1985ApJ. . .291. . .32B -1 7 common featureofextragalacticradiosources(e.g.,CygnusA, (Blandford andRees1974).Theelongatedjetfeaturesmaybe curves over—10°inpositionangleitslengthof~200kpc direction, reflectthepersistenceofdirectionemission (e.g., NGC6251,Readhead,Cohen,andBlandford1978).The curved throughalargeangle,asin3C388(BurnsandChris- The AstrophysicalJournal,291:32-44,1985April1 (Saunders etal.1981),correspondingtoastabilityoforienta- VLBI jetwhichisalreadycollimatedonascaleoffewparsecs tracers ofthecollimatedflowmaterialemittedcontinuously Biretta, Owen,andHardee1983),areusuallytakenas that ofsomepreferredaxis,presumablyanaxisrotation, of the beamofmaterialfromgenerator:forNGC6251,jet straightness ofajet,andtheabsencediscontinuitiesinits tiansen 1980),andareknowninsomecasestooriginatewitha almost straight,asinNGC6251(Saundersetal.1981),or or sporadicallyfromsomecompactengineinagalaxynucleus Perley, Dreher,andCowan1984;3C31,Burch1977;M87, Inc., undercontract withtheNationalScienceFoundation. engine wasformedandfueled bymaterialwhichoriginatedin fueling it,aretopicsofconsiderable speculation.Ifthecentral engine andthehostgalaxy,originofmaterial (e.g., Rees1978)thatthedirectionofjetsinradiogalaxies is determine thedirectionofemissionajetareunknown. so thatthereisbendingofthejetonascale~50pc. kiloparsec-scale jetaremisalignedbyabout10°inthisgalaxy, tion ofthebeamgeneratortolessthanabout10°over (Q 1985.TheAmericanAstronomicalSociety.Allrightsreserved.PrintedinU.S.A. evolution—then itmightbeexpected thattherotationaxisof rates (~10M©yr)arerequiredtofuelit,anditissurmised place inthenucleusofitshostgalaxy,onlysmallaccretion However, oncethecentralenginedrivingradiosource is in the hostgalaxy—forexample, frommasslostduringstellar the accretingengine.Therelationshipbetweenthiscentral 10 yr.Note,however,thattheparsec-scalejetand the 1 Radio “jet”structuresmanykiloparsecsinlengtharea The mechanismsthattriggerradioactivityingalaxiesand OperatedbytheAssociationofUniversities forResearchinAstronomy, intrinsic kinematicparameters,inparticularrotationvelocityandcentraldispersion. likely. Wefoundnosignificantcorrelationsbetweentheradiopowerormisalignmentangleandanyof Subject headings:galaxies:internalmotions—galaxies:jetsstructureradiosources: angles isconsistentwithbeinguniformbetween0°and50°,largermisalignmentssignificantlyless unique alignmentoftheradioaxesandminorhostgalaxies.Thedistributionmisalignment study arepresented,andthestructuresofextendedsourcesdescribed.Noevidenceisfoundfora © American Astronomical Society • Provided by the NASA Astrophysics Data System The resultsofVLAobservations47brightellipticalgalaxiesfromasample54fordynamical THE ORIENTATIONSOFROTATIONAXESRADIOGALAXIES. I. INTRODUCTION I. RADIOMORPHOLOGIESOFBRIGHTELLIPTICALGALAXIES 1 Kitt PeakNationalObservatory,OpticalAstronomyObservatories Milliard RadioAstronomyObservatory,UniversityofCambridge Received 1984July11;acceptedOctober19 Roger L.Davies M. Birkinshaw ABSTRACT AND 32 ment wouldnotbeexpected. in anothergalaxywhichwaslatercapturedbythehost,orif whether theradioaxesarealignedwithrotationof good velocitymappingispossible.Weaimtodetermine maps ofasamplebrightellipticalgalaxieschosensothat cannot reliablybedonefromtheirstellarfigures:theslow tion axisofthestars.However,ifcentralobjectwasformed the engine(andthusradioaxis)wouldalignwithrota- data werenotpreviouslyavailable ;theseobservationsare for all47ofthegalaxiesinthis sampleforwhichgoodradio elliptical galaxiesinasamplechosensothatgoodopticalspec- galaxy. power it.Lackofalignmentwouldperhapsindicatethateither stars onkpcscales.Suchanalignmentwouldsupportstrongly galaxies inordertodeterminetheirrotationaxesforcompari- projected minoraxesmaynotbecoincidentwiththeirrotation rotations andisophotetwistsobservedinellipticalgalaxies the fueloriginatesoutsidehostgalaxy,thensuchanalign- detailed in§IV,andtheradio structuresofthedetectedgal- properties. Radioobservations usingtheVLAhavebeenmade present thesampleof54galaxiesstudiedhereandtheiroptical work intendedtotestthebeammodelthroughstudiesofmor- structures, andtheinterpretationofresultsincontext of stellar-dynamical mapsofthosegalaxieswithsuitableradio troscopy ispossible.Laterpaperswilldealwithdetailed the engineorfuel,both,originateoutside host of theenginedrivingradiosource,andprovidesfuelto the hypothesisthathostgalaxydeterminesproperties son withtheradioaxes.Asafirststep,wepresenthere axes. Wemust,therefore,makevelocitymapsofradioelliptical suggest thattheirfiguresmaybetriaxial,andhence the relativeorientationsof minorandradioaxesofthose axies arediscussedintheAppendix. SectionVthenexamines phological ordynamicaldataonthegalaxies.In§III we the beammodel.SectionIIofthispaperdiscussesprevious 22 galaxiesdisplayingextended radioemission,andidentifies The determinationoftherotationaxesellipticalgalaxies This paperisconcernedwiththeradiostructuresof 1985ApJ. . .291. . .32B -1 25-1 the galaxieswhichareusefulforlaterdynamicalstudy.This dynamical studywillbethesubjectofalaterpaper. Mpc andq^0. figure (asseenondeepplates),andthenhaveexaminedthe cal axisofagalaxyisthesameasminorstellar correlation betweentheminorandradioaxes(seeGuthrie and dynamicalaxesofgalaxieshaveassumedthatthedynami- This approachenablesalargesampleofgalaxiestobestudied isophote twistsofellipticalgalaxiesmayindicatethattheyare cident. not oblatebuttriaxial(Illingworth1977;Binney1978),sothat quickly. However,thegenerallylowrotationvelocitiesand ment oftheradioaxesisthatminoraxispreferredover the projectedminoranddynamicalaxesmaynotbecoin- 1979 andreferencestherein;alsoKapahiSaikia1982). tion. Thisresultisambiguous:thetrendforalignmentexists, the majoraxisforassociationwithradioemissiondirec- seen. Morphologicalcomplicationsintrinsictoellipticalgal- but thepreferenceissmallandmanylargemisalignmentsare are determinedatfaintisophotelevels,farawayfromthe axies complicatetheissue:(1)Theminor-axispositionangles important nuclearregions.Ifthegalaxiesaretriaxial,theymay The presenceoffaintdustlanescanbiasthemeasurement have twistedisophotes,sothattheminoraxisatsmallradiican 0 be significantlymisalignedwiththatmeasuredatlargeradii.(2) the positionangleofstellarcomponent.(3)Manybright radio galaxiesarealmostroundandopticallyfaint,sothe is appropriate,butfewstudiesofthedynamicsradioellip- position-angle determinationscanbequiteuncertain. stellar componentisusuallyfaint;therotationaxes tical galaxieshavebeenmade.Forstrongradiogalaxies,the galaxies, stellarrotationcurveshavebeenmeasured,butthe results areinconclusive,withsignificantmisalignments between theradioandrotationaxesinseveralcases,good alignments inothers.Simkin(1979)concludedthat3C33, have beenmeasuredfornoradiogalaxieswithPiâ: 2 x10WHzsr.Fornearby,andhenceweaker,radio found substantialmisalignmentsbetweentheprojectedminor large rotationvelocitiescomparedwithnormalellipticals. On but thegalaxieswerefoundtobeunusualinshowing very of thestars,andaxisradiosourcearewellaligned, 3C 98,and218theminoraxisoffigure,rotation the otherhand,JenkinsandScheuer(1980)(1981) axes andthekinematicofsevenweakerradiogalaxies, and neitheraxiswasfoundtoalignwiththeradiostructure. between theirradioanddynamicalaxes,whereaslesspowerful terms ofdifferentoriginsforthefuelpoweringradioemis- sources donot.Itistemptingtointerpretthisdichotomy in powerful sourcesthefuelsupply tothecentralenginemight fueled bymaterialoriginating inthegalaxy,whereasless sion. Inpowerfulradiogalaxies,theemissioncould be originate fromanexternalsource, andhenceturntherotation axis ofthebeamgeneratorto an“unusual”orientation.Mis- 78 elliptical galaxiesarerare(Schechter andGunn1979;Davies alignments betweentheminor anddynamicalaxesofnormal and Illingworth1985;butsee Williams1981),althoughthe -1 Throughout thispaperweshallassumeH=50kms Most previousstudiesoftherelationshipbetweenradio The resultoftheseearliermorphologicalstudiesthealign- 0 A directstudyoftherotationaxesradioellipticalgalaxies Thus itappearsthatpowerfulradiosourcesshowalignments ii. previousstudies:thegalaxysample © American Astronomical Society • Provided by the NASA Astrophysics Data System RADIO MORPHOLOGIES OF BRIGHTEGALAXIES33 hypothesis fortriggeringradioactivityandconcludedthatthe sample studiedissmall.Jenkins(1981)rejectedtheinfall anomalous stellarkinematicpropertiesofradioellipticalgal- misalignment oftheircentralengineswithkinematicand axies isdirectlyrelatedtotheoriginoftheirradioactivity.He chosen tostudythedynamicsofalargesamplenearby geometric axes. suggested thatformationbymergerscouldaccountforthe by thelargeamountofobservingtimenecessarytoestablish galaxies. Thedirectdeterminationofdynamicalaxesislimited Nevertheless, theobservationofnearbygalaxiesallowsgood the rotationaxisofevenabrightellipticalgalaxy,andso linear resolutionofboththeradioanddynamicalfeatures small andonlytheweakerradiogalaxiescanbestudied. sample ofgalaxiessufficientlybrightformeasurementisquite envelope ofamoredistantgalaxy. nuclear propertiesmorecloselythandoesastudyofthestellar of thegalaxiestobeachieved,andhenceapproaches The galaxiesusedwerechosenfromallthoseforwhichatleast neous andincompletesampleofellipticalgalaxieswhichare sufficiently brighttoallowgoodstellar-dynamicalmapping. ferometric mapscouldbemadewiththeVLA. were includedinoursample,toensurethatgoodradiointer- one stellarrotationcurvewasavailable,andwhicharelistedin and Jenkins(1981).Onlygalaxiesatdeclinationsabove—40° Davies etal(1983),Simkin(1979),JenkinsandScheuer(1980), mated fromthesizeoferrorinindividualmeasurements in thecentralregionsofgalaxieswastakenfrompublished et al.(1983)andreferencesthereinunlessotherwiseindicatedin Accurate nuclearpositionsformanyofthesegalaxieshavealso their ellipticitiesandprojectedminoraxispositionangles. surface photometry.Uncertaintiesofthesevalueswereesti- the notes.Wherepossible,positionangleofminoraxis request. TheellipticitiesgiveninTable1aretakenfromDavies been measured,andmaybeobtainedfromtheauthorson ment withthecatalogvalues,anderrorstabulatedinTable logs ofNilson(1973)andLaubertseta/.(1981)toestimate galaxies withnosurfacephotometrywemadeourownmea- and thescatterinquotedvaluesatsmallradii.Forthose entered intoourinternalerrorestimate,aswellthedegree to the error.Inmostcasesourmeasurementswereingoodagree- surements ofpositionangletocheckthosetabulatedincata- were intheapproximatedeclinationrange—2?5to—17?5 or which theimagewasconfusedbystarsordust.Afewgalaxies NGC 1316,3C33,and98thepositionanglewastaken were toofaintorroundtohaveentriesinthecatalogs. In our ownmeasurement.Theellipticityandsizeoftheimage these casesourownmeasurementsarequotedinTable1. For notably, thefollowing. ticity andminor-axisposition anglethatcanaffecttheresults, plates) tomeasurethefigures of thegalaxiesassumesthatthere parts ofthegalaxies.Toavoid thisassumptionwehaveused are nostrongisophotaltwists betweentheinnerandouter from individualstudiesofthesegalaxiesthatusedphoto- 1 reflectthedegreeofagreementanderrorweattached to graphic material. In ordertoexaminethisquestionmoreclosely,wehave For thesereasons,wehavechosentoworkonaninhomoge- The sampleof54galaxiesislistedinTable1,togetherwith There areseveraldifficultieswiththemeasurementsofellip- 1. Theuseofdeepplates(e.g., thePalomarSkySurvey III. OPTICALDATA 1985ApJ. . .291. . .32B 34 minor-axis positionangle.Amongthe22galaxieswith published CCDsurfacephotometrytomeasurethecentral extended radiostructuredetectedinthisstudy,allbutfive(3C angles determinedinthisway.Thosepositionfrom The positionanglestakenfromLeach(1981)arelimitedto given inTable1weremeasuredataradiusoftypically2"-5". radii greaterthan30"becauseofcontaminationbyscattered Lauer (1984)andR.Peletier(1984,privatecommunication) 33, 3C98,NGC1316,3557,andIC4296)haveposition NGC 7626measuredbyLaueris90°differentfromthatgiven light atsmallerradii.Largeisophotetwistsareunusual, but in King(1978). close tothecenteraspossible.Notethatpositionangle for 90° twist,andinthesecaseswehavetakenthepositionangle as some dooccur;forexample,both3C33andNGC7626show a deform itsfigureandmayresultinaseriouslyincorrectmea- galaxies withpositionangles determinedfromskysurvey estimates, butuntilsurfacephotometry isavailableforthefive surement oftheellipticityandminor-axispositionangle. plates, theyshouldbeconsidered aspreliminaryvalues. this samplearequiteuncertain. to measurethelocationofminoraxis,andhenceposi- shown inFigure1(brokenline), whereitiscomparedwiththat tion anglesoftheminoraxeseightveryroundgalaxies in 2. Anyundetecteddustpatchesassociatedwithagalaxywill These uncertaintiesare,tosome extent,reflectedinourerror The ellipticitydistributionfor oursampleofgalaxiesis 3. Forgalaxieswithlowellipticity,itisintrinsicallydifficult © American Astronomical Society • Provided by the NASA Astrophysics Data System from theunpublishedCCDdataofHeckman.(9)PositionangleLaubertseta/.1981andreferencestherein.(10) and Schmidt1964.(3)PositionanglefromLauer1984.(4)Davisetal.(5)ellipticity measured directlyfromthePalomarSkySurveyorESOBlueforgalaxiessouthof—17°.(11)PositionangleKing Schweitzer 1980.(6)PositionanglefromLeach1981.(7)Nilson1973.(8)andellipticitymeasured 1978. NGC 584.. NGC315 .. NGC 720.. NGC 596.. NGC 1316 NGC 1052 NGC 741.. 3G 33 NGC 2768 NGC 1700 NGC 1600 NGC 2778 NGC 3605 NGC 3379 NGC 3377. 3C 98 NGC 3904 NGC 3818 NGC 3665 NGC 3608 NGC 3557 3C218 NGC 3962 NGC 3923 NGC 4278 NGC 4261 NGC 4365 Notes.—(1) PositionanglefromR.Peletier1984,privatecommunication.(2)EllipticityandpositionMatthews,Morgan, Galaxy Ellipticity 0.31 0.37 0.37 0.37 0.61 0.02 0.26 0.37 0.31 0.56 0.29 0.30 0.41 0.13 0.37 0.08 0.29 0.26 0.32 0.21 0.19 0.32 0.09 0.35 0.07 0.17 0.25 Position Angle Minor Axis 147 ±2 163 ±10 132 ±3 150 +2 107 +7 160 +3 134 ±3 130 +7 166 ±4 115 +3 168 ±5 120 +8 130 ±5 140 +10 136 ±2 23 ±3 55 ±2 40 +20 98 +2 98 +10 12 ±3 69 +2 73 +6 18 +4 (deg) 4 + 3 +5 2 +3 BIRKINSHAW ANDDAVIES Galaxy Sample Notes 10 10 4 3 2 3 3 TABLE 1 4 3 6 2 5 9 9 6 8 3 1 6 7 7 3 9 6 3 3 1 NGC 4374 NGC 4472 NGC 4458 NGC 4406 NGC 4387 NGC 4473 NGC 4697 NGC 4489 NGC 4486 NGC 4478 NGC 4649 NGC 4636 NGC 4621 NGC 4551 NGC 5813 NGC 4889 NGC 4839 NGC 4742 NGC 5845 NGC 5638 IC 4296.... NGC 5831 NGC 7626 NGC 7562 NGC 7785 NGC 7619 IC 1101.... distribution ofellipticalgalaxies,possessinganexcessflat galaxies. Thisselectioneffectisintrinsictothesampleofgal- ney anddeVaucouleurs1981).Itcanbeseenfromthefigure axies previouslystudiedforrotationmeasurements.Although that thesampleofgalaxiesissomewhatatypicalgeneral Corwin (1976,hereafterRC2),shownasthesolidline(seeBin- for ellipticalgalaxiesindeVaucouleurs,and de Vaucouleurs1981). line) andintheellipticalgalaxies RC2 (solidline;derivedfromBinneyand Fig. 1.—Theellipticitydistribution inthesampleof54galaxies(broken Galaxy Ellipticity 0.10 0.18 0.05 0.24 0.38 0.42 0.19 0.05 0.14 0.15 0.38 0.19 0.34 0.10 0.50 0.34 0.19 0.25 0.09 0.31 0.35 0.09 0.33 0.17 0.09 0.29 0.40 Position Angle Ellipticity Minor Axis 160 ±10 157 +5 133 ±10 152 +2 169 ±3 170+ 10 116 ±5 125 +3 172 +4 44 ±2 40 ±3 70 ±5 32 +2 49 ±12 50 +5 75 +5 42 +3 76 ±5 52 ±6 70 +4 44 +6 60+ 10 58 +5 45 +5 92 +2 10 +5 (deg) Notes 11 10 10 10 3 3 4 6 3 7 6 7 3 3 3 6 7 3 7 3 3 3 3 1 3 1 Vol. 291 1985ApJ. . .291. . .32B -1 2 No. 1,1985 elliptical galaxieshavelowrotationvelocities,ontheaverage wide channels(ofoppositecircularpolarization)simulta- detection ofcentralcomponentsandextendedstructures (1983). Forthosegalaxiesnotintheircompilationtherecession flatter galaxieshaveahigherrotation,sothat,inorderto associated withthegalaxies.Dataweretakenintwo50MHz vations weremadeat4.885GHz,asacompromisebetweenthe array, with24-27antennasinfulluseatanyonetime.Obser- excellent mapsalreadypublished(seeAppendix).Radiodata km sMpc.ThevelocitiesweretakenfromDaviesetal. velocities andassumedauniformHubbleflowwithH=50 scales fromtheobservedquantities,wehaveusedrecession detect rotationtoagivenlimit,observershaveselectedsamples fields inwhichnosignificantfeaturewasfoundwithina 20" corresponding visibilityintheotherchannel). density of7.41Jy(Baarsetal.1978).Thermsnoiselevel galaxies, andthefluxdensityscalewasestablishedbyobserva- phase-calibrated atintervalsofabout30minuteswithrespect to minimizeproblemswithintermittentinterferenceorfaults, low-brightness structuresweremissedthroughtheconstruc- data werethencheckedcarefully,toensurethatnodetectable circle aboutthenominalpositionofgalaxy.Thevisibility since visibilitiesinonechannelwereusedwhentherewasno here areintheIStokesparameteronly(strictly,pseudo-/, achieved ineachfieldwas0.2-0.3mJy,andthemapspresented tions of3C286(1328+308)withanassumed4.885GHzflux to standardunresolvedcalibrationsourceslocatednearthe and toimprovethecoverageofu-vplane.Thedatawere source, withthetimeusuallyarrangedintwo5minuteperiods neously, andabout10minutesofintegrationtimewasusedper In ordertoprovideadequateradioinformationforthese 218, NGC315,1052,4374,and4486)have velocities weretakenfromthestudiesoftheirrotationcurves. is possible. dynamical axeswillbeafifectedbythisbias,butsuchaproblem of theNationalRadioAstronomyObservatoryduring1983 objects, all47wereobservedwiththeVeryLargeArray(VLA) on theremaininggalaxiesareinhomogeneousandincomplete. seems unlikelythatgeneralconclusionsconcerningthe of flattergalaxiestoobtainmoredetectionsrotation.It CLEANed usingthestandard AstronomicalImageProcessing and willnotbediscussedfurther. were alsodetected,butthesearenotrelevanttothisproject data werefurtherprocessed.Severalunrelatedradiosources galaxies showedevidenceofsomeradioemission,andtheir located atthesegalaxiesaregiveninTable2.Theremaining 21 about 60").Twenty-sixgalaxieswerenotdetectedatthisstage, tion ofthesynthesismap(i.e.,structuresonscalesgreaterthan noise levelatthefieldcenterwerethenestablishedforthose resolution synthesismap.Fluxdensitylimitsofthreetimes the onto theu-vplane,andFouriertransformedtoproduceahigh- Universities, Inc.,undercontractwith theNationalScienceFoundation. System (AIPS)programsavailable attheVLAsite(Clark and thefluxdensitylimitsforsmall-angular-scalesources March. 0 2 To deriveabsolutemagnitudes,radiopowers,andlinear During theseobservations,theVLAwasoperatedinC Of the54galaxieslistedinTable1,seven(3C33,3C98, TheNationalRadioAstronomyObservatory isoperatedbyAssociated If radioemissionwasapparent inafield,thenthatfieldwas For eachfield,thevisibilitydatawerecalibrated,gridded © American Astronomical Society • Provided by the NASA Astrophysics Data System IV. THERADIOOBSERVATIONS RADIO MORPHOLOGIESOFBRIGHTEGALAXIES NGC 5813)thesourcesweretooweakforself-calibrationof map wererestoredusingaCLEANbeamofGaussianshape centered onNGC4486,thenCLEANed,andtheresulting 4486 (whichlies~9'away).Inthiscase,amapwasmade final maps.Theseprocedureswerenotadequateinthreecases: the polardiagramofVLAprimaryantennastoproduce data wereself-calibrated,CLEANedagain,andcorrectedfor the data(Cornwell1982)tobeuseful.Forothersources, and thesamehalf-widthorientationas“dirty”beam. calibrated inthesamewayasothermaps. These low-resolutiondatawerethenCLEANedand self- VLA significantlyoverresolvedthesource(withexception NGC 4478.Thehighnoiselevelat4478(Table2)reflects data toproducearesidual(i.e.,NGC4486-subtracted)map of of NGC4261,toshowtheoverallstructuresource. removed fromthesynthesistoproducealow-resolution map Appendix). Dataatbaselinesgreaterthan900mweretherefore of acentralpointsource,andthenarrowjetfeatures; see a hundredfoldimprovementontheoriginalmap. the extenttowhichthisprocedureisinadequate,butrepresents CLEAN componentsforNGC4486thensubtractedfromthe For fourofthefields(NGC3379,NGC3608,3962, angular size—20"(seenasa beambroadeningonthe1407 quencies, withfluxdensities 92 +27and183mJy,an remapped at408and1407 MHz usingtheCambridgeOne quately representedonany map. Thisgalaxywastherefore and theslightvisibilityrise at smallspacingswasnotade- Mile radiotelescope.Thegalaxy wasdetectedatbothfre- 1980), andthentheCLEANcomponentsremovedfrom NGC 4478.—Thedataaresomewhatconfusedby NGC 4261.—Inthiscase,itwasfoundthattheCarrayof NGC 7785.—Forthisgalaxynopointsourcewasdetected, NGC 3605. NGC 1700. NGC 720.. NGC 596.. NGC 584.. NGC 4478. NGC 4458. NGC 4406. NGC 4387. NGC 4365. NGC 3923. NGC 3904. NGC 3818. NGC 3608. NGC 3377. NGC 2778. NGC 4621. NGC 4551. NGC 4489. NGC 4473. NGC 7562. NGC 5845. NGC 5831. NGC 5638. NGC 4742. NGC 4697. Galaxy Limitat3<7(mJy) Flux DensityLimitsfor Undetected Galaxies TABLE 2 4.885 GHzFluxDensity 0.60 0.62 0.64 0.88 0.95 0.52 0.54 0.53 0.44 0.86 0.92 0.65 0.65 0.62 0.68 0.50 0.53 0.57 0.91 0.63 0.56 1.15 1.00 1.48 1.18 1.00 35 1985ApJ. . .291. . .32B 0.8 mJy,startingat—12mJy.ThenucleusofthegalaxyNGC742islocated2".0±0"7northcompactregionineasternlobe. cross, andthesynthesizedhalf-powerbeamwidthisshownasashadedellipse.Negativecontoursaredrawnbroken,(a)NGC741.Contours atintervalsof 36 BIRKINSHAW were fittedontheCLEANedmapsusingCLEANbeam and theassumptionthatunderlyingsourceisGaussianin than 1.1mJycouldbefoundintheVLAdata. these data,shouldbe~3.4mJy,butnopointsourcestronger map bysummingthefluxdensitycontainedinaboxaround found, andangularsizelimitswerederivedusingthefitsto flux densitiesfortheextendedsourceswerederivedfrom MHz map).The4885fluxdensity,extrapolatedfrom objects andthenoiselevelonmap.Inremainingcases, shape. Forsixofthesources,onlyapointlikecomponentwas 10 mJy,thenat5mJyintervals. Fig. 2.—VLAcontourmapsoftheextendedradiosourcesat4885MHzin/Stokesparameter.Onalllocationgalaxynucleus ismarkedasa The locationsofpointsourcesinthefieldsgalaxies Fig. 26.—NGC1316.Contoursare drawn atintervalsof2mJyfromto 03 204948 47 4845 © American Astronomical Society • Provided by the NASA Astrophysics Data System AND DAVIES the visibilitycurves. the regioncontainingsource,andcheckedbyinspectionof Figures 2a-2k,andthe21detectedellipticalgalaxiesarelisted but withoutthezerocontour. in Table3togetherwiththesevengalaxiesthathadalready source, thelinearsizeofanyjetfeature,andpositionangle gives thesourcepowerat4.885GHz,aclassificationof been wellmapped.Table3thereforecontainsthecompletelist of theradioaxis. of galaxieswhichareavailablefordynamicalstudies.Italso Fig. 2c.—NGC1600.Contoursaredrawn at1mJyintervalsfrom—3mJy, The sourceclassificationsaregenerallybasedonthe Maps ofthemoreextendedradiosourcesareshownin from thismap. 1985ApJ. . .291. . .32B Fig. 2/—NGC4261.Contoursaredrawn at—5,10,15,and25mJy.Theasteriskmarksthelocationofapoint sourceof315±5mJythathasbeensubtracted © American Astronomical Society • Provided by the NASA Astrophysics Data System 1985ApJ. . .291. . .32B where wethereforehavedirect informationoftheorientation where thereisnodirectinformationabouttheorientation of those withdistinguishableradio jets(suchasNGC4261), the beampoweringsource. Finally,theJ-typesourcesare cal objects,suchas3C98,orirregular,IC1101, VLA data(onthebasisofabeambroadeningsource). array, andhavenotbeenresolvedinanyotherobservations. NGC 4278,and4374theVLBIdatawerealsoused. D-type sourcesaredoubles,eitherclassical,almostsymmetri- observed kpc-scalestructures,butinthecasesofNGC1052, of abeam,andwherewecan berelativelyconfidentaboutthe E-type sourcesaredistinguishableonlyasextendedin our P-type (pointlike)sourcesareunresolvedtotheVLAin C the E-type,andD-type sourcesrequirefurther,higher that arepreferrredfordynamical study,whereastheP-type, radio axisofthegalaxy.Clearly, theJ-typesourcesarethose 38 at—0.3mJy. Fig. 2h.—NGC4839.Contoursaredrawnatintervalsof0.6mJy,starting © American Astronomical Society • Provided by the NASA Astrophysics Data System Fig. 2g.—NGC4636.Contoursaredrawnatintervalsof0.6mJy,starting—0.3mJy BIRKINSHAW ANDDAVIES with resolutionworsethanthat neededtoresolvethebeam NGC 315,4261).There islikelytobealargeruncer- where weseestraightjetsextending overmanybeams(e.g., systematic uncertaintyinexcess ofabout10°inthosecases generator, butitisnotlikely that thisassumptionintroducesa This limitationisimplicitfor allobservationsusingtelescopes clear thatwemustassumetherearenostrikingbends in the structuresofsources on beam-sizedscalesorsmaller. tion angleswhichareofmostimportancetoourstudy, it is hidden fromourobservations.Sinceitisthecentralradioposi- scope: bendsintheradiostructuresonsmallerscaleswill be only onscaleslargerthanthesynthesizedbeamof tele- useful datafromthisstudy.Thesepositionanglescanbefound galaxies inTable3,15areofJtype. resolution radiodatatobeusefulforthispurpose.Ofthe 28 mJy. The radiopositionanglesgiveninTable3arethemost Fig. 2i.—IC4296.Contoursaredrawnatintervalsof4mJy,starting—2 Vol. 291 1985ApJ. . .291. . .32B No. 1,1985RADIOMORPHOLOGIESOFBRIGHTEGALAXIES39 NGC 1600,IC1101).Detailsofthemapsandderivations long (e.g.,NGC1316)orincaseswherenojetisseen (e.g., tainty incaseswherethemapshowsajetonlyfewbeam sizes dynamical dataexistforthese objects,atpresent,foranexami- position anglesofthesources listedinTable3.Insufficient in thissamplearebetterdefined thaninearlierworkbecauseof relative orientationsoftheradio andminoraxesofthegalaxies nation ofthealignments radioandrotationaxes.The sources arediscussedindividually. of thesepositionanglesaregivenintheAppendix,where the the higherlinearresolutionin bothwavebands.Acomparison of theradioandminoraxesis physicallymeaningfulonlyifthe The primarydataobtainedfromthisstudyaretheradio © American Astronomical Society • Provided by the NASA Astrophysics Data System v. DISCUSSION Fig. 2k.—NGC7626.Contoursaredrawnat-1,1,2,3,4,5,6,7,10,15,20,25, and30mJy Fig. 2j.—IC1101.Contoursaredrawnat—0.4,0.4,1.2,2,2.8,and3.6mJy 15 0828.528.027.527.026.526.0 minor androtationaxesofthegalaxiesarecloselyparallel. characteristic propertyofradio-activeellipticalgalaxiesis that many ellipticalgalaxies,butJenkins(1982)suggeststhat a Davies etal.(1983)concludethatthismightbethecase in figure ofagalaxymaygivenocluetoitsunderlyingdynamics. the rotationandminoraxesarenotparallel,sothatstellar In addition,thereareseveraldifficulties(see§III)withdefining for suchanalignment,andhave concludedthattheradioposi- not tobeexpected.Nevertheless, severalauthorshavesearched alignment oftheradioandminoraxesellipticalgalaxies is the radioandminor-axispositionangles,sothataunique tion anglestendtolieclose theminoraxes.Therehavebeen suggestions (KapahiandSaikia 1982)thatthedegreeofalign- ment maydependonthefraction ofthefluxdensity source appearinginthecentral component,orthatbrighter 1985ApJ. . .291. . .32B 40 sources tendtobebetteraligned(Palimakaetal.1979). We maj oraxis,althoughsomeexamples oflargemisalignmentsare for radiostructurestoaligncloser totheminoraxisthan given inTable3andtheminor-axispositionanglesof 1, extended sourcewerecalculatedfromtheradiopositionangles linear resolution. alignment angleswithmorecertaintybecauseofthehigher be made,butwemayexaminetheoveralldistributionof mis- have toosmallasampletoallowsuchpartitionofourdata to histogram inFigure3b.Thesediagramsindicateapreference angles showingtheerrorsisplottedinFigure3aand as a and aregiveninTable4.Thedistributionofmisalignment radio andprojectedminor-axispositionangles),foreach earlier work,becausetheyare nearby.Wearethuslesslikelyto in oursampleonsmallerlinear scalesthanhasbeenpossiblein present inthesample.Wehave beenabletostudythegalaxies have beenmisledbyoptical orradiomorphologicalpecu- The misalignmentangles,6(thedifferencebetweenthe m © American Astronomical Society • Provided by the NASA Astrophysics Data System (12) VLBImapinJones,Sramek,andTerzian1981a;VLA Jenkins, Pooley,andRiley1977.(11)HydraA:radiomapinEkersSimkin1983. Appendix andFig.2.(6)High-resolutionradiomapinLaing1984.(7)VLA map inBridleetal.1979.(3)Radiostructurewithoutdetectedcentralcomponent scale structureisjetlikebuthaslargeextensionatlowfrequencies(seetext).(16) and Terzian1981h.(13)Large-scaleradiomapinEkers1973 Wrobel, andShaffer1983.(9)GeldzahlerFomalont(10)Radiomapin overlies nucleus.(4)RadiomapinHargraveandMcEllin1975.(5)Thispaper;see Appendix). resolution 408and1407MHzmapfromtheCambridgeOneMiletelescope(see Insufficient apertureplanecoverageatVLA;theseresultswerederivedfromlower and Kotanyi1978.(14)RadiomapinBiretta,Owen,Hardee1983.(15)Small- Wrobel 1984;VLBImapinJones,Wrobel,andShaffer1983.(8) NGC 4278 NGC 3665 NGC 3557 NGC 2768 NGC 1316 NGC 1052 NGC 741.. NGC315 .. NGC 4486 NGC 4472 NGC 4261 NGC 3962 NGC 3379 NGC 1600 3C 33 NGC 4839 NGC 4649 NGC 4636 NGC 4374 3C218 3C 98 NGC 7619 NGC 5813 IC 4296.... NGC 4889 NGC 7626 IC 1101.... NGC 7785 Notes.—(1) Compactcentralcomponentcoincideswithgalaxynucleus.(2)Radio Galaxy -1_ BIRKINSHAW ANDDAVIES (W Hzsr) l°g ^4885 22.39 24.85 23.09 20.96 21.92 25.17 21.24 24.18 21.62 21.96 23.49 20.46 22.02 21.18 22.69 20.23 21.73 20.06 21.79 20.67 22.96 20.33 23.16 18.31 19.93 19.57 19.35 19.89 Detected Galaxies TABLE 3 Source LengthRadioAxis Type (kpc)(deg)Notes D D D D D P P P P E P P J J E J J J J J J J J J J J J J o ities Po-io>F10—20?•••>F_.Theresultingdistribution is Table 4withtheerrorsgivenasafunctiqnofnineprobabil- ment tooptimizetheprobabilityofobtainingresults in 0°-10, 10-20°,...,80-90°,thenwemayuseaBayesianargu- smaller scaleofthecentralengine. typically, akiloparsecisrepresentativeofthestructureon the liarities. Thelargestuncertaintyinallstudiesofthis type shown inFigure3c. acterized byconstantprobabilitiesof0ineach10°range, underlying distributionofmisalignmentanglesthatthese data relates towhetherornotthestructureobservedonscales of, sample. Ifweassumethatthisunderlyingdistributionischar- larger misalignmentsaresignificantly lesslikely.Iftheradio 9 <50°thedistributionisconsistent withbeinguniform,and and minoraxeswereindependent, thenwewouldexpectthe tations ofthesmallsample; however, withintherange0°< 8090 m m 3 3 The uncertaintiesshownin Figure 3cemphasizethelimi- We haveusedthedatainTable4toestimateshapeof 0.6 xlO- 1.4 x10" 32 x10“ 2 x6.4 2 x32 2 x1.5 2 x10 2 x69 2 x15 400 350 Jet Angleof 0.3 3.3 31 ll 106 ±6 131 ±2 126 ±14 101 +1 152 +10 129 ±3 181 +15 Position 130 +2 145 ±10 115 ±15 24 +5 25 +5 63 +5 78 +6 83 ±4 88 +1 33 +8 79 +42 19 ±3 35 +5 10 ± 2 ±1 1, 8,12 3, 5,16 1, 6,13 1, 5,15 1, 5,6 1, 5,9 1, 7,8 3, 10 1, 11 1, 14 1, 12 3.4 3, 5 1,2 3, 5 1, 5 1, 5 1, 5 1, 5 1, 5 1.5 1, 5 1, 5 1, 5 1, 5 1, 5 1, 5 1, 5 Vol. 291 1985ApJ. . .291. . .32B o No. 1,1985 {b) Thedistributionofmisalignments,drawnonahistogramwith10°bins,(c)calculatedunderlyingprobability±1errorbounds ineach10° bin. Seetextfordetailsofthecalculation. fidence level.Theprobabilityofthemisalignmentanglebeing distribution ofmisalignmentanglestobeuniformbetween0° figures ofthegalaxiesunderstudyareoblateor,iftriaxial,then changed significantlyifweexcludethosegalaxieswithoutCCD and 90°.Thisisnotconsistentwiththedataat95%con- surface photometry. in therange0-50°is0.83±0.08.Theseresultsarenot NGC 315131+21323-1+4 NGC 105263+523340 6 NGC 741106+635-77 8 NGC 1600181+1598283 15 NGC 1316126+141502-24 14 3C 3319+31631036 10 NGC 355778+61208-42 10 NGC 3665129+311514 4 3C218 24+54020-16 20 3C98 25+5166439 6 NGC 4486101+175526 5 NGC 43742+144-42± 2 NGC 4278152+10130522 11 NGC 426188+169219 2 NGC 483910+ 152 +23810 NGC 463633+8 76 +5-439 NGC 447283+470513 6 NGC 761979+42 125 +3-4642 NGC 762635+5 92 +2-575 IC 4296130+2 133 +10-3 NGC 7785115+15 45 +57016 IC 1101145+10 116 +52911 Fig. 3.—Themisalignmentanglesbetweentheradioemissionandminoraxes,(a)Theangleerrorforeachextendedgalaxy inthesample. In makingtheabovecomparison,wehaveassumedthat Galaxy ofRadioAxisMinorAngle NGC 3557 NGC 3665 NGC 4374 NGC 7785 NGC 4839 NGC 7626 NGC 4486 NGC 4278 NGC 4636 NGC 1052 NGC 4472 NGC 1600 NGC 7619 NGC 4261 NGC 1316 NGC 315 Radio AxisandOpticalMinorAlignments 1C 4296 NGC 741 © American Astronomical Society • Provided by the NASA Astrophysics Data System IC MOI 3C2I8 3C33 3C98 Position AngleofMisalignment J L 10 20304050607080 TABLE 4 i 1r RADIO MORPHOLOGIESOFBRIGHTEGALAXIES J I^L Misalignment Angle(Degrees) 3(a) (1983) foundthatthelowerluminosityellipticalgalaxiesare figure, sothatthecomparisonofprojectedminoraxiswith close tooblate.Onlyifthesegalaxieshaveoblatefiguresisthe (full line).Itcanbeseenthatthereisnosignificantdifference,so flat rotationcurvesofmanybrighterellipticalgalaxiessuggests likely tobeoblate,andthedifferentialrotationimpliedby projected minoraxiscoincidentwiththeof3D that forthissamplethereisnostrongdependenceofradio galaxies (dashedline)iscomparedwiththatforthefullsample that theyareunlikelytobeprolate. that oftheradioaxisisphysicallyreasonable.Daviesetal. detection probabilityisindependent of ellipticity{solidlines). sample {brokenlines)andinthe asawhole,ontheassumptionthat In Figure4theellipticitydistributionofdetected Fig. 4.—Theellipticitydistribution inthedetectedgalaxiesfromour N7626 N7785N74INI600 Ellipticity i r 3(b) 3(c) - 0.05 4 3 0.30 2 0.25 J o.io 3 0.15 £ 0.20 I -Q (0 a> < Q o- a> 3 41 1985ApJ. . .291. . .32B emission thatmightbeadiffuse jet.Thesourceisclassified,as compact nucleusassociatedwith NGC741,acompacteastern ponent isconnectedwiththe nucleus throughabrightridgeof hot spot,andadiffusewestern component.Theeasterncom- than ourmap,showninFigure 2a.Thesourceshowsa GHz byJenkinsandScheuer (1980),atlowerN-Sresolution central component. spots, andtheslightmisalignmentbetweenthem the without bendsfromthenucleustoeitherhotspot.Theuncer- No radiojethasbeendetectedinthissource,sothatthe (Hargrave andMcEllin1975),withdiffuselobescompact tainty inthepositionanglereflectsonlywidthsof hot position anglegiveninTable3assumesthatthebeam runs hot spots,wellalignedthroughastrongcentralcomponent. geneous tocontradicttheconclusionofHummel,Kotanyi,and 42 sources. properties onellipticity.However,thissampleistooinhomo- magnitude andradiopowerat4885MHz.Nosignificantcor- magnitude, ortheratioofrotationvelocitytodisper- found betweenmisalignmentangleandellipticity,absolute misalignment angles.Nosignificantcorrelationofthistypeis Ekers (1983)thatroundgalaxiesaremorelikelytoberadio made withtheVLA.Togethersevenexistingmaps, present inthesedata.Theabsenceofacorrelationbetween relation betweenradiopowerandrotationvelocity,ellipticity, galaxies withfasterrotationswouldexertalargertorqueon galaxy fuelstheradiosource,wemightexpectthatfuelfrom most ofthesample. show moredustandgasthanthenearlyalignedgalaxies. stellar axesmaybestronglymisaligned.Thiswouldsuggest accreted tothegalaxy(extrinsicfuelsupply),thenradioand ability toretaingasinitscentralregions. presence ofaradiosourceingalaxyisnotrelatedtoits and ionizedgasinNGC1052,thereareinsufficientdatafor Although thisideaissupportedbythepresenceofmuchdust that thosegalaxieswithlargermisalignmentanglesshould radio powerandcentralvelocitydispersionsuggeststhatthe v/a, misalignmentangle,orcentralvelocitydispersionis sion, v/o.Wedofindaweakcorrelationbetweenabsolute present inthissample.Further,nosignificantcorrelationwas the centralobjectandtherefore,onaverage,havesmaller sample ofDaviesetal.(1983).Ifmaterialintrinsictothehost kinematic propertiesofthosegalaxiesincommonwiththe (1979). Thesourceshowsaprominentradiojetextending emission tonorthwestandsoutheast.Sincetheradiojetshows fainter counterjettothesouthwest,anddiffuselobesofradio quately representedonthelowerresolutionmapofBridleetal. angle isreliableandwelldetermined. no largebendsinthefirst~2'ofitslength,radioposition source isdiscussedbyBridleetal.(1984)butalreadyade- ~400 kpctothenorthwestofastrongcentralcomponent, NGC 741.—Thissourcehaspreviouslybeenmappedat2.7 3C 33(A0106+13).—Thissourceisa“classical”double If theinterstellarmaterialthatactsasfuelisonlyrecently We presentsynthesisobservationsof47ellipticalgalaxies We havesearchedforcorrelationsbetweentheradioand NGC 315(B2.20055+30).—Theradiostructureofthis © American Astronomical Society • Provided by the NASA Astrophysics Data System VI. CONCLUSIONS BIRKINSHAW ANDDAVIES APPENDIX classified hereasofJtype. the innerstructureofsource. Theextensionstothenorth- Our mapoverresolvestheouter structure,anddisplaysonly of twolargelobestoeitherside ofabrightcentralcomponent. ture ofthissourceiswellknown (e.g.,Cameron1971)toconsist emission tothesouthwestofnucleusonWrobeFsmap. The (1984). Thisdirectionisoppositetothatoftheweakridge of sible totheVLA,butisjetlikeVLBI,andhence is source ispredominantlydoubleinstructureonscalesacces- (1983) andthedirectionfromnucleustobright,unre- milli-arsec jetontheVLBImapofJones,Wrobel,andShaffer solved knottothenortheast,seenonVLAmapofWrobel 63° +5°,wastakenastheaverageofdirection ~ 10 lies 2'.'0+0'.'7southofthenucleusNGC742.Thestructure for aresearchfellowship,andtheUKScienceEngineering of theradiosourcesuggeststhatthisisachancecoincidence. by JenkinsandScheuer(1980).Notethattheeasternhot spot the averageofridgeandcentralradiopositionangles,or Research CouncilandtheRoyalSocietyfortravelsupport. measured frompapercopiesofthePalomarObservatorySky where thepositionsandpositionanglesofgalaxieswere calibrating thedata.WearegratefultoReynierPeletierand nucleus tobesignificantlyextendedinpositionangle sured accurately.Athigherresolution,Laing(1984)findsthe the positionangleofbrightridge(100°+5°)canbemea- directors oftheInstituteAstronomy,Cambridge,England, Tim Heckmanforaccesstounpublisheddata.Wethankthe galaxies willprovideaclearertestofthathypothesis. correlation betweenopticalandradioluminosity.Thisisnot of Dtype,sincenowell-definedjetisseeninourdata,although allocation oftelescopetimeandforassistanceincollecting Investigation oftheorientationsrotationaxesthese radio galaxiesareintrinsicallydifferentfromthosethatdonot. strong supportforthehypothesisthatgalaxieshost smaller ratherthanlargermisalignmentanglesandtheweak properties ofthissamplegalaxiesarethepreferencefor between centralvelocitydispersionandradiopower. these galaxiesformasamplefortheinvestigationofradio Survey. M.B.thanksGonvilleandCaiusCollege,Cambridge, ticular betweenmisalignmentangleandrotationvelocityor and kinematicpropertiesofthegalaxiesinthissample,par- following: to possessmorepowerfulradiosources. between 0°and50°. ability ofthemisalignmentangleforagivengalaxybeing having asignificantlylowerfrequency.Thereisan83%prob- being uniformbetween0°and50°,withlargermisalignments axies inthesample,22showextendedstructure.Wefind and kinematicpropertiesofellipticalgalaxies.Ofthe54gal- 106° +6°,significantlydifferentfromthepositionanglegiven 112° +5°;thepositionanglereportedinTable3is,therefore, NGC 1316.—(FornaxA;seeFig. 2b).—Thelarge-scalestruc- NGC 1052.—Theradiopositionangleforthisobject, The onlyconnectionswefindbetweentheradioandoptical We wishtothankthedirectorandstaffofVLAforan 2. Thereisaweaktendencyforopticallyluminousgalaxies 3. Therearenosignificantcorrelationsbetweentheradio 1. Thedistributionofmisalignmentanglesisconsistentwith Vol. 291 1985ApJ. . .291. . .32B o misaligned :ahigherresolutionmapofthenucleusNGC west andsoutheastofthenucleusareseentobesignificantly ment intheassignmentoferrors,weclassifysourceasJ double-sided jetstructureandshowsthatthismisalignment persists tosmallerangularscales.Allowingforthismisalign- This doublesourcehasprominenthotspotsembeddedin type, andthepositionangleinTable3ismean diffuse lobessitedsymmetricallytoeithersideofthecentral angle ofthetwosidesjet. No. 1,1985RADIOMORPHOLOGIES clearly double,withthegalaxylyingclosertobrighter estimate oferrorinthepositionangleradioaxisTable mean positionangleofthehotspotswithrespecttogalaxy, line throughthegalaxy.Thepositionangleisderivedas galaxy, butwiththehotspotssignificantlymisaligneda minor axisfrom100°atr=2"to150°8".Thismeasure- was analyzedusingtheGASPpackageatKittPeak(Davisci embedded jetinpositionangle24°±5°whenexaminedat needed todeterminethepositionangleofanyradiojet: northern component.Higherresolutionradioobservationsare plus orminushalfthedifference. 1316 (GeldzahlerandFomalont1983)exhibitsaninner ment maybeinaccuratebecausethegalaxyissmallandalmost CCD dataon3C218waskindlyprovidedbyHeckmanand higher resolution(EkersandSimkin1983).Unpublisheddirect tions. is unresolved. round, andthereisaninterferingimage9"tothesoutheastof al. 1984).Wefoundalargechangeinpositionangleofthe of thecore-halotypeonlargeangularscales,buthasashort 3 isderivedfromthewidthsofradiolobes. long radiojettothenortheast.Thestructuresoftwosides the galaxycenter. well intoatwo-sidedjetlikestructure,withprominentcentral is welldetermined. of thesourcearewellaligned,andpositionanglejet a prominentknottothesouthwestofgalaxynucleus,and map. component associatedwiththenucleusofgalaxy.Theposi- tion angleoftheradiostructureiswelldeterminedfrom this source isgivenbyJenkins(1982).Ourdataresolvethe galaxy nucleushasbeenremoved,showstheoverallstructure strong (315+5mJy)centralcomponentatthelocationof the in Table3reflectsthisstructure. baseline datashowthenuclearsourcetobeunresolved, and of thesourcededucedfromshort-baselinedata.Thelonger VLBI observations(Jones,Wrobel, andShaffer1983)showit region, andthesmallerrorquotedforradiopositionangle to 30"fromthenucleus.ThejetsarealignedwithinIin this the jetstobestraightwithanopeningangleoflessthan5° out tively classifiedasjetlikeinTable 3. to possessa~6milli-arcsec extensioninpositionangle — 28°+10°.Onthebasisof these data,thestructureistenta- 3C 98.—(A0356+10;seeJenkins,Pooley,andRiley1977).— NGC 1600(Fig.2c).—Themorphologyofthissourceis 3C 218(A0915—11;HydraA).—Thissourcehasastructure NGC 2768.—Thisweaksourceisunresolvedinourobserva- NGC 3379.—Thissourceisbarelydetectedinourdata,and NGC 3557(seeFig.Id).—Thisdouble-sidedsourcedisplays NGC 3665(B2.21122+39;Fig.2c).—A2.7GHzmapofthis NGC 4261(3C270;Fig.2/).—Thismap,fromwhich a NGC 3962.—Thissourceisunresolvedinourdata. NGC 4278.—Althoughthissource isunresolvedinourdata, NGC 4374(3C272.1).—The arcsec-andmilli-arcsec-scale © American Astronomical Society • Provided by the NASA Astrophysics Data System OF BRIGHTEGALAXIES43 o hms , (kpc-scale) regions. contain well-defined~3"“jet”structurewiththejetslyingin by lessthanaboutIbetweenitsinner(pc-scale)andouter structures ofthissourcehavebeenreportedbyJones,Sramek, jet orbeamisintrinsicallyuncertain(Table3). mapped oftenandwellintheradio(e.g.,Biretta,Owen, its innerstructureinTable3. position angle83°±4°.ThesourceisclassifiedasofJtypein higher resolutionmapofLaing(1984),whichshowsthecoreto broadening inpositionangle78°+6°,consistentwiththe a ~150"E-Wdouble.Ourmapshowsonly~3"3beam and Terzian(1981a,h)showajetlikestructurewhichtwists containing fivesources.Itsformisjetlike,withastrongridge main radiostructureofthegalaxy. The adjacentradiosource(atR.A.1240190,deck along it,andshowsS-shapedbends—5kpcfromthenucleus. galaxy. Theridgeisresolvedbothtransversetoitslengthand to eastandwestofthenucleus. position angle280?5±0?5,withlowsurfacebrightnesslobes Hardee 1983)andhasaprominentradioopticaljetin Ekers (1973)andKotanyi(1978)haveshownittobe Jenkins (1982)andshowssimilarfeatures.At151MHz, nucleus, suggestingthepresenceofacentralcomponent of radioemissionlyingtoeithersidethenucleus gesting thatmuchlow-brightnessstructurehasbeenresolved however, thesourceisfoundtopossessalarge(~6')extension about 0.5mJy.A2.7GHzmapofthissourceisgivenby brightness oftheridgeisenhancedatlocationgalaxy along itsmajoraxis,whichisatpositionangle10°+10°.The out inourmap. of lowsurfacebrightnesstothesouthwest(Gordey1984),sug- with thegalacticnucleus.Thejetshowsonlyslightbends over lying toeithersideofastrongcentralcomponentassociated regions. Ourmapshowsonlytheinner5'ofsource,where a brightridgetoeithersideofthegalaxyendingindiffusefaint Goss etal.(1977),andshowanobject~40'inoverallsize,with this sourcearegivenbySchilizziandMeAdam(1975) survey andappearsunresolved. for thissourceexceedsthemaximumfluxdensityonsmall its inner10kpcandhasawell-definedpositionangle. the ridgeofGossetal.isresolvedintoathin,symmetricaljet mined. low-brightness emissionlostfromoursynthesis.The map improved determinationof the positionangleofradio mapped at2.7GHzbyJenkins (1982);ourdatagivenan tion, andthepositionangleof theextensionisnotwelldeter- side ofthegalaxynucleus,andradiopositionangle any shows anearlysymmetricaldoublesourcedisposedtoeither spacings foundbytheVLA,andsuggeststhatthereissome hausen, andWielebinski(1978).Thesingle-dishfluxdensity Abell 2029,andwasmappedatBonnbyAndernach,Waldt- + 02°5751"2)isunidentified,andmaybeassociatedwiththe NGC 4472.—ObservationsofthissourcebyEkersand NGC 4636(Fig.2g).—Thissourceisthestrongestinafield NGC 4486(3C274;VirgoA).—Thissourcehasbeen NGC 4839(Fig.2h).—Inourmapthissourceiswellresolved IC 4296(Fig.2i;PKS1333—33).—Low-resolutionmapsof NGC 4889.—Thisistheweakestsourcedetectedinour NGC 4649.—Thissourceappearspointlikeinourdata. IC 1101(Fig.27).—ThisobjectisthecentralcDgalaxy in NGC 5813.—Thisweaksourceisunresolvedinourmap. NGC 7619.—Thissourceisbarely resolvedbyourobserva- NGC 7626(Fig.2k).—This sourcehaspreviouslybeen 1985ApJ. . .291. . .32B jet, rathersimilartoIC4296,andagainthefullextentof Andernach, H.,Waldthausen,andWielebinski,R.1978,Astr.Ap.Suppl, Baars, J.W.M.,Genzel,R.,Pauliny-Toth,I.K.,andWitzel,A.1977,Astr. Binney, J.1978,M.N.R.A.S.,183,501. Biretta, J.A.,Owen,F.N.,andHardee,P.E.1983,Ap.{Letters),274,L27. Binney, J.,anddeVaucouleurs,G.1981,M.N.R.A.S.,194,679. to besubstantialmissingfluxdensity. source isprobablynotrepresentedonthismap;therelikely Clark, B.1980,Astr.Ap.,89,355. Cameron, M.J.1971,M.N.R.A.S.,152,439. Bridle, A.H.,Palimaka,J.J.,Fomalont,E.B.,andHenriksen,R.N.1984,in Bridle, A.H.,Davis,M.M.,Fomalont,E.B.,andWillis,G.1979,24p.J. Blandford, R.D.,andRees,M.J.1974,M.N.R.A.S.,169,395. structure. Thestructureofthesourceisthatawell-defined 44 BIRKINSHAWANDDAVIES 6732 M. 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