198 9ApJ. . .341. .6583 -1 24-1 de laRechercheScientifiqueFrance, andtheUniversityofHawaii. operated bytheNationalResearch Council ofCanada,theCentreNationale Tololo Inter-AmericanObservatory, NationalOpticalAstronomyObserva- Center; GuestObserverattheCanada-France-Hawaii Telescope,whichis Astronomy, Inc.,undercontractwith theNationalScienceFoundation. tories, whichisoperatedbyAssociated UniversitiesforResearchin enough fordetailedopticalscrutiny.Theyarealsoobservable They exhibitthefullrangeofgalaxyactivity,yetremainclose galaxies, theso-calledpowerfulradiogalaxies(PRGs), rep- resent auniquelaboratoryforthestudyofactivityingalaxies. a cosmologyofH=100kmsMpcandq0).These having radiopowerat178MHz,P>5x10WHz for associated withpowerfulradiosources(whichwedefine as optical (broad-band)investigationoftheclassgalaxies The AstrophysicalJournal,341:658-678,1989June15 0 178 © 1989.TheAmericanAstronomicalSociety.Allrightsreserved.PrintedinU.S.A. 2 1 NationalResearchCouncilPostdoctoral Fellow,GoddardSpaceFlight VisitingAstronomerattheKittPeakNationalObservatoryandCerro This isthesecondinaseriesofpapersdedicatedto 24-1 - 2 colors andcolorgradientsforgiantellipticalgalaxies.Third,wenotethestrongsimilaritybetween fraction ofPRGsina“commonenvelope”withneighboringgalaxiesisevenlarger(40%fortheWE/ABS features suchasthesemaybeexplainedbygalaxyinteractionsinvolvingatleastonegas-rich,dynamically (Pi7s >5x10WHz),anddiscusstheimplicationsthesefindingshavefortheoriesconcerningorigin double/multiple nuclei,colors,andsurfacebrightnessprofiles. WE/ABS PRGsandbrightestclustergalaxies.Theyhavesimilarabsolutemagnitudes,incidenceratesof color variationsarerelatedtomerger-inducedstarformation.Incontrast,theWE/ABSPRGshavenormal extended andnotmerelyduetolightfromabrightnucleusoremission-linegas(bothofthesecon- giant ellipticalgalaxies[by~0.2magin(B—K)].Itisimportanttonotethatthesebluecolorsarespatially in form.ThesecondmajorconclusionisthattheSEPRGshaveunusuallyblueaveragecolorsrelativeto ness profilesfortheWE/ABSgalaxiesaretypicallyshallowerinslopethannormalradio-quietellipticalgal- kpc inprojectionfromthemainnucleus(30%ofWE/ABSPRGsandonly10%SEPRGs).The cold galaxy(i.e.,adiskgalaxy).Wefindthatabout20%ofourgalaxieshavesecondnucleuslessthan10 emission linespectra(SEPRGs)—butonly7%ofthePRGswithweakornolines(WE/ABS brightness (ii<25magarsec).Morespecifically,wefindthatabouthalfofthePRGswithstrongoptical Subject headings:galaxies:photometry—stellarcontentstructure the SEPRGsoftenexhibitstrongspatialvariationsincolor.Wehypothesizethatunusualcolorsand tributions havingbeenexplicitlyremoved),andassuchtheymustreflectthestellarcontentofPRG.Also axies, butsimilartobrightestclustergalaxies.SurfacebrightnessprofilesfortheSEgalaxiesaremorediverse sample galaxiesdisplayopticalmorphologicaldeviationsfromellipticalsymmetryathighlevelsofsurface galaxy interactions/mergersplayanimportantroleinthePRGphenomenon.Wefindthatover50%of are detailedinarecentpaperbySmithandHeckman. of activityingalaxies.Sampleselection,observationalprocedures,anddatareductiontechniquesforthisstudy PRGs)—exhibit peculiaropticalmorphologies(tails,fans,bridges,shells,anddustlanes).Narroworsharp PRGs and20%fortheSEgalaxies).Photometricinvestigationsofsampleindicatethatsurfacebright- v © American Astronomical Society • Provided by the NASA Astrophysics Data System We reportthreemajorconclusionsregardingthenatureofpowerfulradiogalaxies(PRGs).Thefirstisthat We presentresultsonthemorphology,photometricstructure,andcolorsof72powerfulradiogalaxies MULTICOLOR SURFACEPHOTOMETRYOFPOWERFULRADIOGALAXIES. I. INTRODUCTION radio sources:galaxies Laboratory forAstronomyandSolarPhysics,GoddardSpaceFlightCenter II. MORPHOLOGYANDSTELLARCONTENT Received 1988August29;acceptedDecember2 University ofMarylandAstronomyProgram 1 1,2 T. M.Heckman Eric P.Smith ABSTRACT AND 658 25-1 that galaxy-galaxyinteractionsmayplayamajorroleininiti- tion (SpinradandDjorgovski1987).Currentlyitisbelieved out tolargeredshifts(e.g.,Chambers,Miley,andvanBreugel phenomena occurringinotherclassesofactivegalaxies (cf. 1988) andthereforeareimportantprobesofearlygalaxyevolu- Hutchings andCampbell1983;Kennicuttetal1987). activity forPRGswoulddovetailwithevidencesimilar ating galaxyactivity.Alinkbetweeninteractions and (especially thosefoundatthe centersofrichclusters).These notions prevaileduntilquite recently,whenimproveddetec- “ D”orcD,”suggesting a kinshiptogiantellipticals powerful radiogalaxies,and typically classifiedsuchPRGsas powerful radiosourceshasbeenlesswelldeterminedexcept in power; P<10WHz)arerathernormalgiantellip- several nearbycases(e.g., Fornax A,CenA).Matthews, ticals. Themorphologyofthegalaxiesassociatedwithmore Morgan, andSchmidt(1964) conductedastudyofthemore 178 Most nearbyradiogalaxies(whicharegenerallylowin 198 9ApJ. . .341. .6583 8 1/4 results. Weconcludein§IXwith suggestionsforfurtherstudy. Section VIIIstatesourconclusions andinterpretationofthe ness distributions,andin§ VII wesummarizeourresults. profiles ofPRGsareinvestigated in§V.InVIwegivean color gradientsofthesample galaxies.Thesurfacebrightness magnitudes ofthePRGs,while§IVdealswithcolors and account ofoureffortsatmodeling thegalaxysurfacebright- will beasfollows:SectionIIdiscussestheopticalmorphol- low-redshift quasars(Smithetal.1986).Theplanofthispaper ogies ofthegalaxies.SectionIIIconcentratesonintegrated photometry, aswelltoourownresultsfromastudy of with previousworkonbrightestclusterandellipticalgalaxy surface photometrystudies.Wewillthencomparetheseresults we willdiscusstheresultsofthesemorphologyandmulticolor images, colorprofiles,andsurfacephotometry.Inthispaper data analysisandhavepresentedalargebodyofcalibrated hereafter PaperI),wehavedescribedourobservations and participants. be supportiveoftheideathatPRGsaremergerorinteraction were dueatleastinparttoapopulationofyoungstarswould nuclei andemission-linenebulae.Evidencethattheircolors galaxies, butthenatureofthesecolorswasuncertainbecause have colorsthatarebluerthanthoseofnormalgiantelliptical of thepresencebrightpointsourceslocatedingalaxy Tinsley 1978),presumablybecauseofenhancedstarformation. bluer thanthoseofnoninteractinggalaxies(Larsonand probes). Interactinggalaxiesareknowntohavecolorsthat Sandage (1972)demonstratedthatmanyofthePRGsalso of theusehigh-redshiftradiogalaxiesascosmological stellar contentisofconsiderableinterest(particularlyinlight galaxy’s past. tortions (afewtimes10yr),theyalsocouldprovidecluestoa after thedisappearanceofmore“spectacular”opticaldis- history. However,ifthegalaxylightprofileremainspeculiar brightness profile)ofagalaxytounderstanditsdynamical elliptical-elliptical anddisk-disk).Inlightofthis,itwould appear difficulttousethephotometricstructure(surface is thenaturalresultofviolentrelaxationinamerger(both (Schweizer 1982)haveshownthatanrlawlightdistribution least oneoftheparticipantscontainsadynamicallycold(disk) structure. Galaxymergersimulations(AW)andobservations nants withsharporcoherentfeaturesareproducedwhenat Quinn 1984;AguilarandWhite1986,hereafterAW).Rem- is ofprincipalinterestinlighttheextensivemodeling galaxy-galaxy interactions(e.g.,Toomreand1972; morphological peculiaritiesfoundinclassAPRGs.Notonly the incidencerate,butalsoformofopticalpeculiarities, radio morphologies.Thesegalaxiesrarely(~10%)exhibitthe absorption linespectra(“WE/ABS”)andusuallyhaveFRI galaxies aredefinedtohaveweakemissionlinesorpure these PRGshavepeculiarmorphologies.TheclassBradio phologies (“FRII”).Wefoundthatalargefraction(~50%)of Fanaroff-Riley (FanaroffandRiley1974)typeIIradiomor- sion lines(“SE”).Theyalsousuallyhave“edge-brightened” Class Aradiogalaxiesaredefinedtohavestrongopticalemis- phologies (Heckmanetal1986,hereafterH86;Hutchings a significantfraction(~30%-50%)hadpeculiaropticalmor- of largerandmorediversesamplesPRGsdemonstratedthat tors, advancedimageprocessingtechniques,andobservations 1987). In thefirstpaperofthisseries(SmithandHeckman1989, In additiontothemorphologyandstructureofPRGs,their In H86wearguedthatPRGsfallintotwobroadcategories. © American Astronomical Society • Provided by the NASA Astrophysics Data System MULTICOLOR SURFACEPHOTOMETRYOFPRGs.II. 2 4 -2 determining apositionangle forsuchroundisophotes).Sub- with ellipticitye<0.1because ofassociateddifficultiesin from Stromand(1978a, b,c)havemajor-axisposition angle twists(AP.A.)greaterthan 10°(afterrejectingisophotes by Galletta(1980),whofound thatonly8%ofallellipticals experience largemajor-axisisophotaltwists.Thedistribution of isophotaltwistinginnormal ellipticalshasbeeninvestigated reveals thestartlingnumberofgalaxiesinthissamplewhich implies arecentinteractionormerger.Sinceonly~4%of the (isophotes whicharenotellipticalinshape,butrather confidence levelusingaxcontingencytableanalysis). “square”). Neitherofthesekindsdistortionnecessarily in 49%oftheclassA(SE)galaxies,butonly10% find thatthesetypesofmorphologicalpeculiaritiesaredetected cold and/oragas-richsystem,presumablydiskgalaxy.We tion ofthephotometricmajoraxis),or“boxyisophotes” strongly twistedisophotes(astrongradialchangeintheposi- B (WE/ABS)PRGs.Thisdifferenceishighlysignificant(99.9% nomenon oftwistedisophotes. actions, provideevidencefortheinvolvementofadynamically These features,ifinterpretedwithinthecontextofgalaxyinter- dominantly azimuthalorientation),“fans”(similartotails,but linking twogalaxies),“shells”(curvilinearfeatureswithapre- from themainbodyofgalaxy),“bridges”(narrowemission (features withalength-to-widthratio>3:1whichextendout less narrow),anddustlanesorpatches(seeFig.1[Pis.10-13]). PRGs showclearlyboxyisophotes,wewillfocusonthephe- which arerelativelynarrowor“sharp”inappearance:tails models ofinteractinggalaxies.Inthefirstcategoryarefeatures several categoriesbasedonthephysicalintuitionprovidedby phological peculiarities,itisusefultosubdividetheminto different. these deviationstakeforthetwoclassesis,however,quite WE/ABS (52%)aremorphologicallydisturbed.Theforms which deviationsfromellipticalsymmetryarenotvisible most likelyonlyalowerlimit,becausetherecouldbecasesfor tions ofthoseobjectsclassedasSE(57%;seeTable1)and being lostintheskybackground.Wenotethatsimilarfrac- because ofthegalaxy’sdistance[aresult(1+z)cosmo- levels brighterthan25Vmagarcsec.Itmustbeemphasized that thefractionofgalaxieswithopticallypeculiarstructureis sample showmorphologicalpeculiaritiesatsurfacebrightness the peculiaritiesfoundinthissample.Wefindthat54%ofour fied someofthefeaturesfoundinopticallydistortedPRGs, and wehaveadoptedtheirterminologyforourclassificationof rather, azoologicalapproachmustbetaken.H86haveclassi- using theFourierdescriptorsforisophotes;seePaperI); good wayofquantifyingtheselargedeviationsfromelliptical emission-line gasmorphology.Thereis,unfortunately,no symmetry (asopposedtosmalloneswhichcanbestudied was donebyoneofus(E.S.)independentanyknowledge (nonelliptical) morphologies.Table1givesalistingofthegal- logical dimminginsurfacebrightness],thesefeaturespossibly images thatmanyofthegalaxiesdisplayunusual axies, catalogingthesedistortions,theclassificationofwhich in oursample.Itisreadilyapparentfrominspectionofthese Inspection oftheisophotalcontourmapsforourPRGs Into thesecondtypeofmorphologicalpeculiarityweclassify To considerfurtherthenatureandsignificanceofmor- Paper Ipresentedtheisophotalcontourmapsofgalaxies II. GALAXYMORPHOLOGY a) Peculiarities 659 00C/} LO PLATE 10

3C 223

(b)

positive image with fain, fan features to the northeast and L, ¿ 30 236 ^^ 'V^ "V™, 3C 382 image from the CFHT (3.6 m) reveals complex knotted structure ( f) 3C 321 negative imaee (n) 3r 171 v 1 themain body of the galaxy, (e) 3C 321 positive (h) 3C 171 negative image. siructure. U ) ^ m negative image, (g) 3C 171 positive image showing two lobes aligned roughly east-west. Smith and Heckman (see 341, 659)

© American Astronomical Society • Provided by the NASA Astrophysics Data System 198 9ApJ. . .341. .6583 Smith andHeckman{see341,659) © American Astronomical Society •Provided bythe NASAAstrophysics Data System E N 45" 30" 3C 236 Fig. 1.—Continued (d) PLATE 11 Smith andHeckman(see341,659) . I—Continued 198 9ApJ. . .341. .6583 Fig PLATE 12 © American Astronomical Society •Provided bythe NASAAstrophysics Data System E 15 N 3C 321 (f) (e) 198 9ApJ. . .341. .6583 Smith andHeckman(see341,659) © American Astronomical Society •Provided bythe NASAAstrophysics Data System Fig. 1.—Continued 3C 171 (h) PLATE 13 198 9ApJ. . .341. .658S 660 NGC 6047 NGC 708 3C 305 PKS 1358-113 PKS 1345+125 3C 285 3C 278 3C 277.3 3C 264 3C 236 3C 234 3C 227 3C 219 3C 198 PKS 0634-206 3C 29 PKS 2104-256B PKS 2058-281.. 3C 424 3C 405 3C 403 3C 390.3 3C 388 3C 382 3C 381 3C 371 3C 353 3C 348 3C 346 3C 338 3C 327 3C 321 3C 317 3C 315 3C 310 3C 303 3C 300 3C 296 3C 293 3C 223 3C 218 3C 196.1 3C 192 3C 171 3C 135 3C 120 3C 109 3C 105 3C98 3C89 3C88 3C84 3C 79 3C78 3C76.1 3C 75S 3C75N 3C 63 3C62 3C40 3C 33 3C 31 3C 17 PKS 2322- 3C 459 3C 449 3C 445 3C 442 3C 444 3C 436 3C 433 PKS 2104-256C Galaxy (1) 122 © American Astronomical Society • Provided by the NASA Astrophysics Data System Class WE WE WE WE ABS WE WE ABS WE WE SE SE WE WE SE SE SE SE SE SE SE SE SE SE SE SE SE WE WE WE ABS WE WE WE WE ABS WE WE ABS ABS ABS WE SE SE WE SE SE SE? WE SE SE SE SE SE SE SE SE SE SE SE SE SE SE SE ABS SE WE SE SE SE SE SE (2) (B-V) 0.77 0.97 0.87 0.85 0.65 0.76 0.64 0.61 0.87 0.83 0.73 0.85 0.96 0.65 0.54 0.87 0.45 0.99 0.68 0.42 0.89 0.58 0.84 0.99 0.94 0.66 0.90 0.39 0.90 0.76 0.77 0.99 0.68 0.87 0.84 0.09 1.06 1.05 1.06 1.15 1.07 1.03 1.06 1.10 1.06 1.15 1.11 1.01 1.22 1.00 1.03 1.12 1.03 (3) * Derived QuantitiesandClassificationsforthePROSample <-21.26 <-21.48 -21.14 -22.01 -21.73 -22.12 -21.31 -21.55 -21.77 -21.43 -20.64 -22.15 -21.08 -21.48 -21.91 -21.02 -21.65 -21.39 -21.49 -21.74 -21.26 -20.20 -21.21 -21.78 -22.52 -20.15 -22.36 -20.63 -21.20 -21.71 -21.37 -21.29 -21.92 -20.73 -21.89 -21.18 -21.98 -22.04 -22.14 -20.70 -21.33 -21.35 -20.83 -21.62 -21.09 -21.47 -20.93 -21.45 -21.76 -21.63 -22.06 -20.45 -22.76 -21.34 -20.52 -22.72 -21.90 -21.14 -21.10 -22.22 -21.56 -22.52 -21.98 -21.61 -20.90 -19.56 -20.53 -22.57 -21.28 -21.56 -21.98 -21.66 M 25 (4) SMITH ANDHECKMAN -20.71 -21.56 -21.59 -21.28 -20.60 -20.53 -21.59 -21.04 -20.27 -21.73 -20.71 -21.21 -21.25 -20.80 -21.72 -20.83 -20.89 -21.17 -21.05 -20.76 -20.94 -21.33 -21.40 -20.15 -21.37 -20.54 -21.00 -21.78 -21.31 -21.20 -23.32 -20.94 -20.49 -21.13 -20.75 -21.85 -21.47 -21.72 -20.07 -19.62 -20.26 -20.91 -20.88 -20.93 -21.47 -20.76 -21.21 -21.24 -21.33 -21.14 -21.87 -22.12 -21.35 -21.01 -21.62 -22.30 -20.83 -21.77 -21.21 -21.04 -20.64 -20.76 -20.72 -21.42 -21.10 -21.63 -21.98 -21.66 -21.21 -19.62 -21.28 -21.93 M (5) 8 kpc TABLE 1 log r e 0.63 0.57 0.54 0.73 0.93 0.80 0.97 0.78 0.91 0.89 0.70 0.95 0.44 0.83 0.65 0.81 0.97 0.66 0.94 0.80 0.49 0.78 0.87 0.79 0.74 1.08 1.02 1.16 1.01 1.39 1.24 1.31 1.61 1.34 1.26 1.56 1.40 1.15 1.46 1.36 1.18 (6) 22.24 20.39 20.76 22.78 24.14 23.69 22.28 21.62 22.63 24.23 22.12 22.25 22.57 22.69 23.07 24.03 22.90 22.43 22.49 24.27 22.92 23.38 21.97 22.56 22.70 22.31 22.45 23.36 22.03 23.12 23.27 24.60 24.40 23.90 23.52 22.31 24.27 22.74 24.21 23.44 19.89 (7) log r2 2 0.95 0.78 0.92 0.79 0.71 0.99 0.86 0.92 0.68 0.86 0.86 0.62 0.75 0.86 0.98 0.53 0.57 0.72 0.59 0.77 0.99 0.92 0.95 0.52 0.62 0.65 0.72 0.82 0.72 0.85 0.69 0.79 0.85 0.75 0.97 0.63 0.68 0.91 0.81 0.66 0.93 0.69 0.96 0.93 0.82 0.74 0.87 0.58 0.86 0.79 0.70 0.79 0.96 0.93 0.68 0.99 0.94 0.78 0.59 0.96 0.86 0.64 0.49 0.69 0.99 0.90 1.01 1.02 1.07 1.14 (8) log r 2i 0.96 0.98 0.91 0.94 0.84 1.15 1.26 1.20 1.11 1.26 1.37 1.25 1.19 1.38 1.30 1.14 1.26 1.19 1.09 1.32 1.13 1.28 1.19 1.16 1.31 1.19 1.22 1.27 1.16 1.06 1.19 1.41 1.44 1.48 1.14 1.11 1.31 1.19 1.24 1.22 1.12 1.16 1.52 1.29 1.46 1.16 1.22 1.42 1.16 1.17 1.21 1.21 1.32 1.35 1.36 1.18 1.02 1.53 1.22 1.21 1.07 1.33 1.29 1.03 1.42 1.04 1.18 1.52 (9) log r 2i 2.01 1.64 1.07 1.31 1.29 1.28 1.49 1.20 1.66 1.39 1.52 1.44 1.07 1.42 1.46 1.43 (10) 1.42 1.25 1.33 1.45 1.52 1.28 1.41 1.48 1.30 1.22 1.43 1.09 1.56 1.40 1.31 1.28 1.38 1.39 1.43 1.51 1.33 1.64 1.28 1.42 1.12 1.73 1.37 1.78 1.48 1.63 1.25 1.30 1.05 1.61 TI T, S,TI TI T, D,B T, F,Dn TI, 2F,B T, F, TI? TI TI? 2F CE 2T TI? TI D, TI? T, F,CE,Dn CE CE, Dn CE S, TI CE S?, BI,TI S CE, Dn CE, Dn CE, Dn CE, Dn TI TI TI TI Dn, TI Dn CE, Dn 2T, D,BI F, T T TI D, Dn,TI 2T BI, TI S?, TI? CE CE Dn CE, Dn CE, Dn 2T Morphology (11) CE Comments 4 4 4 4, 5 4, 7 4, 5 2, 3,4 2, 7 7 7 2,9 2, 2, 6 2, 3, 4 2 2, 3,4 2, 3 7 5 5 5 7 7 7 2,9 2, 5 2, 6 2, 4,7,9 7 5 5 5 12 1 1 1, 2,4,9 1 1 1, 8 Yol. 341 4,9 (12) 3,4 3 5, 10 3,4 10 198 9ApJ. . .341. .6583 9 -2 (Bahcall 1977reportsthatmembersofatypicalclusterare embedded inacommonenvelopewithoneormorecompanion emission). radius fortheimpactparameterevery10yr.SeealsoBorne expected toexperienceacloseencounterorcollisionwiththis ple nucleiifthereweretwobrightnesspeaksinside9.6kpc. double (ormultiple)nuclei.Hedefinedanobjecttohavemulti- envelope (CE)systems.ThehighincidencerateofCEsystems (12) 54"aperture. magnitude wasclosetoSandage1972 Vandthereforeusedasm.(4)Magnitudecalculatedfrompatched dataframe(seePaperI).(5)CaseImagnitude common envelope;D=dustfeatures; Dn=doublenucleus;F1fan,2F2fans;Sshells;Ttail,2T =2tails;TItwistedisophotes. isophote. BCGs andfoundthatapproximately30%ofthesegalaxieshad on brightestclustergalaxies(BCGs).Hoessel(1980)studied among PRGsisparticularlyinterestinginlightofrecentwork the SEPRGsand42%ofWE/ABSareincommon may belarger(59%ofDjorgovski’sand20%Leach’s (1981) indicatesthatthefractionofellipticalswithÀP.A.>10° where fi=25Vmagarcsec.(10)Last isophotedeterminedbyellipse-fittingalgorithmusedforlimitingaperture becauseofuncertainextinction.(11)80"aperture. correction fornonstellaremission(see PaperI).(6)Magnitudecalculatedfrominner16kpcaperture.(7)Case IIImagnitudecorrectionfornonstellaremission.(8) Paper I. galaxies (seeFig.2[PI.14]).Morespecifically,about20%of highly asymmetricisophotes(e.g.,PKS1345+125,3C305). restrict ourÀP.A.measurementstothosegalaxieswith(1)no samples haveÀP.A.>10°).Giventhehighlydisturbednature sequent CCDphotometrybyDjorgovski(1985)andLeach Paper I). obvious interactingneighbors(e.g.,3C40,75)and(2)no of themorphologiesformanyourgalaxies,weneededto Magnitude calculatedfrom30"aperture centeredongalaxy.(9)Finalapertureusedformcalculatedfrom extrapolationofsurfacebrightnessprofiletoradius For theselattertwosubclassesofPRGsthereislittledoubt No. 2,1989 1984.) LaterstudiesbySchneider,Gunn,andHoessel(1983a, yet anothermeasureoftheatypicalmorphologiesforPRGs. phologies. Inlightoftheuncertaintiesassociatedwithfre- isophotal twists.WefindequalnumbersofSEandWE/ABS fication appearstobearnorelationshipthepresenceoflarge isophote twists(meanÀP.A.=~26°).Emission-lineclassi- induced byseeingeffects(Franx,Illingworth,andHeckman elliptical isophotes.ToavoidincludingspuriouslylargeÄP.A. mine whethertheremaininggalaxieshadoverall“quiescent” however, itisunclearatthistimewhetherisophotaltwisting quency andmagnitudeofisophotaltwistsinnormalgalaxies, galaxies withlargeisophotaltwistsandotherwisenormalmor- these otherwisemorphologicallynormalgalaxieshavelarge ÀP.A. (>10°)fromourstudy.Wefindthat55%(18of33) r =10"oneachgalaxy.Table2liststhegalaxieswithlarge about thepresenceororiginofanytwists.Wesoughttodeter- 2625 1988) wemeasuredmajor-axispositionanglesexteriorto 25 1/2- 12- -21/4 1/4 -2 -2 -2 1/2- Col. (2).—Opticalemissionlineclassification.SE=strongoptical lines;WE=weakopticalemissionABSabsorption-linespectrum.See Gol. (1)/—Galaxyname. Col. (9).—Radius(kpc),calculatedas(ah)ofthe24Vmagarcsecisophote (correctedforGalacticextinctionandredshift). Col. (8).—Radius(kpc),calculatedas(ab)ofthe22Vmagarcsecisophote (correctedforGalacticextinctionandredshift). Col. (7).—Surfacebrightness(magarcsec)atrforsamplegalaxies. Corrected forGalacticextinctionandredshift. Col. (6).—Scalelength,inkpc,forthegalaxyderivedfromleast-squaresfit tosurfacebrightnessprofile.Onlythosegalaxiesinthersamplewererecorded(see Col. (5).—AbsoluteVmagnitudeinteriorto8kpcradiusintherestframe ofthegalaxy(correctedforGalacticextinctionandredshiftbutnotnonstellar Col. (4).—AbsoluteVmagnitude(correctedforGalacticextinction,redshift, andnonstellaremission)ofthegalaxyintegratedoutto25magarcsec Col. (3).—{B—V)colorsintegratedouttothe25magarcsecisophote.An asteriskindicatesthatphotometrywasunreliableforcolors. Comments.—(1) CaseIImagnitude correction fornonstellaremission.(2)Surfacebrightnessprofiledidnot reach25magarcsecisophote.(3)Limiting Col. (12).—Commentsonindividual galaxies. Col. (11).—Morphologicalfeaturesdisplayedbytheradiogalaxy:B= bridges;BI=boxyisophotes;CEradiogalaxyandcompanionsurroundedbya Col. (10).—Radius(kpc),calculatedas(ah)ofthe25Vmagarcsecisophote (correctedforGalacticextinctionandredshift). Many (~30%)ofthePRGsinoursampleappeartobe e b) CommonEnvelopeandDoubleNucleusSystems © American Astronomical Society • Provided by the NASA Astrophysics Data System MULTICOLOR SURFACEPHOTOMETRYOFPRGs.II. Notes toTable1 z nuclei. ThereisagainadistinctionbetweentheSEand nuclei (seeTable1).Thesedoublenucleus(Dn)galaxiesarea peaks insidethisradius.Adoptingdefinition,wefindthat b) foundanevenhigherincidenceofmultiplenuclei,with45% (32%) ascomparedwithonlyfourSEobjectsmultiple WE/ABS objects,with10WEgalaxieshavingmultiplenuclei subset oftheCEgalaxiesdistinguishedbyproximity of theirfirst-rankedgalaxieshavingoneormorebrightness fidence level.(TheSEgalaxiesaregenerallyathigherredshift morphology classes. multiple nuclei)andFRII(14%withradio powerful radiogalaxiesweredividedintoFRI(32%with been discernablegivenourseeingconditions,andassuming redshift [0.3056for3C109]anydoublenucleiwouldhave nuclei (10%).Thisdifferenceissignificantatthe~99%con- kpc].) LillyandPrestage(1987)foundsimilarresultswhen separation asthelowerredshiftobjects[mean~5.5 that theSEgalaxieshavedoublenucleiwithsamemean [ =0.049,0.122],yetevenouttoourhighest 19% ofthegalaxiesinoursamplehavedoubleormultiple could beproducedbydustlanesatthecentersofourgalaxies. disturbed instructure,wemustbewaryofclassifyingobjectsas having doubleormultiplenucleiwhen,infact,thesefeatures For example,weregalaxiessuchasNGC708or3C293at SE We addonecaveat:becausemanyofourgalaxiesarehighly logical peculiarities;(?)denotesanobject position-angle twistsandnoothermorpho- with marginalisophotaltwists,AP.A.^10°. PKS 1358-113 3C 303 3C 277.3 3C 198 3C 192 3C 105 3C 76.1 3C 63(?) 3C 62 Note.—Objects withlargemajor-axis Galaxies withAP.A.>10° TABLE 2 PKS 2104-256B 3C 436 PKS 2058-281 3C 424 3C 390.3 3C 388 3C 381 3C 371 3C 353 661 198 9ApJ. . .341. .6583 PLATE 14 Smith andHeckman(see341,661) this systemofellipticalgalaxies. Fig. 2.—PositiveimageofthePRG3C442obtainedwithKPNO2.1 mtelescope.Theradiogalaxyisthecentralobject.Noteasymmetricalenvelopeof American Astronomical Society •Provided bythe NASA Astrophysics Data System E N 3C 442 198 9ApJ. . . 341 . .658S -2 _1 -1 is formallysignificantatonly the 93%confidencelevel.Recent- mean absolutemagnitude=—21.55±0.08.We find for ourdatawhichincorporatesthesecorrectionsnon- determine empiricallymin thesecases.Forgalaxies ly, LillyandPrestage(1987) havealsoreportedthattheSE the 25magarcsecisophote, being=—21.42 that theSEobjectsarefainterby~0.35magthan WE hatching. WithouradoptedcosmologyofH=100km s 0.0 redshifts,theymightbemistakenfordoublenucleus K 25 F 0 0 ± 0.10and= -21.77±0.12.Thisdifference F The smallscatterintheintrinsicbrightnessofthesebright Fig. 3.—AbsolutemagnitudesofPRGs(calculatedassumingH=100;q0)correctedforGalacticextinction,Kdimming,andnonstellaremission. Hatching 0 © American Astronomical Society • Provided by the NASA Astrophysics Data System III. ABSOLUTEMAGNITUDEDISTRIBUTION SMITH ANDHECKMAN 3 -2 reported thattherewasadistinctionbetweentheabsolute that oftheBCGs(SE:=—21.75withadispersion0.32(Sandage same population,wefindthat wecanrejectthenullhypothesis that theradiogalaxiesand QSO hostsaredrawnfromthe tests (FeigelsonandNelson 1985) totestthenullhypothesis sample (takenasawhole).UsingboththeGehanandlogrank (1987) reachedastrongerconclusion, findingradio-loudQSO 1972). Comparisonwithourradiogalaxydatarevealsthat ingly, wehavecalculatedourmeanvaluesandthesignificance sored data(FeigelsonandNelson1985). of thedifferencesusingmethodswhichareabletotreatcen- upper limitsfortheabsolutemagnitudemustbeused.Accord- B f 3 In astudyofthehostgalaxiesQSOs,Smithetal.(1986) Wehaveconsideredagalaxytohost a“true”QSOiftheabsoluteB Brightest clustergalaxieshaveameanintrinsicabsolute =-22.01±0.14, F =-21.25±0.22. k Vol. 341 198 9ApJ. . .341. .6583 -2 nitudes integratedouttotheradiuswhereg=25mag nonstellar continuum)andredshift(seePaperIfordetails). arcsec. Colors havebeencalculatedbysubtractingtheBandVmag- after correctionfornonstellaremission(emissionlinesand distinguished byhatching. content ofthegalaxy,presenceemissionlinesandpoint (a differencelargerthan4a).Itisimportanttonotethatthese color estimationsuspect. nonstellar correctionsstillreveals asignificantdifference,with reveals acontrast,with an estimatedmeanrest-framecolor<(B—F)>= 0.86 rection necessaryforcolorcalculation. tribution analysis(seePaperI): larger amount(1mag).Whilethisprovidessomeevidencefor host galaxymagnitudesbrighterthanPRGbya the sampletothosegalaxieswithout large[Am(ns)>0.2mag] sources havingbeencompensated for.Furtherrestrictionof are therest-framegalaxycolorsgeneratedbystellar comparisons ofthelocalenvironmentstwoclasses. may haveunderestimatedtheinfluenceofnuclearsource mining QSOhostgalaxymagnitudesisverydifficult,andwe radio QSOsandPRGsbeingdifferentclassesofobjects,deter- on thehostgalaxymagnitudes.Bettertestsmaybefoundin No. 2,1989 v PRG ± 0.03.SeparationofthesampleintoSEandWE/ABSclasses Fig. 4.—(B—V)colordistributionforPRGsample.ColorshavebeencorrectedGalacticextinction,redshift,andnonstellaremission.SEgalaxies Figure 4showstheglobalcolordistributionforourPRGs 3C 445.—UnsuccessfulmodelingofBimagepreventscor- 3C 310and338.—Bphotometryuncertain. 3C 109.—Objectdominatedbynuclearpoint-sourcelight. 3C 105and353.—Largeoruncertainextinction. 3C 171.—Verylargeemission-lineequivalentwidthsmake The 51remaininggalaxies(ofthe56withBandVdata)have The followinggalaxieswerenotincludedinthecolordis- © American Astronomical Society • Provided by the NASA Astrophysics Data System <(B —F))=1.01 ±0.02. WE/ABSsmall Am(ns) <(5-nSE>sallAm(„s) =0.83±0.04, m <(B —F)>=0.99±0.02 we/abs <(£-F)se>= 0.79±0.04, a) IntegratedColors IV. COLORS % V-4 MULTICOLOR SURFACEPHOTOMETRYOFPRGs.II. larly atsmallradii.Wethereforechosetostudythecolors of emission greatlyinfluencesthecolorprofilesofPRGs,particu- WE/ABS 0.02±0.03,SE0.22 ±0.07.Incomputingthese line gas,whichispredominantly locatedintheinner3"(Baum to ~6"forourmedianredshift).Thislattercolormeasurement the integratedcolorsforr>5kpc.(5kpcradiuscorresponds these galaxiesafterseparatingthecolorsinteriorto5kpcfrom fitted afourth-orderpolynomialtotheBruzualmodelarrive and SEgalaxiesarethen,for ô(B-V)<5kpc,WE/ABS should alsoplaceusoutside the bulkofnuclearemission- bluer thanexpectedcolors.Weknowthepresenceofnonstellar residuals (Table3)havethesensethatpositivevaluesindicate about thisfitwerecalculatedforeachofourgalaxies. The a giantellipticalwithredshift.Residuals,denotedô(B—V), and foundthecolor(integratedouttoametricdiameterof86 at ananalyticalexpressionforthevariationof(B—V)color of studied thecolor-magnituderelationforearly-typegalaxies For comparisonwenotetheresultsofLugger(1984),who is tocomparethemwiththecolorsofanormalgiantelliptical at thesameredshift.Thatis,ratherthanexplicitlyincluding from Bruzual(1983)andisagoodmatchtotheobserved 1987). Themeancolorsandstandard errorsforbothWE/ABS for agiantellipticalatzeroredshift,(B—V)=0.95.Wedidnot curve tobringthez=0colorsintolinewithtypicalcolor color-redshift relationforgiantellipticalsoverthisredshift extinction correctionsappliedtothecolors.Thelinerepresents giant ellipticalsatthesameredshift.Figure5showsvaria- measured colorsoftheradiogalaxieswith the K-correctiontermforradiogalaxies,wecompare tion shouldnothaveoccurred. back timesaresufficientlysmallthatsignificantstellarevolu- different fromthatofanormalelliptical.Moreover,thelook- star formationhistoryforagiantellipticalisnotradically alter theshapeofcurvebecausewehaveassumedthat range. Wehaveshiftedthezeropointfor(B—V)versusz the fittodataofKristian,Sandage,andWestphal(1978) tion ofcolorwithredshiftforoursample,onlyGalactic 0.97 ±0.04. kpc forH=50,q1)30BCGstobe<(B—F)> -0.01 ±0.04andSE0.15 ± 0.06;for<5(£-F)>5kpc, r 0BCG r Over theredshiftrangeofinterest(05kpc)oftwoclasses.In extinction) andthosegalaxieswithlarge(>0.2mag)nonstellar morphology SEPRGs(thosewithsharp ortidalfeatures)aredenotedbycrosshatchedboxes.Positivevaluesfor ô(B—V)indicatebluerthannormalcolors. similar tothoseofSEPRGswithnormalmorphology structed Figure6,whichshowsthedistributionofcolordiffer- Galactic extinctiononly. Kristian, Sandage,andWestphal(1978)byBruzual(1983)fornormalellipticalsshiftedto(B—V)=0.95atz0hasbeenincluded.Colorshave been correctedfor features andthosewithoutthistypeofdistortion—wecon- ing theSEgalaxiesintotwoclasses—thosewithsharp(ortidal) exhibit unusualmorphologiesshowevidenceforbluecolors— morphology togalaxycolors.Specifically,dothesystemsthat 664 a possibleindicationofenhancedstarformation.Afterseparat- esting effectswesoughttostudywastherelationshipofoptical were particularlyinterestedinthevariationofgalaxyoff- color differentials,wehaveexcludedobjectswithlargenon- nuclear colorswithotherproperties.Oneofthemostinter- stellar fluxcorrections[Am(ns)>0.2mag;seePaperI].We Fig. 6.—Colordifferentialdistribution forouterregions(r>5kpc)ofSEPRGs.Normalmorphology PRGsaredenotedbyopenboxes,andpeculiar Fig. 5.—Integratedgalaxycolorsvs.redshiftforPRGsample.SEgalaxiesaredenotedbyfilledsquares,andWE/ABSopensquares.Fit todatafrom © American Astronomical Society • Provided by the NASA Astrophysics Data System SMITH ANDHECKMAN lation (i.e.,thepopulationshavesamemeancolorresidual). (B— V)colormorphologies.FifteenpercentofthePRGshave maps forseveraloftheobjectsfromoursample.Notsur- the possibilitythattheyareextractedfromsamepopu- the galaxyrestframe)arealignedwithemission-linegas the bluepatches(separatedby5"7,correspondingto4.5kpcin the galaxy’sactivecenter.Thecolormapsof3C33,285, than themeresuperpositionofexcessbluelightonandnear these objectsrevealthattheircolorstructureismorecomplex strong, withA(B—V)~0.2-0.5mag.Yetthecolormapsof sified asNgalaxies.Thesecolorchangesaregenerallyquite these beingtheSEobjects,manyofwhichwereoriginallyclas- strong bluenuclei(e.g.,3C120,218),withthemajorityof prisingly, wefindthatmanyofthegalaxieshavepeculiar show reddenedcenters,straddledbybluepatches.For3C33 3C 293,and218areparticularlyinterestingbecausethey z In Figure7(Plates15-18)wehavereproduced(B—V)color b) ColorMaps Yol. 341 198 9ApJ. . .341. .6583 galaxy. 3C120isapositiveimage,and hencedarkershadesarebluer. Smith andHeckman(see341,664) Fig. 7.{a-g)(B—V)colormapsforasubsetofthePRGsample.Allimages except3C120arenegativesinwhichdarkershadesindicateredderportionsofthe © American Astronomical Society •Provided bythe NASAAstrophysics Data System (b) PLATE 15 198 9ApJ. . .341. .6583 PLATE 16 Smith andHeckman(see341,664) © American Astronomical Society •Provided bythe NASAAstrophysics Data System N Fig. 7.—Continued 3C 285 (C) (d) 198 9ApJ. . .341. .6583 Smith andHeckman{see341,664) © American Astronomical Society •Provided bythe NASAAstrophysics Data System Fig. 7.—Continued 3C 293 (f) PLATE 17 198 9ApJ. l’LATE 18 Smith andHeckman{see341,664) © American Astronomical Society •Provided bythe NASAAstrophysics Data System E N Fig. 7.—Continued 3C 305 (g) 198 9ApJ. . .341. .6583 No. 2,1989 a a a c b d e b f a,e galaxy asawhole,forregionsinteriortoradiusof5kpcintherestframe nonstellar emissionnotappliedtoinnerandoutercolors. cate colorsbluerthanexpectedforaBCGatthatredshift.Correction of thePRG,andforregionsexteriortothisradius.Positiveresidualsindi- PRG andanormalBCGatthesameredshift.Differentialstabulatedfor colors calculated. panion galaxy. 3C17 0.300.450.27 3C 330.140.070.23 3C 31-0.05-0.04-0.13 3C 290.02-0.010.01 3C75N -0.13-0.16 3C 630.380.170.36 3C 40-0.07-0.030.02 3C 78-0.12-0.06 3C 76.10.05-0.040.00 3C75S -0.17-0.18 3C 89-0.03-0.140.01 3C 88-0.16-0.15-0.07 3C 840.270.400.05 3C79 0.531.20 3C 1200.410.510.29 3C 1090.660.790.37 3C 1050.510.301.73 3C 98-0.100.00-0.07 3C 192-0.07-0.040.14 3C 1350.340.270.36 3C 2180.200.210.09 3C 1980.370.380.41 3C 196.10.000.160.03 3C 236-0.07-0.000.02 3C 2340.11-0.170.23 3C 2270.130.41-0.01 3C 223-0.12-0.330.11 3C 2190.120.270.04 3C171 1.070.81 3C 277.30.110.020.24 3C 264-0.09-0.100.04 3C 2850.080.20 PKS 1345+125*-0.06...-0.13 3C 327-0.23-0.32-0.08 3C321 0.27 3C 317-0.06-0.10-0.02 3C296 -0.06-0.05-0.04 3C293 0.18...0.24 3C 3710.200.46-0.16 3C 3530.160.170.14 3C 348-0.05-0.020.16 3C305 0.12-0.020.27 3C303 0.230.140.25 3C 390.30.060.10-0.29 3C 388-0.06-0.100.03 3C 3820.560.610.21 3C 3810.050.080.16 3C315 0.080.14 3C 442-0.09-0.060.02 3C 4360.28 3C 4330.070.020.10 PKS 2322-1220.120.060.19 3C 4590.860.810.44 3C 449-0.120.01-0.08 3C 4450.070.020.18 a f d c b e Note.—Color residualsdeterminedbythecolordifferencebetween Outercolorvaluejudgedunreliable. Outercolorsnotcomputedbecause ofthepresenceanearbycom- [On]A3727emissiondominates outer regionsofimage;no Galaxylightdominatedbypointsource. Uncertainextinction. Innercolorvaluejudgedunreliable. Galaxy ô(B-V)r(<5kpc)r(>5kpc) © American Astronomical Society • Provided by the NASA Astrophysics Data System Color Residuals TABLE 3 MULTICOLOR SURFACEPHOTOMETRYOFPRGs.II. -2 in thecenterof3C218(separatedby~5"or3.7kpc)which bracket thecentralvisualbrightnesspeakofgalaxyare and areroughlyperpendiculartotheradioaxis(cf.Baumetal center oftheimage.Thesenucleicoincideroughlywithtwo gas inthelobesisquitelow(~25-26magarcsec;Baumet galaxies, however,thesurfacebrightnessofemission-line radio axis(cf.Baumetal1988,Fig.26).Forbothofthese aligned withtheemission-linegasandperpendicularto lobes atpositionangle~30°(Smith1988).Thisdoublelobe exhibits averybluecenterthatisbarelyresolvedintotwo nuclei seenbyGilmoreandShaw(1986).Thearequite and theradioaxis(vanBreugeletal1984).Thecolormapof this arenearlyalignedwithboththeopticalemissionlinegas along thepositionangle~20°.Theblueregionsexteriorto 293 displaysarelativelybroadswath(4"8wide)ofreddening stellar lightnearthecenterofgalaxy.Thecolormap3C al 1988),indicatingthatthebluelobesareprimarilyaresultof red [(B—F)~2]andalongwiththelargeIRluminosity galaxy. Perhapsthemostinterestingcolormorphology, showed therichstructuraldetailofinnerregionthis structure wasconfirmedbyHua(1988),whosubsequently suggest thatlargeamountsofdustmaybepresent.3C120 PKS 1345+125showstwohighlyreddenednucleiatthe reddening islocatedatthecenterofthisunusualgalaxy.Part however, belongsto3C305.A“tuning-fork’’-shapedregionof neither appearstobesimilarthebroad-bandcolormor- the radiomorphologyforthisobject(Heckmanetal1982), noted before(Sandage1966)asadustlane.Althoughthereis of thisfeature(P.A.~120°orlowerpartthefork)hasbeen phology. strong correlationbetweentheopticalemissionlinegasand 1988, Fig.2;SimkinandMichel1986).Similarly,thebluelobes (by atleast0.1mag)fortheirredshiftcomparedwithnormal below) ofthesegalaxieshaveoff-nuclearcolorsthatareblue data revealthat20(38%ofthesamplewithexclusionslisted giant ellipticals.Wehaveexcluded3C109,353,and105 galaxies withblueoff-nuclearcolors(18)areSEgalaxies.The only twoWEgalaxieswithblueoff-nuclearcolors,3C293and nucleus. axies withfirmclassificationshaveblueoff-nuclearcolors,and mag, respectively,relativetotheexpectedcolorsforaBCG) in only 3C371,aBLLacertaeobject,hasdominantblue from thislist(see§IVu).Notsurprisingly,themajorityof sample (3C33and3C223)arehighlyreddened(0.3 0.5 galaxies haveprominentbluenuclei.Twoin the 3C 277.3,areborderlineWEcases.NoneoftheWE/ABSgal- in (B—V)atverysmallradii(generally<3"-4")-These the inner3",whileseveralothersshowasmall,sharpincrease in colormapsthatareslightlytooredattheircenters, sur- better thantheseeinginB,adivisionofprofileswillresult red nucleimaynotberealbutrathertheproduct of wings oftheBpoint-spreadfunction [PSF]).Aclearexample unequal seeingdisksintheBandVimages.If V is rounded byabluerthannormalregion(causedthebroader of thiseffectisseeninFigure 8,thecolorgradientplotsfor before (thoseof3C33and 223)aredifferentfromthese,as can beseenfromtheircolormaps andprofiles.Theirnucleiare 3C 109andastarfromthesame frame(BseeingFWHM1'.'64, V seeingFWHMT.'42).The prominent rednucleimentioned Radial colorgradientplotsforthe56objectswithBandV We findthat,inadditiontoblueoutercolors,11ofthese c) ColorGradients 665 198 9ApJ. . .341. .6583 1/4 666 comparison. elliptical (rlaw)galaxies.Hewasabletoderivethefollowing innermost portions(r<3")whichmaynotbeintrinsictothe ing objectshavesmall(radialextent)colorgradientsintheir ent images: unequal seeingdisksonthemeasurementofcolorgradientsin galaxy: 3C40,75,76.1,88,264,296,303, unequal FWHMsofGaussianpoint-spreadfunctionsindiffer- simple analyticexpressionforthecolorgradientinducedby 3C 305,353,388.Sparks(1988)investigatedthiseffectof These colorgradientsareinterpretedasradialmetallicity gra- where ACistheinducedcolordifferenceatradiusrinmagni- elliptical) regionsofbluesurroundingthenucleus.Moreover, even elliptical)symmetry.Iftheseeingdisksaremismatched, red surroundedbyregionsofbluethatdonothavecircular(or dients (AZ,factorof-10changefromoutertoinnerregions of in PRGs,itmayhelptoplace limitsontheamount(or If thesecolorchanges,which may arisefromstellarevolution- the galaxies)andgiveriseto socalledcolor-apertureeffect. (0.3mag) such thatthegalaxiesaregenerallyredderneartheircenters [defined as=o{\+<5)].Foroursample,typicalvalues of e ~ 0.2(B—V)magnearthegalaxycentersmightbeattributable 2 Fig. 8.—Effectsofvariableseeingdisksinthedifferentimagesoncolorprofiles.Colorsforstarhavebeenshiftedtooverlapwiththose3C 109 tofacilitate Because ofunequalseeingdisks,webelievethatthefollow- It iswellknownthatearly-typegalaxieshavecolorgradients © American Astronomical Society • Provided by the NASA Astrophysics Data System > « SMITH ANDHECKMAN Radius (arcsec) -2 235 was (especially interiorto5kpc)evenaftercorrectionforrionstellar influences. Intheprevioussectionwefoundthatmorpho- were madebeforeconstructingthisplot.Hencethewidescatter ent colorstructureofthesesystems.Noattemptsatremoving gas. Ingeneral,theSEgalaxies showlargerscatteratallaper- emission. Giventheapparentcorrelationofmorphological dis- logically peculiarPRGsalsohadlargescatterintheircolors the contributionsofnuclearpointsourcesoremissionlines mean valueofthethreepointsnearestto0(arcsec)/D(O)=0.5 D(0), theface-ondiameterof25Vmagarcseciso- To showtheglobalcolorgradients,wehaveconstructed important todistinguishbetweenthegradualreddeningof gradients maytracethemetallicity gradientspresent,thedirect tures relativetobothWE/ABS galaxiesandnormalellipticals. spectra (§I),wesuspectthat thescatterofnuclearcolorsin tortions withthepresenceofemissionlinesinoptical of thecolorsatsmallradiiis,leastinpart,duetothese (3C 371,aBLLacobject).Thereappearstobemorescatter in with radio-quietellipticalgalaxies.OnlyoneoftheWE/ABS for WE/ABSgalaxiesatrendthecenterstoberedderas D(0)5 =D(l—e)°.Colorshavebeennormalizedtothe de Vaucouleurs,andCorwin(1976),where phote 17(0)25calculatedfollowingthepreceptsfoundin WE/ABS galaxiesand(b)theSEgalaxies.Wehave(following at smallradiicausedbyunequalseeingdisksdiscussedabove. galaxies wearereferringtohereandthesteepcolorgradients gradients. Inparticular,theWE/ABSgalaxiesoftenexhibita Figure 9bisnotduesolelyto pointsourcesoremission-line the PRGcolor-aperturediagramthaninthatofnormalellip- galaxies hasanucleusthatturnsblueratthegalaxycenter to removeuncertaintiescausedbyGalacticextinction.Wefind slight redwardturnintheircolorsnearcenters.Itis ticals andotherearly-typesystems. Sandage andVisvanathan1978)normalizedthedistancesto Figure 9,aplotofthenormalizedcolorgradientsfor(a) 25 25 25 The sameplotfortheSEgalaxiesdepictsradicallydiffer- While fornormalellipticals it isthecasethatthesecolor Several PRGcolorprofilesdisplaysuchsystematic Vol. 341 198 9ApJ. . .341. .6583 No. 2,1989 r SE This scatteristheresult inpartofnuclearcontinuum(point) sources,emission-linegas,dust, andyoungstars. nortMlSd tózCTOaUh^aYCTageœlorof thethreepointsclosestto0(0,=0.5inprofile.Observe thewidescattermnuclearcolorsforthesegalaxies. the shambluenucleusof3C371a BLLacobject.Almostallothergalaxiesshowagradualtrendtoward reddernuclei,(b)Colorgradientsf°8. 25 ar Fig. 9.—(a)ColorgradientsforWE/ABS galaxiesnormalizedtozeroattheaveragecolorofthreepoints closest toe(csec)/D(0)-0.5mtheproflle^Note 25 © American Astronomical Society • Provided by the NASA Astrophysics Data System MULTICOLOR SURFACEPHOTOMETRYOFPRGs.II. Fio. 9a Fig. 9b e(")/D(o)25 667 198 9ApJ. . .341. .6583 1/4 ma -2 1/4 populations obeyeddistinctlydifferentformsoftherelation: HOS separatedBCGsfromnon-BCGsandfoundthatthe two ellipticals arewellrepresented byanrlawfit,butonlyover it istheshape,orlogarithmicslopealongprofile,that the range19<¿i25g arcsec.Afteraninspectionof the ^-rplane.Schombert (1987)determinedthatnormal defined intermsoftheslope thesurfacebrightnessprofilein (1985). meaningful. Measurementofsurfacebrightnessesatasingle exist intheliteratureforellipticalgalaxies.Infinalanalysis emission anddustabsorptionpresentinthesegalaxies,but axies maybepartiallymaskedbythelargedegreeofnonstellar gradients arisingfromthestellarpopulationofSEradiogal- consistent withthoseofnormalellipticalsandBCGs.Color where wehavetransformedtheirr-framemeasurements into an ensemble, regions ofAbellclustersandfound,fortheirsampletakenas mation abouttherestofprofile.Differentinvestigations point onaprofilemaybemisleading(e.g.,theBCGhigh-low which thisbasicparameterismeasured.Becausewewishto galaxies, concernedwithdifferentparts(cores,halos,andso surface brightnessdebate)becauseitignoresimportantinfor- axies. show evidenceforlargerscatterthanthoseofWE/ABSgal- our Vsystemusingthetransformation relationsfoundinKent HOS) analyzedalargenumberofellipticals(372)inthecentral different thoughrelatedsurfacebrightnessparameters.Wefirst both normalellipticalsandBCGs,wehavefounditnecessary on) ofthegalaxieshaveledtomultiplicationwaysin normal ellipticals: brightness atthisradius(fi)inhisstudyofcompactand between theeffectiveradius(r)ofanellipticalanditssurface tical galaxies,thefi-rdiagram. More recentlyHoessel,Oegerle,andSchneider(1987,hereafter turn ourattentiontothenowclassicparameterizationofellip- to analyzeoursurfacebrightnessprofileswithanumberof ascertain thedegreetowhichpowerfulradiogalaxiesresemble in lightofthelargeIRluminositiesandnonstellaremission 668 flux thatsomeofthesegalaxiespossess,wemustconsiderdust, have colorgradientswhosesenseandmagnitudesarebroadly gas, youngstars,andnonthermalcontinuaasmajorcontrib- normal galaxies.Therewillbesomeoldpopulationofstarsin physical causeislessclearinsomeofthesedecidedlynon- K utors totheircolors.Insummary,WE/ABSradiogalaxies HOS non-BCGs:^=10.80(±0.11)+4.56(±0.14)logr , SE PRGswhichmaytraceoutastandardcolorgradient,but e e e e The effectiveradius,r,foran ellipticalgalaxyisfrequently There isaplethoraofsurfacebrightnessparametersthat Kormendy (1977)demonstratedthefollowingrelationship e V. GALAXYPHOTOMETRY:SURFACEBRIGHTNESSPROFILES HOS BCG:fi=19.47(±0.13)+3.14(±0.09)logr, -2 e H(V magarcsecs)=19.77+3.28logr(kpc).(2) e © American Astronomical Society • Provided by the NASA Astrophysics Data System fi =20.24(±0.08)+3.09(0.09)logr.(3) e a) pversusrforPRGs e SMITH ANDHECKMAN (4b) (4a) 1/4 1/4 1/4 -2 1/4 (normal ellipticals)inthesense that,foragivenscalelengthr, relation. Thereisanoffset for thePRGsfromBCGs PRGs tendtohavelower (higher) surfacebrightnessesby BCG linemoreclosely(inslope) thanthenormalelliptical relation foundbyKormendy (1977).ThePRGsfollowthe from HOS.Takenasanensemble,ourdatafalllargelybetween the BCGsandnormalellipticals, approximatelyalongthe sample obeysimilar/i-rrelations. We concludethattheSEandWE/ABSgalaxiesinour r characteristic radii.(Allquotederrorsarestandarderrors.) where VandBarethesurfacebrightnessesinat absent emissionlinesintheirspectra(SE-WE/ABS),wefind Separating thegalaxiesalonglinesofstrongandweak/ ~ 0.4(0.5)Vmagnitudes. e e e powerful radiogalaxiesfollowtherelations using ourrdeterminedfromtheprofilestofindthat ity ofourdeterminations(seePaperI).Henceforth,insurface effect issmall,however,approximatelythesameasreliabil- comparisons wefindAlogr=(fit)-(model) No suchtrendwasfound.Wecanalsocheckforseeingeffects with bizarresurfacebrightnessprofiles(e.g.,PKS1345+125, whose surfacebrightnessprofileswereapproximatelylinearin sample ofourdata.Wedefinethisasthe“rsample.” brightness analysesusingnandr,weusethisrestrictedsub- atmospheric (andinstrumental)seeingeffects.Thesizeofthe profile fitsyieldr’sthathavebeenslightlyenlargedbecauseof 0.05 +0.05.Thusthescalelengthsfromsurfacebrightness by comparingthescalelengthsderivedfromsurfacebright- in determinedrwithlargedifferencestheseeing-disksize. mination ofr,wewouldexpectacorrelationlargechanges for 14objectsobservedinthesamefilter(V)underdifferent thermore, oncetheeffectiveradiiwerefound,wediscarded a /z-rplotoverthespecifiedrangein/lWeexcludedgalaxies performed aleast-squaresfittothedataforthosegalaxies point sources(forthosegalaxieswhichhavesources).We This willrestrictourlinearregressionfitstoregionsoutside brightness forourlinearfitsto21<25magarcsec. the “true”characteristicradiiwithoutsmearing.For10such plus anuclearpointsource,ther’sfrommodelsrepresent To theextentthatgalaxycanberepresentedbyanrlaw ness profilefitstothosefromthegalaxymodeling(see§VI). ed fornotmeetingthiscriterion:3C135,PKS0634—206, from furtheranalysesthosegalaxieswhoserweresmallerthan those thatmightbesignificantlyaffectedbylightfromnuclear seeing conditions.Ifweresignificantlybiasingourdeter- seeing, wecomparedthevaluesofrwithseeing-disksize 3C 120)and109,whichwasonlymarginallyresolved.Fur- our profiles,wechosetolimittherangefurtherinsurface should beminimal(Schweizer1979).Fivegalaxieswerereject- seeing. Beyond5seeing-diskradiithecontributionsofPSF 3C 300,303,and424.Asafurthercheckforinfluencesof 5 seeingdisks(r SEe Vol. 341 198 9ApJ. . .341. .6583 -2 1/4 confidence levelgreaterthan99%. distributions forSEandWE/ABS galaxiesissignificantata log r22-logrrelationforBCGs. Thisdifferencebetweenthe ellipticals. Infact,27ofthe37 SEgalaxiesfallbelowthemean fall above(below)themeanlog r-logrelationfornormal normal ellipticalregion(dashed box):21(14)oftheSEgalaxies widely scattered,fallintheupper(high-luminosity)endof the axies liebelowthemeanlogr-logrelationdefined by plane astheBCGs:abouthalf(14of31)WE/ABS gal- for WE/ABSgalaxiestooccupythesameregioninr -r BCGs, whiletheotherhalflieaboveit.SEgalaxies,though occupied bynormalellipticalsandBCGs.Wefindatendency photal radiiat22and24Vmagarcsec;seePaperI)foreach of ourgalaxies.Figure11showsdataalongwithregions analysis. have unusualprofiles),thisisthepreferredmethodofprofile non-r shapesatlargeradii,andforourgalaxies(whichoften constant surfacebrightnessandcomparesthesetostudythe slope ofthep-rrelation.ForbothBCGs,whichhavedecidedly meaningless forgalaxieswhoseprofilesareunusual.Forthis reason Schombertmeasurestheradiiofhisgalaxiesatlevels dent ontheregionschosenforfit.Furthermore,itis what arbitrarymeasureofagalaxyprofile,becauseitisdepen- in largerthannormalcharacteristicradii.Themagnitudeof questions relatedtomergerscenariosofgalaxyformation. these differenceswillhaveadirectbearingontheanswersto and shallowluminosityprofileslopesforBCGs,whichresulted normal ellipticalsandBCGswerehighinnersurfacebrightness envelopes. Theimportantstructuraldifferencesbetween ellipticals andBCGsbyHOS. 24 2224 inner regionsaswellintheircharacteristicallylarge study theextendedbrightnessassociatedwiththesegalaxies. number ofsurfacebrightnessparametersatisophotalradiito characteristic radiilargerthan5seeing-diskradii.FilledsquaresareSEobjects;openWE/ABSgalaxies.Thelinestherelations found fornormal 2224 22 24 He foundthatBCGsdifferfromnormalellipticalsintheir No. 2,1989 1/4 1/2 Thus theWE/ABS galaxiesinparticular haveshallow Accordingly, wecomputedlogr2andradii(iso- The useofr(usuallydeterminedfromfits)isasome- Fig. 10.—Relationshipofeffectiveradiusr[(ah)]format]tosurfacebrightnessnatthatinVforPRGswellfittedbyadeVaucouleurslaw andhaving In hisstudyofBCGs,Schombert(1986,1987)computeda 224 e e © American Astronomical Society • Provided by the NASA Astrophysics Data System b) IsophotalProperties MULTICOLOR SURFACEPHOTOMETRYOFPRGs.II. log r(e)kpc significant tendency forradioellipticalsto berounderthan malization ofthesetemplates,however,sothepresentinvesti- BCG (3C317,M=—21.30) inFigure12. overlaid thesewiththeprofile ofoneourPRGsthatisalsoa absolute (V)magnitude-20.50, -21.50,and-22.00 purposes wehavereproducedthreeofhiscurvesforgalaxies of gation shouldberegardedaspreliminary.)Forillustrative differences. (Theremaybesomeuncertaintyintheprecise nor- ellipticals ofvaryingabsolutemagnitudetodemonstratethese rior tothe8kpcradius).Heconstructedtemplatemodels of a functionofthegalaxy’sintrinsicmagnitude(measuredinte- that theshapeofsurfacebrightnessprofileanelliptical is with thatofanormalelliptical?Schombert(1987)hasshown surface brightnessisastrongupperlimit. criterion, andthemedianr(arcsec)/HWHM(seeingdisk) for (<0.15 magincreaseinp).Mostofourgalaxiessatisfythis our sampleis~14,implyingthatthis0.15magincrease in ness fortheouterportionsofgalaxywasgenerallysmall disk) isgreaterthan5,thechangeinmeasuredsurfacebright- at largerredshifts.Forcaseswherer(arcsec)/HWHM(seeing degrading thesurfacebrightnessprofileofNGC3379(r= size. E)jorgovski(1983)modeledthiseffectbynumerically will bescatteredawayfromtheircentersbythePSFof influenced byseeing(Schweizer1979;Djorgovski1983).Aswe seeing profile,whichbecomesalargerfractionoftheirangular observe galaxiesatgreaterdistances,progressivelymorelight 8 kpc 56", z=0.003),therebysimulatingobservationsofthisgalaxy criminant, wefindroughlythesameseparation(FRII= strength ofemissionlineswithFRclass,thisisnotsurprising. normal E;FRI=BCG),and,giventhecorrelationof non-BCG giantellipticals.UsingFanaroff-Rileyclassasadis- The SEPRGshavethesteeperprofilescharacteristicof surface brightnessprofilessimilartothosefoundfortheBCGs. e e e Disney, Sparks,andWall(1984) havefoundthatthereisa How, then,doesaPRGsurfacebrightnessprofilecompare Measurement ofmetricsurfacebrightnessescanbegreatly c) EllipticityDistribution 669 198 9ApJ. . .341. .6583 oq cocm *-• cotocm © American Astronomical Society • (od^)**J íoj 670 Provided bythe NASA Astrophysics Data System 1 « S "8 «» ■Si H « £ Ö J ^ 43 ÿa w 'S < g O eö 4) **3 V » CO ^ «5 g ^ X O d 85 CÖ =* -* (Uo o. g ei «3 O M «’S a © 198 9ApJ. . .341. .6583 -2 -2 ellipticities fornormalellipticalsfrom Stromand(1978a,b,c). absolute magnitudeandaPRGwithshallowprofile.M(8)istheVinteriortoan8kpcradius. exception ofpossiblyafewmorehighlyeccentricPRGs,the slightly rounder(by0.06,a1.7crdifference).Contrastingellip- a <0.65inoursample.Thereissmalldifferencebetweenthe We alsonotethat~23%ofthePRGshaveaxialratiosb/ distribution ofellipticityissimilartothatnormalellipticals. mag arcsecisophote,whichshouldroughlycoincidewith excluding galaxieswithverynearbycompanions.Theoverall found themeanellipticity<€>=0.28±0.02(for60galaxies), with b/a<0.65.Wedeterminedtheaverageellipticityofeach SE andWE/ABSgalaxiesinthesensethatare the radiusofourVmeasurements.Wefindthat,with distribution ofellipticitiesforoursampleispresentedinFigure nonradio ellipticals,findingthattherewerenoradioellipticals Strom andmeasuredtheiraxialratiosatthefi=~24 Strom and(1978a,b,c)normalizedtooursamplesize. of ourradiogalaxiesnearthe25Vmagarcsecisophoteand 13, alongwiththedistributionforclusterellipticalsfoundby R -2 Fig. 13.—Distributionofellipticities ofthe25VmagarcsecisophoteforourPRGsample(solidlines). Dashedhistogramistheexpecteddistributionof Fig. 12.—Comparisonoftheshapesurfacebrightnessprofilesfornormalellipticals{solidlines)fromSchombert(1987)templatesgalaxies ofspecified © American Astronomical Society • Provided by the NASA Astrophysics Data System MULTICOLOR SURFACEPHOTOMETRYOFPRGs.II. Ellipticity (1-b/a) log rkpc 26 -2 -123 This effectwillbesmallforourellipticities,however,because (Djorgovski 1983;Franx,Illingworth,andHeckman1988). Wall; themedianradiopowerofoursampleisP~10W galaxy verydifferentfromthatstudiedbyDisney,Sparks,and round). Alikelyexplanationisthatwearestudyingaclassof the 25magarcsecradiusislargecomparedwith Disney, Sparks,andWall(1984)(radiogalaxiesareunusually our results(radiogalaxieshavenormalellipticities)andthatof ticity differencesalongFRclasslinesrevealsevensmallerdif- seeing, causingonetounderestimatethetrueellipticity Hz ascomparedwith~10Wfortheirsample. ferences (i.e.,betweenFRIandIIgalaxies).Becausethese determination (seePaperI),wefeelthatthisdifferenceisnot differences areverynearthelimitofreliabilityforellipticity significant. 178 We donotunderstandtheoriginofdiscrepancybetween Ellipticity studiesareinhibitedbyimageblurringdueto 671 198 9ApJ. . . 341 . .658S 2 1/4 (Djorgovski 1983).WilliamsandBhattacharya(1987)report dients de/dr>0.2. have ellipticitygradients,thereisoftenlittleattentionpaidto yielded theexpectedlowpoint-to-galaxyfluxratios(<0.03). control objectswemodeled(3C218,NGC6047,and3C 353) we hadnoreasontosuspectstrongpoint-sourcecontami- check wealsomodeledseveralmoretypicalgalaxiesforwhich red nucleusor(2)anNclassificationforthegalaxytype.As a brightness profilewithanaddedpointsourceinthenucleus; date formodeling(constructionofamodelgalaxysurface underestimation oftrueellipticitiesbyasmuch0.2-0.3 seeing whichcanmaskgradientsfortheinner~5",causing to thedata. we listthescalelength,inkiloparsecs, thepoint-to-galaxyflux with thoseobtainedfromthesurfacebrightnessprofilefits. We nation toexaminethereliabilityofourmodels.Thethree see PaperIandSmithetal1986):(1)thepresenceofblue/very From oursamplewefindthat~40%displayellipticitygra- 86% (of37total)ellipticalshavesomeaxis-ratiovariations. best-fit model.Exceptwhere noted, allgalaxiesweremodeled ratio, andtheabsolutemagnitude ofthepointsourcefrom present theresultsofourmodels inTable4.Foreachgalaxy the /valuesforfitswere high.Webelievethatforthese using adeVaucouleursr law.Wehavereproduced,in Moreover, thescalelengthswerealsoinreasonableagreement Figure 15thedata+model plots forthosegalaxiesinwhich could beanticipatedafterinspectionofthecontourimages. confidence level(F-ratiotest).Thusthemoreellipticalsystems This trend,showninFigure14,issignificantatthe~99% ellipticity measurementsunderestimatethetrueflatteningof their outerreaches(CarterandMetcalfe1980;Binggeli1982). are diffusesystems,themselvesgenerallyquiteellipticalat This resultmayberelatedtothethatcDgalaxies,which appear tobethosewhicharethemostdiffuse,aresultthat of ellipticitywiththesurfacebrightnessateffectiveradius. these galaxiesby<0.1. HWHM oftheseeingprofile.Atmostweestimatethatour 672 -2 We chosethefollowingcriteriatoselectagalaxyascandi- Fig. 14.—Ellipticityofthe25Vmagarcsecisophotevs.surfacebrightnessinatcharacteristicradiusgalaxy.Thestraightlineisaleast-squaresfit Finally, thoughmanynormalellipticalsareobservedto One weaktrendtoemergefromourdatawasthecorrelation © American Astronomical Society • Provided by the NASA Astrophysics Data System VI. IMAGEMODELING SMITH ANDHECKMAN 1/4 1/4 1/4 more definitiveandquantitativestatement. cases (3C223and3C327)thebestmodelsweredeVaucou- departures fromellipticalgalaxysurfacebrightnessprofiles in with thatofthehost.Amuchlargersampleisneededfor a restricted sampleofgalaxieswithmodelednuclei(13),we find host galaxyhavebeenmadeforQSOs,withsome(Hutchings, magnitude ofthenucleusitself.Variousclaimsabout for nonthermalpointsources.Asaby-product,wegetthe correction factortoapplytheobjectmagnitudeaccount the formofexponentialdisk-typestructures.Inallbut two no evidenceforacorrelationoftheluminositynucleus Crampton, andCampbell1984,hereafterHCC;Gehrenetal relationship ofthemagnitudepointsourcetothat Smith etal1986)findingnosuchtrend.Withourvery leurs rfits.Bothofthesegalaxieshadspiralorexponential profile for3C327isprobably artificiallyflatbecauseofscat- difficult (andpossiblymeaningless). Theouterpartofthelight highly unusualmorphologyof thisgalaxymakesclassification be modeledasanellipticalgalaxyplusapointsource. The disk-type profiles.Hutchings(1987)alsoperformedasimilar much largerinangularsizethanourpreviouslystudiedQSOs mathematically “good”fits.Becausethesegalaxiesareoften many ofourgalaxies,thereisnoapriorireasontoexpectthey model parametersforthepointsource.Wewerenotsurprised ness withradiuscloselyenoughtoallowususethederived galaxies themodelsreproducevariationinsurfacebright- profiles ofPRGsareconsistent withanrlawshapethe tered lightfromaverybright nearbystar.Withtheexception type ofimagedeconvolutionon3C223andfoundthatitcould 1984) findingapositivecorrelationandothers(Malkan1984; would followanormalellipticalmodelcloselyenoughtoyield occasional pointsourceadded. of thesetwo(perhapsunusual) galaxies,wefindthatthelight satisfactory fits.Giventheunusualopticalmorphologyof at thenumberofgalaxiesforwhichwewereunabletoobtain (Smith etal1986),theirprofilescontainmoreinformation. dust features,causetheprofiletodeviatefromitsrorexpo- Any unusualbumpsordips,causedbyknotsofemission nential (diskgalaxyprofile)shapeandresultinapoorfit. |i(e) Another objectiveofourmodelingstudywastolookfor The primaryuseforthesemodelshasbeentoderivethe Vol. 341 198 9ApJ. . .341. .6583 2 fraction ofPRGsthatexhibit morphologicalpeculiaritiesat high levelsofsurfacebrightness. Approximatelyone-halfofthe radio galaxiesinoursample showlarge-scale(severalkpc) obtained. Asteriskshavesamemeaningasincol.(3). acceptable ratios.Udenotesgalaxiesforwhichnofits were of marginalmathematicalquality,butreasonabletotheeye;seeFigs15a-15c. modeled. Valuesfollowedbyanasteriskcorrespondtomodelswithxvalues indicates fitsofmarginalquality.NMdenotesgalaxieswhichwere not scale lengths.Udenotesgalaxiesforwhichnoacceptablefitswereobtained. M by aspiralgalaxy(disk)lightdistribution,aswas3C327. by modelsotherthandeVaucouleur’slaw.3C223wasfittedinbothBand V No. 2,1989 PKS 2322 3C459 .... 3C445 .... 3C 390.3.. 3C382 .... 3C371 .. 3C353 .. 3C 327f. 3C227 .. 3C223f . 3C219 .. 3C218 .. 3C198 3C192 . 3C109 . 3C84 .. 3C79 .. 3C63 .. 3C33 .. 3C17 .. One ofthefindingsthisstudy isthatthereexistsalarge Col. (5).—Absolutemagnitudeforthepointsourceofbest-fitmodel. Col. (4).—Point-to-galaxyfluxratioforbest-fitmodelalongwithrange of Col. (3).—Scalelengthforbest-fitmodel(kpc)andtherangeofacceptable Cols. (1)and(2).—Galaxynamefilter.Adaggerindicatesgalaxiesfitted Name (1) © American Astronomical Society • Provided by the NASA Astrophysics Data System a) MorphologyofPRGs Model GalaxyParameters Filter (2) B B B B B B B B B B B B B B B B B B V V V V V V V V V V V V V V V V V V V V VIL SUMMARY TABLE 4 Scale Length 0 Unresolved Unresolved A 21.2t™ 10.4tí;I 12.1 tí? 11.5t¿;° 12.2t5;S 14.9 ±2.0 4.2 ±0.7 4.3 ±0.5 6.3ti;J ^-0.08 44 +0.07 5.0 ±0.2 6.6 ±0.4 A 6+0.01 -°-0.03 i r+0.06 1.8 +0.3 (kpc) NM 41.5 37.3 19.1 19.1 5.5* 6.1* 5.0* M M M M (3) U U U U U U 2.7 u 1.4 MULTICOLOR SURFACEPHOTOMETRYOFPRGs.II. o UA 1 02 0.02 ±0.01 0.06 ±0.02 o.oi ± o.oo t™; 0.15 ±0.2 0.05t;°i ’ -0.02 0 11+0-0! U.Ul -0.00 0 01+ LpJLgui 0.00 0.00 0.44* 0.68* 0.94* 0.91* NM 0.11 0.09 0.11 0.14 0.10 0.03 0.13 0.19 0.24 1.02* 1.74* 1.60* (4) U U U U U U U U U M(point) -17.87 -18.73 -17.03 -19.24 -18.13 -17.60 -17.15 -16.04 -18.16 -19.83 -18.91 -19.20 -18.52 -17.28 -19.35 -19.85 -19.10 -21.74 -21.92 -21.17 -20.68 -15.31 -18.83 (5) 1/4 1/4 -2 addition, thereisalargerdispersion inPRGabsolutemagni- brightest clustergalaxies(by 0.2 maginVforoursample).In luminosity distributionofgalaxies butarelessluminousthan those ofBCGs. Furthermore,wefindthat the radiogalaxies systems haveabsolutemagnitudes thatarecomparableto tudes thanfoundinBCGs(~2 timesaslarge).TheWE/ABS surface brightnesses. dency fortheflattenedsystemstohavelowercharacteristic differ significantlyfromthatfoundfornormalellipticalgal- than radio-quietellipticals.Inaddition,wehavefounda ten- results thatindicatedradiogalaxiestendtoberounder axies evenwithoutseeingcorrections.Thiscontradictsearlier bear norelationshiptothepresenceoflargeisophotaltwists. tions greaterthan10°.Emission-lineclassificationappearsto powerful radiogalaxiesasa class fallatthebrightendof and strengthenedtheresultsofpreviousstudies(e.g.,Sandage removal ofnonstellaremission-lineflux,wehaveconfirmed have beenremovedviaimagemodelingtechniquesandexplicit tions mentionedabovehavemajor-axisposition-anglevaria- one-half ofthePRGswithoutlargemorphologicaldistor- are largerthanthosefoundinotherellipticalsystems.Nearly nificant fractionhavemajor-axisposition-anglevariationsthat peculiarities foundinmanyPRGs,wehavethatasig- quiet hadhostswithexponentialprofiles. ness profileswererinshape,andQSOswhichradio- radio-loud tendedtohavehostgalaxieswhosesurfacebright- HCC). AlltheseinvestigationsfindthatQSOswhichwere like galaxieshostingapowerfulradiosource.Thisisinquali- case havewefoundunambiguousindicationsofnormaldisk- modeled asrgalaxieswithaddedcentralluminosity.Inno on thehostgalaxiesofradio-loudQSOs(Smithetal.1986; tative agreementwithearlierresultspresentedbyusandothers point sourcesindicatethatthesesystemscantypicallybe nuclei, andoftenexhibitasymmetricenvelopes.Suchfeatures common envelopesystems,havegreaterincidenceofmultiple are seeninelliptical-ellipticalinteractions(e.g.,Lauer1988). trast, theWE/ABSgalaxiesaremorelikelytobefoundin liarities. Itisimportanttonotealsothatmanyofthedistor- with strongemissionlinesintheirspectrashowsuchpecu- and notmerelyextendedemission-linegas(seeH86).Incon- tions intheSEradiogalaxiesareusuallystellarcomposition Toomre 1972;Quinn1984).About50%oftheradiogalaxies (i.e., disk-ellipticalordisk-diskinteractions;cf.Toomreand could remainbelowourdetectionthreshold. (Lauer 1985).Furthermore,itislikelythatthetruefractionof 1972; Lilly,McLean,andLongair1984)whichfound that distances ofsomethesegalaxies,peculiarfeatures galaxies withdistortionsmaybelarger;becauseofthelarge mildly boxyisophotesfoundinnormalellipticalgalaxies immersed incommonenvelopes,buttheyaregenerallyquite large (severalkpc)inextent.Theyarequitedifferentfromthe bridges, tails,fans,shells,asymmetricisophotes,andgalaxies deviations themselvesarevariedintheirform,takingshapesof ucts ofinteractionsthathadatleastonediskgalaxyinvolved deviations fromellipticalsymmetryintheirisophotesat surface brightnesslevelsbrighterthan25Vmagarcsec.The The ellipticitydistributionofourPRGsampledoesnot By includinggalaxieswhosebrightnuclearpointsources In additiontothepreviouslymentionedmorphological Image modelingofseveralthegalaxieswithbrightnuclear The bridges,tails,fans,andbrightshellsareprobablyprod- b) AbsoluteMagnitudes 673 198 9ApJ. . .341. .6583 1/4 1/4 2 galaxy hasadeVaucouleursrlaw light distribution. output oftheimagemodeling3C 382. ModelgalaxyhasadeVaucouleursrlawlightdistribution,(c)Sample outputoftheimagemodeling3C445.Model brightness datawerecalculatedbythe methodsoutlinedinPaperI.Thejaggedappearanceofthemodelfitis anartifactofthereproductiontechnique,(b)Sample PSF ofastarinthesameframe.This iscomparedwiththeimageprofile(crosses)yieldingabest-fitmodelthrough minimizationofx-Errorbarsforthesurface 674 1/4 Fig. 15.—(a)Sampleoutputoftheimage modelingof3C371.ModelgalaxyhasadeVaucouleursrlaw light distribution,whichisthenconvolvedwiththe © American Astronomical Society • Provided by the NASA Astrophysics Data System 0 102030405060 SMITH ANDHECKMAN Fig. 15a Fig. 15b Radius O Vol. 341 198 9ApJ. . .341. .6583 concentrations ofemission-line gas. not merelybluenucleiproduced bynuclearpointsourcesor measure ofthestellarpopulations ofthesegalaxies.Theyare deduce thattheresultantspatially extendedbluecolorsarea colors. Havingremovedthe nonstellarcontributions,we spectra, implyingthattheymay beresponsibleforthegalaxy that manyofthesebluegalaxies haveemissionlinesintheir higher thanthatreportedbySandage(1972),whofound that correction fornonstellaremission.Thispercentageisslightly giant ellipticalgalaxiesfoundatthesameredshift—evenafter (B— V)colorsthatareblueby0.4magcomparedwithnormal there issomefraction(23%ofoursample)PRGs with 18% (of59)radioellipticalshadcolorsthisblue.Healsonotes in derivingourconclusions. radii ofinterestwerelargerthan5seeing-diskused were takentominimizetheinfluenceofseeingonourcharac- explicit seeingcorrectionsweremadeforeachgalaxy,steps teristic metricandisophotalproperties.Onlygalaxieswhose measure becauseofastronomicalseeing)andhigherouter surface brightnessesrelativetonormalellipticals.Althoughno surface brightness,aquantitywhichwecannotaccurately surface brightnesses(note:wearenotreferringtocentral shallow slopeswillcauseobserverstomeasurelowerinner than thoseofnormalellipticalsandsimilartoBCGs.These have surfacebrightnessprofileswhoseslopesareshallower galaxies, respectively). which havestrongemissionlinesintheiropticalspectraare be fainterby~0.2and0.6Vmag(fortheWE/ABSSE host galaxymagnitudesofradio-loudquasarsrevealsthemto fainter thanWE/ABSsourcesby~0.35Vmag(seealsoLilly and Prestage1987). No. 2,1989 Perhaps themostimportantnewresultwereportisthat We havefoundevidencethatindicatesWE/ABSPRGs Comparison ofradiogalaxyabsolutemagnitudeswiththe © American Astronomical Society • Provided by the NASA Astrophysics Data System c) SurfaceBrightnessProfilesofPRGs d) ColorsofPRGs MULTICOLOR SURFACEPHOTOMETRYOFPRGs.II. Fig. 15c indication thatoneormore mergers(orextremelyviolent ties theyarequitesimilartobrightest clustergalaxies. and highincidenceofmultiple nuclei.Inthetwolatterproper- somewhat shallowerthannormal surfacebrightnessprofiles the extremeendofelliptical familywereitnotfortheir phologies, colors,andmagnitudes) thatwouldplacethemat class (classB),thosewithfewornoopticalemissionlines in and morphology)exhibitedbyellipticalgalaxies.Thesecond FR Itype,appeartohaveopticalproperties(extendedmor- their spectraandwhoseradiomorphologyisusuallyof the exhibit themostextraordinarydeviationsfromnorms(incolor and whoseradiomorphologyisusuallyoftheFRIItype, A), thosewhoseopticalspectrahavesignificantemissionlines and Longair1979;Heckmanetal1986).Thefirstclass(class fundamentally differenttypesofpowerfulradiogalaxy(Hine the nucleus. knots ofbluecolortypicallyhaveseparations(centertocenter) ized byrednucleiwithflankingbluelobesorregions.These of ~5kpcandacolorcontrast~0.5magin(B—V)from normal giantellipticalsandBCGs. and colorgradients)appearindistinguishablefromthoseof the colorpropertiesfortheselattergalaxies(integratedcolors WE/ABS galaxiesaremoremundaneinbothregards.Infact, colors arepreferentiallyassociatedwithSEgalaxies.The phological deviationsfromellipticalisophotesandabnormal 0.2 mag)fortheirredshifts[<(£-F)>=0.79±0.04inthe PRG restframe],whileonly8%oftheWE/ABSsystemsdo have bluercolorsthantheWE/ABSgalaxies.Fully44%of [<(£— F)iiwe/abs)=0*99±0.02].Thusboththeopticalmor- SE galaxieshavecontinuumcolorswhichareblue(byatleast all SE a One featurethesesystemshave incommon,however,isthe From earlierinvestigationsitisclearthattherearetwo Several ofthePRGs(five)havecolorstructurescharacter- The galaxieswhosespectrahavestrongemissionlinesalso a) GalaxyMergers/CollisionsandTheirRoleinthe Formation ofPRGs VIII. IMPLICATIONS 675 198 9ApJ. . .341. .6583 1/4 8 87 1/4 1/4 1/4 interactions) appeartohaveoccurredinthesystem’spast.In able presenceoflarge,coherentstellarfeaturesreminiscent the caseofSEgalaxiessignatureisoftenunmistak- by AW;seebelow)unusuallyshallowsurfacebrightnesspro- envelope systems(withdistortedisophotes),and(assuggested axies taketheformofdouble(ormultiple)nuclei,common the tidalinteractionmodelsofToomreand(1972)or 676 will nodoubtbeacomplexfunctionofparameterstheinter- files. Thecausesofdifferentmanifestationsthesemergers Quinn (1984).MergerindicationsintheWE/ABSclassofgal- involved, andthetimeelapsedsincemergerorinteraction. relative velocityoftheencounter,impactparameterandorien- mergers ofspiral-spiralorspiral-ellipticalsystems.Theinter- tation oftheangularmomentumvectorssystems action, suchasmergerparticipanttypes(spiralorelliptical), profiles ofmergingsystemsforunusualstructurewillonly pick distribution, tellsusthatexaminationofsurfacebrightness intensities andstrongthermalinfraredemission.Thedynami- fuel intheformofgasanddustforlargeemission-line Heckman etal.(1986)havesuggestedthattheSEgalaxiesare which theprofilerisesaboveprojectedrlawshape coherent stellarfeaturessuchastailsandfans.Thebluecolors cally colddiskinadditionallowstheformationofextended stellar medium(ISM)ofthedisksystemssuppliesnecessary defined bytheinnerpartofgalaxy(seetheirFig. 2) is out veryrecentmergers(timesincemerging<~2x10 yr). found inregionsofloweraveragedensitythanPRGswith participants orfromstarformationstimulatedbythemerger. then resulteitherfromtheblueinitialcolorsofmerger local crossingtime[i= 2r/i;(r)] isequaltothetime related tothetimesinceclosestapproachof two For timeslessthanthis,AWdemonstratedthatthepoint at mergers involvingdiskgalaxiesarenotfoundindenseclusters normal opticalmorphology.Thatis,thesystemspositedtobe systems. Thisprofileinflectionoccursattheradiuswhere the where largevelocitydispersionsinhibitmergingandfew we canestimateAi—thetime elapsedsincethe“collision” since closestapproach.Several ofourprofileshavethesechar- disk and/orgas-richgalaxiesarefound. Moreover, theopticallypeculiarsystemsarepreferentially the mostobviouscases(PKS 1345+125,3C293,and321) acteristic inflectionsandarelikely mergerobjects.Forthreeof ed. TheshallowsurfacebrightnessprofilesoftheWE/ABS line featuresandwhose“hot”dynamicalstatewouldreduce nificant coolISMwouldsuppresstheformationofemission- of thesystems.Thesetimesare ~1.0x10,~4.5and galaxies deservespecialattention.SimulationsbyAWhave the likelihoodofsharptidallydistendedfeaturesbeingproduc- tical galaxiesareflattenedbytheirtidalinteraction,increasing shown thatthesurfacebrightnessprofilesforinteractingellip- from mergersofelliptical-typesystemswhoselackasig- Kormendy 1977,whodiscussesthis“tidalheating”ofthe the surfacebrightnessforouterpartsofgalaxy(seealso indeed, evenmodelswhichinitiallyhadKing(1966)model retained byinteractingparticipantsaftertheencounter— outer partsofgalaxies). This theoreticalrealizationoftherobustnature r surface brightnessprofilesbecamerlawinshapeafterward. and referencestherein),whodemonstratedthatthemerger of shape, alongwiththeobservationalstudiesofSchweizer(1982 two spiralgalaxiescanproduceanobjectwithrlight cross cross coll 1/4 WE/ABS galaxiesintheinteractionscenariowouldresult Significantly, AWalsofoundthattherlawshapesare © American Astronomical Society • Provided by the NASA Astrophysics Data System SMITH ANDHECKMAN 7 7 7 8 respectively. AlthoughtheAWsimulationswereforelliptical- morphological distortions,confirmthatthesegalaxiesarefun- WE/ABS galaxies(or,equivalently,classAandB galaxies), alongwiththeirotherdifferencessuchastypeof had theircolorsalteredbyaburstofstarformationinduced that involvediskgalaxiessuchasthese.Inaddition,thesetime elliptical encounters,weareencouragedbytheresultsof multiple nucleiand/orcommonenvelopesystems.Thecolors have reachedthesameconclusiononbasisofsomewhat damentally distinctcreaturesoneofwhosecommonfeaturesis a tidalencounter. scales areconsistentwiththoseexpectedforgalaxiesthathave different dataandarguments. a pastencounterwithanothergalaxy.LillyandPrestage(1987) Whether theradio-loudgalaxiesthatharborQSOswereini- distinct classesofactivegalaxy.Onthebasisasmaller Schweizer (1982)toexpectthesameprofilebehaviorinsystems most likelytheresultsofasuperpositionpopulation of found inregionsofveryhighgalaxydensity.Thus,fromoptical and colorgradientsofthesetwosystemsarealsoquitesimilar. sample, Hutchings(1987)reachedthesameconclusion. of radio-loudQSOsandPRGssuggestthatthese,too,maybe young starsproducedinaburstonanexistingolderpopu- normal giantellipticalsatthesameredshift.Thesecolors are evidence aloneitisrelativelydifficulttodistinguishbetween appear distendedrelativetonormalellipticalprofiles.Both are mation isgreatlyincreased.Ifthisthecase,magnitudediffer- energy output,createdalocalenvironmentinwhichstarfor- tially differentfromPRGscannotbedeterminedthe with burstsofstarformation lasting —2x10yrandinvolv- lation. LarsonandTinsley(1978)foundthatgalaxieslisted in these twotypesofgalaxies. Surface brightnessprofilesforWE/ABSPRGsandBCGs equivalent (thoughthePRGsmayhavealargerdispersionin powerful radiogalaxieshavemanysimilaritiestoBCGs. magnitudes betweenthetwotypescannotberegardedas ences willbeoflittlehelpindistinguishingbetweenprogenitor above testalone.ItmaybethattheQSOhas,throughitslarge ing <5%ofthemassgalaxy. Thusthetimerequiredfor the Arp(1966)AtlasofPeculiarGalaxieshadcolorsconsistent 266], 3C317[Abell2052]).Theirabsolutemagnitudesare Indeed, someofthePRGsareBCGs(e.g.,NGC708[Abell firmly established,inourview.HubbleSpaceTelescopeobser- galaxy types.Moreover,therealityofdifferenceinabsolute -5.0 x10yrforPKS1345+125,3C293,and321, before collision[Toomreand Toomre1972]lastingtoafew the appearanceofmorphological peculiarities(—5x10yr their distribution).Themorphologiesofthetwoclassesgal- vations oftheQSOhostswillbeveryvaluableinthisregard. time overwhichtheburstsof starformationwillappreciably times 10yrforthebulkof the galaxy)iscomparableto axies arealsoquitesimilar.Bothhaveahighincidenceof The intrinsicmagnitudedifferencesfoundbetweenSEand The absolutemagnitudediscrepancybetweenapopulation Throughout thisstudywehaveseenthattheWE/ABS The extranuclearcolorsforsomePRGsarebluerelativeto c) RelationshipofWE/ABSRadioGalaxiestoBCGs b) RelationshipbetweentheTwoClassesofRadio d) Colors,StarFormation,andDust Galaxies andRadio-loudQSOs Vol. 341 198 9ApJ. . .341. .6583 -1 12 which thesesystemsarefound. Alreadythereisconsiderable lives ofPRGs,itisnaturalto investigatetheenvironmentsin are oftentheproductofhead-oncollisions. fi-r relationcanbethoughtofasprojections this because theoreticalsimulationsshowthatcompletemergers suggests thatmergerremnantswillhavelowangularmomenta disk embeddedinsomeofthesegalaxies(EkersandSimkin “ fundamental”planeontotheprincipalplanesthatdefine the known Faber-Jacksonrelationandthepreviouslydiscussed plane inthethree-dimensionalspacedefinedbyluminosity, found evidencethatellipticalgalaxiesarewelldescribedbya surface brightness,andstellarvelocitydispersion.Thewell- system, wemightbeabletoobservetherotationofaremnant are indeedtheproductofamergerinvolvingatleastonedisk have high(~140kms)rotationvelocities.Ifthesesystems ellipticals. Interestingly,Heckmanetal1985didfindevidence to suggestthatthemorphologicallypeculiarradiogalaxies sions androtationvelocitiescomparabletothoseofluminous as aclass,powerfulradiogalaxieshavestellarvelocitydisper- et al1985)havefailedtoconfirmthesefindings,showingthat, 1983; FranxandIllingworth1988).White(1982),however, and Simkin1983;Jenkins1984).Laterstudies(e.g.,Heckman ities thataredifferentfromthoseofnormalellipticals(Ekers galaxies havestellarvelocitydispersionsandrotationveloc- e galaxies. Alreadytherehavebeenreportsthatpowerfulradio large sampleofPRGsforwhichwehavegoodimages and program toobtainstellardynamicaldataonamoderately To addresstheseandrelatedissues,wehaverecentlybegun a etry willatleastenableustodeterminewhetherPRGsare also tion isthenatureofstellardynamicalstructurethese surface photometry. described bya“fundamentalplane”consistingof/x,r,and cr. space. Theadditionofvelocitydispersiondatatoourphotom- presumably concentrated)ofaninteractingsystem(Lonsdale, dust cancauseadimmingoftheinteriorpart(whereis magnitudes). Suppressionofshorterwavelengthlightbythe Persson, andMatthews1984). can playaroleindeterminingtheappearanceofgalaxysurface brightness profiles(internalreddeningcanbeseveral is definitelyoccurringingalaxieslikePKS1345+125,which are abnormallyredinthegalaxycenter[(Æ—V)=2.2].Dust has averylargeIRluminosity(~10L),andwhosecolors work oppositetheeffectobservedbyLarsonandTinsley.This powerful IRsources(Golombek,Miley,andNeugebauer but IRASobservationsofPRGsshowthesegalaxiestobe tion. No. 2,1989 their colorstohavebeeninfluencedbyenhancedstarforma- derived forsomeofourgalaxiesarethecorrectorder alter agalaxy’scolor.WealsonotethatthevaluesofAi 1988). Thisdustwilltendtoreddengalaxycolorsandhence, 0 coll Because galaxyinteractionshave playedavitalroleinthe Dressier etal(1987)andDjorgovskiDavisboth One ofthemostinterestingquestionsthatbearscloseratten- So farinthisdiscussionwehaveignoredtheeffectsofdust, © American Astronomical Society • Provided by the NASA Astrophysics Data System a) StellarDynamicsofPRGs b) EnvironmentsofPRGs IX. FUTUREDIRECTIONS MULTICOLOR SURFACEPHOTOMETRYOFPRGs.II. 1/4 grant AST85-15896.E.P.S.also acknowledgesthesupportof H. acknowledgethesupport of NationalScienceFoundation anonymous referee,werealso quitehelpful.E.P.S.andT.M. Goddard SpaceFlightCenter.ConversationswithGreg copy ofS.Djorgovski’sthesis.Forthecomputertimeallocated Bothun andFrançoisSchweizer, andcommentsfroman to uswewouldlikethankGeorgeMileyatSpaceTelescope galaxy photometry.H.Spinradgraciouslysupplieduswith his data andnumerousdiscussionsonthepracticepitfalls of Science Institute,andSaraHeapKeithFeggans at a NationalResearchCouncil Postdoctoral Fellowship. normal galaxies(e.g.,3C29,296)mayalsoyieldinteresting modeled byourmethod. r lawstructureinapparentlyotherwise(morphologically) pointlike nuclei(e.g.,3C234,459)couldnotbesuccessfully data ondistant(z>0.2)galaxiesbecauseofseeingeffects. Unfortunately, severalofthegalaxieswithobviousbright properties ofgalaxies.Itisespeciallyvaluablewhenanalyzing a powerfultoolforstudyingthemorphologyandphotometric (e.g., magnitudes,half-lightradii).Wefeelthatthistechniqueis optical appearance. can revealinterestingstructuresinthegalaxiesthat are sources cansignificantlyalterthegalaxy’smeasuredproperties galaxies wemodeledsuccessfullyfoundthatthenuclear contributions forsomeofthegalaxiesinoursample.For unusual insomerespect,yetareapparentlymundanetheir galaxy. Whilethisisnotalwaysusefulforpeculiargalaxies, it bar structures)otherwiseobscuredbytheluminousbulkof features (suchastidaldistentions,ripplesorshells,andhidden evolutionary linkbetweenthemthatmightbediscernible have shownthatthistypeofanalysiscanbringoutorenhance results. Severalinvestigations(Lauer1988;Djorgovski1985) of thetwoenvironmentscouldconstrainanysuchhypotheses. through studiesoftheirenvironments?Adetailedcomparison ogies ofsomeQSOhosts(HCC;StocktonandMacKenty and SEPRGs,alongwiththedetectionofdistortedmorphol- optical spectraandradiopropertiesoftheradio-loudQSOs between thesetwotypesofactivegalaxies.Thesimilaritythe radio-loud QSOsmayhelptoilluminateanyrelationship metric properties(e.g.,opticalluminosity). correlation betweenmeasuresofclusteringandcertainphoto- more, LillyandPrestage(1987)havefoundthatthereisa 1984; Smithetal1986),suggestasimilarorigin.Istherean axies, thenthisisjusttheresultonewouldexpect.Further- indeed activityissometimestriggeredbymergingofdiskgal- regions ofsparsergalaxydensitythanotherradiogalaxies.If interactions involvingatleastonediskgalaxyarelocatedin radio galaxieswithmorphologicaldistortionsindicativeof galaxy wasrelatedtothelocaldensity.Theyfoundthat Heckman etal(1986)wasthattheopticalmorphologyofa HCC; YeeandGreen1984).Anintriguingfindingby and Heckman1982;Heckman,Carty,Bothun1985; regions ofspacethannonactivegalaxies(seereviewbyBalick evidence thatactivegalaxiesarepreferentiallyfoundindenser E. S.wishestothankJamesSchombertforhisgalaxyprofile Computer processingofgalaxydataframestorevealnon- We havemadeuseofimagemodelingtechniquestoremove A comparisonoftheenvironmentsPRGswiththose c) ImageProcessing 677 198 9ApJ. . .341. .6583 Timothy M.Heckman:AstronomyProgram,UniversityofMaryland,CollegeParkMD20742 Eric P.Smith:LaboratoryforAstronomyandSolarPhysics,Code681,NASA/GoddardSpaceFlightCenter, Greenbelt, MD 20771 .1985,Ph.D.thesis,UniversityofCalifornia,Berkeley. Jenkins, C.R.1984,M.N.R.A.S.,207,361. Hutchings, J.B.,andCampbell,B.1983,Nature,303,584. Hutchings, J.B.1987,Ap.J.,320,122. Hoessel, J.G.,Oegerle,W.R.,andSchneider,D.P.1987,A.J.,94,1111(HOS). Golombek, D.,Miley,G.K.,andNeugebauer,1988,A.J.,95,26(GMN). Dressier, A.,Lynden-Bell,D.,Burstein,Davies,R.L.,Faber,S.M.,Terle- Djorgovski, S.,andDavis,M.1987,Ap.J.,313,59. Disney, M.J,Sparks,W.B.,andWall,J.V.1984,M.N.R.A.S.,206,899. de Vaucouleurs,G.,A.,andCorwin,H.G.1976,Second Chambers, K.,Miley,G.,andvanBreugel,W.J.M.1988,Ap.{Letters),327, Arp, H.A.1966,Ap.J.Suppl,14,1. Aguilar, L.A.,andWhite,S.D.M.1986,Ap.J.,307,97(AW). Borne, K.D.1984,Ap.J.,287,503. Binggeli, B.1982,Astr.Ap.,107,338. Baum, S.A.,Heckman,T.,Bridle,vanBreugel,W.,andMiley,G.1988,Ap. Baum, S.A.1987,Ph.D.thesis,UniversityofMaryland. Balick, B.,andHeckman,T.M.1982,Ann.Rev.Astr.Ap.,20,431. 678 Kent, S.M.1985,Pub.A.S.P.,97,165. Kennicutt, R.C,Keel,W.vanderHulst,J.M.,Hummel,E.,andRoettiger, Hutchings, J.B.,Crampton,D.,andCampbell,B.1984,Ap.J.,280,41(HCC). Hua, C.T.1988,Astr.Ap.,199,105. Hoessel, J.G.1980,Ap.J.,241,493. Hine, R.G.,andLongair,M.S.1979,M.N.R.A.S.,188,111. Heckman, T.M.,Smith,E.P.,Baum,S.A.,vanBreugel,W.J.Miley,G.K., Heckman, T.M.,Miley,G.K.,Balick,B.,vanBreugel,W.J.andButcher, Heckman, T.M.,Illingworth,G.D.,Miley,K.,andvanBreugel,W.J.M. Heckman, T.M.,Carty,J.,andBothun,G.D.1985,Ap.288,122. Gilmore, G.,andShaw,M.A.1986,Nature,321,750. Gehren, T.,Fried,J.,Wehinger,P.A.,andWyckoff,S.1984,Ap.278,11. Galletta, G.1980,Astr.Ap.,81,179. Ekers, R.D.,andSimkin,S.M.1983,Ap.J.,265,85. Djorgovski, S.1983,J.Ap.Astr.,4,271. Carter, D.,andMetcalfe,N.1980,M.N.R.A.S.,191,325. Bruzual, G.A.1983,Rev.MexicanaAstr.Ap.,8,63. Bahcall, N.A.1977,Ann.Rev.Astr.Ap.,15,505. Franx, M.,Illingworth,G.D.,andHeckman,T.M.1988,preprint. Franx, M.,andIllingworth,G.D.1988,Ap.J.(Letters),327,L55. Feigelson, E.D.,andNelson,P.1.1985,Ap.J.,293,192. Fanaroff, B.L.,andRiley,J.M.1974,M.N.R.A.S.,167,31P. Illingworth, G.D.,Bothun,andBalick,B.1986,Ap.J.,311,526(H86). J. Suppl.,6S,643. K. A.1987,A.J.,93,1011. H. R.1982,Ap.J.,262,529. vich, R.J.,andWegner,G.1987,Ap.313,42. Reference CatalogueofBrightGalaxies(Austin:UniversityTexasPress). L47. 1985, Ap.J.,299,41. © American Astronomical Society SMITH ANDHECKMAN REFERENCES Provided bythe NASA Astrophysics Data System Yee, H.K.C,andGreen,R.1984,Ap.J.,280,79. Williams, T.B.,andBhattacharya,B.1987,inIAUSymposium127,Structure White, S.D.M.1982,inMorphologyandDynamicsofGalaxies,ed.L.Martinet .1988,Ap.J.,325,49. .1972,Ap.J.,178,25. .1982,Ap.J.,252,455. .1987,Ap.J.Suppl,64,643. —.19836,Ap.J.,268,476. -.19876,A.J.,83,732. .1978c,A.J.,83,1293. Quinn, P.J.1984,Ap.J.,279,596. Leach, R.1981,Ap.J.,248,485. Lauer, T.R.1985,M.N.R.A.S.,216,429. Larson, R.B.,andTinsley,B.M.1978,Ap.J.,219,46. Kristian, J.,Sandage,A.,andWestphal,J.A.1978,Ap.221,383. Kormendy, J.1977,Ap.J.,218,333. King, I.R.1966,A.J.,71,64. Schweizer, F.1979,Ap.J.,233,23. Schombert, J.M.1986,Ap.Suppl,60,603. Schneider, D.P.,Gunn,J.E.,andHoessel,G.1983u,Ap.J.,264,337. Schmidt, M.,andGreen,R.1983,Ap.J.,269,352. Sandage, A.,andVisvanathan,N.1978,Ap.J.,223,707. Sandage, A.1966,Ap.J.,145,1. Matthews, T.A.,Morgan,W.W.,andSchmidt,M.1964,Ap.J.,140,35. Malkan, M.1984,Ap.J.,287,555. Lugger, P.M.1984,Ap.J.,278,51. Lonsdale, C.L.,Persson,S.E.,andMatthews,K.1984,Ap.J.,287,95. Lilly, S.J.,andPrestage,R.M.1987,M.N.R.A.S.,225,531. Lilly, S.J.,McLean,I.S.,andLongair,M.1984,M.N.R.A.S.,211,833. Lilly, S.J.,andLongair,M.1984,M.N.R.A.S.,211,833. Toomre, A.,andJ.1972,Ap.J.,172,623. Spinrad, H.,andDjorgovski,S.1987,1AUSymposium124,ObservationalCos- Sparks, W.B.1988,A.J.,95,1569. Smith, E.P.,Heckman,T.M.,Bothun,G.D.,Romanishin,W.,andBalick,B. Smith, E.P.,andHeckman,T.M.1989,Ap.J.Suppl,69,365(PaperI). Smith, E.P.1988,Ph.D.thesis,UniversityofMaryland. Simkin, S.M.,andMichel,D.1986,Ap.J.(Letters),300,L5. van Breugel,W.,Heckman,T.,Butcher,H.,andMiley,G.1984,Ap.J.,277,82. Strom, K.M.,andS.E.1978a,A.J.,83,73. Stockton, A.,andMacKenty,J.W.1984,Ap.J.,283,64. and DynamicsofEllipticalGalaxies,ed.T.deZeeuw(Dordrecht:Reidel),p. and M.Mayor(Sauverny:GenevaObservatory),p.291. 391. mology, ed.A.Hewitt,G.Burbidge,andL.Fang(Dordrecht:Reidel),p.129. 1986, Ap.J.,306,64.