterjet can- A 2.2 mJy source at (B1950.0) 09h 03m 48?90, +16° 58' h m didate is marked by large perturbations in the 2, 6, and 16 49:3 and a 1.6 mJy source at (B1950.0) 09 03 43?29, +16° 57' 27"0 are not shown in our figures but their effects were times 75 /Jy/beam contours between B and A in Fig. 14(a), subtracted from all images of 3C 215. Neither of these and by smaller perturbations in all the other contours along sources aligns with the radio structure of 3C 215 in any way its path—see also the grey scale representation in Fig. 14(b)]. that suggests a physical relationship to the quasar. Figure 15, also at r.'2 resolution, plots the polarization Figure 14(a) shows the total intensity image at 1'.'2 reso- data on contours from Fig. 14(a). At this resolution, the po- lution from the B configuration data only. The source has a larization structure of the jet is smeared by the beam, but a complex structure —60" (19kpc) in extent. The com- complex distribution of polarization is evident across both pact feature C coincides with the optical identification. The lobes. The degree of polarization is greatest (45% to 60%) on north lobe is edge-brightened and broad with an extended the south and west edges of the north lobe and in the south region of enhanced emission that peaks at A. The south lobe lobe immediately below the jet. The E vectors are roughly is edge-darkened and resembles a multiply twisted plume. A perpendicular to the plume-like extensions of the south lobe, jet enters it on a twisted path almost at right angles to the and to the ridge line of A. Elsewhere, the polarization distri- axis of elongation of the plume on its southward path. There bution is complex and the E vectors show no simple (parallel is an elongated spine of emission in the north lobe that may or perpendicular) relationship to the major features.

3C208 Degree of Polarization & Position Angle 4.9 GHz

Fig. 13. Distribution of degree of linear polarization p and E-vector position angle x over 3C 208 at 0"37 resolution, superposed on contours from Fig. 12. A vector of length 1" corresponds to p = l.

© American Astronomical Society • Provided by the NASA Astrophysics Data System Fig. 14. Distribution of total intensity (Stokes/) over 3C 215 with 1"2 (FWHM) resolution. C is the central feature and G is the jetted hot spot. The counterjet candidate is B and the faint ridge linking it to A. (a): Contours drawn at —1 (dotted), 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, 24, 30, 40, 60, 80, and 100 times 75 /¿Jy per CLEAN beam area. The peak intensity is 16.2 mly per CLEAN beam area, (b): Greyscale display emphasizing the flux density range containing the counterjet candidate.

3C215 Degree of Polarization & Position Angle 4.9 GHz Figure 16 shows the total intensity image at 0"37 resolution from the A and B configuration data. Figure 17(a) shows an enlargement of the inner region, which includes a series of bright curved knots (D,E,F) marking major bends in the path of a multiply twisted jet. A higher-resolution MEM deconvolution of this region shows feature G to be much brighter and more compact than the immediately preceding jet knots E and F. We classify G as the hot spot because it is also the site of a sudden change in the ridge line direction. (It meets our brightness contrast criterion for a hot spot on the normal high-resolution image after deconvolution of the synthesized beam.) The diffuse feature H resembles a strongly, but smoothly curved section of jet, however, so that G might also be clas- sifiable as a jet knot. On this alternative interpretation, there would be no hot spot terminating the jet. This might be consistent with the lobe’s plume-like morphology, which resembles that of a low-power Fanaroff-Riley (1974) Type I source. The north lobe also lacks a clear hot spot, although it is edge-brightened. Figure 17(b), also at 0'.'37 resolution, plots the polarization data for the jet and its environs on contours from Fig. 17(a). The jet knots are —10% to —20% linearly polarized. In most regions of the jet, the E vectors are perpendicular to the curved ridge line, and at the hot spot G, they are parallel Fig. 15. Distribution of degree of linear polarization p and E-vector position angle x over 3C 215 at 1"2 resolution, superposed on contours from Fig. 14. to the incoming jet direction (as expected if it indeed marks A vector of length 1" corresponds to p=0.33. an abrupt compression of an incident flow). Much of the © American Astronomical Society • Provided by the NASA Astrophysics Data System PQ UD r" 780 BRIDLE ETAL.: TWELVE 3CR QUASARS 780

3C215 Total Intensity 4.9 GHz ridge (L) along its southern boundary. A jet enters it on its extreme southern edge and terminates abruptly at K, only T.l (22/z-1 kpc) from the central feature D. There is enhanced emission at C and B along a plausible counterjet path from the central feature D toward region A in the west lobe. Figure 19, also at 171 resolution, plots the polarization data on contours from Fig. 18. At this resolution, the polarization structure of the jet is smeared by the beam, but a complex distribution of polarization is evident across both lobes. The degree of polarization is greatest at the edges of the lobes, particularly east of feature K at the end of the jet, where it reaches 55% to 65%. The E vectors are roughly perpendicular to the main ridge in the east lobe and to the outer boundaries of the west lobe. Elsewhere, the polarization distribution at this resolution is complex and the vectors show no simple (parallel or perpendicular) relationship to the major features. Figure 20 shows the total intensity of the jet and west lobe at 0735 resolution from the combined A, B, and C configuration data. All structures in the east lobe are fully resolved. The jet bends at least twice, near E and F, on its path to the resolved terminal hot spot K at its east end. A feature suggested by this image, and strongly supported by a higher- resolution MEM deconvolution, is that the jet bends sharply to the north and turns south again before entering the hot spot K from the northwest. There is also a curious, extended feature (H) running north-south that appears to connect to Fig. 16. Distribution of total intensity (Stokes I) over 3C 215 with 0'.'37 the jet near its most southern point, just west of knot I. A (FWHM) resolution. C is the central feature and G is the jetted hot spot. The broad ridge joins the enhanced southern boundary feature L counterjet candidate is B and a faint ridge linking it to A (see also Fig. 14). Contours are drawn at -1 (dotted), 1, 2, 3, 4, 6, 8,10,12,16, 20, 30, 50, 70, in the outer part of the east lobe to the region near the jet. 100, and 200 times 60 /¿Jy per CLEAN beam area. The peak intensity is The hot spot A in the west lobe is well resolved, with a hint 16.5 mJy per CLEAN beam area. of a shell structure reminiscent of that in the north lobe of 3C 219 (Perley et al. 1980; Clarke et al. 1992). region around the jet segment from E to G is >60% polar- The emission along the putative counterjet path is a nar- ized. row elongated ridge for the first 3" from the compact feature The relationship of the extended hook-like feature H to D, but peak C resolves into a diffuse arc whose status as the jet is unclear. The E vectors in this region are perpen- counterjet-related emission is arguable. This arc is similar in dicular to the boundaries of the extended emission. Both the size and luminosity to the “rings” in Hercules A (Dreher & polarimetry and the total intensity data are consistent with Feigelson 1984). Feature B, also on a plausible path for a the region north of the jet being the brightest part of a counteijet, has a similar flux density and size but is less twisted plume that eventually meanders south to form the obviously ring-like. edge-darkened south lobe. Figure 21 plots the polarization data at 0735 resolution on 3C 215 is evidently an ambiguous source. It lacks many contours of total intensity. There is little polarization de- characteristics typical of strong sources, except for the com- tected within 4" of the central feature, and the degree of pact appearance of knot G in the MEM image. It is notewor- polarization peaks at 25% near knot I. The E vectors are thy that this source, which has the most distorted jet and lobe oblique to the local ridge line of the curved jet at several structures in our sample, also has the longest continuous locations, notably knot E and in the region south of feature counterjet candidate. H. The polarization structure in the east lobe around the jet is complex, with high (65% to 75%) polarizations near the end 4.8 3C 249.1 of the jet. The polarization in the west outer lobe is well organized with the E vectors generally perpendicular to the Figure 18 shows the total intensity image at lr.T resolution adjacent lobe boundary, but the polarization distribution ap- from the B configuration data combined with data from a pears more confused in the inner lobe. The highest degrees snapshot observation in the C configuration kindly made of polarization are again at the edges of the lobes, 45% to available to us by R. Barvainis. The two lobes are asymmet- 55% on the south edge and 35% to 45% on the north edge. ric in size, intensity and surface brightness. The structure is No significant polarization is detected near the putative —53" {149h~l kpc) in extent. The west lobe is edge- counterjet features. brightened with a well resolved hot spot (A) near its western Richstone & Oke (1977) and Boroson & Oke (1984) de- end. The east lobe is edge-darkened except for a resolved scribe an emission line system extending for several arcsec-

3C215 Degree of Polarization & Position Angle 4.9 GHz

Fig. 17. (a): Enlargement of jet and north part of south lobe from Fig. 16. (b): Distribution of degree of linear polarization p and E-vector position angle x near the jet in 3C 215 at 0'.'37 resolution, superposed on contours from (a). A vector of length 1" corresponds to p = l. onds around the quasar, plus an extended optical continuum metrically placed and unequally bright, the jetted lobe being that may be of stellar origin. brighter and closer to the central feature C. A previously undetected jet links C to a bright hot spot (K) in the east 4.9 3C 263 lobe. Figure 22(b) is an enlargement of the eastern third of Figure 22(a) shows the total intensity image at 0"36 reso- the source. The jet is strikingly linear, but it does not point 44 lution from the A and B configuration data. (Little extra directly at feature K. There is evidence for a curved hook” structure was seen on the lower-resolution images.) The (J) to the northwest of K, which may mark the final path of structure is 51" (198Ä-1 kpc) in extent. The lobes are asym- the deflecting jet. There is also a diffuse “bar” of emission

Fig. 18. Distribution of total intensity (Stokes /) over 3C 249.1 with 1"1 (FWHM) resolution. Contours are drawn at -1 (dotted), 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, 24, 30, 40, 60, 100, 160, and 300 times 100 /¿Jy per CLEAN beam area. The peak intensity is 97.3 mly per CLEAN beam area.

3C249.1 Degree of Polarization & Position Angle 4.9 GHz

Fig. 19. Distribution of degree of linear polarization p and E-vector position angle x over 3C 249.1 at 1.1 resolution, superposed on contours from Fig. 18. A vector of length 1" corresponds to p=033.

© American Astronomical Society • Provided by the NASA Astrophysics Data System Fig. 20. Distribution of total intensity (Stokes I) over the jet and west lobe of 3C 249.1 from a composite MEM/CLEAN deconvolution restored with 0"35 (FWHM) resolution. D is the central feature and K is the jetted hot spot. The counterjet candidate is the straight ridge linking D to the north end of the hook-like feature C. Ais the counterjetted hot spot. Contours are drawn at -1 (dotted), 1, 2, 3, 4, 6, 8,10, 12, 16, 20, 24, 30, 40, 60,100,160, 300, and 1000 times 65 /¿Jy per restored beam area. The peak intensity is 71.0 mly per CLEAN beam area.

(I) roughly perpendicular to the jet about 2" upstream from Figures 23(a) and 23(b), also at (06 resolution, plot the the hot spot, reminiscent of the jet-crossing feature H in 3C polarization data on contours from Figs. 22(a) and 22(b). 249.1 (Sec. 4.8). The jet contains a series of bright, elongated There is measurable (15% to ~25%) polarization at jet knots knots (D,E,F,G,H) and fainter, apparently continuous emis- D, F, and G, with the E vectors perpendicular to the jet axis. sion. (The image of the jet is corrupted by undeconvolvable The degree of polarization is <40% over most of the east sidelobes of the bright hot spot K, and only the features that lobe, but rises to about 50% in the region north of hot spot K we believe to be significant are labeled.) The west lobe ap- and toward the southwest. The polarized signal from the dif- pears more relaxed, with a recessed hot spot (B) and a bright fuse emission to the north is weak, but there is evidence for resolved rim (A) to the northwest. There is no emission 50% to 60% linear polarization near its northern boundary. along the expected path of any similarly straight counterjet. The area between I and J is only weakly (4% to 8%) polar-

3C249.1 Degree of Polarization & Position Angle 4.9 GHz

Fig. 21. Distribution of degree of linear polarization p and E-vector position angle x over the jet and west lobe of 3C 249.1 at 0'.'35 resolution, superposed on contours of total intensity. A vector of length 1" corresponds to p = l.

3C263 Total Intensity 4.9 GHz

11 37 12 11 10 09 08 07 06 05 04 RIGHT ASCENSION (B1950)

3C263 Total Intensity 4.9 g Hz

Fig. 22. (a): Distribution of total intensity (Stokes I) over 3C 263 with 0'.'36 (FWHM) resolution. C is the central feature and K is the jetted hot spot. J has been considered part of the jet. B is the counterjetted hot spot and there is no counteijet candidate. Contours are drawn at -1 (dotted), 1, 2, 3, 4, 6, 8,10, 14, 20, 30, 50,100, 200, 400, 800, 1600, and 3200 times 75 /Jy per CLEAN beam area, (b): Enlargement of central feature, jet and east lobe. The peak intensity is 347 mJy per CLEAN beam area.

ized. This low polarization, together with the pattem of the 4.10 3C 334 surrounding E vectors, suggests that the magnetic field direction in feature I is almost orthogonal to that of the adjacent The data were confused by an 88 mJy compact source at lobe emission and roughly along the ridge of feature I. The (B1950.0) 16h 18m 18?96, +17° 47' 01". This is not shown in degree of linear polarization in the west lobe is up to 50% our figures but its effects were subtracted from all the im- and the vectors are highly organized, with the E vectors per- ages. pendicular to the adjacent boundaries of the lobe and parallel Figure 24 shows the total intensity image at 1"15 resolu- to the jet axis near the compact hot spot B. tion from the B configuration data only. The lobes are

RIGHT ASCENSION (B1950) Polarization scale: 1 arcsec « 1.00

3C263 Degree of Polarization & Position Angle 4.9 GHz

Fig. 23. Distribution of degree of linear polarization p and E-vector position angle x over 3C 263 at 0'.'36 resolution, superposed on contours from Fig. 22. A vector of length 1" corresponds to p=T. (a): Central feature, jet and east lobe, (b): West lobe.

roughly symmetric in size, intensity, and surface brightness. of the jet (the first 13" from the central feature E). There are, The structure is —58" (215/t-1 kpc) in extent and has an however, two relatively compact features on the counterjet overall S symmetry. The northwest lobe is sharply bounded axis. The closer, D, is an elongated knot that is connected to to the north and west, but has a plume-like extension to the the bright complex B in the northwest lobe by a weak bridge south. The southeast lobe is weakly edge-brightened on its of emission. The second is a detached compact 1.8 mJy southeast side, but the lobe emission is everywhere fainter source (A) 55" from the central feature, well aligned with the than the jet, which deflects as it enters it from the west. straight segment of the jet at this resolution. Its position is There is no sign of emission opposite the straight segment (B1950.0) 16h 18m 04?86, +17° 44' 14'.'1.

3C334 Total Intensity 4.9 GHz between feature A and the northwest lobe. While it is con- ceivable that feature A is an outlying remnant of earlier ac- tivity in 3C 334, we do not treat it as part of the source structure in what follows. Figure 25(a) shows the total intensity of the jet and southeast lobe at 0735 resolution from the A and B configuration data. All structures in the lobe and the jet are at least partially resolved. The ridge line of the jet oscillates in the first 4" from the central feature E, but the oscillation does not grow appreciably beyond knot H until the large-scale deflection near knot N. The jet consists of several elongated knots (F,G,H,I,J,K,M,N) embedded in fainter structure. The transverse profile of the jet is clearly asymmetric beyond knot M. A slim “ray” of emission (L and its extension to the northwest) joins the jet from the west near knot N. The sudden >50° change in direction of the ridge line, coupled with the brightness and compactness of feature O, identifies O as the hot spot. Downstream from O, an undulating ridge links fea- 16 18 09 08 07 06 05 RIGHT ASCENSION (B1950) tures P, Q, R, and S. Beyond Q, this forms the edge- brightened boundary of the lobe. The brightness contrast and appearance of collimation of this ridge might classify it as a Fig. 24. Distribution of total intensity (Stokes I) over the field of 3C 334 jet if it emanated from a central feature rather than from a hot with r.15 (FWHM) resolution. E is the central feature and A is a confusing source, discussed in the text. O is the jetted hot spot and D is part of the spot. The ridge may therefore be an example of extended counterjet candidate (see also Fig. 25). Contours are drawn at -2 and -1 secondary outflow from a hot spot. It illustrates the difficulty (dotted), 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, 30, 40, 50, 70, 100, 150, 200, 300, of distinguishing uniquely between jet and hot spot features. 500, 700, and 1000 times 110 /xJy per CLEAN beam area. The peak intensity is 138 mJy per CLEAN beam area. Figure 25(b) shows the total intensity of the northwest lobe, also at 0735 resolution from the combined A and B configuration data. The first knot (D) on the putative coun- We calculate the probability that feature A is a random terjet path is resolved, is elongated along this path, and is confusing source as follows. First, we note that the angle brightened toward the central feature (E). This knot is at between the straight jet axis and the line joining the central o almost the same distance from the central feature as the hot feature to A is I . We then assume that our attention would spot O in the southeast lobe. The most compact feature in the have been drawn to any similarly well aligned neighboring northwest lobe (C) lies at the other end of the weak emission source that was within two source diameters of the central ridge that traces the lobe’s northern boundary. The weak feature of any of the 12 sources that we imaged. We use the emission ridge and knot D are therefore candidates for coun- rms largest angular size (47") of the 12 sources that we ob- terjet emission, though the presence of ridges at the edges of served to estimate the mean area (0.041 sqarcmin) per other lobes in this sample makes this identification contro- source of the sector in which we would have noticed such a versial. The bright “head” of the lobe breaks into a complex good alignment with a particular axis of the source. Further, tangle of knots and filaments for several arcseconds around we consider that there are four axes per source for which an the peak B at this resolution. Neither B nor C has sufficient alignment of a neighboring object might be considered “interesting” (e.g., the straight jet axis, the axis opposite to this, brightness contrast with their surroundings to qualify as hot and the axes joining the central feature to either hot spot). spots by our definition, however, so we adopt the view that The 5 GHz source counts of Condon (1984) predict 0.0076 there is no hot spot in the northwest lobe. Several filaments sources per square arcminute brighter than 2 mJy at 5 GHz. appear to trail into the plume-like extension toward the Taking all these factors into consideration, we would expect south. to find only 0.015 “well aligned” confusing sources among Figures 26(a) and 26(b), also at 0735 resolution, plot the our 12 target sources, whereas we observe 1. This estimate of polarization data on contours from Figs. 25(a) and 25(b). the expected number of confusing sources does not account Linear polarization is detected all along the jet. The degree for the fact that compact, flat-spectrum objects dominate the of linear polarization tends to decrease outward, from ~40% source counts at high frequency. Feature A is noticeably re- near the base to 20% to 30% in the outer jet. Most E vectors solved and has a steep spectral index (1.1 between 1.5 and 5 are within 10° of the perpendicular to the local ridge line. GHz), which makes it less likely that we would have ob- The narrow “ray” L that joins the jet from the west near its served such a well aligned object by chance. southern limit is apparently >70% polarized, with the E vec- Although this conservative statistical calculation suggests tors perpendicular to its ridge line. The undulating line of that A may be associated with 3C 334, we have no other knots beyond hot spot O also has E vectors perpendicular to reason to believe that it is an outlying part of the source. the adjacent lobe boundary, except in the region P immedi- Specifically, an image of 3C 334 and its environs tapered to ately downstream from O. In the most highly polarized re- 372 (FWHM) resolution showed no evidence of a connection gions away from feature L, on the east edge of the southeast

© American Astronomical Society • Provided by the NASA Astrophysics Data System 787 BRIDLEETAL.:TWELVE3CRQUASARS (b) RIGHT ASCENSION(B1950) DECLINATION (B1950) © American Astronomical Society • Provided by the NASA Astrophysics Data System 16 1806.606.406.2 06.0 05.805.605.4 3C334 Total Intensity 4.9 GHz Fig. 25.(a):Distributionoftotalintensity(Stokes/) mJy perCLEANbeamarea. 5, 6,8,10,12,16,20,24,30,36,50,60,70,90,120, hot spot.Contoursaredrawnat—1(dotted),1,2,3,4, 3C 334with0'.'35(FWHM)resolution.Oisthejetted over thecentralfeature(E),jet,andsoutheastlobeof and theridgelinkingittoC).Thepeakintensityis130 area, (b):Northwestlobeandcounterjetcandidate(D 150, 200,300,and500times50/xJyperCLEANbeam 787 PQ UD r" 788 BRIDLE ET AL. : TWELVE 3CR QUASARS 788

3C334 Degree of Polarization & Position Angle 4.9 GHz

Fig. 26. Distribution of degree of linear polarization p and E-vector position angle x over 3C 334 at 0'.'35 resolution, superposed on contours from Fig. 25. A vector of length 1" corresponds to /?=0.91. (a): Central feature, jet, and southeast lobe, (b): Northwest lobe and counterjet candidate.

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1994AJ 108. . 7 6 6B -1 jet, butthereisaconspicuousknot(I)onthejetaxisto placed andunequallybrightlobes.Ajetconsistingofastring jet increasesfrom<13%atthefirstknot(G)to23%by posed onfainterextendedemissionlinksthecompactfeature tion fromtheAandBconfigurationdata.Thestructureis highest onthelobe’snorthedge,whereitreaches50%to 50%. H toarecessedandelongatedfeature(B)inthesouthlobe.C of brightknots(G,F,E,D,C)increasingbrightnesssuper- about 28"(118/îkpc)inextentwithasymmetrically 60%, andinafewfilamentswhereitreaches70%. detectable atthisresolution.Thedegreeofpolarizationis ridge andknotthatarepossiblypartofthecounterjetisun- the filaments.Unfortunately,polarizedsignalfrom dicular tothelocallobeboundariesandridgelinesof ness distribution.Thevectororientationsareagainperpen- ingly wellorderedconsideringthecomplexityofbright- lobe, thedegreeoflinearpolarizationrangesfrom45%to west ofthenorthlobe.Thisknotisfollowedbya“hook” the previouslystraightjet,butBqualifiesashotspotby marks anabruptchangeinthedirectionandcollimationof west ofKconnectthehotspottomoreextendedlobe brightness thanIatthisresolution,butbarelyqualifiesasa unclear atthisresolution. ture (A)liesbeyondthehotspotbutitsrelationshiptoitis its surfacebrightnessandcompactness.Amorediffusefea- polarization (40%to50%)occurneartheedgesofboth tours fromFig.27.Thedegreeoflinearpolarizationthe emission. brightest partsofacurvedcounterjetcandidate.TheMEM largest extentofthesource.AnMEMdeconvolution(not hot spotbecauseitsangularsizeissolargerelativetothe leads ultimatelyintoK.FeatureKhasahighersurface marks amajorchangeindirectionof(hithertoundetect- extended ridgeontheeastsideofnorthlobe.Iprobably emission (J)thatcurvestowardthebrightestpart(K)of sion northoffeatureH,oppositethestraightsegment 789 BRIDLEETAL.:TWELVE3CRQUASARS lobe. TheEvectorsareroughly perpendicular totheadjacent lobes, andreach50%to70%attheeastedgeofnorth of beingperpendiculartothejetaxis.Thehighestdegrees D and20%atknotC.TheEvectorsaregenerallywithin20° edge-brightened, andthatfilamentaryfeaturestothesouth- deconvolution alsosuggeststhatthenorthrimofthislobeis in thecounterjetlobe,andconsiderfeaturesIJtobe able) counterjet.Jmaythusbepartofadeflectedflowthat within 15"ofthequasaratVand Ibandsandconcludedthat lobe boundaries. indeed brighterthanI.WethereforeadoptKasthehotspot shown) suggeststhatKcontainsfiner-scalestructureis et al.(1992)detected[OII]line emissionwithavelocity 3C 336isatthecenterofarich clusterofgalaxies.Bremer The polarizationdistributioninthenorthwestlobeisstrik- © American Astronomical Society • Provided by the NASA Astrophysics Data System Figure 27showsthetotalintensityimageat0'.'34resolu- There isnosignofacounterjetwithinthediffuseemis- Figures 28(a)and28(b)plotthepolarizationdataoncon- Hintzen etal.(1991)foundan over-densityofimages 4.11 3C336 -1 peak intensityis50.4mJyperCLEANbeamarea. tion fromourBconfigurationdataandtheC plied byR.Barvainis.Thisshowsthatbothlobeshavedif- date. Contoursaredrawnat-1(dotted),1,2,3,4,6,8,10,14,20,30,50, contains thecounterjettedhotspot.IandJarepartofcounteijetcandi- Fig. 27.Distributionoftotalintensity(Stokes/)over3C336with0'.'34 plex. Thesouthwestlobehasabright feature(A)onitsouter Kronberg etal.(1980),andseveralfilaments.Alarge,faint complex ofbrightfeatures(J,L,M),previouslydetectedby greatly inintensityandsurfacebrightness.Thestructureis resolution data,whichgivedetailsonlyofthebrighter fuse extensionsthatarenotwellimagedinourhigher- from abriefVLAC-configurationobservationkindlysup- center ofastrongcoolingflow. 70, 120,200,400,600,and1000times50/JyperCLEANbeamarea.The brightest featuresareatHandI, maycontinuethisjettoward snapshot. Thelobesareroughlysymmetricinsizebutdiffer GHz contourmapof3C351byLeahyetal.(1989). structures. Theseextensionscanalsobeseenonthe1.45 shear aroundthequasar,andsuggestthatquasarisat (FWHM) resolution.HisthecentralfeatureandBjettedhotspot.K central complextowardthebrightest feature(J)inthenorth- edge. Anabbreviatedjetpoints fromthepartiallyresolved east lobe.Amarginallydetected curvedemissionarc,whose “fan” ofemissionextendssome 30"tothewestofthiscom- ~75" (230/îkpc)inextent.Thenortheastlobeincludesa Figure 30showsthetotalintensityimageat1.15resolu- Figure 29showsthetotalintensityimageat3"5resolution 3C336 TotalIntensity4.9GHz 4.12 3C351 789 PQ UD r" 790 BRIDLE ETAL. : TWELVE 3CR QUASARS 790 ooo

^0 (T\

3C336 Degree of Polarization & Position Angle 4.9 GHz

Fig. 29. Distribution of total intensity (Stokes I) over 3C 351 with 3'.'5 (FWHM) resolution. Contours are drawn at —1 (dotted), 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, 24, 30, 40, 50, 70, 100, 200, 400, 800, and 1200 times 200 ply per CLEAN beam area. The peak intensity is 506 mJy per CLEAN beam area.

bright complex of emission to the north and west of the hot spot J. The E vectors are perpendicular to the lobe and fan boundaries near the edges of these structures, but are parallel to the axis of greatest elongation of the fan at its center. The degree of polarization reaches 50% to 65% toward the west edge of the fan. Figure 31(b) shows the polarization data for the southwest lobe at the same resolution. The basic pattern is similar to that in the northeast lobe except that there is apparently little perturbation at feature A, unlike the strong perturbation near J. Figure 32 shows the total intensity of the central region 16 22 32.3 32.2 32.1 32.0 31.9 31.8 and the bright complex in the northeast lobe at 0''37 resolu- PolarizationRIGHT ASCENSION scale: 1 arcsec (B1950) = 1.00 tion from the A and B configuration data. The curved inner jet (features E, F, G) points toward the hot spot J at the lobe’s Fig. 28. Distribution of degree of linear polarization p and E-vector position extreme eastern edge. There is marginal evidence of a con- angle x over 3C 336 at 0'.'34 resolution, superposed on contours from Fig. 27. A vector of length 1" corresponds io p = l. (a): North lobe, (b): Central tinuation of this curved jet through features H and I into J, feature, jet, and south lobe. but this emission is too faint to represent in the contour display. It is also confused by sidelobe responses to the hot spot, which limit our sensitivity in this region. A narrow filament J. The brightness and compactness of J nominate it as the hot K joins J to the bright resolved feature L on the lobe’s north spot and it is likely, but we cannot be certain, that it also side. A network of filaments extends both south and west marks the termination, or deflection point, of the jet. from this feature. Figure 31(a) shows the polarization data from the B con- The extended central region of Fig. 30 is here resolved figuration data only at 1715 resolution on contours of total into two knots D and E, of almost equal brightness, with a intensity for the northeast lobe and the jet only. The degree further, weak knot C to the southwest. The available evi- of polarization rises rapidly to 20%-25% away from the dence strongly favors identifying the compact knot D as the

© American Astronomical Society • Provided by the NASA Astrophysics Data System PQ UD r" 791 BRIDLE ETAL.: TWELVE 3CR QUASARS 791 ooo 3C351 Total Intensity 4.9 GHz true central feature, and knot E as a jet knot, while C may be ^0 part of a counterjet. First, the optical position for the nucleus of 3C 351 (see Table 5 below) is within 0?022 in a and 0"15 in ô of our radio position for D. The accuracy of the optical position (Clements 1983) is ±0!011 in a and O'.'OS in Ä Our radio error is ~0'.'2 relative to the position given for 3C 345 in Table 3. The optical nucleus and D thus coincide to within the positional errors. Second, VLBI observations of 3C 351 by Hough et al (19xx) rule out C as a candidate for the central feature—the VLBI correlated flux density at 8.4 GHz is ~5 mJy. Third, analysis of the residual fringe rates for these VLBI data yields a position for the compact structure that is incompatible with our position for E but agrees well with that of D. Note that feature B, which is near the projected axis of the main jet, might mark a point of deflection of a counterjet in the southwest lobe toward the brighter region A. Feature A itself has insufficient brightness contrast with the lobe to be termed a hot spot using our definition. Figures 33(a) and 33(b) show the polarization data on contours from Fig. 32. Figure 33(a) covers the bright complex in the northeast lobe while Fig. 33(b) displays the region close to the central feature. In the lobe, most E vectors are perpendicular to the ridge lines of the filaments. In the extended jet, where the degree of polarization ranges from 11% to 31%, they are nearly perpendicular to the jet axis. Fig. 30. Distribution of total intensity (Stokes /) over 3C 351 with 1'.'15 The relatively low (7%) polarization at knot D (compared (FWHM) resolution. J is the jetted hot spot. H and I are part of the outer jet. with the 13% polarization at knot E) supports our view that Contours are drawn at -1 (dotted), 1, 2, 3, 4, 6, 8,10,12,16, 20, 30,40, 60, D contains the central feature. (The degrees of polarization at 80, 100,120, 160, 200, 300, 400, 600, 800, 1000, 1200, and 1600 times 120 yuJy per CLEAN beam area. The peak intensity is 318 mJy per CLEAN central features are usually much lower than those at jet beam area. knots—compare Tables 5 and 11 below.) At this resolution, which is too high to detect the “fan” emission, the highest degrees of polarization in the lobes are 35% to 50% on the

3C351 Degree of Polarization & Position Angle 4.9 GHz

Degree3C351 of Polarization & Position4.9 GHzAngle

Fig. 31. Distribution of degree of linear polarization p and E-vector position angle x over 3C 351 at r.15 resolution, superposed on contours of total intensity. A vector of length 1" corresponds to p=0.33. (a): Northeast lobe, outer jet, and central feature, (b): Southwest lobe.

north side of the northeast lobe, and north of feature A in the southwest lobe (not shown).

4.13 3C 432 Figure 34 shows the total intensity image at 0''37 resolution from the A and B configuration data. The lobes of this small (15", 63/t_1 kpc) source are roughly equally bright but are asymmetrically placed around the central feature C, the jetted lobe being further from this feature. The (previously undetected) jet contains an elongated knot (D) and possibly a weak ridge in the southeast lobe pointing toward the brightest part of the hot spot H. This ridge is not well resolved from other lobe substructure, so we cannot be certain that it is a continuation of the jet, but we include it in our integration of the jet flux density in Sec. 5.2.1. The structure on the west edge of the southeast lobe (features E, F, G) resembles a barely resolved ring girdling the path of the jet. There is no sign of a counterjet. The hot spot in the northwest lobe is hard to identify uniquely at this resolution, but both an MEM deconvolution and Gaussian model-fitting imply that B is compact, bright, and exactly opposite the jet. We therefore believe that B marks the end of a counterjet in the northwest lobe, but emphasize that the MEM image was needed to confirm that it is a hot spot meeting all our criteria. Fig. 32. Distribution of total intensity (Stokes /) over the central region, jet Figure 35 plots the polarization data on contours from (E, F, G, and a faint ridge from H to the hot spot J through I), and northeast Fig. 34. The most strongly polarized features (30% to 50%) lobe of 3C 351 with 0"37 (FWHM) resolution. D contains the central feature and C is the counteijet candidate. Contours are drawn at —4, -2, and -1 are E, F, and G on the west side of the southeast lobe; the E (dotted), 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, 24, 30, 40, 50, 70, 100, 150, 200, vectors are perpendicular to the ridge line in and between 400, 600, and 800 times 70 /¿Jy per CLEAN beam area. The peak intensity these features. The jet and the southeast hot spot are unpo- is 159 mJy per CLEAN beam area. larized at this resolution. The northwest lobe is most highly polarized (40% to 50%) on the outer edge, the E vectors

Fig. 33. Distribution of degree of linear polarization p and E-vector position angle x over 3C 351 at 0'.'37 resolution, superposed on contours from Fig. 32. A vector of length 1" corresponds to p=0.S. (a): Northeast lobe, (b): Inner jet and central feature.

21 20 26.0 25.8 25.6 25.4 25.2 RIGHT ASCENSION (B1950)

Fig. 34. Distribution of total intensity (Stokes /) over 3C 432 with 0'.'37 (FWHM) resolution. C is the central feature. D and its weak extension to the southeast are the jet. H contains the jetted hot spot. There is no counteijet candidate, but B contains fine structure that we believe is the counterjetted hot spot (see text). Contours are drawn at —1 (dotted), 1, 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, 24, 30, 40, 50, 70, 100, 200, 400, and 800 times 50 /uJy per CLEAN beam area. The peak intensity is 73.1 mJy per CLEAN beam area.

3C432 Degree of Polarization & Position Angle 4.9 GHz

21 20 26.0 25.8 25.6 25.4 25.2 RIGHT ASCENSION (B1950) Polarization scale: 1 arcsec = 1.00

Fig. 35. Distribution of degree of linear polarization p and E-vector position angle x over 3C 432 at 0'.'37 resolution, superposed on contours from Fig. 34. A vector of length 1" corresponds io p = \.

© American Astronomical Society • Provided by the NASA Astrophysics Data System PQ UD r" 794 BRIDLE ETAL. : TWELVE 3CR QUASARS 794 ooo everywhere being perpendicular to the adjacent lobe bound- FWHM given by fitting two-dimensional Gaussian models ^0 ary. and a background baseline level to a small region around the peak using the AIPS task IMFIT. For 3C 334, a single-component model gave unusually 5. PHYSICAL PROPERTIES large residuals and an unusually high upper limit (0''12) to the fitted FWHM. A two-component model in which El has In what follows, we combine the results from the above the listed parameters and a second feature (E2) has FWHM observations with those derived from the 4.9 GHz image of 0'.'27 along PA 14174 fits the data much better. We therefore 3C 47 by Fernini et al (1991), which we reprocessed treat El as the true central feature, and E2 as part of the through all the parameter-estimation steps described below. extended jet emission. For the other sources, any evidence Figure 36 shows the total intensity image of 3C 47, together for such extended emission on scales of —072 near the cen- with our labeling for the major features described below (this tral feature is marginal. The flux densities of the possible labeling differs from that of Fernini et al, to identify some emission on this scale in the other sources are less than the features that they did not distinguish). uncertainties in the integrations over the well resolved jet emission. Table 5 also lists the positions for the optical identifica- 5.1 The Central Features tions of these quasars from the references cited by Laing et al (1983), from Clements (1983), or from Argue & Ken- Table 5 lists observed parameters for the central features worthy (1972), whichever has the smaller quoted error. The of the 13 quasars. For each source, we estimate the param- optical positions are generally accurate to better than 075 in eters of the part of the central feature that is unresolved to the their reference frame and the radio positions to —072 relative VLA. The positions are therefore those of the peak intensi- to the calibrators listed in Table 3. As the positions of the ties of these features. The quoted flux densities and size lim- radio central features and the optical objects usually agree its are the peak flux densities and the 1er upper limits to the within 1" in both coordinates, we believe that the identifica- tions are unambiguous. For 3C 208, the optical position given in the identification paper by Sandage & Wyndham (1965) disagrees with ours for the central radio feature by over 20". Inspection of the Palomar Sky Survey shows that the object in the Sandage & Wyndham (1965) finding chart is within an arcsecond of our radio position, however. Thus Sandage & Wyndham’s identification is correct even though its quoted optical position is erroneous. Table 5 also lists the linear polarizations observed at the

Table 5. Parameters of central features.

Position (B1950.0) Flux Fitted Source Density FWHM p h m s o'" (mJy) {") x 3C 9 r 00 17 49.908 15 24 16.23 4.9 ± 0.2 <0.104 o 00 17 49.944 15 24 16.21 3C 47 r 01 33 40.422 20 42 10.40 73.6 ± 0.1 <0.086 0.001 o 01 33 40.425 20 42 10.16 + 64.6 3C 68. 1 r 02 29 27.245 34 10 34.43 1.1 ± 0.1 <0.133 <0.04 o 02 29 27.24 34 10 34.1 3C175 r 07 10 15.387 11 51 24.47 23.5 ± 0.6 <0.077 <0.002 o 07 10 15.379 11 51 23.95 3C204 r 08 33 18.143 65 24 04.20 26.9 ± 0.2 <0.048 <0.003 o 08 33 18.146 65 24 03.86 3C208 r 08 50 22.686 14 04 17.36 51.0 ± 0.2 <0.030 0.007 o 08 50 22.70 14 04 16.9 -19.1 3C215 r 09 03 44.126 16 58 16.00 16.4 ± 0.2 <0.047 o 09 03 44.14 16 58 16.1 3C249. 1 r 11 00 27.443 77 15 08.41 71 ± 0.7 <0.053 0.004 o 11 00 27.439 77 15 08.57 -21.6 01 33 42.0 41.5 41.0 40.5 40.0 39.5 39 0 3C263 r 11 37 09.292 66 04 26.90 157 ± 0.5 <0.034 RIGHT ASCENSION (B1950) o 11 37 09.343 66 04 26.94 3C334 r 16 18 07.287 17 43 30.32 111 ± 1.7 <0.07 0.004 Fig. 36. Distribution of total intensity (Stokes I) over 3C 47 with 1"45 by o 16 18 07.309 17 43 30.40 +74.5 1713 (FWHM) resolution (major axis in PA—81!8), as imaged by Fernini 3C336 r 16 22 32.212 23 52 01.35 20.4 ± 0.2 <0.038 0.003 et al (1991). G is the central feature and A contains the jetted hot spot. o 16 22 32.214 23 52 02.0 +27.9 There is no counteijet candidate, and H does not meet our compactness 3C351 r 17 04 03.488 60 48 31.23 6.5 ± 0.2 <0.077 0.072 criterion for being a hot spot. Contours are drawn at — 1 (dotted), 1, 2, 3, 4, o 17 04 03.466 60 48 31.08 -58.7 5, 6, 8, 10, 12, 14, 16, 20, 24, 30, 40, 50, 60, 80, 100, 120, 140, 160, 200, 3C432 r 21 20 25.537 16 51 45.82 7.5 ± 0.2 <0.062 240, 300, and 400 times 120 /xJy per CLEAN beam area. The peak intensity o 21 20 25.532 16 51 46.4 is 196 mJy per CLEAN beam area.

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1994AJ 108. . 7 6 6B _1- _1 proper motionsonmilliarcsecondscaleswithpatternspeeds These VLBIobservationshavealsomeasuredoutward Hough 1986;3C263:Zensusetal.1987;334; much lowerthanthoseofthejetknots(seeTable11below). central features;thedegreesoflinearpolarizationareusually the brighter,morecompactcomponentaslarge-scalejet. ness ofthemilliarcsecond-scaleextendedstructurenear et al.1992),VLBIclosurephasedatadeterminesthesided- 204: Houghetal.1993;3C208:1994;249.1: of 3.7Acin3C47,=s/i204,l.S/T'c of twodominantVLBIcomponentsisonthesameside central feature.Inallsixcases,thefainterandmoreextended 795 BRIDLEETAL.:TWELVE3CRQUASARS the lengths,measuredinarcsecondsfromcentralfeature, candidate counterjetemissionineachsource,togetherwith of theregionsoverwhichintegrationwasdone.These 263, and1.6ftcin3C334. region oftheimagethatcontainsjetlikefeaturewere priori haveanyparticularsymmetry relativetothoseofthe jet candidatesinournewimagesunambiguouslymeetsallof made asfollows.Wedefinedtwosimilarlyshapedcompari- cility TVSTATasfollows.Thepixelintensitiesinacurvilinear integrated fluxdensitieswereestimatedusingtheAIPSfa- on thiscurvilinearregionoftheimage.Thisestimatewas summed andnormalizedtoafluxdensity.Wethensubtracted with theaveragesurfacebrightnessofanyadjacentlarge- son regionsoneachsideofthejetregion.Thesizesand an estimateoftheextendedlobeemissionthatissuperposed clude readilyidentifiableconfusingfeaturessuchasbright integrations ascloselypossible,butwereadjustedtoex- shapes ofthesecomparisonregionsmatchedthoseforthejet when jetsrunnearlobeboundaries,discrepanciesinthein- from thejetintegration.Thisprocedurecorrectsinte- those inthejetregionsbeforebeingaveragedandsubtracted gions wererenormalizedtothesamenumberofpixelsas knots orfilaments.Thepixelsumsfromthecomparisonre- flux densityofajet. grated fluxdensitiesforthejetsanextendedcontribution lobes arefilamentary.Thejetiseasytodistinguishfrom our adoptedcriteriaforjethood.Forexample,in3C334both the integration.Wealsoemphasizethatnoneofcounter- exacerbates ambiguitiesaboutwhichfeaturestoincludein and soaremoreconfusedbylobeemission.Theirfaintness assess accuratelybecausecounterjetsarefainterthanthejets dominate theuncertaintyinourestimateofintegrated tegrated fluxdensitiesofthetwocomparisonregionsmay scale structure.Inlobeswithmuchinternalstructure,or prominence relativetothefilaments. Thismethodofidenti- counterjet candidateisnot.It acandidatebecauseitlies confusing filamentsbyitsbrightnesscontrast,butthefainter fying counterjetcandidatesisfallible, however,becausewe along aplausiblepathfortheother beam,notbecauseofits cannot predicttheirpathsuniquely. Thesepathsneednota © American Astronomical Society • Provided by the NASA Astrophysics Data System In 6ofthe13sources(3C47:Vermeulenetal.1993;3C Table 6(a)liststheintegratedfluxdensitiesforjetand The integratedfluxdensitiesofcounterjetsareharderto 5.2 TheJetsandCounterjets 5.2.1 Integralproperties jets ifcanbebentbylocal“weather”ingalacticenvi- when obtainingupperlimitsforundetectedcounterjets.For path problemalsoaffectsthechoiceofanintegrationregion many sourcesinthissample,theuncertaintiescoun- ronments oriftheycanhaverelativisticpatternspeeds.The through aridgeinitslobe,excludedTable6,couldin- corrections. Thefollowingcasesareparticularlytrouble- large as,orlargerthan,theuncertaintiesinbackground terjet integrationsstemmingfromambiguitiesoverwhat ridge isnotsufficientlydistincttobeconsideredpartofthe crease thecounterjetfluxdensityfrom0.36to6.2mly.The some: areas oftheimagetoincludeascounterjetcandidatesare points towardacurvedridgeofemissionleadingintofeature uncertain. Theaxisofthestraightinnersegmentjet counterjet onthepresentevidence,however. H, butthisridgehastoolittlebrightnesscontrastrelativeto counterjet integrationpathandthelobeemissioncorrection of ahotspotinthecounterjetlobemakeappropriate the restoflobetobeconsideredacounterjetcandidate. Our upperlimitforthecounteijetisconservativeandde- termined entirelybyscatterinthepossiblecorrectionsfor background inthelobe.Useofsoutherncomparisonre- terjet featureatthisfluxdensitylevel. lobe emission,ratherthanbysuspicionofanexplicitcoun- feature. Insettinganupperlimittotheintegratedcounteijet confusing lobeemission,notasabroadcounterjet-related tributable toacounterjet,butuseofthenorthernpathpro- gion alonesuggeststhatthereisnoexcessfluxdensityat- they containdifferentcontributionsfromfeatureHandother that ofthejet,traversingridgefeatureHbeforebend- adjacent comparisonpathsdisagreebyalmost5mJybecause ing northwardtowardthehotspotJ.Theintegrationson emission, weuseanintegrationregionwhosewidthequals 3C 9:apossiblecontinuationofthecounterjetcandidate 3C 47:thecombinationoflarge-scalestructureandlack 3C 208:theresolvedfeatureHhasbeeninterpretedas Table 6.Integratedfluxdensitiesofjetsandcounteijetcandidates. 3C204 3C175 3C 68. 3C 47 3C 9 3C336 3C334 3C263 3C249. 3C215 3C208 3C432 3C351 3C263 3C249.1 3C215 3C208 3C204 3C432 3C351 3C336 3C334 3C175 3C 68.1 3C 47 3C 9 38.5 12.4 1.18 ±0.04 0.47 ±0.05 2.4 2.1 4.4 7.5 2.9 5.1 6.2 7.4 3.9 9.7 116 331 9.4 (mJy) 14 52 27 27 26 25 66 51 23 (nvjy) Jet Jet 1.5 0.5 0.2 0.1 0.1 0.1 3.3 0.9 0.1 0.1 0.1 0.7 0.5 (b) straightjetpath 3 5 1 4 2 3 3 6 5 3 6 (a) wholepath (") (mJy) Length Counterjet Length 13.0 19.6 24.3 17.0 15.6 12.1 27.5 21.0 36.5 12.1 3.1 4.1 8.4 1.5 7.0 4.8 2.2 2.7 3.7 8.7 3.6 6.7 6.8 6.9 9.7 8.0 (") <0.19 <0.20 <1.7 <1.88 <0.12 <0.68 <5.1 <0.1 <0.41 <0.22 <0.22 <0.19 <0.32 <4.2 Counterjet 2.52 ±0.06 1.0 0.36 ±0.02 3.3 3.3 1.0 4.2 2.52 0.11 0.18 0.18 0.36 (mJy) 2.1 0.2 0.04 0.03 0.2 0.5 0.2 (") Length Ratio >3.7 >5.2 >27 >12 >34 >4.7 >9.5 >17 5 (1.2) 26 3.3 26.0 24.1 21.0 52 12 15.4 14.0 19.0 11.0 29.0 4.7 3.7 4.8 0.7 1.5 795 1994AJ 108. . 7 6 6B projected counterjetpathandisthemostpromisinghotspot duces aformalexcessof5.1mJyonthecounterjetpath. qualifies asacounterjetcandidate,wetakethe5.1mJyvalue Because weseenonarrowfeaturewithinHthatproperly 796 BRIDLEETAL.:TWELVE3CRQUASARS jet wasunresolved)and(b)thereisnoobviousconfusionby integration wouldincreasetheestimatefrom3.3to6.55mJy. qualify asahotspotbyourdefinitionbutwhichliesonthe from 0.95to6.75mJy. terjet candidate,itsintegratedfluxdensitycouldbeincreased less collimatedfeatureswerealsoassociatedwiththecoun- hook-like featuresBandCneartheputativecounterjetpath cluded inourcounterjetintegration.Eachoftheextended rection. candidate againstanextendedlobewithotherweakinternal The counterjetpathsareperhapsleastambiguousopposite the oppositeof3C334,whereknotCwasexcludedfrom terjet thatdeflectsintoKafterbrighteningatI.(Thiscaseis gration, becausethereisahotspot(K)elsewhereinthelobe candidate inthecounterjetlobe.AddingCto contains anintegratedfluxdensityof2.9mJy.Ifboththese structure leadstoalargeuncertaintyinthebackgroundcor- as aconservativeupperlimit. these inner,straighterjetsegments.Regionswherejetsand ties inTable6(a).Althoughnoneofthejetsisperfectly significantly totheuncertaintiesinintegratedfluxdensi- counterjet candidateinthissource. should showthatknotIisthehotspot,therewouldbeno date inthecounterjettedlobe.)Ifhigher-resolutiondata integration becauseitisthemostpromisinghotspotcandi- and becauseJcanplausiblybeinterpretedaspartofacoun- AIPS tasklgeom).Thejetfluxdensitywasintegratedovera by changesintheinternalvelocityfieldinducedsuch counterjets bendmayalsobethesitesofparticularlystrong straight, manyhavelong,relativelystraightinnersections. interactions. Wethereforedeterminedasecondsetofflux are whereitisleastlikelythatjetbrightnessesdominated interactions withtheirenvironments.Thestraightersegments rectangular regionwithinwhich(a)theridgelineofjet that wererotatedandregriddedtomaketheinitialsegments the straighterregionsofjetsandcorrespondingrect- densities forthejetsandcounterjetcandidates,usingonly large gradientsinthelobeemission.Thisintegrationwas radius (orbylessthanthesynthesizedbeamHWHMif deviates fromthecenterlineofboxbylessthanajet of thejetsliealongrowsorcolumnsdata(using angular areasofskyonthecounterjetside. segment exceededthoseinboth comparisonregions(i.e.,if If theintegrationinrectangle oppositethestraightjet any counteijetemissionopposite thesestraightjetsegments. rectangles onthecounteijetside, toestimateorsetlimits the jet.Wealsointegratedover thegeometricallyequivalent integrations inthetwoidentically sizedrectanglesalongside corrected forlobeemissionbysubtractingthemeanof © American Astronomical Society • Provided by the NASA Astrophysics Data System Ambiguities aboutthepathsofcounterjetscontribute 3C 334:wedidnotincludeknotC,whichdoes 3C 249.1:onlytheinitialnarrowridge-likefeatureisin- 3C 336:weincludedknotsIandJinthecounterjetinte- 3C 215:thelowbrightnesscontrastofalongcounterjet These “straightjet”integrationsweremadefromimages T| 1:Initial(nearestcentralfeature) minusfinal(nearesthotspot) jet whenclosesttothecentralfeatureand brighten astheybendawayfromtheaxisofstraightjet, there isevidenceforacounterjetcandidateoppositethe boundaries oftheintegrationregions,andresultingjet/ side—by subtractingtheaverageoftwoadjacentintegra- straight jet),thelobecorrectionwasmadeasonjet reference. Inthisapproach,theinitialpositionangleisthat tinguished fromotherlobefeaturesbyhigher-resolutionob- ment ofthejet.Iftheseemissionhookscouldbebetterdis- line projectedintothelobefromaxisofstraightseg- theses. grated fluxdensityofthecounterjetcandidateexceedsthat counterjet intensityratio.Notethatfor3C68.1,theinte- gular lengthofthepathfromcentralfeaturetoouter tions. Otherwise,anupperlimitwasderivedbysubtracting servations, theymightalsobeevidenceforcounteijetsthat the jetinthisrestrictedregion,sowelistratioparen- sity integrationsobtainedinthisway,togetherwiththean- the lowerofadjacentintegrations. of thelinejoiningcentralfeaturetofirstjetknotand in twoways. terminal hotspot.Thepositionanglecanitselfbemeasured as in3C334and336. directions ofthejet,i.e.,betweenpositionangles six deflectionmeasuresthatwehaveconsidered. several ways,reflectingdifferentscalesofjetbendingand alternative deflectionmechanisms.Figure37illustratesthe “hooks” ofemissionthatlinktheirhotspotcandidatestothe 3C175 3C432 3C 68.1 3C351 3C336 3C204 3C 47 3C263 3C208 3C215 3C334 3C249.1 3C 9 Mean CounterJet of CandidateT|iil2n3 The counterjetlobesin3C47and175containcurved Table 6(b)liststhe“straight”jetandcounterjetfluxden- The first,henceforthrj,usesthecentralfeatureasa The angle7ftisthedifferencebetweeninitialandfinal Table 7(a)quantifiestheapparentdeflectionsofeachjetin lc CounterJet Detected? Candidate Detected? (°){°) Was A Was ACentralFeature No No No Yes Yes Yes Yes Yes NO Yes Yes ri :Largestglobaldifferencealong jet 2 1)3: Largestlocaldifferencealong jet Table 7.Jetdeflectionangles. 5.2.2 Deflectionsandbending (a) IndividualSources 28.7 25.4 31.2 16.3 2.8 2.4 7.4 7.0 4.4 7.7 1.6 4.0 6.9 6.7 6.1 TI i (°) Central Feature Referred to Referred to (b) SampleMeans Notes toTable7 31.2 33..4 25.4 13.6 10.5 18.7 7.4 7.2 4.4 3.7 7.5 3.0 6.1 9.1 5.3 Î1 2 n 20.3 10.2 7.4 2.4 2.3 2.0 3.7 1.5 4.2 3.0 3.0 6.6 3.2 9.6 8.1 n 3 n 23.4 30.9 34.7 10.6 55.0 36.0 16.9 18.4 87.3 4.2 4.4 1.2 8.7 n i n ! (°) (°) Polynomial Tangent Polynomial Tangent Referred to Referred to 43.1 74.1 31.4 10.6 27.7 40.5 25.5 32.4 24.7 34.7 26.0 87.3 97.4 54.6 8.4 n 2 n 2 n n 37.5 48.9 85.8 15.9 18.2 23.7 15.8 19.1 35.5 12.2 15.0 18.3 33.4 7.4 8.4 n 3 n 796 1994AJ 108. . 7 6 6B 1 jet. Inapurelyballisticinterpretation,77measuresthelarg- jet knots.Theleftcolumnshowsthecentrallyreferenceddeflectionmea- between anytwovectorscharacterizingtheorientationof based onpurelyballisticoutflowfromanenginewhoseori- the positionsofthesefeatures. Table 7.Thefilledcircleslabeledcfandhsdenotethepeaksofcentral between anytwopositionsalong thejet. changes indirectionofthejetaflowmodelwhich ture. (Thismethodcanbethoughtofasmeasuringthe polynomial curvetothepositionsofcentralfeature,jet feature totheterminalhotspot.(Thismethodcanbethought tangents tothejets,asestimatedbyfittingapolynomial(dashedcurve) feature andjettedhotspot,respectively.Theopencirclesdenotethepeaksof Fig. 37.ThesixmeasuresofjetdeflectionintroducedinSec.5.2.2and tation, r)2imeasuresthelargest differenceinflowdirection est possibleexcursionthatcouldbeascribedtothecentral outermost segmentofthejetratherthantocentralfea- that usedfor7jbutthefinalpositionangleisreferredto the fit.Inthisapproach,initialpositionangleiscloseto creased untilaminimumwasreachedinthereducedxof knots andhotspot.Theorderofthepolynomialwasin- entation varies.) the earliestandlatestepochs,inamodelofjettrajectory of asmeasuringthe“swing”centralenginebetween the finalpositionangleisthatoflinejoiningcentral sures. Therightcolumnshowsthedeflectionmeasuresobtainedfrom engine onthetimescaleofjet.Inastreamlineinterpre- streamlines liealongthefittedpolynomial.) of thetangentstojetdirection,asestimatedbyfittinga 797 BRIDLEETAL.:TWELVE3CRQUASARS the largestdifferenceinposition angles,measuredwithref- largest localdeflectionanywhere alongthejetpath,is angles betweenanypairofadjacent knotsinthejet,i.e., 2c lc © American Astronomical Society • Provided by the NASA Astrophysics Data System The angletjisthelargestdifferenceinpositionangles The second,henceforth7}usesthelocalpositionangles The angle773measuresthelargest differenceinposition 2 lh 0 with outflowoveraconeofdirectionswithinwhichsome nomial fittedtothejetridge-lineneednottraceaflowline, features appearbrighterthanothers.Insuchmodels,apoly- kinematics, wedonotwishtorestrictourselvesjustthese pend muchmorecriticallyoninterpretationofambiguous ponents, someofwhichrepresentedthebackgroundgradi- could alsomeasurejetdeflectionappropriatelyformodels models. Forexample,thecentrallyreferencedanglesrj ria) inthecounterjettedlobes. features, andtherearesometimesnohotspots(byourcrite- partially blendedorconfusedbysteepgradientsintheun- Well isolatedknotswerefittedbytwo-dimensionalelliptical below. with andwithoutcounterjetcandidates,have6<78°. may characterizethejetdeflectionswellifridge-line cone. Tosummarize,the“locallyreferenced”estimatesrji and r)mayestimatethe(projected)openingangleof surement oftheseanglesintermstwosimplemodelsjet candidates aremarginaldetections,theirinferredpathsde- mate theseanglesreliablyforthecounterjets—thecounterjet these 13quasars,inorderofincreasingt).Wecannotesti- in thejet. change injettangentdirectionsbetweenanyadjacentknots the jet(includingterminalhotspot).773/islargest knot toareferencedirection.The distributionsofAând ents. Table8givestheresultsof thismodel-fitting. derlying emissionweremodeledbymultipleGaussiancom- to accountforunderlyingextendedemission.Knotsthatare didates byfittingmodelstothemusingtheAIPStaskIMFIT. distinguishable discreteknotsinthejetsandcounteijetcan- ues ofallsixangles77forthesourceswithoutcounterjet The “largestdeflection”measurer)predictscounterjet tection by7)mustbecoincidental,however:sixjets,both traces astreamline,whilethe“centrallyreferenced”esti- erence tothecentralfeature,betweenanyadjacentknotsin Gaussian models,superposedonasecond-orderbackground sources withcounterjetcandidates.Thisconnectionbetween candidates arewellbelowthecorrespondingaveragesfor candidates: allsourceswithnocounterjetcandidateshave measure 7)toemphasizeabroadcorrelationwithinthis mates r)couldcharacterizethembetterifitdoesnot. tions A^reach69°.Because most ofthefeaturesthatwe is quantified.WeexploreitsimplicationsinSecs.6and7 dates evidentlydependslittleondetailsofhowthebending apparent jetbendingandthepresenceofcounterjetcandi- candidate detectionalmostaswell77. sample betweenjetdeflectionandthedetectionofcounterjet A0j<2O° and84%haveA^ <20°, althoughtheinclina- A0j bothpeakstronglynear0°—87% ofthejetknotshave 77>6!8. This“perfect”orderingofcounterjetcandidatede- 77=ss6!8, whereasthosewithcounterjetcandidateshave c lc lc 1c ck 2c Xc u c lc etck et 1c 1c Note thatalthoughwehavejustcharacterizedthemea- Table 7(a)listsourestimatesofall6anglesforthejetsin We derivedapproximateparametersforthemostreadily Both A(ândAi^measure the inclinationofjet Table 7(b)showsamorerobustresult—theaverageval- Table 7(a)isorderedbythe“initialminusfinal”bending cket 5.2.3 Internalstructure 797 1994AJ 108. . 7 6 6B 798 BRIDLEETAL.:TWELVE3CRQUASARS knots whoseAândAi^valuesdiffersignificantlyfrom ited angularresolutiontransversetothejets.Wecan,how- identify asjetknotsalignsowellwiththelocalaxis, larger atsmall0.Thisisapattern exhibitedbymanywell 0°. WereturntothepropertiesoftheseknotsinSec.5.2.7. ever, legitimatelyrecognizeaclassofstronglymisaligned emission maybesomewhatsubjective,especiallywithlim- distinction betweenaknotandunderlyingmorecontinuous <£> generallydonotgrowinlinear proportionto0,however, sources: thetransverseknotwidths tendtogrowwith as theywouldinafreelyexpanding jet.Instead,O/0isoften angular distance0fromthecentral feature.Theknotwidths etck \|/: positionangleoflinefrompeakknottocentralfeature : FWHMofknottransversetothelinefromitcentralfeature Knot ID:fromFiguresinSec.4,fitswithtwoGaussiancomponentscarry ck © American Astronomical Society • Provided by the NASA Astrophysics Data System Table 8showsthatwedetect jetspreadinginseveral LAS,SAS: majprandminoraxesoffittedellipticalGaussiancomponent 3C 68.1 3C 47 3C 47 3C 47 3C175 3C175 3C175 3C 68.1 3C 47 3C 47 3C 47 3C 9 3C 9 3C208 3C208 3C208 3C204 3C204 3C204 3C175 3C175 3C175 3C175 3C 68.1 3C 68.1 3C263 3C249.1 3C215 3C215 3C215 3C204 3C204 3C263 3C263 3C263 3C249.1 3C249.1 3C263 3C263 3C336 3C336 3C336 3C336 3C336 3C334 3C334 3C334 3C334 3C334 3C334 3C334 3C334 3C334 3C334 3C334 3C334 3C334 3C351 3C351 3C351 3C336 3C336 3C432 3C432 3C351 Table 8.Parametersofknotsinjetsandcounterjetcandidates. A\jf: anglebetweenfittedmajoraxisandlinetocentralfeature Vjet :localpositionangleoftangenttojet(frompolynomialfit) ck Ay: anglebetweenfittedmajoraxisandlocaltangenttojet ©: angulardistancebetweenpeakofknotandcentralfeature jet Knot 0 ID (") \y: positionangleofmajoraxisfittedcomponent 23.73 22.68 21.72 20.75 19.31 15.57 25.23 11.92 11.64 15.38 15.22 15.17 13.96 11.63 10.00 19.73 11.81 13.69 13.70 1.03 0.360.44 7.96 3.06 7.26 5.42 3.57 2.78 0.99 2.72 8.46 5.21 2.22 9.23 1.72 7.85 5.83 3.79 8.68 9.63 6.47 4.42 8.25 5.84 3.60 0.77 1.63 9.35 2.39 6.95 1.90 5.97 5.19 1.01 4.91 8.26 3.76 1.30 9.35 3.12 6.29 0.03 1.21 0.40 0.61 1.72 0.97 6.03 1.85 S|. :integratedfluxdensityofknot in additional designations1and2 (mJy) (") 22.9 0.31 95.5 25.3 16.8 38.3 Sine LAS 1.16 0.45 2.45 1.73 1.23 2.04 0.66 0.70 1.29 3.14 1.12 1.13 0.72 1.23 1.44 2.09 1.26 1.26 1.59 1.79 1.96 8.82 1.23 1.59 0.56 0.63 3.22 2.680.14 1.75 6.31 6.89 2.78 2.72 2.23 2.02 1.88 9.19 6.72 2.14 4.69 3.01 1.42 0.41 0.88 1.17 1.59 1.74 3.04 1.05 0.98 8.27 0.18 6.70 0.72 0.42 0.57 0.18 0.49 0.76 5.2.4 Spreading Notes toTable8 <0.89 <0.43 <0.26 2.58 2.20 2.41 3.89 0.56 1.05 0.79 1.09 0.67 0.58 2.66 0.28 0.69 1.97 0.91 0.86 0.51 0.47 0.67 0.35 0.46 0.33 0.60 0.33 0.88 0.55 0.02 0.49 0.20 • 0.59 1.07 0.55 0.43 0.55 2.22 0.81 1.69 1.15 0.65 2.04 3.28 1.49 1.34 0.50 0.10 1.64 0.27 0.39 0.67 0.15 1.82 0.20 1.07 0.14 0.63 1.27 1.08 0.92 0.37 0.60 <0.60 0.40 <0.40 0.29 0.25 0.10 0.06 0.51 0.15 0.45 0.34 0.25 .16 <0.16 42 <0.11 <0.16 ;0.89 :0.17 C) SAS 0.23 0.42 0.24 0.26 0.24 0.23 0.22 0.08 0.37 0.20 0.82 0.54 0.36 0.28 0.13 0.33 0.32 0.08 0.22 858187 0.06 0.24 0.09 0.29 0.35 0.45 0.27 0.10 0.12 0.17 0.21 0.44 0.38 0.15 0.17 0.27 0.32 0.44 0.42 0.27 0.09 0.15 0.30 158 160 171 112 133 146 133 167 103 109 109 112 114 131 118 145 158 102 110 109 107 131 137 136 144 146 127 132 148 141 43 98 84 81 33 2325108 26 2150 52 18223430 (°) Vck VjetA\|fAVj«í>/0 161 156 175 143 150 172 177 134 139 141 ck 177 100 103 143 140 109 109 109 142 141 141 142 148 147 158 110 109 109 138 139 141 142 29 78 97 11121 96 99 98 153 25 133 513 133 100 134 1733 118 615 103 120 123 110 139 141 110 109 108 139 142 142 141 138 144 151 128 109 108 110 122 127 136 137 31 1412 81 2231 80 85 17 102.8 1 40.21 <0.17 <0.019 <0.098 <0.07 <0.22 <0.20 0.22 0.045 0.044 0.025 0.023 0.10 0.18 0.044 0.074 0.088 0.042 0.13 0.074 0.024 0.028 0.042 0.038 0.026 0.064 0.021 0.053 0.043 0.13 0.043 0.055 0.028 0.022 0.003 0.012 0.016 0.022 0.023 0.029 0.042 0.023 0.024 0.012 0.018 0.015 0.033 0.065 0.025 0.025 0.022 0.027 0.048 0.053 0.067 0.10 0.035 0.12 0.15 0.031 0.041 0.046 0.058 0.19 0.013 0.041 0.14 _1 -1 25-21 1262 _1 jets. ThesetransverseprofileswereanalyzedusingH.S. resolved jetsinradiogalaxies(e.g.,Willisetal.1981;Fanti jets inthesepowerfulsourcesthereforeseemstobeaprop- peaks thatdominatethetwo-dimensionalmodel-fitting.Itis fainter emissionbetweentheknotsinadditiontolocal beamwidth intervalsalongthestraightersegmentsofthese more detail.WeusedtheSLICEfacilityinAIPStomake rapid spreading,followedbyslowerorrecollima- et al.1982;Perley1984;Killeen1986;Morganti projected length.Thespreadingratesfromthepresentstudy scribed assuperposedGaussianfeatures.Figures38to41 also freeofthe(attimesunwarranted)assumptionthat This procedureallowsustoexaminethespreadingof nomial baselinesandfitone-dimensionalGaussianmodels. Liszt’s drawspecprofileanalysissoftwaretoremovepoly- many profilestransversetotheaveragejetaxesatone- tively straightjetsin3C175,204,263,and334 tion. et al.1987;Bridle1991;Clarke1992)—aninitial when theyareclosesttothenucleus—noneofthesespread- piled byBridle(1995a)forjetsthatare>10/ikpcin knot modeling.Forsomecases,especially3C175,thereis one-dimensional profile-fitting(filledcircles)andthetwo- show spreadingplotsforthesejetsderivedfromboththe longitudinal brightnessvariationsalongthejetscanbede- widths inthe~8/ikpcinnerjet3C351,whichistoo common insourceswithP^ClO/*WHzbutrare powerful radiogalaxiesandquasarspreviouslynotedina the brightknots. evidence thatthefainterinter-knotemissionisbroaderthan the profilefittingtendstoestimatelargerwidthsthan to withintheerrorinprofilefitting.Wheretheydisagree, triangles forupperlimits).Thetwoapproachesusuallyagree dimensional modelfits(opencirclesformeasurements,open sources withPb>10/î”WHz”. clear thatspreadingrates>0.10on>10/îkpcscalesare true spreadingratedistribution.Despitethisselection,itis much smallersamplebyBridle(1984).AsFig.42shows ingly confirmtheabsenceofspreadingrates>0.1among superimposed onanensembleofsuchspreadingdatacom- these 3CRquasarjetsagainsttotallobepowerat1465MHz, marginally detectedouterjetappearstobebettercollimated ing plotsextrapolatestotheorigin.(Thetransverseknot average spreadinginthejets3C204,263,and334 determined, itmayrepresentonlytheupperenvelopeof are themselvesuncorrelatedwithlobepower,buttheystrik- than this.)Thelowaveragespreadingrateofthelarge-scale initial spreadingrateof0.13forthisjetsegment,whereasthe short tobeshowninFig.42,arealsoconsistentwithahigh data onlyforjetswhosespreadingrateshavebeendirectly The spreadingratesandinternal morphologiesofthesequa- explore thedetailedstructuresof thejetsinrecollimation ond scales,todeterminethescale oftherecollimationandto scales, notby“initialconditions” nearthecentralobjects. erty thatisimposedbyinteractions onmany-kiloparsec sar jetsshouldthereforebeexamined directlyonsubarcsec- 1oe We analyzedthecollimationpropertiesoflong,rela- Figure 42plotstheaveragespreadingrates((O/0))for Figures 39to41givedirectevidenceforfaster-than- 798 PQ UD r" 799 BRIDLE ETAL.: TWELVE 3CR QUASARS 799 ooo Spreading of Jet in 3C175 Spreading of Jet in 3C263

^0 • Profile fitting O Knot modeling

8 •Sg 0 0.6 5

ft 5.0 10.0 15.0 Angular Distance 0 from Central Feature (arcsec) Angular Distance 0 from Central Feature (arcsec)

Fig. 38. The deconvolved FWHM transverse to the jet in 3C 175 plotted Fig. 40. The deconvolved FWHM transverse to the jet in 3C 263 plotted against angular distance 0 from the central feature. Filled circles show against angular distance 0 from the central feature. Filled circles show one-dimensional Gaussian fits to the transverse intensity profiles, with their one-dimensional Gaussian fits to the transverse intensity profiles, with their lo- errors. Open circles show the results of two-dimensional Gaussian mod- 1er errors. Open circles show the results of two-dimensional Gaussian modeling of knots. eling of knots.

regime. The jets in 3C 204 and 3C 263 also show evidence knots after the first. (If the central feature was itself part of of “flaring” (accelerated spreading) as they approach the hot this train, the first entry in this column would match the later spots. entries.) Table 9 shows that the knot trains from I to F in 3C 204 5.2.5 Trains of knots and from D to H in 3C 263 are particularly close to periodic, It has been suggested (Rees 1978; Sanders 1983; Smarr with periods near 2.1 in 3C 204 and 2'.'5 in 3C 263. In nei- et al. 1984; Hardee & Norman 1989) that quasiperiodic ther source does the central feature participate in the period- trains of knots in jets arise from shock cell patterns in con- icity of the knot train—in both, it is closer to the first knot in fined flows. The jets in 3C 175, 3C 204, 3C 263, and 3C 334 the train than the periodicity would require. In 3C 175 the all contain trains of knots with an appearance of periodicity. inter-knot separation lengthens with increasing distance from Table 9 tabulates their main properties. A strictly periodic the central feature, while in 3C 334 there is no steady trend. knot train would have equal values of A0 (Column 4) for all 3C 334 has the lowest values of the ratio between the knot

Spreading of Jet in 3C204 Spreading of Jet in 3C334

• Profile fitting • Profile fitting O Knot modeling O Knot modeling V Knot modeling limit V Knot modeling limit

8 ÜL ra, e ® 0.6 ¿I. . $ T ä * • £ 'S Kfo, ° ■ - -g 0.4 O ? ? V i

0.0 5.0 10.0 15.0 5.0 10.0 15.0 20.0 Angular Distance 0 from Central Feature (arcsec) Angular Distance 0 from Central Feature (arcsec) Fig. 39. The deconvolved FWHM transverse to the jet in 3C 204 plotted Fig. 41. The deconvolved FWHM transverse to the jet in 3C 334 plotted against angular distance 0 from the central feature. Filled circles show against angular distance 0 from the central feature. Filled circles show one-dimensional Gaussian fits to the transverse intensity profiles, with their one-dimensional Gaussian fits to the transverse intensity profiles, with their 1(7 errors. Open circles show the results of two-dimensional Gaussian mod- 1er errors. Open circles show the results of two-dimensional Gaussian modeling of knots, triangles show upper limits from the knot modeling. eling of knots, triangles show upper limits from knot modeling.

© American Astronomical Society • Provided by the NASA Astrophysics Data System PQ UD r" 800 BRIDLE ETAL.: TWELVE 3CR QUASARS 800

Average Jet Spreading Rates feature to be brighter than the more distant knots until the jet (Jets >10 kpc long only) is close to its terminating hot spot. This statement holds for ♦ Radio Galaxies 3C 175, 3C 204, 3C 208, 3C 215, 3C 249.1, 3C 263, 3C 334 O'! o Quasars (published) O'! • Quasars (this paper) (interpreting E2 as the first jet knot and not as part of the central feature), and 3C 351. In 3C 68.1 and 3C 432, the jets do not contain long well resolved knot trains with which to test this statement. Only in 3C 9 and 3C 336 is it clearly false, in the sense that both jets have long segments in which they brighten with distance from the central feature. In several sources, a large fraction of the integrated jet flux density arises within a few hot spot diameters of the terminal hot spot: examples are 3C 68.1 (82% of the integrated jet flux density is in knot C), 3C 204 (28% of the integrated jet flux density is in knot E), 3C 263 (62% of the integrated jet flux density is in knot J), and 3C 336 (58% of the integrated jet 0.0022.0 L— 24.0 25.0 26.0 flux density is in knot C). in w 2 at 1465 MHz Logi0(P|obe H ’’ ) 5.2.6 Magnetic field strength, minimum pressure, and synchrotron lifetime Fig. 42. Average spreading rates of jets that are longer than 10A 1 kpc in Where the jet and putative counterjet features are re- projection, plotted against lobe power in h~2 WHz-1 at 1.5 GHz. solved, we can estimate the equipartition magnetic field strengths i?eq, minimum internal pressures, and the synchro- separation and the transverse FWHM (between 3.5 and 7). tron lifetimes fsyn of the electrons radiating in the equiparti- 3C 175 and 3C 263 exhibit higher values (between 12.5 and tion field strength at the observed frequency, subject to the 14 for 3C 175, and between 14 and 25 for 3C 263), while conventional assumptions about synchrotron-emitting plas- those for 3C 204 are ill defined (17 to 100) but evidently mas (Pacholczyk 1970). Table 10 summarizes the results, larger than in 3C 334. with limits to quantities for the unresolved features. These There is a trend for the jet knot closest to the central parameters may be used, subject to the caveats given in the table, for studies of jet confinement, recollimation, and sta- Table 9. Trains of jet knots. bility. Table 10 also computes the ratio £ between the light-travel time t from the central feature to the jet knot and the syn- Source Knot 0 A0 1, one or more of the fol- lowing will apply: (a) the radiating particles have been reac- 3C175 2.22 2.22 0.08 celerated since leaving the quasar nucleus, (b) the radiating 3C175 5.21 2.99 0.22 3C175 8.46 3.25 0.23 particles did not (in their own frame) travel the entire dis- 3C175 11.92 3.46 0.27 tance from the nucleus radiating with their present emissiv- ity, or (c) the field strength is below that given by the equi- 3C204 I 1.63 63 <0.16 3C204 H 3.79 16 0.09 partition assumptions, f will be underestimated if the jets are 3C204 G 5.83 04 <0.11 oriented away from the plane of the sky, if much of the 3C204 F 7.85 2.02 0.02 detected knot emission is in small structures such as sheets 3C204 E 11.64 3.79 0.25 or filaments that do not fill the dimensions estimated here, or 3C263 D 1.90 1.90 0.12 if there is more energy in ions than in radiating electrons. £ 3C263 E 4.42 2.52 0.14 will be overestimated if the spectra of the knots steepen 3C263 F 6.95 2.53 0.10 3C263 G 9.35 2.40 0.17 above, or flatten below, 4.9 GHz. 3C263 H 11.81 2.46 0.15 Finally, note that if Doppler boosting is important in these jets, the values in Table 10 should be modified by beaming 3C334 F 1.30 1.30 0.27 3C334 Gl 2.39 1.09 <0.16 correction factors (see Sec. 7.1). 3C334 H 3.76 1.37 0.38 3C334 I 6.29 2.53 0.42 5.2.7 Polarimetry 3C334 J 8.26 1.97 0.44 3C334 Kl 10.00 1.84 0.48 Table 11 lists the polarimetric properties of the total emis- 3C334 K2 11.63 1.63 0.32 sion at the positions of the peaks of the knots in the jets and 3C334 M 13.70 2.07 0.30 3C334 NI 13.96 0.26 0.35 counterjet candidates. We have not corrected these polariza- 3C334 N2 15.17 1.21 0.38 tion parameters for the contribution of more extended emission to the total or polarized intensities at these positions. Thus, if the jet is superposed on lobe emission, the quoted Notes to Table 9 polarization is the sum of the jet and lobe contributions. The values of the degree of polarization p at the knot 0: separation of peak from central feature À0: separation of peak from previous peak peaks range from 5% to —50%, but are typically —25%. The : FWHM of knot transverse to jet degrees of polarization are uncorrelated with the orientation

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1994AJ 108. . 7 6 6B >m 801 BRIDLEETAL.:TWELVE3CRQUASARS tangent tothejetasreferencedirection. feature againsttheorientationA70°. The degreeofpolarizationalsodoesnotdependsystemati- the knot(A^)ortodirectioncentralfeature). of theEvectorsrelativetojet(A*j),majoraxis the tangenttojet(A^j),orrelativedirection cally ontheorientationofknotsthemselvesrelativeto central feature(A0-). jet tangentthanwiththedirectiontocentralfeature,and with thedirectiontocentralfeature—noteclustering within 20°ofthelocaljettangentandmajoraxis A*jet>70°. Itisalmostaswellorganizedrelativetothema- the localaxisofjet,78%jetknotshaving each other.TheE-vectororientationissystematicrelativeto the knot,respectively).Figure43illustratesthatpolariza- Table 8)differsmarkedlyfromthatoftheknotswith both panels. toward theupperleft-handcorners(A*=90°,A^=0°)in tion andtheknotsareoftenwellalignedwithjets within 20°ofthecentralfeature).Incontrast,Fig.43(b) orientations forthemoremisalignedknots(A0ck15° jets. Thus,thetrendformisaligned polarizationatmisaligned (These correspondtotheapparentmagneticvectorlying ck ck jets. (Inallbutonecase—3C215—the sharpestbendisalso that theirorientationrelativetothejetisinsensitive have AY>70°(i.e.,theirapparentmagneticvectorpointing Aif/<15°. Themisalignedknotsaremuchlesslikelyto knot’s orientationrelativetothejet. shows thattheEvectorsatmostknotsalignbetterwith k kck et et knots isdominatedbydatafrom thesharpestbendsin A^>20° and<70°represent thelargestbendsintheir ck at theendof jetthatisfarthestfromthequasar. Inallbut (ck ck ck © American Astronomical Society • Provided by the NASA Astrophysics Data System By contrast,theorientationalparameterscorrelatewith Figure 43(a)alsoshowsthatthedistributionofE-vector Note alsothatsixoftheseven pointsinFig.43(a)with Relative toLinefromCentralFeatureKnotLocalJetAxis Polarization AngleAx ckjet 70°andtwo complex for3C334.) one othercase—3C9—itisatthebrightestknot,orknot bends inthejetalsoperturbspatternofmagneticfields A0j>2O° [Fig.43(b)]alsorepresentthesharpestbendin A^jet70. Itisevidentlyhardertomisalignthepolarization the jetwithdirectiontoquasar. the directiontoquasar. polarization attheknotpeaksdecreaseoutwards,butin3C dicular tothejettangentisstrongerthananymemory”of along thejetaxis.ThetrendforEvectorstostayperpen- knot peaksfluctuaterandomly. tral feature.In3C47,263,and334,thedegreesof ization pattheknotpeakswithseparation0fromcen- 336 theyincreaseoutwards,andin3C175204 with increasingdistancealongthesejetsegments,butthere the polarizationpropertiesbetweenpeakslistedinTable they arerelativelyunconfusedbylobeemission,toexamine decline andrecover.Inothersources,thepolarizationsat along theridgelinesofstraighterjetsegmentswhere ization ofthejetin3C47apparently increasesasthejet are significantlocalfluctuationsinmanyofthem. ridges ofotherjetsinthissample alsochangesnoticeablyas enters thesouthlobe.Thedegree ofpolarizationalongthe et et is oftenhighlypolarizedatthese resolutions,theapparent the ridgescrossintolobes,but thechangeissometimesa 11. Wefoundnogeneraltrendforptochangesystematically decrease. Astheemissionfrom theextendedlobestructures Five ofthesevenpointswithknotmisalignments These resultsshowthattheprocessmisalignsknotsat There isnocommonprogressionofthedegreepolar- We alsoplottedprofilesofthedegreepolarizationp Fernini etal(1991)commentedthatthedegreeofpolar- 801 1994AJ 108. . 7 6 6B just changesintheblendofpolarizationsbeingsummed bly wheneverthemixtureofjetandlobeemissionalong with distancefromthecentralradiofeature. whether suchchangesintheapparentpolarizationatajet degree ofpolarizationalongajetridgecanchangeapprecia- 802 BRIDLEETAL.:TWELVE3CRQUASARS that thedegreeoflinearpolarizationchangessystematically ments thatarenotconfusedbylobeemission,wedofind this paper.Weemphasizehoweverthat,instraightjetseg- line ofsightchanges.Furtheranalysisisneededtoestablish along thelineofsight.Suchanalysisisbeyondscope ridge reflectchangesinthepolarizationstateofjets,or Table 10.Derivedparametersofknotsinjetsandcounteijetcandidates. © American Astronomical Society Luminosity integratedfrom10MHzto 100GHzinquasarfrar 3C Elliptic cylindricalemittingvolume, fullyfilled 3C 3C 3C 3C 3C 3C 3C 47 3C 47 3C 68.1 3C 47 3C 47 3C 47 3C 47 3C175 3C175 3C175 3C175 3C175 3C 68.1 3C 68.1 3C 68.1 3C175 3C204 3C204 3C204 3C175 3C215 3C208 3C208 3C204 3C204 3C215 3C208 3C249.1 3C249.1 3C215 3C263 3C249.1 3C334 3C334 3C263 3C263 3C263 3C334 3C334 3C334 3C263 3C263 3C336 3C336 3C334 3C334 3C334 3C334 3C334 3C334 3C334 3C334 3C336 3C336 3C336 3C336 3C336 3C432 3C351 3C351 3C351 3C351 3C432 Electrons inconstantfieldthroughout lifetime Major, minoraxes=LAS,SASfromTable 8 Assumptions madewhencomputingTable 10: Electrons movewithrandompitchangles Equal energiesinionsandelectrons Knot ID D G2 G1 N2 N1 E2 1 H=100h kms'Mpc,q=0.5 0o Depth =SASfromTable8 >2 . >1. 7. 4. 4. 2. 2. 5. 1. 2. 3. 3. Spectral index=0.6 4. 3. 4. 5. 1. 8. 1. 5. 6. 6 6 (Gauss) .6E-05 .6E-05 .2E-05 . 3E-05 .3E-05 .0E-04 .0E-05 . 6E-04 .4E-05 .IE-04 .4E-05 .2E-05 .3E-05 .IE-05 .9E-05 .5E-05 .2E-04 .IE-04 .6E-04 .IE-04 .8E-04 .8E-04 .7E-04 .5E-04 .9E-04 .3E-05 .2E-05 .5E-04 .IE-04 .2E-04 .4E-04 .2E-04 .0E-05 .9E-05 .2E-04 .5E-04 .5E-05 .0E-04 .0E-04 .IE-04 .0E-05 .3E-04 .3E-05 .0E-04 .9E-05 2H 4E-04 2E-04 3E-04 IE-04 8E-04 8E-04 5E-04 h 4E-05 IE-05 IE-05 8E-05 3E-04 8E-04 2E-05 8E-05 5E-05 0E-05 0E-04 0E-05 2E-04 2E-04 2E-04 4E-04 3E-05 5E-04 >1.8E+13 >9.2E+10 >1.2E+13 >8.5E+12 >3.6E+12 >1.OE+12 >3.6E+12 >5.7E+11 3 2.OE+14 8.2E+13 3.7E+11 3.9E+11 2.3E+11 2.8E+13 9.9E+13 6.1E+13 6.6E+12 2.3E+12 3.5E+13 1.7E+11 1.1E+12 3.6E+12 1.1E+12 6.8E+11 4.4E+12 1.4E+12 1.4E+12 1.3E+12 8.7E+11 9.4E+12 3.8E+13 8.9E+12 3.1E+12 2.2E+13 3.4E+13 4.5E+12 1.1E+13 1.0E+13 7.3E+12 5.5E+12 1.2E+13 1.4E+12 2.9E+12 5.5E+12 2.3E+12 7.7E+12 2.6E+12 5.2E+12 1.3E+12 5.1E+13 6.9E+11 1.6E+12 1.1E+12 5.6E+11 9.3E+11 9.2E+11 8.2E+11 6.4E+12 5.0E+12 3.7E+12 7.7E+12 4.9E+12 5.5E+12 4.2E+13 1.9E+12 3.6E+12 9.8E+11 1.7E+12 6.2E+13 6.5E+12 (nf K) Prain <8.2E+04 <5.6E+06 <1.7E+05 <1.3E+05 <3.8E+05 <2.7E+05 <1.6E+06 <6.4E+05 2.6E+04 1.7E+05 2.3E+04 1.3E+04 3.3E+04 4.3E+05 7.6E+05 3.7E+06 2.1E+06 2.1E+06 3.0E+06 5.9E+04 7.3E+05 7.1E+05 7.5E+05 3.6E+05 1.6E+05 2.8E+05 1.0E+06 8.6E+05 5.8E+04 1.4E+06 1.8E+05 2.8E+05 1.5E+05 5.7E+04 4.5E+05 8.3E+05 1.0E+05 1.4E+05 2.7E+05 2.5E+05 3.0E+05 1.7E+05 6.1E+04 2.8E+05 4.3E+05 4.7E+05 2.5E+05 8.2E+05 5.3E+04 1.3E+06 2.1E+05 5.3E+05 1.5E+06 1.0E+06 1.0E+06 1.1E+06 6.9E+05 9.3E+05 7.1E+05 4.1E+05 4.9E+04 2.2E+05 2.7E+05 3.3E+05 1.9E+05 2.7E+05 2.5E+05 5.5E+04 6.1E+05 1.0E+06 -3/7 (yr) h >0.16 >0.02 >0.18 >0.47 >0.08 >0.10 >0.004 >0.06 3.8 5.4 1.5 1.4 0.08 0.09 1.7 0.02 0.08 0.10 0.95 0.85 5.0 0.02 0.10 0.16 0.21 0.29 0.35 0.31 0.16 1.9 0.58 0.16 0.18 0.09 0.28 0.35 0.20 0.08 0.37 0.16 0.06 0.13 0.09 0.22 0.23 0.31 0.01 0.18 0.93 0.32 0.24 0.15 0.08 0.10 0.07 0.04 0.14 0.02 1.5 0.30 0.17 0.12 0.16 0.27 0.03 0.08 0.95 0.71 0.04 0.03 Provided bythe NASA Astrophysics Data System which carrythedesignation1afteralphabeticknotcode. that contributedtoourclassificationoftheregion.Table represented byfittingasinglecomponenttoalltheemission hot spotscontaincompactsubstructurethatwasnotwell these parametersareonlyroughguidestothetotalfluxden- hot spotstructuresarewellrepresentedbyGaussianmodels, sities, angularsizes,andorientationsofthehotspots.Some Gaussian modelsfittedtothehotspots.Becausenotall 12(b) listsparametersforthesemorecompactsubstructures, p: fractionalpolarization(or2aupper limit)atpositionofpeak Ax: anglebetweenEvectorandline frompeaktocentralfeature ck Table 12(a)liststheparametersofsingle-component 0: angulardistancebetweenpeakof knot andcentralfeature Table 11.Polarizationofknotsinjetsandcounterjetcandidates. (knots arelistedinorderofincreasing 0alongthejets, %: apparentpositionangleoftheE vector atthepeak and ofdecreasing0alongthecounterjet candidates) Ax jet•anglebetweenEvectorandlocal tangenttojet 3C 3C 3C 3C 3C 3C 3C 3C 47 3C 47 3C 47 3C 47 3C175 3C175 3C175 3C 68.1 3C 68.1 3C 68.1 3C 68.1 3C 47 3C 47 3C175 3C175 3C175 3C204 3C204 3C175 Source Knot© 3C204 3C204 3C204 3C215 3C215 3C208 3C208 3C208 3C249.1 3C249.1 3C215 3C334 3C334 3C334 3C334 3C334 3C263 3C263 3C249.1 3C336 3C336 3C336 3C336 3C334 3C334 3C334 3C334 3C334 3C334 3C334 3C263 3C263 3C263 3C263 3C351 3C336 3C336 3C336 3C351 3C351 3C432 3C432 3C351 Áx: anglebetweenEvectorandmajor axisofknot k ID (") G D2 Dl 20.75 23.73 15.57 19.31 21.72 25.23 22.68 11.92 11.64 19.73 15.38 11.81 11.63 10.00 15.22 15.17 13.96 13.70 13.69 2.78 7.96 7.26 3.57 1.03 3.06 6.47 5.42 0.99 9.23 2.22 8.68 8.46 5.21 9.35 9.63 7.85 3.60 2.72 3.79 1.63 4.42 5.19 1.01 8.25 5.84 1.72 0.77 5.83 1.90 5.97 2.87 2.39 1.30 8.26 3.76 9.35 6.95 6.29 2.79 2.02 1.21 4.91 3.12 1.72 0.97 1.85 0.40 0.61 6.03 5.3 TheHotSpots Notes toTable11 <0.21 <0.14 <0.14 <0.10 <0.10 <0.14 <0.20 <0.10 <0.11 <0.14 <0.08 <0.17 <0.13 <0.40 <0.10 0.16 0.25 0.10 0.09 0.29 0.30 0.16 0.29 0.14 0.19 0.31 0.21 0.49 0.09 0.05 0.25 0.11 0.11 0.17 0.20 0.46 0.20 0.40 0.32 0.19 0.19 0.25 0.29 0.19 0.05 0.27 0.15 0.20 0.43 0.21 0.30 0.39 0.48 0.18 0.11 0.31 0.13 0.20 0.23 0.19 0.13 0.20 0.39 0.28 0.19 0.27 0.31 0.21 0.29 -65 -16 -56 -40 -40 -10 -16 -11 -64 -40 -30 -24 -38 -53 -31 -11 -65 -50 -57 41 74 41 23 86 48 68 80 19 58 47 36 66 27 36 14 -6 73 31 41 56 58 61 64 68 (°) X 6 1 0 1 AXck 78 36 82 86 30 82 62 72 20 83 89 71 87 39 86 87 17 83 78 37 50 58 57 50 (°) 75 76 73 82 72 78 85 73 78 43 80 88 38 80 86 83 69 84 88 67 90 2 4 AXjet (°) 79 77 70 88 52 84 83 83 83 90 75 78 85 19 86 10 90 71 47 30 82 53 54 62 86 77 71 89 81 71 81 83 72 75 89 86 83 84 65 74 39 80 83 89 7 AXk (°) 84 72 57 88 19 52 88 83 82 67 85 56 75 87 15 45 37 82 84 56 83 19 36 65 60 77 73 85 85 90 76 78 88 87 83 82 54 77 73 58 81 86 83 83 90 90 86 62 90 1 802 1994AJ 108. . 7 6 6B 1 1 803 BRIDLEETAL.:TWELVE3CRQUASARS brightness <25mJypersqarcsec,whereasthefeaturesthat jetted hotspotissmallerthanits counterjettedcounterparton presence ofcounterjettedhotspotsandthelinearresolution the mostpromisingcandidate[Table12(c)]hadasurface some notabletrends: by morethan25%.Inallnine,thejettedhotspotis projected linearextent.(Themeansizefor met ourcriteriaallhavebrightnesses>50mJypersqarc- SW) areonthecounterjettedsideofsource.(Inallfive, real, forthereisnocomparablyclearconnectionbetweenthe more extendedsourcestolackcounterjettedhotspotsmaybe hot spotsis127±62h~kpc.)Thisapparenttrendforthe the fivesourceswithoutcounterjettedhotspotsis the samplebyangularextent,andamongsevenlargest their counterjettedlobesarealsothefivelargestsourcesin sec.) Thefivesourceswithouthotspots(byourcriteria)in solely bydifferingrelativeresolutionsforsourcesofdiffer- of ourimages(asmightbeexpectediftheeffectisproduced 226±26h~ kpc,whilethatfortheeightwithcounterjetted the hotspotsdifferinareaby less than2%.In3C175,the candidate (byarea)inthecounterjetted lobe;inbothsources, compact. Onlyin3C175and334isthesmallerhotspot ent sizes). (3C 47N,3C68.1S,215334NWand351 the minoraxis,butnoton majoraxis.In3C334,the feature inthecounteijetlobe(C) doesnotqualifyasahot spot becauseoflowbrightness contrast, andmightbeaknot Despite themodel-fittinguncertainties,Table12contains © American Astronomical Society • Provided by the NASA Astrophysics Data System (a) Allfivelobesthatcontainnohotspotsbyourcriteria (b) Inninesourcesthehotspotcandidatesdifferinarea Source Knot 3C 9A 3C208 3C204 3C175 3C175 C 3C 68.1B 3C 47A 3C 9K 3C215 3C208 3C204 Source Knot0SLASSASYYchAy 3C263 K 3C263 B 3C249.1 K 3C249.1 A 3C336 B 3C334 0 Source Knot0 3C432 H 3C432 B 3C351 J 3C336 K 3C175 Cl 3C 68.1Bl 3C 47A1 3C 9Kl 3C175 01 3C432 3C334 01 3C 47H31.19 intch 3C215 A21.90 3C 68.1H26.64 3C351 A36.58 3C334 C26.72 Table 12.Parametersofhotspotsandspotcandidates. 0 ID HI ID (") ID (")(mJy)C)(°) 28.31 21.72 38.20 21.04 27.76 10.19 18.29 12.99 16.25 15.63 25.18 17.68 15.27 28.19 21.61 38.25 21.11 17.69 7.85 4.98 5.17 7.65 7.67 6.46 7.62 5.23 7.96 (") 7.65 96.60.230.19 (b) MostCompactComponent (a) Single-ComponentFits (c) RejectedCandidates 268. 203. 362 . 152. 528. 188. 201. 254. 105. (mJy) 128. 239 . 166. 4.761.87 (mJy) 47.3 27.7 42.2 15.2 20.8 63.5 86.3 61.4 95.1 19.7 33.9 88.0 23.4 2.492.23 7.3 5.7 5.6 9.6 2.7 1.280.76 3.3 0.550.27 6.0 1.190.70 0.62 0.24 0.21 0.90 1.37 0.45 0.26 0.25 0.25 0.51 0.34 0.39 0.30 1.03 0.39 0.76 0.31 0.26 0.22 LAS 0.36 0.23 0.79 0.33 0.50 0.34 LAS (") (") 0.36 0.21 0.22 0.21 0.38 0.35 0.22 0.63 0.28 0.30 0.26 0.29 0.26 0.98 0.29 0.29 0.16 0.23 0.18 0.61 0.13 0.62 0.25 0.22 SAS 0.30 0.26 SAS (") (") ( °) 122 168 110 ( °) 165 146 178 118 128 107 139 3879 119 3089 72 20 77 32 51 43 16 71 23 V 16 53 94 15 19 20 89 Y 50 14981 67 17671 91 13342 7 1 ( °) ( °) 144 170 124 106 112 111 100 Y=h 135 135 132 170 125 135 132 Ych 50 33 99 62 25 46 37 92 51 33 63 AYch AYch ( °) ( °) 72 44 75 18 89 32 83 15 61 53 88 89 69 48 87 63 11 16 61 61 43 13 6 jetted andcounterjettedlobesaremuchweakerthanthose for all13sources).Theextremaofthistrendaredefinedby the jettedhotspottobemorecompactwhenthereisa in thecounterjet.Weconcludethatthereisastrongtrendfor hot spotareas(jetted/counterjetted),whilethefourwith the sourceswiththreeleastpowerfulcentralfeatures(3C counterjetted hotspotsalsodependsontheapparentpower significant sizeasymmetry. 3C 334)havesimilar-sizedhotspotsorcandidatesonboth most powerfulcentralfeatures(3C204,3C208,263,and 68.1, 3C215,and351),whichhavethesmallestratiosof of thecentralfeature(linearcorrelationcoefficientr=0.83 weaker. tegrated fluxdensitybetweenthehotspotcandidatesin compactness ratiosdirectlywithredshift. sides. Thereisnosimilarlycleardependenceofhotspot deeply recessedintotheirlobesthanarethoseonthecoun- the hotspotsurfacebrightnessesisalsocorrespondingly described aboveforhotspotcompactness.Theasymmetryin terjet side(Fig.44).Wemeasurehotspotrecessionbythe the peakofhotspot(Table12)tolargestangular ratio Roftheangulardistance0fromcentralfeatureto the counterjetsidehasi?<0.82,but7of13jettedhot mation (asdefinedbytheanglesubtendedhotspotat lobe powers(andredshifts)inoursample. spots arein3C215and249.1,whichhavethelowest spots haveÆ<0.73.Thetwomostdeeplyrecessedjettedhot extent ofthelobe(Table15,Sec.5.4below).Nohotspoton teijetted lobes.Ristheratiobetween angulardistancefromthecentral Fig. 44.Distributionsofhotspotrecession parameterRinjettedandcoun- feature tothehotspotandlargestangular extentofthelobe. (c) Theratioofthecompactnessjettedtothat (d) Inthissample,anysystematicasymmetriesinthein- There arenosample-widetrendsinvolvinghotspotcolli- (e) Hotspotsthatarefedbyjetsmorelikelytobe _Q C/D CO n CD o E ZJ O 3 E © Recession RofHotSpot 803 1994AJ 108. . 7 6 6B wise withthesameassumptionsasinTable10.The“reac- 5.5. between theirhotspots. celeration indicator”f=i/iisgenerallyhigherforthehot assuming thattheirspectralindicesareof=0.8,butother- cance ofthistrenddependsstronglyonjusttwosources,3C is wellcollimated(r=—0.76,seeTable22),butthesignifi- the centralfeature).Thefluxdensityratiobetweenjetted spots thanforthejetknots(Table10),becausehot 68.1 and3C351,withunusuallylargefluxdensityratios and counterjettedhotspotsislargerwhenthejettedspot 804 BRIDLEETAL.:TWELVE3CRQUASARS csyn hs p: fractionalpolarization(or2oupper limit)atpositionofpeak Ax: anglebetweenEvectorandline frompeaktocentralfeature ch 0: angulardistancebetweenpeakof hot spotandcentralfeature AXjet *anglebetweenEvectorandtangent tojetbeforehotspot Table 13.Derivedparametersofhotspotsandspotcandidates. © American Astronomical Society • Provided by the NASA Astrophysics Data System Table 13listsderivedphysicalpropertiesforthehotspots, We discusstrendsinvolvinghotspotprominenceinSec. Luminosity integratedfrom10MHzto100GHzinquasarframe X: apparentpositionangleoftheE vector atthepeak A%: anglebetweenEvectorandmajor axisofhotspot h Elliptic cylindricalemittingvolume,fullyfilled Source Knot0 3C175 3C175 3C 68.1 3C 47 3C 9 3C 9 3C215 3C208 3C208 3C204 3C204 3C432 3C351 3C336 3C336 3C334 3C263 3C263 3C249.1 3C249.1 3C432 3C 47 3C 9 3C 9 3C336 3C336 3C334 3C334 3C263 3C263 3C249.1 3C249.1 3C215 3C215 3C208 3C208 3C204 3C204 3C175 3C175 3C 68.1 3C 68.1 3C 47 3C432 3C432 3C351 3C351 Electrons inconstantfieldthroughoutlifetime Major, minoraxes=LAS,SASfromTable12 Assumptions madewhencomputingTable13: Electrons movewithrandompitchangles Equal energiesinionsandelectrons Table 14.Polarizationofhotspots. ID {") 1 (for jettedhotspotsonly) H=100h kms'Mpc",q=0.5 Depth =SASfromTable12 o 38.20 21.04 28.31 21.72 27.76 18.29 12.99 25.18 15.27 17.68 16.25 15.63 10.19 7.85 7.67 4.98 7.62 7.65 5.17 6.46 5.23 Spectral index=0.8 4.8E-04 7.8E-04 4.5E-04 4.8E-04 4.0E-04 7.4E-05 2.0E-04 4.1E-04 2.7E-04 4.1E-04 2.3E-04 2.8E-04 1.1E-04 1.3E-04 3.5E-05 5.5E-04 3.0E-04 9.9E-04 5.7E-05 3.9E-04 5.6E-05 1.5E-04 1.1E-04 6.3E-04 1.0E-03 5.4E-04 (Gauss) Notes toTable14 2n h 0.23 0.37 0.02 0.17 0.17 0.14 0.04 0.03 0.15 0.29 0.16 0.02 0.30 0.20 0.02 0.13 0.13 3 7.1E+13 8.4E+13 2.2E+14 1.1E+14 5.6E+13 3.3E+13 2.OE+12 3.6E+14 1.4E+13 3.7E+14 1.1E+12 2.6E+13 8.OE+12 4.6E+12 1.4E+14 1.8E+13 2.8E+13 4.7E+12 6.OE+12 4.4E+11 8.4E+13 1.2E+12 6.2E+13 5.5E+13 1.0E+14 6.0E+13 4/7 (nr K) h Pmin -16 -48 -38 -30 -67 -17 -18 -51 -44 -23 -63 27 72 24 29 44 88 61 62 -6 (°) X 2.6E+04 2.5E+04 4.6E+04 4.9E+05 3.3E+04 2.7E+05 3.5E+04 3.1E+04 1.0E+04 1.4E+05 8.8E+03 3.7E+04 3.3E+04 7.9E+04 4.2E+04 2.1E+05 3.2E+05 2.4E+04 1.1E+05 3.4E+05 1.9E+06 1.5E+04 6.8E+04 9.2E+05 9.8E+05 9.0E+04 AXch 43 52 74 25 86 34 88 82 60 16 31 30 17 56 11 56 63 (°) 54 65 6 -m (yr) h AX jet (°) 12 46 16 1 7 30. 12 . 7.2 2.9 3.3 2.7 2.0 7.7 2.7 8.3 5.5 0.77 0.36 2.5 1.0 8.7 3.2 0.40 0.12 5.9 6.1 1.9 0.38 1.0~ 0.78 0.42 AXh (°) 73 37 48 74 41 81 85 84 70 36 24 54 55 54 13 13 56 89 50 64 67 with linearsize(r=0.66),butanticorrelatessignificantly(r propriate. Table15alsoshowsthedistancesfromcentral contributions fromthejetsandcounteijetcandidatesasap- the TVSTATfacilityinAIPS,thensubtractingintegrated intensities andnormalizingbytheCLEANbeamareausing the hotspots.Therearenostrongtrendsinvolvingde- Note, however,thatwefindvaluesof^>1inbothjettedand with thelargestandsmallest lobe-to-lobe intensityratios, pend systematicallyontheratio oftheintegratedlobeflux feature tothefurthestpointthatcanreliablybesaidin- candidates, ifany.Theywereobtainedbysummingpixel include thefluxdensitiesofembeddedjetsorcounterjet counterjetted lobesineachsource.Theseestimatesdonot meet itarepoorlyresolved. grees ofpolarization,ortheE-vectororientations,hot counterjetted hotspots(3C175,3C204,208,seeSec.7). tend tobebothbrighterandfurtherfromthecentralfeatures. respectively. Counterjetdetectability alsodoesnotseemto data for3C68.1and351. the centralfeature,lattertrenddependingstronglyon increases withtheprojectedlinearsizeofsource{r rameters, however.Theratiofortheextendedemissionalone from thecentralfeaturethandoescounterjettedlobein7 than thecounterjettedlobein8of13andextendsfurther further orlessfarfromthequasar.(Thejettedlobeisweaker than thecounterjettedlobe,nordoesitextendsystematically lobe. clude lobeemission,tomeasurethe“largestextent”of the internalpolarizationdistributionsofmoststructuresthat the strictnessofourcompactnesscriterionforhotspots,as among thesequantitiesinoursamplemaybeinfluencedby spots onthejettedandcounterjettedsides.Thelackoftrends candidates, in3C68.1and215, arefoundinthesources densities. Forexample,thetwo mostconvincingcounteijet counterjetted lobescorrelatessignificantlywithseveralpa- of the13.)Theratiofluxdensitiesbetweenjettedand = -0.75)withtheanglesubtendedbyjettedhotspotat =0.74). Theratioincludingthehotspotscorrelateslesswell 3C215 3C208 3C204 3C175 3C 68.1 3C 47 3C 9 3C351 3C336 3C334 3C263 3C249.1 3C432 Table 14liststhepolarizationpropertiesatpeaksof The detectabilityofthecounterjet candidatesdoesnotde- Table 15liststheintegratedfluxdensitiesofjettedand The jettedlobeisnotsystematicallystrongerorweaker * excludingjetsandcounterjetcandidates Flux Density Integrated Table 15.Integratedpropertiesoflobes. 1046 (mJy) 739 234 259 205 175 159 177 612 690 156 45 90 Jetted Side 5.4 TheLobes Largest Integrated Extent FluxDensity 29 29 31 24 42 37 17 32 18.0 11.5 7.5 8.5 8.2 (" )(mJy) 454 400 367 402 110 276 199 122 191 523 45 Unjetted Side Largest Extent 21 30 35 27 18.2 33 18 38 16.3 32 5.8 6.5 6.4 (") 804 1994AJ 108. . 7 6 6B , jet emissionexcised,andthesecondwithboth lobe inhomogeneity.Asweareinterestedprimarilyinthe where landarepixellags,I(x,y)istheimageintensity S(l,l) ofanimageisgivenbytheexpression values intheSobel-filteredimageoverregioncontaining filter (see,e.g.,Pratt1978),asimplementedintheAIPS3X3 neity usingtwoindependentmethods. ited imagesofeachlobewerethenanalyzedforinhomoge- removed fromeitherofthesesetseditedimages.Theed- hot spotsremoved.Theputativecounterjetemissionwasnot sets ofeditedimages,thefirstwith(potentiallybeamed) lobe emission,weusedtheAIPStaskblanktopreparetwo teristics ofthelobesthesequasarsusingtwomeasures of thelobes. supply mightmanifestitselfasanasymmetryinthecontent from thenucleus.Conversely,arealasymmetryinpower should reflecttheunderlyingsymmetryofpowersupply in theDopplerfavoritismmodelofjetone-sidedness, 249.1) withcounterjetcandidatesandone(3C175)without. to counter]ettedlobeextentsincludetwo(3C9and3C pixel extremaoftheinputimage.BycomputingS(l,l) proportional totheintensitygradient filtering taskniner.TheSobelfiltercomputesaquantity extended lobeemission,whichislikelytobeunbeamed, sidedness, astestsofmodelsforjetasymmetry.Forexample, For example,thesourceswithlargestratiosofjettedlobe depend systematicallyontheratioofextentslobes. two-dimensional structurefunctionforeachlobeconsisting over arangeof25pixelsinland,weconstructed mented intheAIPStaskstfun.Thestructurefunction the areaoverwhichintegrationisperformed,evenif we obtainameasureofintegratedlobeinhomogeneitythat up toscalesizescorresponding to about2'.5.Theinhomoge- measures thedegreeofinhomogeneity intheoriginalimage of 51X51elements,withtheoriginblanked.Thisfunction noise ratios<3beforeapplyingthisfilter. blank toexciseallregionsoftheimagewithsignal-to-rms this measureoftheintegratedinhomogeneityincreaseswith Because theoutputofSobelfilteriseverywherepositive, depends onlyonthelobestructure(notintensity). the lobe,andnormalizingbyintegratedlobefluxdensity, 805 BRIDLEETAL.:TWELVE3CRQUASARS neity measurewasderivedbycomputing themeanvalueof as afunctionofposition,andx,*.yiarethe some oftheareacontainsonlynoise.Wethereforealsoused as afunctionofpositionontheimage.Bysumming the structurefunction,andnormalizing bythesquareof the measurederivedfromSobel filterinthatitdepends integrated lobefluxdensity.The resultingquantityresembles xy xy xy xy minaxn Lx,l) 7 We haveattemptedtoquantifythemorphologicalcharac- ^y (-x•ïïv-v) The firstmethodemployedtheSobeledgeenhancement We havelookedforlobepropertiesthatcorrelatewithjet © American Astronomical Society • Provided by the NASA Astrophysics Data System The secondmethodusesstructurefunctions,asimple- ç/i i\_min-y^min x + l,y)f xy for pact features(ridges,filaments,orotherfinestructure)in but onlyatthela-level.Theseinhomogeneitymeasuresre- neous. Ifthehotspotsareremoved,asmalleffectremains, the 2.5(jlevel,forjettedlobetobemoreinhomoge- mating lobeinhomogeneityagreewellwitheachother.Ifthe range 0.0±0.2.Weconcludethatourtwomethodsforesti- ratios oftheinhomogeneitymeasuresforjettedto ness gradients. into accountaswellthosethatcontributetolocalbright- filter measureinthatittakesmoderate-scaleinhomogeneities only onthestructureoflobe,butdiffersfromSobel- the contributionstoinhomogeneityfromanylesscom- inforce ourconclusioninSec.5.3thatthemorecompacthot hot spotsarenotremoved,thereisatendency,significantat the moreinhomogeneouswheneitherestimatorisoutside counter]etted lobes.Theestimatorsagreeoverwhichlobeis either lobe. inhomogeneity betweenthetwolobes.Notethatthisincludes show thatthesehotspotsrepresentthemaindifferencein spots preferentiallyappearinthejettedlobes.Theyfurther 5.2.2 fromcomparingcounterjetdetectionsdirectlywithjet from collinearityandsymmetry.Forexample,apart3C bending parameters. bations (wiggling)ofthejetsthemselves.Thesourceswith terjet detectabilityreinforcetheconclusionsdrawninSec. ported byconsideringthealignmentsbetweenpeaksof logical distortion(toCsymmetry).Theseresultsaresup- the emission“rings”inwestlobe,thereissomemorpho- the leastevidenceforcounterjetemission(3C175,3C204, the underlyingbeam,independentofevidenceforpertur- dence foralong-termperturbationofthesymmetryaxis ted lobesaredisplacedtooppositesidesofthejet-counterjet that forthesixwithoutcounterjetcandidatesis4!0. the sevensourceswithcounterjetcandidatesis15!1,while The meanhotspotalignmentangle(parsec)scalesistherewidespreadevidencefor data areavailable,weassume that themilliarcsecond-scale 1993; Zensusetal1987;Houghunpublished),toestimate © American Astronomical Society • Provided by the NASA Astrophysics Data System When tryingtodiscriminateamongalternativeradio For thiswork,wenormalizeprominencemeasuresbythe A furthersubtletyinvolveshowtopartitionthefluxden- We donot,however,have5GHzVLBIdatatoshow 5.5 ProminenceParametersandTheirCorrelations 5.5.1 Choiceofprominenceparameters Table 17.Fluxdensitiesofcentralfeaturesandjetswithintermediate-scale emission assignedtojets. known. Theeffectoftheseassumptionsonthederivedcen- tral featureprominenceisneverdramatic. average (—75%)forthesourceswhoseVLBIpropertiesare creases significantlyiftheintermediate-scalefluxdensityde- that theintermediate-scaleemissionisalsomainlyonjet toward theVLAjet.Itthereforeseemsreasonabletoassume terjet, sincewheneveraVLBIjethasbeenimageditpoints the jetprominencebothwithandwithoutitinwhatfollows. this intermediate-scalefluxdensity.Wethereforeestimate ducted fromtheVLAcentralfeatureisaddedtothatof density isassignedtothejets. and jetsforthecaseinwhichintermediate-scaleflux side.) Table17liststhefluxdensitiesofcentralfeatures arcsec, wecannotdetermineunambiguouslywheretoplace extended jet.Withoutimagingonscalesfrom—0.01to0.4 nence ratiosforthecentralfeatures,jets,hotspots,andex- tended lobeemissioninthissample,subjecttothealternative normalizations andflux-densityassignmentsdiscussed (We donotconsiderassigningthisfluxdensitytothecoun- prominence ofthestraightestsegmentsjets(asdefined of thesourcesthatwediscussindetailbelow. the logarithmsofprominenceratiosandotherparameters above. Table20listslinearcorrelationcoefficientsrbetween by thecorrespondingfluxdensity ofthecounterjettedlobe, weaker (r=0.65)iftheprominence measuresarenormalized correlation isstrong(r=0.83forthelogarithmsofpromi- represented by3C263and334(centralfeatures in Sec.5.2)andofthecentralfeatures.Theextremaare extended fluxdensityofthejettedlobe,asinFig.45(a).Itis nence ratios)whenbothfluxdensitiesarenormalizedbythe straight jetsbothprominent)andby3C68.1351 (central featuresandstraightjetsbothinconspicuous).This density betweentheirjettedand counteijettedlobes). 68.1 and3C351,bothofwhich havelargeratiosofflux strengths withthesetwonormalizations ismainlydueto3C as inFig.45(b).(Thedifference betweenthecorrelation In contrast,thederivedjetprominencesometimesin- Table 18liststheluminositiesand19promi- Figure 45(a)showsapositivecorrelationbetweenthe Source FeatureJet 3C 68.10.8 3C 4773.6 3C 93.7 3C208 35.7 3C204 18.8 3C175 14.1 3C249.1 50.0 3C215 13.1 3C432 5.6 3C351 5.2 3C336 15.3 3C334 95.2 3C263 141.0 5.5.2 Jets,counterjets,andcentralfeatures Central WholeStraight (mJy) 332.2 2.38 116.3 2.4 23.0 6.2 71.6 9.5 73.0 34.4 30.4 6.3 41.3 25.0 15.5 13.2 34.4 11.8 43.0 23.5 15.6 11.0 67.8 54.3 6.4 2.47 806 1994AJ 108. . 7 6 6B feature, andtheintermediate-scalefluxdensityisassignedto the milliarcsecond-scalefluxdensityisusedforcentral or tothejet,butcorrelationisindeedtightestwhenonly 807 intermediate-scale fluxdensitytothecentralfeaturereduces the jet,asshowninFig.45.Forexample,assigning intermediate-scale emissionisassignedtothecentralfeature weaker (r=0.65)correlationwhenboth arenormalizedbytheextendedflux the prominenceofcentralfeatures. The leftpanel(a)showsthestrong Fig. 45.Theprominenceofthestraight segmentofthejetsplottedagainst density ofthecounterjettedlobe. extended fluxdensityofthejettedlobe. Therightpanel(b)showsthe (r=0.83) correlationwhenbothprominence measuresarenormalizedbythe © American Astronomical Society • Provided by the NASA Astrophysics Data System These resultsdonotdependheavilyonwhetherthe BRIDLE ETAL.:TWELVE3CRQUASARS (.a; (b) / \LOGfCentralFeatureProminence)LOG(Central Straight JetProminence Relative toExtendedJettedLobeCounterjetted 3C432 25.1725.04 3C336 25.1225.00 3C263 25.7325.69 3C215 24.4024.30 3C204 25.3825.22 3C 4725.08 Source Pcf,APcf,BPj,APj,BPcjPjhPcjhPx 3C351 23.9123.82 3C334 25.4725.40 3C249.1 24.8124.66 3C208 25.6525.50 3C175 25.0424.82 3C 68.124.0723.93 3C 925.0624.94 (i) Featureidentification (ii) Intermediate-scalefluxdensityassignment (iv) extendedlobeemission,1.0. (ii) jetsandcounterjets,0.6 (iii) hotspots,0.8 (i) centralfeatures,0.0 x =extendedlobeemission. A =assignedtocentralfeature(asinTables5and6), B =assignedtojet(asinTable17). jh =jethotspot,cjhcounterjet cf =centralfeature,jjet,cjcounterjet, (b) Spectralindicesassumedforcorrectionstorestframe: 2-1 Logarithmic Luminositiesat5GHzemitted,P(h'WHz) (a) Parametercodessignifythefollowing: Table 18.Luminositiesofradiofeatures. 25.01 25.33<23.42 24.66 <23.93 25.21 25.36<23.64 24.33 24.3722.44 25.80 25.8424.50 25.25 25.3724.05 25.10 25.30<23.50 24.74 24.8923.03 24.70 24.7523.90 25.56 25.76<24.85 25.22 25.36<23.33 26.30 24.63 27.18 24.21 Notes toTable18: prominence data.Thefalsecorrelationcoefficientwasbelow wherein thecentralfeatureandjetfluxdensitiesin13-source forth emphasizeresultswiththeintermediate-scalefluxden- in Fig.45(b)tor=0.57.Tosimplifywhatfollows,wehence- the linearcorrelationcoefficientinFig.45(a)tor=0.76,and random trials.Weinferthatthere isabetterthan98%prob- relation coefficientsforthe90000setsofrandomlog- samples werefullyrandomizeduptotheirobservedmaxima from thenormaldistribution.Wethereforeran90000trials that thesignificanceofthesecorrelationscannotbeinferred merators. Thisandouruseoflogarithmicquantitiesimply normalizing fluxdensitiesissimilartotherangeofnu- ized bythesameextendedfluxdensityandrangeof some “falsecorrelation”becausebothquantitiesarenormal- sity assignedtothejet. tributed betweentheirminimaandmaximathanthoseinthe r=0.83 in98%ofthetrials.Thisshouldunderestimate domized withintheobservedrange.Wethencomputedcor- and werenormalizedbyextendedlobefluxdensitiesran- served extendedemissionfluxdensitiesarelessevenlydis- significance levelofthetruecorrelation,becauseob- relations inthissampleweresignificantly weaker.Second, ment. First,allotherapparentprominence-prominence cor- central featureprominenceand straight jetprominence. ability thatthe13quasarsexhibit arealcorrelationbetween The centralfeatureandjetprominencedatawillexhibit This conclusionissupportedby fourotherlinesofargu- 26.67 25.4127.13 25.51 23.9926.20 26.02 26.4526.68 24.87 24.0926.25 26.43 25.0326.34 24.99 25.3325.69 24.17 24.6725.87 25.65 26.5126.68 26.00 25.8326.52 25.67 26.0526.53 26.86 24.7426.84 25.76 25.5526.18 25.93 26.4326.81 807 1994AJ 108. . 7 6 6B jet, or(r=0.06)thatofits“bent”portionalone(theinte- direct correlationofthecentralfeatureandstraightjetflux 808 BRIDLEETAL.:TWELVE3CRQUASARS densities, withoutnormalizationtoprominences,yieldsa would beexpectediftherelationshipwasanartifactpro- Third, allotherdirectcorrelationsbetweenthefluxdensities correlation coefficientofr=0.63,whichisalsosignificantat tion ofpointsinthiscorrelationbythefractiontotaljet milliarcsecond-scale featuresandofthestraighterlarge- duced entirelybythenormalization. result, 0.63±0.12,issignificantlybelowtheunitslopethat prominence data,usingtheobservedmeanerrorratioof York (1966)toallowforthepresenceoferrorsinbothsets slope oftherelationshipanditserrorusingmethod(b) central featureandthestraightjet.Fourth,weestimated in thissamplearesignificantlyweakerthanthatbetweenthe of thecentralfeatures,jets,counterjets,hotspots,andlobes the 98%levelundernormalstatisticalassumptions. that isincludedinthestraightsegment,orbyprojected scale jetemissionarephysicallyrelated.Thereisnosepara- uncertainties coulddegradethecorrelation. ties fromcomplicatedbackgroundsubtractions,andthese grated jetlessthestraightsegment).Note,however,that of thejettedlobe)ifweuseintegratedfluxdensity feature prominence(normalizedbytheextendedfluxdensity no correlation(r=0.20)betweenjetprominenceandcentral length (inkiloparsecs)ofthestraightsegment.Thereisalso features. Ourdatashownosignofsuchanticorrelations. some ofthesejetfluxdensitiesaresubjecttolargeuncertain- ments, normalizingbothbythefluxdensityoftotalex- candidates isuncorrelatedwiththatofthestraightjetseg- should anticoutXdXtwiththatofthejetsandcentral tended emission.Toaccountfortheupperlimitsincoun- asymmetries predictthattheprominenceofcounterjets 1.7:1 betweenthejetandcentralfeatureprominences.The terjet candidateprominences,weestimatethecorrelation the ASURVsurvivalanalysispackage(Isobeetal.1986; coefficients thatinvolvethemusingtheSpearmanmethodin normalized bythetotalextendedfluxdensity ofbothlobesandthetriangles segments (b—rightpanel).Inbothdiagrams, theprominencemeasuresare prominence ofthestraightjetsegments (a—leftpanel)andthebentjet Fig. 46.Theprominenceofthecounteijet candidatesplottedagainstthe are upperlimits. -3.0 -Z.0«l.üU.O1.0-z.u-i.ou.u (a) (b) , StraightJetProminence-Bent © American Astronomical Society • Provided by the NASA Astrophysics Data System Our resultsthereforesuggestthattheprominenceof Pure relativisticbeamingmodelsforthejet/counterjet Figure 46(a)showsthattheprominenceofcounterjet x Counter JetCandidateProminence Relative toAllExtendedEmission I Vupperlimit| I •detection CounterJet CandidateProminence Relative toAllExtendedEmission = positive correlationwithr=0.62fromtheSpearmanmethod jet’s prominenceisnormalizedbyitsownlobe’sextended LaValley etal.1992).Thisanalysisgivesr=0.01forthe data showninFig.46(a).Furthermore,ifthereisanyrela- tionship betweentheprominenceofcounteijetcandidates the hypothesisthatcounteijetcandidateprominenceisdomi- prominence data,butourdatacontainnodirectevidencefor tendency tofalsepositivecorrelationinprominence- in ASURV). flux density,ratherthanbythecommontotal,asabove. spicuous). Theseresultsarenotmateriallychangedifeach candidate andthebentjetsegmentareprominent,butin3C and thatofthebentjetsegments[Fig.46(b)],itisaweak nated byDopplerboosting/hiding. are alsouncorrelated(r=-0.01fromtheSpearmananalysis (in 3C9,68.1,215,and336,boththecounteijet presented inTable7. radio featuresandthesixmeasuresofapparentjetdeflection The formalcorrelationcoefficientsaremuchsmallerforthe correlations betweentheprominenceofjettedhotspot 175, 3C204,351,and432botharerelativelyincon- the entiresample,notjusttheseoutliers.Theanticorrelation 47). Theextremesarerepresentedby3C9,215,and source sample)forallthreecentrallyreferenceddeflection is significantatthe1%levelorbetter(|r|>0.68fora13- 334 (bentjetswithweakterminalhotspots),and3C263 and thecentrallyreferencedmeasuresofjetdeflection(Fig. corresponding locallyreferenceddeflectionangles angles [r(77)=-0.68,r(r]-Q.ll,r(J7=-0.83]. markedly diminishedby3C68.1,whoselargestlocaldeflec- ['■(’7i() =“0-37,r(77i)-0-28,r(j7-0.07]butare (straight jetandaprominenthotspot),butthetrendinvolves therefore sensitivetointerpretation. tion occursinthecomplexregionnearhotspotandis bend lessthanthoseinthefivewhosecounterjethotspot large deflectionoccursabruptly(thusproducingavalue generally decreaseswiththebendingofjet,particularly referenced deflectionanglesdisplaythisrelationshipbetter candidates failtomeetourcriteria.Onceagain,thecentrally eight quasarswithdetectedcounterjethotspotshavejetsthat tween jetbendingandcounterjethotspotdetection.The as referencedtothecentralfeature,andparticularlywhena prominence contrastwiththesituation fortheprominenceof than thelocallyreferencedones. of %c)- the centrallyreferencedbendangles andshowsonlyaweak the centralfeaturesandof straightjetsegments.The central featureprominenceiscompletely uncorrelatedwith dependence onthelocallyreferenced measuresr¡iand lc2c3c 23i 2 The interpretationoftheseresultsiscomplicatedbythe The counteijetcandidateandcentralfeatureprominences The strongestsuchrelationshipsinoursampleareanti- We nowexaminecorrelationsbetweentheprominenceof We concludethattheprominenceofjettedhotspots There isalsoevidenceforarelationship(Table21)be- The strengthsoftheseanticorrelations forthehotspot 5.5.3 Prominenceoffeaturesandjetbending 808 PQ UD r- 809 BRIDLE ET AL. : TWELVE 3CR QUASARS 809 ooo The prominence of the straight jet emission is uncorrelated and 3C 215. Improved upper limits for the sources without ^0 with any of the deflection measures. counterjet candidates, especially 3C 47 and 3C 208, could The prominence of the integrated jet emission correlates strengthen the evidence for such dependence. weakly with the centrally referenced deflection measures (r To summarize, the evidence for relationships between fea- =0.51 for the best case—rju) and slightly better with the ture prominence and jet bending is stronger for the features locally referenced measures (r=0.68 for the best case—rju). farther from the quasar nuclei. The inner, straight jet seg- As the straight jet segments show no sign of such a correla- ments exhibit no hints of such relationships. For the outer tion, we might infer that this weak relationship, if any, is jets and counterjets, the putative relationships are positive contributed by the bent jet segments. This cannot be shown correlations, as yet poorly established. For the hot spots, they directly from this sample, however. The prominence of the are negative correlations, much better established. bent jet segments correlates weakly with the centrally referenced deflection measures (r=0.47 for the best case—r]lc) and slightly better with the locally referenced measures (r 5.5.4 Prominence correlations that are absent =0.58 for the best case—rju), both formally weaker than the trends for the whole jets. This apparent inconsistency prob- We looked for correlations of central feature, straight jet, ably stems from the small sample size, which makes signifi- bent jet, integrated jet, counterjet, and both jetted and coun- cance estimates unstable to discrepant data from individual teijetted hot spot prominence with several physical param- sources. Unlike the anticorrelation for the hot spot promi- eters (Table 20). In all cases involving ratios of jet-to- nence, which involves the whole sample, the weak positive counterjet side parameters, we evaluated correlation correlation of jet prominence with the locally referenced coefficients for the logarithms of the quantities. No signifi- bend angles arises primarily from two sources—3C 9 and 3C cant correlations (at the 0.5% level or better—|r| >0.73 for a 68.1. 13-source sample) were found with (1) largest projected lin- The dependence of the counterjet prominence on jet de- ear size, (2) lobe flux density ratio (with or without the hot flection is still harder to assess as we have only high upper spots), (3) jet spreading rate, (4) jetted hot spot collimation, limits to the prominence for both 3C 47 and 3C 208. There (5) hot spot flux density ratio, (6) hot spot compactness ratio, appears to be only a weak dependence of counterjet candi- (7) hot spot surface brightness ratio, (8) arm length ratio (the date prominence (as opposed to detection) on jet bending, ratio of the length of the jetted side to the counterjetted side, itself heavily influenced by the favorable data for 3C 68.1 using either the angular distance from the central feature to

Initial to Final Largest Along Jet Largest Local Tangentially Referenced Tangentially Referenced Tangentially Referenced

0.0 30.0 60.0 90.0 0.0 30.0 60.0 90.0 0.0 30.0 60.0 90.0 Initial to Final Largest Along Jet Largest Local Centrally Referenced Centrally Referenced Centrally Referenced

CDO

10.0 20.0 30.0 10.0 20.0 30.0 40.0 0.0 10.0 20.0 Jet Bend Angle iij Jet Bend Angle t\2 Jet Bend Angle TI3

Fig. 47. The relationships between hot spot prominence measures, and six measures of jet bending, showing the tendency for hot spots to be less prominent when the jets are more bent. The upper row plots the prominence against measures of jet bending based on changes in the angles of the tangents to polynomials fitted to the jet paths: the change from the initial to the final segments of the jet, the largest difference in angle between any two tangents along the jet, and the largest difference in angle between tangents at adjacent jet knots. The lower row plots the prominence against similar bending measures referred to the central radio features instead of the local tangents. Note that the angular scales on the deflection axes are not all the same.

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1994AJ 108. . 7 6 6B paths (r=0.25).Nocorrelations areapparentbetweenjetted lobe hotspotprominenceandcentral featureprominence(r prominence and(1)theratioof fluxdensitiesofthejetand counterjet candidatesfortheirstraight segments(r=0.52),or tween thejettedandcounterjettedlobes. the hotspotorlargestangularextentoneachside),(9) any ofourmeasuresthedifferenceininhomogeneitybe- (2) thefluxdensityratioper unit lengthovertheirentire 810 We findnosignificantcorrelations betweencentralfeature © American Astronomical Society • Provided by the NASA Astrophysics Data System BRIDLE ETAL.\TWELVE3CRQUASARS 3C351 3C336 3C204 3C175 3C 68.1 3C 47 3C 9 Source Fjst^cjxFjst,A,xFjst^xFjbt,jxFjbt,x Source 3C432 3C334 3C263 3C249.1 3C215 3C208 3C204 3C175 3C 68.1 3C 47 3C 9 Source 3C432 3C351 3C336 3C334 3C263 3C249.1 3C215 3C208 3C432 3C351 3C336 3C334 3C263 3C249.1 3C215 3C208 3C204 3C175 3C 68.1 3C 47 3C 9 Fj,A,jx Fcf/A^x Fcf,B,jxFcf,A,cjxFcf,B,cjxFjs^A^xFjst,B,jx -1.243 -1.836 -0.336 -0.557 -0.979 -0.510 -0.854 -0.509 -1.250 -0.993 -0.473 -1.325 -1.280 -2.251 -0.345 -1.160 -0.411 -0.884 -1.169 -0.912 -1.263 -1.017 -0.342 -0.437 -2.706 Logarithmic ProminenceRatiosat5GHzemitted,F 2.800 1.379 1.842 0.854 1.953 1.442 0.902 0.927 437 324 446 052 643 917 (iii) Extendedemissionusedfornormalization (i) Featureidentification (ii) Intermediate-scalefluxdensityassignment. (b) Spectralindicesassumedforcorrectionstorestframe: Table 19.Prominenceparametersofradiofeatures. A=assigned tocentralfeature(asinTables5and6), B=assigned tojet(asinTable17). cj=counterjet, jh=jethotspot,cjh=counterjetspot. cf=central feature,j=jet,jst=straightjet,jbt=bent jx=jet lobe,cjx=counteijetx=sumofbothlobes. (a) Parametercodessignifythefollowing: Fj,B,jx -1.026 -0.911 -1.360 -1.410 -1.642 -1.080 -0.300 -0.777 -0.801 -0.308 -0.929 -0.854 -0.472 -1.325 -0.952 -0.944 -1.513 -1.607 -1.407 -2.348 -0.588 -1.257 -0.566 -1.788 -0.441 -0.353 -2.100 -0.845 -1.589 -0.780 -1.141 -0.409 -0.391 -1.040 -1.389 -2.845 -0.912 -1.385 (iv) extendedlobeemission,1.0. (iii) hotspots,0.8 (ii) jetsandcounterjets,0.6 (i) Centralfeatures,0.0 0.856 Notes toTable19 <-1.836 <-3.100 <-3.207 <-2.257 <-3.479 <-2.835 Fcj ,x -1.556 -1.670 -2.333 -2.285 -2.087 -2.086 -2.041 -2.102 -1.125 -1.792 -1.571 -2.134 -2.174 -2.664 -1.972 -2.204 -2.601 -3.759 -2.192 -2.900 -1.865 -1.144 -1.405 -0.583 -0.251 -0.691 -1.180 -0.911 -0.797 -1.209 -1.940 -0.660 -1.586 from (possiblydifferential)interactions betweenthebeams prominence (r=0.08). alone, fromcombinedorientation andrelativisticbeaming,or other thantheprominencemeasures, arisingfromorientation = -0.05),straightjetprominence(r-0.13),orbent We mightexpectcorrelationsamong physicalparameters <-1.812 <-3.379 <-2.485 <-1.717 <-2.753 <-2.927 Fcj,cjx -1.641 -2.245 -2.087 -1.365 -2.433 -1.776 -2.619 -2.025 -1.995 -2.473 -1.681 -1.985 -1.738 -0.978 -1.992 -1.241 -1.530 -0.649 -0.298 -0.844 -1.278 -1.066 -0.953 -1.431 -2.078 -0.660 -1.708 -2.201 .136 .804 .145 .257 .302 5.6 OtherCorrelations Fjh,jx -0.630 -0.712 -1.758 -1.036 -0.481 -1.462 -2.319 -0.362 -1.142 -1.121 -0.902 -2.215 -2.008 -1.564 -0.687 -1.536 -1.123 -1.822 -0.938 -1.412 -2.010 -1.594 -0.651 -0.120 -0.940 -0.539 -0.228 -0.388 -1.292 -2.218 -1.894 -0.258 -1.392 -0.417 -0.266 0.853 0.224 0.355 0.091 Fcjh,cjx -2.017 -1.358 -0.549 -1.655 -2.351 -0.899 -1.580 -1.378 -1.078 -1.213 -1.331 -1.494 -1.940 -1.485 -0.526 -0.999 -1.318 -2.169 -1.894 -1.289 -0.186 -0.218 -1.978 -1.177 -0.540 -1.045 -0.680 -1.624 -1.073 -0.082 -1.958 -0.176 -0.201 -1.263 -0.955 -0.905 -0.052 -0.342 0.361 810 1994AJ 108. . 7 6 6B 811 BRIDLEETAL.:TWELVE3CRQUASARS of thesourceaxestolinessight)orbecausestronger ther purelygeometrically(becauseofdifferingorientations size mightanticorrelatewithapparentjetbendingangleei- and thesurroundingmedium.Forexample,projectedlinear pactness ratio,(8)hotspotsurfacebrightness(9)arm better (|r|>0.73fora13-sourcesample):(1)apparentjet interactions producelargerbeamdeflectionsandsmaller flux densityratio,(4)jetspreadingrate,(5)jettedhotspot source sizes. length ratio,and(10)thelobeinhomogeneitymeasures. collimation, (6)hotspotfluxdensityratio,(7)com- deflection angle,(2)largestprojectedlinearsize,(3)lobe eters andfoundnonethatissignificantatthe0.5%levelor found betweenanytwoparametertypes. Table 22liststheresultsonlyforstrongestcorrelation the totallobeintensityratioversushotspotbrightness ratio), Table22suggestsonlythree correlationssignificantat eters thatbothinvolvetheintensitiesofhotspots(e.g., the 0.5%levelorbetterthatare notmentionedabove.(1) Larger extendedfluxdensityratios betweenthelobesare has r=0.91);(2)hotspotsurface brightnessratiocorrelates correlated withlargerinhomogeneity differencesbetween them (e.g.,QxvstheSobelmeasure withhotspotsremoved © American Astronomical Society • Provided by the NASA Astrophysics Data System We lookedforcorrelationsamongthefollowingparam- Excluding the(likelytrivial)correlationsbetweenparam- F -prominencemeasurefor Table 20.Linearcorrelationcoefficients,r,betweenprominencemeasuresandotherphysicalparameters. Measure Measure Fcjh,cjx Fcj ,x Fjh,jx Fj,B,jx Fcjh,cjx Fcj ,x Fj,B,jx Fjbt,jx Fjst,B,jx Fcf,B/jx Fjbt,jx Fjst,B,jx Fcf,B,jx Fjh,jx Prominence Prominence cf normalized by- B cj jh 3 jbt jst cjh bent jetsegment total jet central feature assigned tojet all >masscalecfemission counterjet straight jetsegment extended lobeemissionon counterjetted hotspot jetted hotspot counterjetted side jetted side extended lobeemissionon -0.20 -0.30 -0.04 -0.54 -0.48 -0.69 -0.68 -0.20 -0.68 0.31 0.51 0.47 0.09 0.02 1c -0.73 -0.40 -0.44 -0.41 -0.52 -0.50 -0.17 -0.77 0.10 0.00 0.31 0.45 0.41 0.42 hs 2c Qcom -0.22 -0.83 -0.02 -0.20 0.09 0.03 0.20 0.01 0.53 0.38 0.20 0.19 0.24 0.64 3c hs -0.27 -0.58 -0.70 -0.37 -0.56 -0.46 -0.59 QTb 0.01 0.29 0.23 0.12 0.68 0.58 0.18 11 hs T1 Col Spr LLS Qar - QTb Qcom Str Sob -0.33 -0.31 -0.22 -0.10 -0.28 -0.22 -0.48 Qar Parameter Parameter 0.38 0.55 0.57 0.03 0.09 0.17 0.26 with hotspotsremovedhasr=0.79);and(3)extendedflux with lobeinhomogeneity(e.g.,QTbhsvstheSobelmeasure density ratiocorrelateswithhotspotbrightness(r They donotappeartobepropertiesextendingthroughthe hot spotsurfacebrightnessesareexceptionallyasymmetric. sources, 3C68.1and351,whoselobefluxdensities concentrated intoridgesandfilamentsratherthaninabroad rest ofoursample.Theysuggest,however,thatinthemost notably inconspicuous. though theinnerpartsofjets,andcentralfeatures,are strongly tothistrend,the“extra”powerisinjettedlobe, emission plateau.Notethatinbothsourcescontribute extreme casessome“extra”powerinthebrighterlobeis biguous counterjetsinanysource. Wedo,however,find counteijet candidatesinseven. Thepropertiesofthecoun- =0.77). Allthreecorrelationsarestronglyinfluencedbytwo terjet candidatescorrelatewith several otherattributesofthe reinforced bymoredetailedmorphological evidence.Most sample. Section5.2.2showedthat thedetectabilityofthese candidates isincreasedbyjet bending. Thisconnectionis 21 hs x As detailedinSecs.4.4and5.2.1,wedetectnounam- 1 mean jetspreadingrate deflection measure(Sec5.2.2) most compacthotspotcomponents density ratio(jet/cjsides) x :basedonfurthestextent hs :hotspotsorcandidates x :extendedlobeemission cf) ofhotspot collimation (anglesubtendedat hs :hotspotsincluded hs :basedonhotspots logarithm ofintegratedflux largest linearsize(h'kpc) no :hotspotsexcluded lob :totallobeemission Structure functioninhomogeneity Sobel inhomogeneityratio of lobes(jet/cjsides) components ratio logarithm ofarmlengthratio ratio formostcompacthotspot logarithm ofarearatiofor -0.07 -0.38 -0.59 logarithm ofsurfacebrightness -0.01 -0.07 -0.11 -0.36 0.43 0.33 0.43 0.30 0.04 31 Sob -0.43 -0.49 -0.29 -0.43 -0.56 -0.34 -0.24 -0.05 -0,22 -0.59 -0.53 -0.44 -0.23 0.28 hs 6.1 CounterjetDetection Str -0.45 -0.37 -0.33 -0.24 -0.05 -0.35 -0.21 -0.40 -0.56 -0.67 -0.55 -0.41 -0.22 Spr 0.32 hs 6. DISCUSSION -0.23 -0.29 -0.55 -0.58 -0.07 -0.51 -0.53 -0.12 0.50 0.45 0.54 0.47 0.54 0.55 no jh -0.16 -0.30 -0.16 -0.69 -0.65 -0.41 -0.38 -0.55 0.21 0.11 0.10 no 71 48 66 811 1994AJ 108. . 7 6 6B -1 vent, theuseofglobaljet/counterjetintensityratiosfortests perturbing theflows.Thisclearlycomplicates,andmaypre- of “unifiedschemes”thatassumeuniquevaluesthe magnitude ordirectionwheremostjet!counterjetintensity ground. Jet/counteijetratiomeasurementisevenharder,be- Lorentz factorineachbeam. II sources,counterjetsmaybedetectableonlyafterunfavor- flow velocitiesareoftenrelativisticinFanaroff-RileyType ther case,flowvelocitiesareunlikelytobeconstantineither correcting faintfeaturesforaspatiallyvariablelobeback- recognition (e.g.,confusionbyfilamentsinthelobes)andof terjet powersarecomplicatedbyproblemsbothofcounteijet able beamingfactorsareremovedontherecedingsideby ratios canbemeasuredfromourdata.Ifkiloparsec-scale entation ofthecentralenginehaschangedovertime.Inei- interact stronglywiththeirenvironmentorbecausetheori- tion. Thebeamsmayappeartodeflecteitherbecausethey in partsofsourceswherethebeamsappeartochangedirec- counteijet axis(Ssymmetry)andwhosehotspotsaremis- lobes aresignificantlydisplacedtooppositesidesofthejet- the bettercounteijetcandidatesarealsoinsourceswhose region roughlyoppositethecounterjetcandidate.)Manyof tion. (Inallthreesources,themainjetalsobrightensina the distanceatwhichmainjetshowsalargelocaldeflec- candidate isbrighterintheouterpartofsource,beyond parts ofthemainjetsthatarestronglycurved,orrapidly aligned (Sec.5.4). 334, 3C336).In215,and336,thecounterjet changing inbrightness,orboth.Counterjetcandidatesare 812 BRIDLEETAL.:TWELVE3CRQUASARS especially hardtofindoppositelong(>15/*kpc),straight segments ofthejets(3C47,3C175,204,263, (but notall)ofthecounteijetcandidateemissionisopposite Table 21.Meanjetdeflectionanglesandcounterjethotspotdetection. Mean CounterJetHot1c2c3c112131 © American Astronomical Society • Provided by the NASA Astrophysics Data System As discussedinSec.5.2.1,estimatesofintegratedcoun- The counteijetcandidatesarethereforemostconspicuous of SpotDetected?(°) 5 No14.616.88.424.550.634.2 8 Yes8.29.84.326.235.621.5 Was ATJT| 6.2 Jet/CounterjetRatios Table 22.Linearcorrelationcoefficients,r,fortestsamongvarious physicalparameters. Central FeaturePolynomialTangent Till, Sobno-0.35 1130, Qarhs-0.27 Till, QTbhs-0.36 TI31, Qcomhs-0.44 TjSc, Qhs-0.32 Î13C, Coljh0.30 T131, Qx0.32 X\3c Spr0.15 pli, LLS-0.40 LLS, Sobno0.67 LLS, Qarx-0.27 LLS, QTbhs0.59 LLS, Qcomhs-0.43 LLS, Qhs0.43 LLS, Coljh-0.67 LLS, Spr0.21 LLS, Qx0.74 t Parameter Pairr Referred to Coljh, Qhs-.76 Qx, Sobno0.91 Qlob, Sobhs0.86 Qlob, Qarx-0.44 Qx, QTbhs0.77 Qlob, QTbhs0.89 Qx, Qcomhs-0.56 Qx, Qhs0.61 Qlob, Qhs0.84 Qlob, Coljh-0.75 Qx, Spr0.62 Spr, Sobno0.70 Spr, Qarx-0.15 Spr, QTbhs0.54 Spr, Qcomhs-0.23 Spr, Qhs0.51 Spr, Coljh-0.42 Parameter Pairr oc plain them. mean thatthejet/counterjetratiosfromTable6shouldbe plicated ifthejetdoesnotfillpathfromcentralfea- interpreted cautiously,eveninthesimplestofbeamingmod- segment inTable6(b).Theuncertaintiesoutlinedabove and overaregionwiththesameextentasstraightjet entire distancefromcentralfeaturetohotspotinTable6(a), both sides,anexponentof3+a,isappropriate,butifmul- tral index,definedviaS^v~)thatisappropriatefora may differfromthevalueof2+a^(wherectjisjetspec- sion forrandomizedmagneticfieldsandparticlemotions exponent oftheDopplerfactorinfluxboostingexpres- can becomparabletothevelocityoflight,appropriate ture tothehotspot.Ifflowandpatternspeedsinjets Even ifthejetisrelativelystraight,analysisstillcom- logical symmetrywhendecidingwhichregionstocompare. we mustresortto(poorlyjustified)assumptionsofmorpho- which segmentsofthejetsandcounteijetstocomparewhen main jets.Wethereforefacetheextraambiguityofdeciding cause thecounterjetcandidatesarenotfaintreplicasof ceed, thejetandlobepowersofmostFanaroff-RileyTypeI Fanaroff-Riley TypeIIsourcesaresimilarto,orevenex- teijet, butalsoonthesourcemodelandhistoryusedtoex- depends notonlyonthemorphologiesofjetandcoun- els. Theappropriateexponentinthefluxboostingexpression and counteijetscontainwellorderedmagneticfields the rangefrom2+ayto3+aymaybeappropriateifjets exponent becomesunclear.Notealsothatexponentsoutside tiple jetsegmentsarepresent,theappropriatevalueof et al.1992).Ifasingle,isolatedpieceofjetispresenton smooth jetthatendsatahotspot.Consider,forexample,the the trajectoryofinvisiblecounterjetislesscertain,and hard toassessifnocounterjetisdetected.Ifthejetcurved, global parameters. us moreaboutlocaldisturbancesintheflowsthan (Begelman 1993). deriving theratio. (plume-like) sources(exceptinthemostopticallyluminous ably notuseful:knot-to-knotbrightnessdifferencesmaytell “born-again” relativisticjet(Bridleetal.1986,1989;Clarke We integrateboththejetandcounteijetsidesover The absolutepowersofthecounterjetcandidatesinthese The integratedfluxdensityratios(orlimitstothem)are The ratioofpeakintensitiesiseasilyfoundbutprob- Qarx, Strhs-0.55 QTbhs, Sobhs0.94 QTbhs, Sobno0.79 QTbhs, Qarx-0.38 Qcomhs, Strno-0.66 Qcomhs, Qarhs0.30 Qcomhs, QTbhs-0.63 Qhs, Sobno0.58 Qhs, Sobhs0.80 Qhs, Qarx-0.51 Qhs, QTbhs0.84 Qhs, Qcomhs-0.16 Coljh, Sobno-0.49 Coljh, Qarhs-0.30 Coljh, QTbhs-0.55 Coljh, Qcomhs-0.05 Parameter Pairr 812 1994AJ 108. . 7 6 6B 24 5-21 jets, whichareoftenjustpriortothehotspotandatplaces for thebentjetsegments(though itcouldbediminished velocity relativistic-jetmodels (implying somedeceleration, kiloparsec scales.First,theslopeofrelationbetween there byobservationaluncertainties alone). see Sec.7.1).Second,theprominence relationshipisabsent significantly lessthanthatof1.3expectedinconstant- straight jetandcentralfeatureprominence,0.63±0.12,is features. Twoaspectsofthejetprominencedatareinforce the smallest-scaleemission—thecentralmilliarcsecond-scale nence oftheinner,straightsegmentsjetsandthat scale) propertiesofthejetsastheypropagatetomany- idea thatongoinginteractionsmodifytheinitial(parsec- jets onthesescalesin,orshortlyafter,aregimeofstrong acts withjetprominence.The prominenceoftheinner, they traveloutwards. themselves, thattheirpropertiesaremodifiedsignificantlyas medium. may alsobegovernedbyinteractionswiththesurrounding where thejetbrightenssubstantially.Theseextremecases misalignments tendtooccuratthemostseverebendsin 5.2.5), andthemagneticfieldtendstobeparalleljetin these knots(Sec.5.2.7).Themostextremeknotandfield tent withmodelsofjetpropagationinwhichstrongshocks are drivenintothejetsastheyrecollimated. ing andrecollimationarecloselyconnected.Thisisconsis- interactions withtheambientmedium,i.e.,thatjetbrighten- the terminalhotspot—Sec.5.2.5)suggeststhatwedetect recollimate. Thestrongtendencyfortheclosestknotto radio galaxies,thejetsinitiallyexpandrapidlyandthen flatter thanthoseofconfusingfinestructure. by confusionwithlobefinestructure,andproblemsof central featurealsotobethebrightest(untilregionnear full-synthesis observationsat8.4GHzmay,however,enjoya suggests that,inseveralofthesequasarsasmanypowerful slight advantageoverourdataifthespectraofjetsare counteijet recognitionsimilartothosedescribedhere.VLA tions. Highsensitivityanddynamicrangewillbefrustrated that formplumes. measurements giveninTable6,evenwithlongerobserva- hot spotsareintrinsicallymoreradio-luminousthanthose that thebeamsformedge-brightenedlobescontaining radio powers(similartothoseinTypeIsources).Inthis these sourcesareDoppler-boostedbeamswithlowintrinsic features), thisrulesoutanypossibilitythatthemainjetsin parts ofcounterjets(i.e.,theyarenotmerelyconfusinglobe sense, ourobservedcounteijetpowersaddtotheevidence galaxies, plume-likestructureisuncommoninsourceswith5 GHz totalpowersabovePf=10/zWHz,e.g.,Owen 813 BRIDLEETAL.:TWELVE3CRQUASARS 1993). Ifthesecounteijetcandidatesareindeedthebrightest ot Section 5.5.5alsoshowedhow apparent jetbendinginter- © American Astronomical Society • Provided by the NASA Astrophysics Data System In contrast,Sec.5.5.2showedalinkbetweenthepromi- We thereforehaveseverallinesofevidence,fromthejets Most jetknotsalignwellwiththedirection(Sec. The detailedevolutionofthespreadingrates(Sec.5.2.4) It willbedifficultforVLAdatatorefinetheintensityratio 6.3 JetProperties pact knots.Healsonotedthetendency ofbright,compacthot properties ofhot spotsdependonwhetherthey are fedbythe lobes. Comparingourdatawith Laing’s, itisunclearwhether brighter hotspotonthesamesideasajetorlineofcom- well definedinlargersources(Sec.5.5.5). spots tobelocatedawayfrom theextremeendsoftheir sources (including9incommonwiththisstudy)hadthe signal-to-noise ratiothanours,foundthat26of30powerful the counterjettedside.Counteijettedhotspotsarealsoless but decreasesthechancethatcounteijetfeedsacompact jetted hotspotsaccountforthemostsignificantdifferences side, butwefirmlysupporthis broaderconclusionthatthe surface brightnessorcompactness correlatesbetterwithjet suggest someanticorrelationofjetandhotspotpropertieson hot spot(Sec.5.5.5).Theserelationshipsareimperfect,but the chanceofdetectingacounterjetcandidate(Sec.5.2.2), when thebendinjetisabrupt.Thecounteijettedhot initial jet/counteijetasymmetries. compete withwhatevercoupleshotspotpropertiestothe that iscloselyconnectedtojetbendingthereforeappears to formcompactstructuresinthelobes.Asecondprocess Both trendsimplythatbendingthejetsreducestheirability spots alsotendtobeilldefinedwhenthejetismorebent. nent whenthejetbendsthroughagreaterangle,particularly the jet/counterjetsidednessasymmetry. whenever thereisa>25%differenceincompactnessbe- placement betweenthehotspotsinjettedandcounteijet- therefore seemtoretainsomememoryofwhateverinitiates hot spots,butpossiblynototherstructuresinthelobes, in inhomogeneitybetweenthejettedandunjettedlobes.The lobe edges.Section5.4showedthatthepropertiesof ted lobes(Sec.5.5).Theonlythatlackhotspotsbyour mine counteijetprominence. spots arealsomorelikelytobedeeplyrecessedfromthe is alwaysmorecompactthanthecounteijetted.Jettedhot tween thehotspotsorspotcandidates,jetted new definitionareonthecounterjettedside.Moregenerally, spots inseveraldistinct,andatfirstsightcontradictory,ways. rounding medium,andthattheseinteractionshelptodeter- distance fromthecentralobjectviainteractionswithsur- the jets’intrinsicpropertiesthatjetparameterschangewith paths). Theprominenceofthesecounteijetcandidatesisun- bent, jetsegments,andclearlyinteractswithourabilityto bending weaklyaffectstheprominenceofouter,more may beweaklycorrelatedwiththatofthebentjetsegments correlated withthatofthecentralfeaturesorstraightjets,but find counterjetcandidates(thebrightestofwhichareinthe outer partsofthesources,beyondmajorbendsinbeam straight jetsegmentsisuncorrelatedwithbending.But (Sec. 5.5.2). Laing (1989),usingdatawithhigherresolutionbutpoorer Note thatwealsofindincreasedjetbendingenhances There aresystematicdifferencesincompactnessand Section 5.5.5showedthatthejettedhotspotislesspromi- Our newimageslinkthepropertiesofjetsandhot The jetprominencedatathusreinforcetheevidencefrom 6.4 HotSpots 813 1994AJ 108. . 7 6 6B jet orthecounterjet.Modelsthatattributedifferencesin jets, andbetweentheprominenceofcentralfeatures jet hotspotdetectionwithallthreecentrallyreferencedmea- prominence primarilytodifferencesinrelativisticbeaming jets, onthegeneralgroundsthat themoreseverepertur- beyond thehotspots,however. properties ofthemoreextendedlobeemissionsuggeststhat with theinitialasymmetrythereforepersistsbeyond ments aregenerallybrighterthanthecounterjetcandidatesat of theinner,straightersegmentsjetsimplythatwhat- milliarcsecond-scale extendedfeaturesandofthelarge-scale found onlyin7sources.Hotspotsmeetingourcompactness this further. should thereforeaddresswhethersomepropertiesofthehot 814 BRIDLEETAL.:TWELVE3CRQUASARS this influence,whateveritsnature,doesnotextendmuch to theendsofjets. lobes. Evidently,someofthisinitialinfluencepersistseven fact thatjettedandcounterjettedhotspotsshowsystematic comparable distancesfromthequasars.Someconnection correlated withthecentralfeatureprominence,theseseg- of thecounterjettedlobes. criteria weredetectedineveryjettedlobe,butonlyeight our augmentedsample,whereascounteijetcandidateswere prominence oftheouter,morebentjetsegments,andanti- differences intheircompactnessandrecessionintothe straight jetsegments.Thisconclusionisreinforcedbythe of kiloparsec-scalejetemission. scale featuresalsoinfluencesthesidednessandprominence ever determinesthesidednessandprominenceofparsec- spot emissionareaffectedbybeaming.Section7.1discusses bation, themoreinternalenergy willultimatelybeconverted plants theinitialconditionstodetermineprominenceof phenomenon, closelycoupledtojetbending,eventuallysup- crooked segmentsofthejets,alackcounterjetcandidates tween prominenceanddeflection forthebentpartsof some featuresfarfromthecentralregion. correlations betweenjettedhotspotprominenceandcounter- correlation betweencounterjetcandidateprominenceandthe didates whenboththejetsandlobesaredistorted,aweak opposite longstraightjetsegments,apresenceofsuchcan- tween theprominenceofcentralfeaturesandmore of rbeing0.58forrju).Wenote, however,thatthemain tions areweakforoursampleas awhole(thehighestvalue to synchrotronradiation.Table 20 showsthatthesecorrela- sures ofjetbending.Theseallimplythatanother The lackofclearjet-relateddifferencesbetweenany Although theprominenceofbentjetsegmentsisun- The goodcorrelationsbetweenthesidednessof Jets andcentralfeaturesweredetectedinall13quasars © American Astronomical Society • Provided by the NASA Astrophysics Data System We mightthereforeexpecttofindsomecorrelationbe- In contrasttotheabove,wefoundapoorcorrelationbe- 6.5.3 Evidencethatlarge-scaleinteractionsmodifyjetproperties 6.5.2 Linksbetweenthecentralfeatureandlargerscales 6.5 SummaryofEmpiricalResults 6.5.1 Detectionrates brightens substantiallynearthesebendsinsevenofthem(3C bends ineightofthejetsoccurtheirouterpartsandjet scribed inSec.1. the threespecificviewsofenergytransportprocessde- tributes ofthesourcemorphologies. systematically connectedtooneanotherandsomeat- hot spotsrelativetothemoreextendedlobeemissionare loud quasars.Themostimportantofthesearetheresults bring newconstraintstotheissueofwhatdetermines 68.1, 3C175,204,208,263,334,and336). bution ofLorentzfactorsandorientations.Ifthedispersion related, and(c)thattheslopeofprominencerelationship region producestheasymmetrybetweenjetsanddomi- beams. Thebulkvelocityoftheflowthroughemitting stem mainlyfromdifferentialDopplerboostingofemission asymmetries andprominenceofjetshotspotsinradio- ness isknown,(b)thattheprominenceofcentralfeatures milliarcsecond-scale radiofeatureasthemoreextended large-scale jetsareonthesamesideofmostcompact nates theapparentprominenceofcentralfeaturesand from intrinsicallysymmetrical,relativisticallymoving showing thattheprominenceofcentralfeatures,jets,and relativistic jetmodelswouldrequiresuchacorrelation,with of intrinsicsourcepropertiesinthissampleisnottoolarge, and thecentralfeaturescontainflowswithsamedistri- and theprominenceofstraightpartsjetsarecor- small-scale emissioninallsixcaseswherethisinnersided- some portion,perhapsall,ofthelengthbothjets. given inclination0tothelineofsight,slopeexpected flows throughthecentralfeatureandjet.Atany (0.63±0.12) islessthanexpectedifthestraightjetsegments where nisintherange210° fromboththelineofsightandplanesky. ; ; y =^2resultfrommostmodelsinwhichextendedquasarsare 815 BRIDLEETAL.:TWELVE3CRQUASARS ; c ; The ideathatdecreasestoavalue^2onmany- © American Astronomical Society • Provided by the NASA Astrophysics Data System The distributionof“straightsegment”jettocounterjet It isalsointerestingthatthecorrelationshowsnosorting Our datathereforesuggestthattheflowindetected jet flow.Forarelativistic-jetmodel,thefactthatbent be onthejettedside,modelsin whichrelativisticbeaming require recentenergysupply(e.g.,hotspotsOin3C175,L fore consistentwithfeaturesonthecounterjettedsidethat lifetimes areshorterthanthelight traveltimetothem—Table in 3C204,andJ208, whose inferredsynchrotron governs jetprominencemust consider thepossibilitythat tinuously andequallytobothsidesofthesources.Itisthere- relativistic-jet modelassumesthatenergyissuppliedcon- tion oftheirprominencewiththatthecentralfeatures. disordered andredirectedsufficientlytoremovethecorrela- ing remainsatlargedistances,eveniftheflowshavebeen the outerpartsofsamesourcesimpliesthatsomebeam- binations ofslowing,disordering,orredirectingthecounter- jet bendingandcounterjetprominence.Theseexpectations segments aregenerallybrighterthancounterjetcandidatesin ments fromchangesincounteijetbeamingproducedbycom- prominence ofthecounterjetcandidatesisdifferently 13). directly distinguishinteraction-inducedemissivityenhance- detection withjetbendingreinforcesthisresultbutcannot distributions, orboth.Thepositivecorrelationofcounterjet dium, orbybeamingbasedondifferentvelocityandangular which largeapparentbendanglesareasymptomofsmall bending canbeamplifiedbyprojection.Forthereasonsde- bending couldbeaninclinationindicator,becausetruejet determined—either byinteractionswiththesurroundingme- beam model. would meanthattheabsenceofsize-prominencecorrelations dominates theprominenceofstraightjetemission, straight jetsegmentsshowsthat,evenifDopplerboosting counterjet candidatesandthatofthecentralfeaturesor that apparentjetbendingisaninclinationindicatorinthis relations betweenjetbendingandtheprominenceofcen- relativistic-jet modelswemightexpecttofindpositivecor- inclinations tothelineofsight.Iftheywere,thenin scribed above,thissampleisunlikelyabinitiotobeonein plane ofthesky(byexcludingradiogalaxies).Suchanatypi- sample. that canbeunderstoodiftheapparentbendanglesmeasure should notbeconstruedasevidenceagainsttherelativistic- posed byarangeofintrinsiclinearsizes,oursamplemay intrinsic jetbending.Wethereforeseenoreasontosuppose tral featuresandstraightjets,ananticorrelationbetween cally smallrangeoforientationsrelativetotheobserver all conflictwithourdata,butwefoundseveralcorrelations avoid thelineofsight(asdescribedabove)andalso sample, however.Aswellashavingtheusualproblems may beaparticularlypoororientationindicatorinthis might beexpectedonthesimplestrelativistic-beammodels, central featureprominenceorstraightjetprominence,which are eitherweakorabsent(Table20).Projectedlinearsize may becoincidental. earlier analyses,ourapparentagreementwiththeirresults To explainthetendencyfor morecompacthotspotto Like themodelsdescribedinSec.7.2below, The lackofcorrelationbetweentheprominence For sourcesorientednearthelineofsight,apparentjet The correlationsbetweenlargestprojectedlinearsizeand 815 1994AJ 108. . 7 6 6B (2+a) ward thevaluesinsheath, wheretheresultsof At angles0>2O°tothelineof sight,wewouldpreferen- timate ofÿfromthissamplewould thereforebebiasedto- tially seeemissionfromtheslower partsofthejet.Oures- [r;(l-/3; COS0;)p7 mate ofthecharacteristicLorentzfactorisaweighted ity vbetweenßcand(ß+dß)cisf{ß)dß,thenouresti- Laing (1993).Ifthefractionofmaterialflowingatveloc- moving sheath(ashearedboundarylayer)assuggestedby ties, e.g.,anultrarelativistic“spine”surroundedbyaslower- average satisfying neous, butcontainmaterialflowingwitharangeofveloci- unlikely thatpost-bend,post-shockLorentzfactorscould preserve aflowintothehotspotthatisfastenoughforpost- significantly. stay highenoughtomodifytheappearanceofhotspots and jetprominencedata,thejetsarehomogeneous,itis the jetisindeedonly~2,assuggestedbyourcentralfeature oblique shocks?IftheLorentzfactorinstraightpartof shock Dopplerbeamingtobesignificant,evenwithhighly nence ofthehotspot.Howcouldsourceswithverybentjets bending ajetrobsitofitsabilitytogenerateprominenthot prominence andjetbendingchallengesthesimplestformof spots, i.e.,inwhichthehistoryofjetgovernspromi- this interpretation,however.Itarguesforapictureinwhich oblique shockswereexploredbyBegelman&Kirk(1990). which hassloweddownand/orchangeddirection.Conse- with theflowimmediatelybeyondshock,butthosein velocity [comparethe3DhydrodynamicsimulationsbyWil- quences forparticleaccelerationmechanismsinrelativistic counterjetted lobesareidentifiedwithdownstreammaterial liams &Gull(1985),Coxetal.(1991),andNormanBal- flow fromthehotspotthatstillhasasignificantforward sara (1993)].Inthispicture,thejettedhotspotsareidentified ; sistent withthisidea,asitallowsforthepossibilityofout- spots aresetbackfromtheleadingedgeoflobeiscon- ing canremainsignificant.Theobservationthatjettedhot because itallowsthepost-shockflowtoremainsupersonic, ; model (inwhichtheshocksareoblique)iscruciallydifferent and (givenhighobliquity)possiblyrelativisticsothatbeam- be themechanismbywhichhotspots“remember” sonic andbeamingeffectsareminor(Wilson&Scheuer relativistic effectsalsomodifytheappearanceofhot axisymmetric, thenthepost-shockflowisinevitablysub- erage advancespeedofthelobeis<0.3c,soifflow Rees 1974).Therearegoodreasonstosupposethattheav- marking thedisruptionofanaxisymmetricjet(Blandford& simplest modelofahotspotasstrongperpendicularshock small-scale asymmetry.Thiscannotbeachievedwithinthe spots (Laing1989).Onthisview,Dopplerfavoritismmight 816 BRIDLEETAL.:TWELVE3CRQUASARS 1983). Laing(1989)pointedoutthatanonaxisymmetricflow 2 + © American Astronomical Society • Provided by the NASA Astrophysics Data System This problemmaybesolubleifthejetsarenothomoge- Our discoveryofaclearanticorrelationbetweenhotspot = COS0,)r( "Pdß. 7.1.1 Aninhomogeneousrelativisticjet propagate, allmodelsofthisclass encounterthedifficulty asymmetry wouldbe,forexample, anasymmetricdensity orders ofmagnitudeinscalesize. Plausibleformsofthis tion asymmetryisunlikelyto manifest itselfoverseveral that anenvironmentalasymmetry whichgeneratesadissipa- modified byinteractionswith the environmentasjets which theasymmetriesoriginateonparsecscales. gradients intheenvironmentsofquasars,andthose those inwhichtheasymmetriesareimposedbylarge-scale tors inthespine. the proposedspine-sheathstructurewithhigherLorentzfac- to bea<5functionatanydistancealongthejet,because They aremorerealisticthanamodelinwhichf{ß)istaken not theonlyreasonforconsideringsuchmodels,however. inter-knot regionsofthesejetscouldtestwhethertheyhave occur intheboundarylayerunderawiderangeofcircum- confined jetthatcontainsknotsandbendsmustdevelop small-scale featuresinoursample.Weemphasizethatthisis some, butperhapsnotall,correlationsbetweendistantand inhomogeneous-jet modelsmayallowthemtoaccommodate for intrinsicallysmallredirectionanglesatthehotspots. power, butthesignofcorrelationopposesthatexpected prominence weakerthanthatdirectlywithcentralfeature stances. Ahigh-resolutionsearchforcenter-darkeninginthe some dispersioninß,andthelowestvaluesofßwould be hardtoincorporateinsuchmodels,however.Section5.3 jetted hotspot,beingderivedfromthespineofjet,could the correlationofhotspotasymmetrywithcentralfeature feature ismorepowerful.Ifrelativisticflowimportantat central featureismoreprominent.Inthissample,notonly ness asymmetrybetweenthehotspotstoincreasewhen the hotspots,wemightinsteadexpectapparentcompact- the sensethatasymmetryissmallerwhencentral correlates withtheapparentpowerofcentralfeature,in showed thatthecompactnessasymmetryofhotspots in thesheath. beaming factorandthusberelativelysuppressed.Theemis- pact hotspot.Thecorrespondingpartsoftheflowon dominated byslower-movingmaterialderivedfromtheflow sion fromthecounterjettedhotspotswouldthereforebe counterjetted sidewould,however,haveanunfavorable ß. Thecentralpartofthedecollimatingflowthrough The connectionbetweentheinitialsidednessasymmetryof acquire afavorablebeamingfactor,producingbright,com- the centerofjettoremainultrarelativistic,i.e.,ifinter- moving materialinthejetbutallowsomeofflownear understandable ifinteractionsincreasethefractionofslow- the jetsandhotspotcompactnessasymmetrywouldbe interactions withthesurroundingsshouldbemostapparent. actions skewf(ß)whileretainingmostofitsupperrangein Although ourdatashowthatjetpropertiesareindeed Models ofthistypecanbedividedintotwomainclasses: We inferthattheadditionalcomplexityinherentin One aspectofthehotspotcompactnessasymmetrymay 7.2.1 Large-scaleenvironmentalasymmetries 7.2 AsymmetricDissipation 816 1994AJ 108. . 7 6 6B jet candidates(3C9,3C351)aredetectedassingleknots, both ofwhichareoppositetheinnermostknotsinstraight consistent withboththejetandcounterjetbeingbright- the brightest,mostseverelybentportionsofmainjets, 3C 334,and336)aremoredistant,bentfeaturesopposite shocks relativelynearthequasar.Threecandidates(3C215, counterjet arebrightenedlocallyby“pressureadjustment’’ These couldbeexplainedascasesinwhichboththejetand site long,straightjetsegments.Notethattwoofthecounter- nence, andexplainthedeficitofcounterjetcandidatesoppo- leave apositivecorrelationbetweenjetandcounterjetpromi- by dissipation.Alarge-scaleasymmetryinthisprocesscould bent jetsegmentsandthecounterjetsmightbothbegoverned prominence correlation.Inparticular,ifjetbendingenhances profile inthegalaxyinducedbyatidalinteractionoran between theprominenceofinnerjetsegmentsand wards. Itwouldthennotbesurprisingtofindarelationship beams, oroftheirkinematics)anditseffectspropagateout- which interactionsdominatetheappearanceofallcounterjets posite aparticularlybrightsegmentofthejet.(Itwouldbe produced aninner,elongatedcounterjetcandidate,againop- segments ofjetswithpronouncedbrightnessvariations. dissipation tosynchrotronradiation,thentheemissionof sipation couldreadilyaccommodatetheweakjet-counterjet engine andthecenterofmassgalaxy. pling toparsecscales. plain whytheprominenceandsidednessofparsec-scale features inbentcounterjets. for weakfeaturesin“straight”counterjetsandbrighter terjet segmentsin3C249.1athigherresolution).Models interesting todeterminethecurvatureofthesejetandcoun- ened bybend-induceddissipation.Onlyonecase,3C249.1, external wind,oranoffsetbetweenthelocationofcentral relationship. (Iftheinitialasymmetrywasentirelyin ture oftheasymmetriescouldpredictdifferentformsfor content ofrelativisticparticlesand/ormagneticfieldsinthe try beginsonparsecscales(e.g.,asanasymmetryinthe modify jetpropertiessignificantly.Modelsthatattemptto that interactionswiththelarge-scaleenvironmentindeed the asymmetriesontwoscales.Ourdatasupportidea ments. Thisimpliesastrongcouplingofthemechanismsfor central featurescorrelatewiththoseofthestraightjetseg- kiloparsec-scale jetsandcounterjetsentirelytolarge-scale should thereforeexploremechanismsthatcanaccountboth pected, butanasymmetryinfield strengthorfieldconfigu- density ofrelativisticparticles, an approximateproportional- central features,thoughdifferentassumptionsaboutthena- these interactionsmust,however,seektoexplainthiscou- environmental asymmetriesmust,however,beaskedtoex- prominence ondistancedownthe jetasthefieldsevolve.) ity betweencentralfeatureand jet prominencemightbeex- ascribe theobservedasymmetriesentirelytoin 817 BRIDLEETAL.:TWELVE3CRQUASARS ration wouldproduceamore complicated dependenceof © American Astronomical Society • Provided by the NASA Astrophysics Data System Source modelsinwhichjetbrightnessisgovernedbydis- The aboveobjectioncanbecircumventediftheasymme- Models thatascribetheintensityasymmetrybetween Dissipative modelscanclearlyaccommodate therelation- 7.2.2 Asymmetriesinitiatedonparsecscales jet detection.Liketherelativistic-jetmodel,asymmetricdis- modate thepredominantlydouble-lobedappearanceof trend forthejettedhotspottobemoredeeplyrecessedinto only intrinsicasymmetrymayhaveproblemsexplainingthe would beexceeded61%ofthe time becauseofthecommon power asymmetrybetweenthetwosidesisconnectedto general radiosourcepopulation(andthedetailedsymmetry lobe thanisavailableonthecounterjettedside.Toaccom- its lobe. hot spot].Amodelinwhichasymmetricdissipationisthe time tothem(seeTable13).Asymmetricallydissipativejets inferred synchrotronlifetimesareshorterthanthelighttravel lobe powerandtheintegratedjetpowersinthissampleare might insomeformsoftheflip-flopmodel.Although produce suchcorrelationswithinaflip-flopmodel. bending, andbetweentheprominenceofstraightjets with strongsecondaryfinestructure—3C68.1and3C351— the twosidesmustvarywithtime,along-termaverage of someindividualsources),theratiopowersuppliedto side, atthetimeweobserveit,suppliesmorepowertoits served [thoughitisnotclearwhythemoredissipative are alsolikelytogeneratedissimilarhotspots,asoftenob- sipation allowsforhotspotsonthecounterjettedsidewhose indeed correlatedwithr=0.70, thiscorrelationcoefficient correlate withthepowersofjetsthatfeedthem,asthey directional stabilityofjets.Amechanisminwhichthepower central features,mightbeexplicableinthismodelifthe have suchstructureonlyinthejettedlobe). not showsignificantadditionalinhomogeneityinthejetted the source.(Notethatalthoughoursampleasawholedoes ing collimatedflowsneededtosupportsuch“multiplehot for hotspotsthatareassociatedwithstrongsecondaryfine more prevalentinthelobewithbrighterjet.Afurther generate lesscompacthotspots(asweobservedin11of13 riving flow,whilethelatterarenot.Counterjets,beingintrin- the jettedandcounterjettedhotspots.Theformerarebeing of unity. ships amongjetbending,hotspotprominence,andcounter- between thejetsandcounterjet candidatesarefreeofthis asymmetry increasedwhenthejetdirectionissteadymight lobe oncethecompacthotspotsareexcluded,bothsources spots” wouldthenoccuronlyonthecurrentlyactivesideof structure tobeonthejettedside(Lonsdale1989):ongo- difference thatcouldbeexplainedbythismodelisthetrend channel intoitslobecanexplainwhyrecessedhotspotsare cases). Theneedforthe“born-again”jettoreexcavatea (brighter) jetshouldpreferentiallyformthemorecompact dependence ofbothpowerson the redshift,eveniflobe sically lesspowerfulonthismodel,mightbeexpectedto actively resuppliedwithparticlesandcompressedbyanar- and jetpropertieswereintrinsically unrelated.Thefluxden- sity ratiosbetweenthejetted and counterjettedlobes This describesthehypothesisthatbeamonjetted We cannotuseourdatatotestwhetherthelobepowers The connectionsbetweencounterjetdetectionandjet This modeltriviallyaccountsforthedifferencesbetween 7.3 IntrinsicPowerAsymmetries/Flip-flop 817 1994AJ 108. . 7 6 6B but finite,powerasymmetry. bias, however.Theseratioswouldbecorrelatedinsome forms oftheflip-flopmodel,butinoursampletheirloga- 818 when confrontedwiththesedetailedconstraints,thesimplest its strictestform,butwithatwo-beammodelvariable, would alsoavoidlargeratiosofarmlengthbetweenthe variations inthejet/counteijetpowerratioisshortcompared rithms areuncorrelated(r=—0.20).Ifthelobepoweris that areprovidedbyournewimages.Section7showedthat, et al1992),andemissionlinesplittingonthecounterjetside of one-sidedjetsunattractive.Opticalsynchrotronemission oped thatmakethestrictflip-flopinterpretation sources. Thus,wecannotbedealingwithaflip-flopmodelin gests thatbeamsarepresentonthecounterjettedsideofthese 3C 204L,and208J.Asdescribedearlier,thisresultsug- in whichwefindnocounterjetcandidates,suchas3C1750, lobes.) to thelobegeneration/decaytimescales.(Thisconstraint model, thislackofcorrelationrequiresthatthetimescalefor energy transportinpowerfulsources? forms ofallthreetypesmodelthatweintroducedinSec. central feature,jet,counterjetcandidateandlobeproperties evidence forongoingflowwithoutdetectablecounterjets. in 3C120(Axonetal1989)alsoprovidecircumstantial on thecounterjetsideinM87(Stiavellietal1992;Sparks compact hotspotswithshortsynchrotronlifetimesinlobes dominated bythetime-integratedenergysupplyinaflip-flop beaming alone),butinsteadappears tobeenhancedsignifi- form ofthemodel,however:wesuggestthatflowsin parsec-scale features.Theslopeoftheprominencecorrela- herent explanationofsuchtrendsinkiloparsec-scalejetsid- the twin-relativistic-beammodelisthatitoffersasingleco- milliarcsecond-scale centralfeaturesandofthestraightjet prominence ofthesecandidates is notanticorrelatedwiththat hibited systematicpropertiesconnected withjetbending.The continuous counterjetsatisfying allofourcriteriaforjet- the larger-scalejetsaremildlyrelativistic(ÿ~2). central featuresarehighlyrelativistic(ÿ~5)whilethosein tion impliesadeparturefromthesimplest,constant-velocity central featuresandthejetsarebothrelativistic.Astrengthof explanation ofthesecorrelationsisthattheflowsthrough motion inquasarnuclei,webelievethatthemostattractive these features.Giventheampleevidenceforrelativisticbulk of thestraightjetsegments(as expectedfromrelativistic hood, thecounterjetcandidates foundinsevensourcesex- self-Compton x-rayluminositiesofsourceswithprominent apparent superluminalmotions,rapidvariability,andlow edness andprominenceforextendedsourcesaswellofthe segments thatreinforcesthecorrelationinsidednessbetween 1 areinadequate.Where,then,doourresultsleadmodelsof ; c © American Astronomical Society • Provided by the NASA Astrophysics Data System The flip-flopmodelconflictswiththepresenceofbright, We findacorrelationbetweentheprominenceof Several otherlinesofevidencehaverecentlybeendevel- Although noneofthesourcesdisplayedanunambiguous, Section 6summarizedtheempiricalcorrelationsamong BRIDLE ETAL.:TWELVE3CRQUASARS 8.1 SummaryofConsequencesforModels 8. CONCLUSIONS viability ofthemodifiedmodeldependsonwhetherve- Unfortunately, themodelcontainsmanyfreeparameters,so cally plausible:allowingvelocitystructureacrossthejetsat patible withmanyofourresults,whetherornotthelarge- cantly byjetbending.Nocounterjetcandidateswerefound locity structurecanevolveappropriatelywhilethejetbends. outer layersastheyinteractwiththeirsurroundings.The the parsec-scalefeatures.Therequiredmodificationisphysi- prominence andsidednessofthekiloparsec-scalejets nence andasymmetriesofthehotspotswiththoseon gest thatjetsbendmorereadilyfurtherfromthequasars,and opposite long,straightsegmentsofjets.Ourdataalsosug- relations insteadrequirethatanyintrinsicasymmetriesorigi- entirely tolarge-scaleasymmetriesindissipation.Thesecor- models thatascribeasymmetriesinthelarge-scaleemission nence ofthejetsonparsecandkiloparsecscalesruleout ruled outbytrendsinourdata. theless, somesimpleformsofthesemodelsappeartobe models alsorequireparametersthatcannotpresentlybe it ishardtotestquantitativelywithouthigher-resolutionob- all distancesfromthenucleus,plusdecelerationoftheir model mustbemodifiedtounifyourresultsonthepromi- that thisbending,particularlywhenabrupt,decreasestheir in theirpurestformalsohavedifficultieswiththejet-related nate onthesmallestscales.Asymmetricdissipationmodels quantified andthusmakethemhardtotestindetail.Never- servations oftheinternalstructuresjets. scale flowhasacomponentwithbulkrelativisticvelocity. Mach number)decreasesonmany-kiloparsecscales,iscom- model, inwhichtheaveragejetvelocity(andpresumably ability toformcompacthotspots.Inthissense,a“tiredjet” viable, allmodelsmaytherefore needtointroducefurther flip-flop, cannotbereconciledwithourevidenceforcompact asymmetry inhotspotrecession. predictions. Furtherworkmaytherefore havetoaimmoreat lobes. hot spotswithshortsynchrotronlifetimesincounterjetted rather thanattestinganysimple model’sdetailedpredictions. free parametersthatcompromise theirabilitytomakeunique the observedcorrelationsofasymmetriesamonghotspots, collimation), mayalsobeasymmetric,andthuscontributeto not infinite.Otherproperties(e.g.,theirmeanvelocityand the lobesaswelltheirbrightness.Ifjetshaveintrinsic the flowparametersenoughtoinfluencemorphologyof originate onsmallscalesnearthenucleusandalsomodify in thesourcesappearstodecreasewithdistancefrom degree towhichDopplerfavoritisminfluencesasymmetries effects thatdominateatvarious distancesfromthequasar, establishing whichbroadclasses ofmodelcangeneratethe counteijet candidates,jets,andcentralfeatures.Toremain asymmetries, theirpowerratioatanygiventimeisevidently quasar. Ifasymmetricdissipationisalsoimportant,itmust ships shownbyourdataliesinblendsofthesemodels.The The asymmetric-dissipationandintrinsic-asymmetry In thepresenceofsucheffects,twin-relativistic-beam The simplestformofintrinsicpowerasymmetry,thepure The strongcorrelationsbetweenthesidednessandpromi- It seemslikelythatthecorrectexplanationofrelation- 818 1994AJ 108. . 7 6 6B 26-21 Axon, D.L,Unger,S.W.,Pedlar,A., Meurs, E.J.A.,Whittle,D.M.,& Argue, A.N.,&Kenworthy,C.M.1972, MNRAS,160,197 jet modelsofkiloparsec-scaleasymmetries.Asamplecon- kiloparsec-scale jets,butlessthanitaffectsthatofthecentral galaxies. Theseresultsarequalitativelyconsistentwiththe prominent straightjetsegments,andmuchless Baars, J.W.M.,Genzel,R.,Pauliny-Toth, 1.1.K.,&Witzel,A.1977,A&A, idea thatrelativisticbeamingaffectstheprominenceof nence is42timesgreaterinthequasarsthanradio frame ofthesource)for25quasarsis4.3timesgreater prominence isdeterminedsolelybyrelativisticbeaming,the Barthel, P.D.1989,ApJ,336,606 samples, thegeometricmeanofcentralfeaturepromi- than thatforthe14radiogalaxies.Forsametwosub- their restframes.Thegeometricmeanofthejetprominence problems discussedhere. powerful sourcesthat“unified”modelsseektorelateinthis posite thestraightestsegmentsofjets,andmaygivemis- radio galaxieswouldalsohavemoreprominentcounterjets, central features,thanthoseinthissample.(Ifthecounterjet Type IIquasarsareindeeddrawnfromthesamepopulation double-lobed structures.Thesedataillustratethatmanyqua- Riley TypeIIradiogalaxiesandquasarswithunambiguous tected jetsandcentralfeaturesinasampleof89Fanaroff- manner, andwhetheradistributionaroundthisvalueiscon- leading resultsifattemptedwithwhole-jetandwhole- however, thatthistestshouldbeconfinedtotheregionsop- systematically closertoourlineofsight(Bridle&Perley consistency ofrelativistic-beammodels.IfFanaroff-Riley in largersamples,itwillallownewtestsoftheself- ture prominences.Ifthisapproachcanbeusedconvincingly (relative tothetotallobeemissionat1.5GHzandinrest sample havez