197 5ApJS. . .29. .193D The AstrophysicalJournalSupplementSeriesNo.284,29:193-218 by Perrine(1922).Photographs andpreliminarypho- tometry ofthenucleushave beenreportedbyEvans faint, butregular,outerring structurefirstdescribed lar galaxyNGC1291issurroundedbyalargeand © 1975.TheAmericanAstronomicalSociety.Allrightsreserved.PrintedinU.S.A. (1951), andofthewholegalaxy, includingtheouter The brightmainbodyorlensofthebarredlenticu- © American Astronomical Society •Provided by theNASA Astrophysics DataSystem _2c_2 -25 2 _2c_2 -1 _1 be typical. detached outerring(21x19kpc)fromwhichemergetwofaintspiralarmsshowingincipientresolutionat stage betweenlatelenticularsandearlyspirals.Thecentrallens(12x10kpc)issurroundedbyalarge,semi- smaller scaleapproximatingtheratioofJeanslengths.Otherexamplessuggestthatthisrepetitivepatternmay m »20.5.Inthenuclearregionatcenterofprimarybar(10x2.5kpc),asecondary(1.80.2kpc) and secondarynucleus(0.5x0.4kpc)havebeendetected,repeatingtheprimarylens-bar-nucleuspatternona jii=24.5 mags^10£Patanaverageradiusr«8kpcfromthecenter;maximum ring doesnotobeythesimpleexponentialdistributionpreviouslyfoundindisksoflate-typespirals. as p(Q)=13.46mags2.2x10£pc.Theflatcomponentcontributingtothelensanddominantin contributes 57percentofthetotalluminosity;ifitisvaliduptor=0,truecentralbrightnessmaybeashigh for M31,andindicatingagiantsystem. brightness intheringisonlyslightlygreater,about24.0mags~. 20' x18'(atthedetectionthresholdp&28.mags=0.3£P)correspondtoM(B)=—20.63and parameters). Thetotalapparentmagnitudem(B)=9.37(photoelectricallycalibrated)andmaximumdimensions reflector andtheMcDonald205-cmispresented(isophotes,luminosityprofiles,photometric Subject headings:galacticstructure—,individual photometryof at lowresolutionwithanimage-tubespectrograph(McDonald)isatypicalK-type,approximatingG5HandK at SO/a. Appendix; suchstructuresareobservedonlyaroundlenticulars and spiralsearlierthanScwithasharpmaximum upper limittothevelocitydispersion(o-<200kms)are9J?^1xlO^JÍo?wAh~0-025and optical andoneradioobservationsisF=+830kms.Thetotalmass,neutralhydrogenmass- and KOIIIatHywithweak23727emissionnoHa.Themeanheliocentricradialvelocityfromthree D =52kpc,with(B—V)0.92,(UB)0.47,ifmM30.0andA8.9Mpc(estimatedfrombrightest andredshift).Theaveragesurfacebrightnessinthe“dark”zonebetweenlensringisabout luminosity ratioestimatedfromcorrectedvaluesofthe21-cmlineparametersgivenbyLewisandanoptical 9R/ £«4.ThesevaluesareaboutnormalfortypeSO/a(t=0). B Ä0 B0 B0T r mT r5 SOUTHERN GALAXIES.VII. 1/4 Detailed surfacephotometryfromlong-andshort-exposurephotographswiththeMountStromlo75-cm The nuclearspectrumobservedintheblueregionatmediumresolution(MountStromlo)andred The lenticularbarredgalaxyNGC1291isthelargestexampleofrevisedtype(R)SB(s)0/aattransition The effectiveequivalentradiusoftheisophoteenclosinghalftotalfluxisr*=1!544.0kpc,sameas The frequencyofouterringstructuresaroundthemainbodiesgalaxiesdifferenttypesisdiscussedinan The spheroidalcomponentobeyingtherlawdominatesfightdistributionwithinlensand Supplement E75-S3 THE REMARKABLELENTICULARBARREDGALAXYNGC1291 I. INTRODUCTION McDonald ObservatoryandDepartmentofAstronomy, Received 1974September24;revisedNovember18 SOUTHERN GALAXIES.VII. G. deVaucouleurs The UniversityofTexas ABSTRACT 193 morphological classification(R)SB(s)0/adescribes collected inTable1. this structureintherevisedHubblesystem(deVau- ring, bythewriter(deVaucouleurs1956a,b)and couleurs 1963h).SomeelementsofNGC1291are Sérsic (1968).Thereisnotraceofaninnerring.The of thegalaxydetectedon microphotometer tracings, the ReferenceCatalogue,and themaximumdiameter largest ofallamonglenticular galaxiesofthistypein The apparentdiameterof theouterringis 197 5ApJS. . .29. .193D 194 ders 1940;Danby1965;deVaucouleursandFreeman barred SB,isfairlywellunderstoodinprinciple(Ban- ring structuresingalaxies,whetherordinarySAor about 20',suggeststhatitmaybe,togetherwithNGC spiral structureoutsidetheouterringhasnotbeen rings islacking,andtheoccasionalpresenceoffaint 4736, oneofthetwonearestringedsystems. investigated. Vaucouleurs 1956b).Theoutstanding apparentmag- nitudes anddiametersofthe threeobjects,compared spiral NGC1365,typeSB(s)b,andtheFornaxradio- some 6°intheoutskirtsof theFornaxIcluster(de source galaxyNGC1316, awidetripletspreadover spectroscopic observationsofNGC1291madewith short-exposure platestakenin1956atMount “nucleus” ofNGC1291discoveredonlarge-scale, 205-cm reflectorsofMcDonaldObservatory the 75-cmand188-cmreflectorsofMountStromlo study. Thepresentpaperreportsonphotometricand tory (deVaucouleurs1974)deservesmoredetailed Stromlo andverifiedin1960atMcDonaldObserva- Observatory (1952-1956)andwiththe91-cm 1972), detailedquantitativeinformationonouter (1960-1973). 1,2 1,2 1,2 1,2 3 5 3 4 3 1,2 1,2 5 =-2 Although theformationmechanismandstabilityof NGC 1291forms,withthewellknownbarred Finally, amostremarkablebarstructureinsidethe Inner dimensionsxd Type Concentration indexC Inner axisratio(ens)R¿ R.A. (1950) Outer dimensionsDxd Supergalactic L,B Galactic l,b Deel. (1950) Corrected velocityV Revised velocityV Observed velocityV(heliocentric) Revised “Face-on”diameterD(0)5 “Face-on” diameterD(0) Outer axisratio(ring)R Ring dimensionsDxd 1956b); (2)CordobaAtáis(Sérsic1958);(3)Reference Revised correctedvelocity BGC (inpreparation);(5)thispaper,§XI. Catalogue (BGC);(4)atg-b25.0magarcsec,Revised f 0 0 2 0 R © American Astronomical Society •Provided by theNASA Astrophysics DataSystem Notes.—(1) MountStromloSurvey(deVaucouleurs II. DISTANCEOFNGC1291 Elements ofNGC1291 TABLE 1 h -1 1 1 1 0 0.32 0.86 0.83 11:7 X10:3 9:8 4:9 257? 1,—36?9 315? 8:2 X7:2 3:75 x3:1 (R)SB(s)0/a 247?51, —57?04 + 802kms + 674kms" + 646kms” + 830kms~ — 4117' DE VAUCOULEURS _1 _1 -1 _1 physically connectedwiththecluster.Thiswas with thebrightestellipticalandlenticularmembersof actually larger.Sincethe(radial)velocitydispersion gest thatthetripletisinforegroundandnot difficult toestimateitsdistance. from it,stronglysuggeststhatthegalaxyisnota three fromtheclustercenter,beingsome7°away the factthatNGC1291ismostdistantof cluster velocitybyalmost3o.Thislargeresidualand than thatofthepair,anddepartsfrommean NGC 1291(V=+646)isabout1000kmsless cluster. Ontheotherhand,radialvelocityof the pairisentirelyconsistentwithmembershipin in theclusteriso&300kms~\meanredshiftof NGC 1316(V=+1715)and1365+ interpretation adoptedinthesurveyofnearbygroups locations anddiscrepantmorphologicaltypes,sug- For I(Hodge1959,1960),aswelltheiroutlying and weakspiralarmsareatM»—9.5 galaxies inourneighborhood,andaccordinglyitis NGC 1291mightformaphysicalpair.Apparently There isnootherlargegalaxynearbywithwhich pected galacticextinctionisA=0.25mag,andthe NGC 1291isoneofthefewgenuineisolatedfield cluster memberandisactuallyintheforeground. m æ20.5(§IV),theapparentmodulusis (de Vaucouleurs1965).However,theredshiftsof linear withanexpansionrateH=100/zkms assumption thatthevelocity-distancerelationis ulus (m—M)=29.135logb,ontheusual data, §XI)correspondstoanominaldistancemod- agreement, consideringtheirlargeuncertainties;the 29.75 +0.75. Mpc; thenif/z=0.75+0.25,(m—M) corrected modulusis(m—M)«29.75. ing distanceisA=8.9Mpc,andthescalefactor 29.75 +0.3:(m.e.),withA=0.25.Thecorrespond- following valueswillbeadopted:(m—M)= in bluelightwiththeMount Stromlo75-cmReynolds 12 brightmembersofForI(V=+1464),andare 1571) areincloseagreementwiththemeanredshiftof (m -M)k30.0.At/=247°,b-57°,theex- V =+674kms(meanofallopticalandradio v 0 v 0 B T =2.6kpc. B B 0 0 0 B 0 0 b 0 Assuming thatthebrighteststarsinouterring The twoindependentestimatesareingood This studyisbasedonthe followingobservations: The revisedcorrected(galactocentric)velocity 1) Photometricallycalibrated directphotographs IE. OBSERVATIONS 197 5ApJS. . .29. .193D reflector. Unfortunatelythesoutherndeclinationof ¿¿4500-8500 regionwithanimage-tubespectrograph at theCassegrainfocusofMcDonald205-cm the nucleusin>U3900-4900regionwithZeiss reflector (§VIII). reflector andtheMcDonald205-cmStruve the objectdoesnotpermitgoodspectrumscanner spectrograph attheNewtonianfocusofMount in theUBVsystemwithMcDonald91-cm velope (Fig.3).Inbarredlenticulars,thebarBB' Stromlo 188-cmreflector(§XI)andinthe the majordiameterofslightlyellipticallensL appears asadiffuseenhancementofluminosityalong dage 1961,1974),threemaincomponentscanbe early spiral.Outerringstructures(R)aremost atthetransitionstagebetweenlenticularand observations fromMcDonaldObservatory. NGC 1068and4736 intheHubbleAtlas).The at thehighestresolution (see, e.g.,photographsof the faintenvelope.Thisringappearsverysmoothin when present,ismerelyaslightlyenhancedzonein nucleus, (2)abrightlens,and(3)faintouteren- identified inalenticulargalaxy:(1)verybright inner ring(r)structure. axies suchasNGC1291,whichshownotraceofan frequent atthisstage(seeAppendixI),eveningal- about 5"resolutionontheMountStromloplates into starseveninthenearest examplesphotographed late lenticularsandearly spirals; itisnotresolved (Table 2). (Fig. 1[PI.1])isagoodexampleoftypicalSB(s) (when seenface-on).Theouterringstructure(R), IV. DESCRIPTIONOFNGC1291ANDMORPHOLOGY 2) Photoelectricintegratedmagnitudesandcolors Following Hubble(deVaucouleurs1959a;San- The grossstructureofNGC1291observedat 3) Low-andmedium-dispersionspectrogramsof © American Astronomical Society •Provided by theNASA Astrophysics DataSystem -1 OF BARREDLENTICULARGALAXIES S(82)C-V7 1960Nov.1465103a-O13.6McDonald205Í7.5 R(30)N-33 1952Nov.1960103a-O4MountStromlo75|67 R(20)N-19 1952Oct.1960103a-O6MountStromlo75*67 Plate No.Date(min)Emulsionf/Aperture(cm)(arcsecmm) * 50-cmaperturestop,fFullAperture.JCassegrainfocus. Exposure TelescopePlateScale Plate MaterialforNGC1291 SOUTHERN GALAXIES195 TABLE 2 f photographs indicatesthepresenceofaveryfaint with themajoraxisoflens,andbar exposure onIla-OwiththeCordoba152-cmreflector are faintbackgroundgalaxies).However,a46-min m æ20)showsonlyahintofstructureandnotrace direct (counterclockwise). tions nearthetwostableLagrangianpointson /?, ßhavebeeninterpretedasduetostellarconcentra- cuous enhancementsarealsopresentattheextremi- b, b'arestillonthemajoraxisoflens.)Insome shown intheHubbleAtlas,luminous“bridges” The symmetryaxisofthisenhancementcoincides photometry shows(cf.Figs.9-11),isfarfromdark. ring byslightenhancementsb,b'ofthediffuselumin- faint outerspiralarms,a,a',emergeattheperiphery at f/5(estimatedmæ21)showstracesofresolution a' emergingfromtheouterring(Figs.1,3).This the left-handedandpresumablytrailingspiralarmsa, the barnearitsends.Thefactthatenhancementis luminosity enhancementt,t'onthetrailingsidesof in NGC1291.Instead,carefulinspectionofavailable axis ofsymmetryadiskandbarconfiguration ties ofthebarinsidelens;theseluminous“blobs” systems discussedbySandage(1961),twoconspi- there isnobar,asinNGC1068,4736,etc., osity fillingthespacebetweenringandlenswhich,as of theringinroughlydiametricallyoppositelocations of resolutionintostars(thefewdiffuseimagesseen 75-cm reflectoratf/4(estimatedlimitingmagnitude implies thatthesenseof rotationofthegalaxyis on thetrailingsideisestablishedbycomparisonwith BB' whenabarispresent,asinNGC1291.(When [PI. 2]). (Sérsic 1968)inthebrighterpartsofring(Fig.2 (see Figs.1and3). (Danby 1965).Nosuchconcentrationsaredetectable 1-hour exposureofNGC1291on103a-Owiththe 1291, however,isthatwhich isusuallyhiddeninthe l z The primarylensisfaintlyconnectedtotheouter The mostremarkablepart ofthestructureNGC Occasionally, asinNGC1291and4736,two 197 5ApJS. . .29. .193D (see page195) Smaller high-contrastprints(negative isamirrorimage)showbetterthefaintouterringstructure RR'andspiralarmsa’a'.Northattop. © American Astronomical Society •Provided by theNASA Astrophysics DataSystem Fig. 1.Low-resolutionphotograph ofNGC1291withMountStromlo75-cmReynoldsreflector (103a-O,60min,1952Nov.19). PLATE 1 PLATE 2

§

Fig. 2.—Medium-resolution photograph of NGC 1291 with Cordoba Observatory 152-cm reflector (Ila-O, 46 min, 1960 Aug. 23, courtesy J. L. Sérsic). This low-contrast print shows better the structure of the primary lens I^Li, bar B^, and nucleus Nx which are overexposed in Fig. 1. Note also faint, curved dust lanes dd' on right side of nucleus and bar. North at top. [see page 195)

© American Astronomical Society • Provided by the NASA Astrophysics Data System 197 5ApJS. . .29. .193D from theouterringatdiametricallyoppositepointswellaway frombb'.ThemajoraxesofLandRaredifferent.lensis weak dustlanesdd'areseenonthe(near?)sideofprimary barandnucleus.Thelensisconnectedtotheouterringstructure primary barBjBiwithtrailingtipstt'.Insomebarredgalaxies, suchasNGC1543(Fig.5),butnotin1291,luminosity probably atriaxialspheroid,theringRcirculartoroidwhose apparent majoraxisindicatesthepositionoflinenodes.Seetext maxima formbrightblobsßß'nearthetipsofprimarybar. Thebarmarksthemajoraxisofprimarylens1^14;some secondary lensLwhichappearsastheprimarynucleuson long-exposurephotographs.This“nucleus”isatthecenterof for furtherdescription;compareFigs.1and2. RR' byfaint“bridges”bb'acrossthedark(notblack)annulus betweenRR'andI^Li.Weakspiralarmsaa'emergetangentially 2 Fig. 3.—KeytothestructureofNGC1291.Anunresolvedinner nucleusNisatthecenterofasecondarybarB2in 2 © American Astronomical Society •Provided by theNASA Astrophysics DataSystem DE VAUCOULEURS SOUTHERN GALAXIES 197 TABLE 3 Geometry of NGC 1291

D x d Major Axis p.a. (1875) Arcmin kpc Maximum detected dimensions ... 20.: x 18.: 52.: x 47.: Outer ring diameters 70° 8.2 x 7.2 21.4 x 18.8 Primary lens ... 4.5 x 3.7 11.7 x 9.6 Primary bar 170° 3.8 x 1.0: 9.9 x 2.6: Primary nucleus (secondary lens) ... 1.6 x 1.5 4.2 x 3.9 Secondary bar 200° 0.7 x 0.1: 1.8 x 0.26: Secondary nucleus ... 0.2 x 0.15: 0.5 x 0.4: overexposed “nucleus.” On high-resolution, short- galaxy type which had not been previously exposure photographs, this “ nucleus ” is seen to con- recognized because of insufficient resolution and/or sist of an inner or secondary lens L2 measuring overexposure. L6 x 1'5, and along its major axis a maximum of There are not enough short-exposure, large-scale luminosity forms a secondary bar B2B2 some 0.7 long photographs of barred lenticulars to make any mean- and 0.1 wide; at the center of this inner bar, a very ingful estimate of the frequency of barred structures bright secondary nucleus N2 is about Oil in diameter. in their nuclei. However, a second example was found This structure was first detected at Mount Stromlo in in another southern galaxy, NGC 1543, initially 1956 on plates taken with the long-focus Yale- classified as (R)SB0+ (de Vaucouleurs 1956h), but Columbia 66-cm refractor during a search for gal- later revised to (R)SB(s)0° (de Vaucouleurs 1963è). It axies with sharp “ astrometric ” nuclei (G. and A. de consists of a bright central primary lens (3.'5 x 2.'4) Vaucouleurs 1961, p. 76). It was confirmed in 1960 at crossed by a primary bar (2'.5 x L0)and surrounded the 29-m Cassegrain focus of the 205-cm reflector by an extremely faint outer ring (47 x 47). There are (Fig. 4 [PI. 3]) with an angular resolution limit of two slightly brighter blobs ßß' with trailing exten- about 2". By reference to nearby stars it can be seen sions toward the ends of the bar, in the center of that the two bars are not parallel, but form an angle which is a very bright nucleus (0.'35). This nucleus is of about 30°, with the inner bar leading the main bar. overexposed on the Mount Stromlo plate taken with There is even a hint of a third bar structure, or at least the 75-cm reflector, but a shorter exposure (30 min. of a diameter of maximum luminosity in the inner on Ila-O) taken with the Cordoba 152-cm reflector nucleus in p.a. ~ 130°, but shorter exposures at still and kindly communicated by J. L. Sérsic (Fig. 5 higher resolution will be needed to analyze the struc- [PI. 4]) reveals in it a secondary bar about 035 in ture of this inner nucleus. length, at the center of which the very bright secon- Some dark clouds and curved filaments d, d' are in dary nucleus is probably less than 0.'2 in diameter, evidence in the secondary lens on the east side of its since it is still overexposed even with this exposure. nucleus and of the primary bar ; these clouds are also The long axes of the primary and secondary bar again visible on blue and red light photographs taken by form a 30° angle, but here the secondary bar is on the Evans (1951) with the Radcliffe Observatory 188-cm trailing side, while it is leading in NGC 1291.* reflector and by Sérsic (1968) with the Cordoba Hence the repetition of a lens-bar-nucleus structure 152-cm reflector (Fig. 2). None are seen on the west on two different scales in barred lenticular galaxies is side of the nucleus. probably not rare, and it raises an interesting prob- Table 3 summarizes the geometry of the ring and lem in the dynamics of stellar systems. This problem bar structures in NGC 1291. is probably related to another characteristic of early- The question arises as to whether the presence of a type barred spirals and lenticulars previously noted secondary bar and nucleus structure within the nucleus of a primary bar and lens of a lenticular * A nuclear bar structure was noted in a third southern galaxy, NGC 1326, type (R)SB(r)0+, on a short-exposure plate with the galaxy is a remarkable “oddity of nature” and a Yale-Columbia refractor (G. and A. de Vaucouleurs 1961, p. 76), peculiarity of NGC 1291, or whether it is a fairly but no prints were made, and the original plate is no longer common, perhaps typical structural feature of this available to the author.

© American Astronomical Society • Provided by the NASA Astrophysics Data System 197 5ApJS. . .29. .193D (see page197) Elongation ofstarimagesiscaused byatmosphericdispersionatseczss3.Northtop. shows secondarybarstructure B B'andcentralnucleusNinwhatappearsasanunresolved primarynucleusinFigs.1and2. 2 Fig. 4.—High-resolutionphotograph ofcenterNGC1291withMcDonald205-cmStruvereflector (103a-O,65min,1960Nov.14) © American Astronomical Society •Provided by theNASA Astrophysics DataSystem PLATE 3 197 5ApJS. . .29. .193D PLATE 4 (see page197) shows barstructureinprimarynucleusatcenterofbar.Notealsobright“blobs”ßß'nearextremities Fig. 5.—PhotographofcenterNGC1543withCordoba152-cmreflector(Ila-O,30min,1960Nov.23,courtesyJ.L.Sérsic) © American Astronomical Society •Provided by theNASA Astrophysics DataSystem 197 5ApJS. . .29. .193D -2 intervals fromfi=16.78magarcsec(innersolidline)to21.28(outerdottedline).Smallblacksquareshows sizeof microdensitometer scanningaperture;hatcheddiskhalf-powerdiameterofstarimages. Isophote levelsandsizesofscanning aperturesareidentified;severalfieldstarsmarked.Axis1 islongaxisofprimarybarinp.a.170°. size ofscanningapertureareidentified ;severalfieldstarsaremarked. B Fig. 8(oppositepage).—Isophotes ofprimarylensNGC1291fromMountStromlolong-exposure plateN-33.Isophotelevelsand Fig. 7(oppositepage).—Isophotes ofprimarynucleusandmainbarNGC1291fromMount Stromloshort-exposureplateN-19. Fig. 6.—IsophotesofsecondarynucleusandbarNGC1291fromMcDonaldhigh-resolutionplate.Isophotesareat0.25 mag © American Astronomical Society •Provided by theNASA Astrophysics DataSystem 198 197 5ApJS. . .29. .193D © American Astronomical Society •Provided by theNASA Astrophysics DataSystem 197 5ApJS. . .29. .193D examples areNGC1433,3081and7079(see,e.g.,G. always stronglyinclinedtothebaraxis.Good often anelongatedobjectwhosemajoraxisisalmost and A.deVaucouleurs1961,plates12;Sandage 5 (de Vaucouleurs1959a),namelythatthenucleusis 4 200 1961, plate11;Sérsic1968,p.35). Vaucouleurs andFreeman1972,pp.259-275).On reasons forbelievingthatthetrappedparticlesin primary lens(p.a.~170°).Thedirectionoftheline for exampleNGC1068,1326,2859,3368,4736,and somewhat uncertain.Nevertheless,examinationofa tangent planetothecelestialsphereis,therefore, nodes oftheequatorialplanesystemwith circular toroidorannulus.Therearealsotheoretical and thattheouterringdoesnotdepartmuchfroma triaxial spheroidwhoseequatorialsectioniselliptical, number ofgalaxieswithsimilarouterringstructures, down tolowerbrightnesslevels;Figure9,fromthe nucleus at~2"resolution;Figure7,fromtheshort- McDonald plate,showsthesecondarylens,bar,and structure ofthegalaxyatseveralresolutionsand than dostarsintheimmediatevicinityofbar(de outer ringtendtodescribemorenearlycircularorbits 7217, suggeststhattheprimarylensisactuallya down tolessthan6percentofthenightskylevelat0.'2 shows thelensregionfromlong-exposureplate lens, bar,and“nucleus”at~0'2resolution;Figure8 exposure MountStromloplate,showstheprimary isophote levels.*Figure6,fromthelarge-scale which coincideswiththemajoraxisofelliptical to 0.'5resolutions.Notethatthemajoraxisof line oftheprimarylensandouterringregion long-exposure MountStromloplate,showstheout- right anglestothebaraxis(horizontalinFigs.69) outer ringisinpositionangle~70°andalmostat point-by-point, asexplainedinPaperIIofthisseries(deVau- plates weretracedfromseveralthousandpointslocatedmanually, contours calibratedbymeansoftheappropriateplatecharacter- plotting routinewiththeCDC6600 computerfromasquarearray couleurs andPage1962).Theconstant-densitycontoursonthe istic. ThecontoursofconstanttransmissionontheMountStromlo McDonald plateweretracedbymeansofadoubleinterpolation Skylab projectbycourtesyofDrs. J.WrayandF.Benedict.Forthe 40 nspotat//spacingwiththe PDSmicrodensitometerofthe array of720x460»3.310 density readingsrecordedwitha of 250x=6.2510data points outofatwo-dimensional The contourmapsinFigures6to9showthe * Strictlyspeaking,the“isophotes”inFigs.6-9areisodensity © American Astronomical Society •Provided by theNASA Astrophysics DataSystem V. ISOPHOTESANDSPACEORIENTATION DE VAUCOULEURS -1 -1 -2 the directionoflinenodesderivedfrom this assumption,thepositionangleofline absorption patterninthesecondarylens(§IV); shape oftheouterringandasymmetry the lattersuggeststhatobscuredeastsideof the formerrequiresthateithersoutheastor the barmarksnearsideoflens,while the northwestsideofringbeonnearside. nodes ofthediskNGC1291mustbecloseto~70° 0.88), correspondingtoaninclinationiæ29°,and Because theellipticityofringisslight(axisratio the strongestabsorptionlanesareactuallyon southeast sideofthenucleus,disagreementisnot (1875). serious, anditmaybeconcludedthatthesoutheast emerging fromthering,aradialvelocitydifferential side ofthegalaxyisinfactnearside. may beexpected. of approximately100kmsbetweenthenortheast side (approaching)andthesouthwest(receding) but thetotalwidthof21-cmemissionline the MountStromloplatesareshowninFigures10 ring (~8')shouldbesufficienttoallowatleasta observations ofthevelocityfieldwouldbedifficult, and 11,wherethelevelsofisophotesaremarked. rough estimateofthedirectionmaximumvelocity is consistentwithexpectation;thediameterof Parkes telescope(Lewis1970)centeredatthenucleus gradient, whichshouldbeclosetothatfoundabove for thelineofnodes. (axis 1)andatrightanglestoit2)derivedfrom (~ 100kms)observedwiththe14'beamof mean errorsrangingfrom+0.01atlog/ä0to±0.02near by meansofthelogIvaluesattheir18pointsintersectionwith nine luminosityprofilestracedat20°intervals—haveinternal Mount Stromloplates,thelog/levelsofisophotes—checked precision decaysrapidlytoroughly ±0.1nearlogI=—1.5and traced byanalogtechniquesatfainterlevels,wherethephotometric log /=—1.ThefaintestisophotelevelinFig.9isatJ level isthepracticallimitforusable photometry,althoughnotthe extreme detectionlimit,whichis about1maglower(§VI). 1.23 or¡i=25.1mag(arcsec).Closedisophotescouldnotbe ±0.2 nearlog/=-2(i.e.,1percent ofnightskylevel).Thislatter B There is,however,apossibleinconsistencybetween Combined withtheleft-handedspiralpattern The luminositydistributionsalongtheprimarybar Because ofthefaintnessouterring,optical VI. LUMINOSITYPROFILES 197 5ApJS. . .29. .193D -2 2 tit 24.5mags,correspondingto~10£pc brightness intheregionofminimumexceeds10 relative minimum(Alog/~0.1-0.2nearx=±3') at adistanceræ8kpcfrom thecenter. percent oftheluminositynightskyor bar majoraxis(Fig.10)andshowsonlyaslight along theminoraxis(Fig.11).Theaveragesurface monotonically decreasingbeyondthelensalong parently “vacant”zonebetweenlensandringis plate (1houratf/4on103a-O) madeinninedirec- x =±4').Actually,thesurfacebrightnessinap- luminosity enhancementintheenvelope(near ring (cf.alsoSandage’sdescriptionofNGC4736in minima existbetweentheprimarylensandouter phote maps.Thevisualimpressiongivenbyinspec- however, thattheringisonlymarkedbyaslight the HubbleAtlas);photometrydemonstrates, The directionsoftheaxesareidentifiedoniso- on tracingsofthelong-exposure MountStromlo tion ofthephotographsisthatdeepluminosity sizes ofscanningaperturesareidentified;severalfieldstars,includinglocalstandardA,andnorthdirectionmarked. B0 Fig. 9.—IsophotesoffaintouterstructureandringNGCJ291fromMountStromlolong-exposureplate.Isophotelevels and The maximumdimensions ofthegalaxydetected © American Astronomical Society •Provided by theNASA Astrophysics DataSystem SOUTHERN GALAXIES -2 -2 diameter (Figs.1,3),buttheyspreadoutanddisap- fi ~24.0mágs=13£pc. brightness ofthering(averageaxes1and2)near pear notfarfromtheminoraxisofring.Thepeak x= ±4'isatlog/ä—0.8,correspondingto arms. Thesearmsemergefromtheringnearitsmajor the galaxy,whichisinfluencedbyouterspiral tal levelfiæ28.2mags. lation oftheluminosityprofiles)toreferanisopho- Table 4.Thesedimensionsareestimated(byextrapo- not coincidewiththedirectionofmaximumextent tions at20°intervalsinpositionangleareasgiven B0 B Note thatthemajoraxisofring(~70°)does o o D (kpc)20'±1'«52 18'±1'«47 Position angle150-330° 60-240° m Maximum DetectedDimensionsofNGC1291 Diameter Maximum2a Minimum 2b m m TABLE 4 201 197 5ApJS. . .29. .193D © American Astronomical Society •Provided by theNASA Astrophysics DataSystem 197 5ApJS. . .29. .193D primary lensnearx=±L5and shghtluminosityexcessinouterringnearx=±4'. near Xj=±2'andabsenceofluminosity minimuminsideouterring. and exponentialdecayoutsideouterringbeyondx=5'.Inset:Centralregiononlargerscale;peakvalueinsaturatednucleus isnot significant. outer regionsarelesscertain(dashed lines);levelsofisophotes1to17aremarked.Notechange ofslopeatedgeprimarylens 2 2 Fig. 10(oppositepage).—LuminosityprofileofNGC1291along axis1(bar)identifiedinFigs.7to9.Saturatednucleusandfaint Fig. 11(oppositepage).—Luminosity profileofNGC1291alongaxis2identifiedinFigs.7to 9.Notechangeofslopeatedge Fig. 12.—MeanluminosityprofilesofNGC1291alongtwomainaxesshowingexcessinprimarylensaxis1nearx= F5 © American Astronomical Society •Provided by theNASA Astrophysics DataSystem 203 197 5ApJS. . .29. .193D -2 -2 /(x) alongaxes1and2oftheMountStromloplates 204 are showninFigure12.Notethegreaterluminosity between itandtheringnearxæ3'.Thereisverylittle regions ofrapidchangeslopenearx=±2'25on along axis1(baraxis)nearxæF5,correspondingto but thetransitionwithlensisgradual,especially x =±075isatlog/æ+0.2(fi»21.5mags), axis 2perpendiculartoit(Fig.11),atlogI&—0.5 the mainbaraxis1(Fig.10)andnearx=±1.'75on main componentsofalenticular galaxy:thenuclearregion(inset),lens,disk,andexponential outerenvelope. the majoraxisofprimarylensandinspace along theaxis2. difference betweenthetwoaxesoutsidering (fi ä23.2mags). B B The edgeoftheprimarylensismarkedby The edgeoftheprimary“nucleus”near Fig. 13.—Equivalentmeanluminosity profileofNGC1291asafunctionequivalentradiusr* ofisophotesshowsclearlythefour The mean(folded)luminosityprofileslog5')intheregionofouterspiralarms. couleurs 1958,1959h;Freeman1970;deVaucouleurs decay characteristicofthedisksspirals(deVau- axes 1and2.Theannulusringregionsappearin Photometry inthisregionwherelog/<—1.2 and Freeman1972)isinevidenceonlyoutsidethe log /»—0.8(2.'5 25magarcsec)istoouncertaintoplace B When theisophotesandcrosssectionsare 197 5ApJS. . .29. .193D -1 -2 just goodenoughforaroughcomparisonwiththe particularly meaningful.Forexample,Fig.13.giveslog7(0)« brighter thantheaveragevaluehefoundformajorityofnormal a valuederivedbyFreemanfrompreliminaryreductionofthe the exponentialcomponentishighlyuncertainandperhapsnot Freeman (1970),buttheextrapolatedcentralluminosity£(0)of much confidenceintheluminositygradientG(r*)= Mount Stromlodata(deVaucouleurs1956a,1959a)and2.5mag mediate betweenA=2.4kpcforNGC6744(deVau- A =—0.434/G(a)3.0kpcforNGC1291isinter- exponential disksofotherlargespirals.Interms d logI/dr*=—0.40arcmin—0.15kpc;itis spirals. does notapplytothemainbodyofgalaxyinside Vaucouleurs 1973).However,itisclearfromFigure couleurs 1963a)andA=3.3kpcforNGC1566(de the scalelengthofflatcomponent, the ring.* 13 thatinNGC1291theexponentialdistribution +1.0 orB(0)«19.2magarcsec,whichis0.5brighterthan c c * ThiskindofluminosityprofileisdesignatedtypeIIby © American Astronomical Society •Provided by theNASA Astrophysics DataSystem -2 2 for p=22.54(B)magarcsec . A inarcmin;r*arcmin;a" in arcsec;p* e Log I -1.1 -1.0 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -2.0 -1.9 -1.8 -1.7 -1.6 -1.5 -1.4 -1.3 -1.2 * CentralregionfromMcDonald plate;I 2345 2199 1472 1035 575 260 777 127 10 417 167 27.4 23.2 92 62.2 11.3 43.2 5.4 0.2 lo “p 21.8 26.6 23.1 20.2 10.3 25.9 14.5 18.5 11.7 30.7 11.2 6.5 2.3 6.1 4.0 8.7 7.6 Mean LuminosityDistributioninNGC1291* Nuclear RegionfromMcDonaldPlate 10*ZP 249.7 223.1 101.4 192.4 166.5 121.6 143.4 26.6 68.5 56.8 13.0 45.6 35.3 19.0 83.0 6.5 2.5 0.1 SOUTHERN GALAXIES 0.0358 0.0233 0.0134 0.2401 0.1117 0.0918 0.0742 0.0594 0.0464 0.0028 0.5539 0.4818 0.4027 0.3395 0.2870 0.1983 0.1614 0.1334 r* TABLE 5A = r*/r*withr*L54( scale arbitrary(notthe e variable log(P/A/)versus/(deVaucouleurs half-power integratedflux,i.e.,k(a)=is L(r*)/L isshowninFigure14.Correspondingmag- The relativeintegratedluminositycurvek(r*)= system isgivenbyphotoelectriccalibration(§VIII). and axisratiob/aarealsotabulated. where theareaAandequivalentradiusr*withineach nitude differences,m(r*)—m,arelistedincolumn derived byashortextrapolationoftheauxiliary nulus Ar*,EPistheintegratedluminositywithinr*, duct P=TxAAistheluminositywithineachan- from whichthetotal(asymptotic)luminosityLis isophote arelistedat0.1intervalsinlogI.Thepro- (12) ofTable5B.Thesemimajoraxis(along1) couleurs andPage1962)isgivenintables5A5B, by integrationoftheluminosityprofiles(deVau- 1960). ThecorrespondingtotalmagnitudeintheB e T T T b/a 0.904 0.874 0.830 0.781 0.857 0.872 0.872 0.795 0.744 0.752 0.902 The effectivemajoraxisa,definedasusualbythe The luminosityL(r*)derivedintheusualmanner e VH. INTEGRATEDLUMINOSITYDISTRIBUTION 0.0232 0.0725 0.0596 0.0482 0.0386 0.0301 0.0151 0.0087 0.0018 0.2615 0.2205 0.1559 0.1288 0.1048 0.3597 0.3128 0.1864 0.0866 log J as inTable5B);J=1 +2.40 same asinTable5B); 2.10 2.20 2.00 2.30 0.80 0.90 0.70 1.80 1.30 1.70 1.90 1.10 1.20 1.40 1.50 1.00 1.60 m-ra 2.25 5.43 6.48 9.72 2.07 4.68 2.44 2.66 2.87 3.90 3.31 3.59 4’: 26 3.07 1.47 1.59 1.75 1.91 T 20.28 17.28 20.03 17.03 16.78 20.78 20.53 18.28 17.78 17.53 16.53 19.28 18.78 18.53 18.03 19.78 19.53 19.03 205 197 5ApJS. . .29. .193D 206 © American Astronomical Society •Provided by theNASA Astrophysics DataSystem for fi=jn22.54. e 2 2 log I 7.9 1.2 1.3 0.9 7.5 7.7 7.8 Î.0 1.1 0.6 0.7 0.8 7.1 7.6 0.0 0.1 0.2 0.3 0.4 0.5 1.3 1.4 1.5 1.6 1.8: 7.2 7.3 7.4 1.0 1.1 1.7 * Units:fiinBmagarcsec; 1=1forn=22.04;Ainarcmin;

Fig. 14.—Relative integrated luminosity curves of NGC 1291 give the fraction k = L(r*)/LT of the total luminosity emitted within -2 -2 equivalent radius r* (left scale) or in regions brighter than ¿í (mag s ) (inset). Effective radius r* = 1!54 where fie = 22.54 (B mag s ) encloses half-total power (k = 1/2).

ae = 1!82 = 4.73 kpc, and the equivalent effective average for its type (cf. Fraser 1972; de Vaucouleurs radius, defined by k(r*) = is r* = 1.'54 = 4.00 kpc. and Agüero 1973). These high values indicate that the

Comparable values are ae = 4.9 kpc with dominant contribution (~ 60 percent) to the lumino- r* = 3.8 kpc for NGC 6744 (de Vaucouleurs 1963a), sity arises from the spheroidal component obeying 1/4 and ae= 7.1 kpc with r* = 4.0 kpc for M31 (de Vau- the r law for which theoretical values are couleurs 1958). NGC 1291 is clearly a giant galaxy, C2i = 2.74, C32 = 2.55; nevertheless, the contribu- almost comparable in size to the Andromeda . tion from the flat component with an exponential

(Note that ae, r* are intrinsic, i.e., metric radii, luminosity function for which C21 = 1.75, C32 = 1.61 independent of luminosity levels or detection thre- is far from negligible ( ~ 40 percent). sholds in the absence of variable nuclear point The spheroidal component dominates the lumino- source). sity distribution in the inner regions, the flat compon- The quartiles, defined by k = ^ and k = f, are at ent in the outer regions. This is made obvious by rf = 0.'62 = 1.61 kpc and rf = 3.'66 = 9.5 kpc, and Figure 15, where the relative integrated luminosity the corresponding concentration indices are curve is plotted in normalized, dimensionless units of

C2i = r*/r? = 2.48, C32 = rf/r* = 2.38, indicating a Am(p*) = m(p*) — mT versus log p* = log (r*/r*). rather strong fight concentration, perhaps above- The curve for NGC 1291 is close to the theoretical

© American Astronomical Society • Provided by the NASA Astrophysics Data System 197 5ApJS. . .29. .193D 208 dominant inN1291outtologp*=+0.3(r*ä2r*3'). disk (exponential)distributions.OrdinatesareAm(p*)=m(p*)—m,abscissaelogp*(r*/r*).Thespheroidalcomponent is 0.3. Thetransitionregioncorrespondswiththerela- approaches theexponentialintegralforlogp*>+ tively darkerannulusbetweenringandlens. spheroidal distributionforlogp*<+0.2and provisional unitofphotographicsurfaceintensityIis galaxies atthestartofthis program.AsUBVdata absence ofphotoelectricBmagnitudesforsouthern procedure wasbothconvenientandnecessaryinthe the sky(deVaucouleursandPage1962).This the zero-pointofprovisionalphotographicmag- that ofthenightskyonagivenplate(hereN-33),and derived bycomparisonof the provisionalmagnitude become available,thezero-point correctionCis nitude scaleisacalculatedsurfacemagnitudepof m, calculatedbyintegration ofthephotographic T s pg 1/4 Fig. 15.—NormalizedintegratedluminositycurveofNGC1291comparedwiththeoreticalcurvesforpurespheroidal(r) and As explainedinpreviouspapersofthisseries,the © American Astronomical Society •Provided by theNASA Astrophysics DataSystem VIII. PHOTOELECTRICCALIBRATIONAND TOTAL MAGNITUDES DE VAUCOULEURS Vaucouleurs 1972andunpublished). Angione, andFraser1968;Abies1971). several apertures(forexamplesseedeVaucouleurs, B-system magnitudesmeasuredthroughoneor included inaperture. luminosity distribution(§VII)withthephotoelectric measurement withthelargestaperture,which measured withthe91-cmreflectoratMcDonald 1973 Nov.15:6f9.020.950.46(-0.03) 1960 Dec.21L99.550.940.54-0.19 1973 Nov.10:5510.521.000.62-0.20 Observatory arecollectedinTable6.Ignoringthe 1973 Nov.12'.89.320.960.50-0.08 f Galaxymagnitudescorrectedfor starA(12.20,+0.53,0.00) * McDonaldObservatory,91-cm reflector(G.andA.de Photoelectric magnitudesandcolorsofNGC1291 Photoelectric MagnitudesandColorsofNGC1291* Date A=2rVB-VU-BC(B-P) g TABLE 6 197 5ApJS. . .29. .193D -2 where D(0)=419istheface-ondiameterinBGCstandardsystem,(b)AbscissarelativeintegratedBfluxthroughaperture and galacticextinction. k(r*). Horizontalasymptoteat(L7—V)k1.38isintegratedcolorindex.Scalerightshows(Uindexcorrectedforredshift are listedinTable7. in previoussectionsandcorrectedtothiszeropoint With theadopteddistancemoduliandanassumed colors derivedfromTables5and6are magnitudes areM(V)=—21.49andB)— galactic reddeningE(B—V)=+0.06,theabsolute 0.04; mag,andtheBsurfacemagnitudeofsky zero-point correctionis(C}=B—P0.16± required correctionsfortheincludedtwelfthmagni- Table 6areplottedinFigure16aversusaperture 20.63, orabout0.3magbrighterthanM31(deVau- couleurs 1958). Agüero 1973).* arcsec, aboutaverageforMountStromlointhe tude starA(Fig.9),theadoptedmeanvalueof unit isl¿{B)=22.20(pg)—0.1622.04mag T0 This conventionisdifferentfromthatusedbyWalker(1973),who sec z~1.0;thelatterisnotcorrectedforatmosphericextinction. seen throughtheatmosphereatvarious elevations.Acorrectionof quotes skymagnitudesreferred to apparentstellarmagnitudesas of astarmatchingtheobservedvalueskybrightnessnear McDonald figurestoplacethem ontheWalkersystem.Iam 1950s (deVaucouleurs1960;deand indebted foDr.M.Walkerfora clarificationofthispoint. T g s + 0.3to+0.5magshouldbeapplied totheMountStromloand Fig. 16.—U—Vcolor-apertureandcolor-fluxrelationsforNGC1291.(u)AbscissaislogarithmicapertureratioX=logA/D(0), The photometricparametersofNGC1291derived The total(asymptotic)apparentmagnitudeand Remarks oncolors.—TheobservedU—Vcolorsof * Notethatthismagnitudeistheextra-atmospheric V =8.45±0.04,(B-V)0.920.02, T © American Astronomical Society •Provided by theNASA Astrophysics DataSystem (U -B)=0.47±0.03. t SOUTHERN GALAXIES dard face-ondiameter(Table1);andinFigure16ft, ratio X=log^/D(0),whereD(0)istheBGCstan- reflect differentevolutionratescausedbydifferencesintotaland/or Talbot andArnett(1975)havesuggestedthatthisscattermay versus relativeintegratedluminosityk(r)(Table5B). tion. Becauseofthedominance of thespheroidalcomponentina determines therateofstarformationandheavy-elementproduc- definite valuescanbereadforX=0,(U—F)(0) The asymptotic(total)colors(B—V),{UB) can accountforthecolorexcess ofNGC1291,butquantitative galaxy ofearlytype,itisnotclear whetherthismechanismalone gas densityintheflatcomponentofdiskgalaxies,whichturn quoted above,derivedbyextrapolationtoX^+0.5 tests ofthisinterestingsuggestion willbemadeinthenearfuture or k—►1,arenecessarilyalittleuncertain.More cal dataoneffectivecolorswithinthestandard on alargesampleofgalaxies various types. 0.85 +0.42=1.27.Thecorrespondingstandard galactic extinction(—0.06,—0.05);theinclination (—0.01inB—F,0.00UB)andfor face-on diameterD(0)(G.andA.deVaucouleurs 0.98 (G.andA.deVaucouleurs1972,Table4 correction isprobablynegligible.Thusthecorrected well knownthatthereisaconsiderablecosmicscatter Fig. 7),indicatingthatNGC1291isredderthan average foritstypebyA(U—V)=+0.3mag.Itis (U —V)=1.44.Thereareasyetnoreliablestatisti- Hubble type.* in theintrinsiccolorsofgalaxieswithinagiven 1972). Theobservedcolorsmustfirstbecorrectedfor T = 1.42,andfork^(i.e.,ateffectiveradius), U —VcolorfortypeSO/a(i=0)is^^a^)* Minor axisatthreshold Major axisatthreshold Minor axis(2) Threshold surfacebrightness() Major axis(1)atp=25,0magsec" Integrated luminosityC) Equiv. gradientofexpon,component Luminosity withinp=25.0magsec“ Inclination Notes : Parameters atk=3/4 Observed peakbrightnessi,*) Peak brightnessofexpon,component() Gradient ofExpon.Comp,(baraxis) Parameters atk=1/4 Concentration indices Parameters atk=1/2(effective) 2 4 3 ! 2 3 3 3 () mag.persquareminutecorrectedby-0.16 mag.toBsystem () resolutionlimited, notsignificant () mag.persquare second (corrected) () skyunitspersquareminute Axis ratio Mean surfacebrightness() Axis ratio Axis ratio(lens) Equivalent radius Semi-major axis(baraxis) Equivalent radius Surface brightness() Equivalent radius Surface brightness() Semi-major axis(baraxis) Surface brightness() Semi-major axis(baraxis) Photometric ParametersofNGC1291 DE VAUCOULEURS TABLE 7 m -M= m -M= 0 2b(25) = 2a(25) = 1 Logi, = k(25) = G(r*) = G(a) = P(0) = J = 2b* = 2am = b/a b/a = b/a = a = a= a z 1 M = mr Li* T Vo * Vl l ^3 V r? = e r* 3 3 2 e n A = q = i = 0 = = = = r 1 1 -20.63 - 0.33:min"=0.13:kpc" - 0.31:min'=0.12:kpc" 2 32 29.75 30.0 30.9 10.412 13.31 (pg) 28.2: 29° 70° 20* ±1»= 18» ±1»= 11» 10 I75 20.7: =3.1-10oSo/pc 24.07 22.54 21.04 17.5: =5.9•10^/pc 12.30 9.37 8.9 0.88 0.915 0162 0.72 0.88 o:68 0.9: 3*92 1*82 3*66 1*54 \/T* f/r* 2 2 = 1.61kpc = 9.5kpc = 10.2kpc = 225o?/pc = 1.77kpc = 13.8o?©/pc = 2.48 0 2 196 -So/pc 2 56.5 <$®/pc 4.73 kpc 4.00 kpc 2.38 - 0.16=13.15(B) 47 kpc 52 kpc^ (lens 170°) 2 0.3; oL/pc 197 5ApJS. . .29. .193D 1/4 0.26. 0.74 (Sab,t=2).Thisresultisconsistentwiththe fact thatNGC1291isagiantsystemwithdominant ellipticals forwhich<(U—V)}=+1.34(G.and average colorofearlySO’s(L~,t=—3)andgiant values withintheprecisionof measurementsandoftheconvolutioncorrection.Evenat the verycenterwherecorrections both thehigh-resolutionMcDonald plate(dots)andthelow-resolutionMountStromlo (crosses)agreewiththecalculated presence ofafaintspiralstructureandfewblue approximates theintegratedcolorofearlyspirals(Sa, mately by extrapolation ofthecurvesinFigure16tofc-►0and component mayberoughlyestimatedasfollows:by A. deYaucouleurs1972);thisisconsistentwiththe r*(N) =48"isequivalenteffective radiusofspheroidalcomponent. exceed 2and3mag,respectively, theresidualsareonly±0.2magandaveragezero.Abscissa is fourthrootofpj=r*/r*(N),where convolved rlaw(eq.[1])inspheroidal componentofNGC1291.Within30"fromcenter,the observeddistributionsmeasuredon that inlate-typespiralsforwhich<(U—F)>æ+ the diskpopulationinanearlyspiralisnotasblue /c -»1,thecolorofspheroidalcomponentis spheroidal component(§IX).Thecoloroftheflat from thecenter,andespeciallyinnuclearregion supergiants intheouterring,butitalsoindicatesthat Sab) forwhich<(U-V)}x0.86(Sa,t=1)and or (U-V)"x0.95and{UV)'¿0.83;thiscolor of theflatcomponent(U—V)"isgivenapproxi- 57 percentofthetotalBluminosity(§IX),color (U —V)&1.38;sincetheformercontributesabout (U —V)'æ1.1andtheintegratedcoloris (r* <0.'5),theflatcomponentisabsentoratleast 0c 0c 0c T The integratedcolorofNGC1291matchesthe Fig. 17.—Comparisonofobservedequivalentluminosityprofile O=fi(r*)withcalculatedluminositydistributionCforaseeing- It maybeassumedthatinthelenswithinr*æT B EX. THESPHEROIDALCOMPONENTOFNGC1291 © American Astronomical Society •Provided by theNASA Astrophysics DataSystem 0.43(U -V)"+0.57(UV)'=1.38, r 0"l 0"5I"2"5"10"20"*30" SOUTHERN GALAXIES 1/4 5 1/4 much internalstructure.Ifthelawreallyappliesupto galaxies (deYaucouleurs1948,1953),shoulddescribe since p(0)=13.46correspondstoaspecificintensity r =0,thepeakcentraldensityisexceedinglyhigh, spheroidal componentofagalaxywhichshowsso so closelythe(equivalent)luminosityprofileof Table 8,thevaluesgivenbyequation(1)havebeen This isconfirmedbyFigure17andTable8,which very large(2to3mag)andaccordinglymoreuncer- gible. Attheverycentercalculatedcorrectionsare corrections arereliableandtheflatcomponentnegli- values agreewithin+0.15mag(A.D.=+0.05mag) volved byGaussianspreadfunctionswitherf=1"165 where =r*/r*(N).IncalculatingtheO—Cin law, whichwasfirstthoughttoapplyonlyelliptical average ofthetwoplatesagreeswithin0.02magwith short-exposure plate.Theobservedandcalculated corrected forinstrumentalresolution,i.e.,werecon- the calculatedvalues.Itisremarkablethatr tain, buttheresidualsarestillonly+0.2mag,and over mostoftherange0.005I/I1)inwhichbothobservationsand (af /rfæ0.024)fortheMcDonaldplateand r*(N) =48", B e 1/42 fi =13.46+8.3265(p$)mags",(1) B 211 197 5ApJS. . .29. .193D 1/4 c_2 an6 212 Vaucouleurs 1958,1974), peak valuesfi^15.0are where therelativelinearresolutionisgood,r extremely highstellardensities.Innearbygalaxies per cubicparsec.Thishighvalueofthepeaklumino- component ofM31(Johnson 1961;Kinman1965;de law canbetracedmuchclosertothecenterwithits order. high luminositypeak;forexampleinM32(Hubble sity isnotatallunusual,evenifitseemstoimply observed, implyingcentral densitiesofthesame £ Pdaluminositydensityinexcessof10 1930; deVaucouleurs1953)orinthespheroidal 0 0 20.37 28.91 24.16 11.90 17.22 14.41 2 0 6.70 0.17 2.15 0.80 r*(”) 2.78 1.40 5.51 3.56 4.45 9.68 8.00 © American Astronomical Society •Provided by theNASA Astrophysics DataSystem * r*(N)=48";O—Cju(obs.)(n+A/¿);fi13.46mag(arcsec). Äc0 McDonald Data(af*l"165) 0.0291 0.0167 0.0035 0 0.0742 0.0448 0.2017 0.0927 0.0580 0.1396 0.4244 0.2001 0.2479 0.1667 0.1147 0.3587 0.6022 0.5033 0 0.4130 0.243 0.4600 0.3595 0.6112 0.5518 0.5219 0.8809 0.7739 0.7401 0.6701 0.4907 0.8071 0.7056 0.6390 0.5820 0.8423 0.00 6.44 6.16 3.44 2.99 2.02 6.72 4.08 4.34 3.83 5.87 5.58 5.32 4.59 4.84 5.09 7.33c 7.01 5 5 5 -0.05 -0.05 -0.06 -0.00 -0.00 -0.01 -0.01 -0.01 -0.02 -0.02 5 -0.03 -0.00 5 5 5 5 5 0.06 0.35 3.24 1.22 0.00 0.00 A0C Spheroidal ComponentofNGC1291* ^c * DE VAUCOULEURS ♦ 0.07 ♦0.1 ♦ 0.03 +0.05 ♦0.4 -0.17: -0.17 ♦ 0.01 -0.02 -0.15 -0.09 -0.04 -0.26: -0.19 -0.12 0.00 0.00 0.00 TABLE 8 -2 a With fi=21.786mags,r*48",thecorrespond- comparison, andcorrectingforanumericalerrorin B luminosity(m=4.36). ing magnitudeism'=9.98or£'/£57percentof of thespheroidalcomponentis(deVaucouleurs1962) M31 ism'=4.91or£'/£ =60percentofthetotal tegrated magnitudeofthe spheroidalcomponentof the originalpaper(deVaucouleurs 1958),thein- the totalluminosityofgalaxy(m=9.37).For 0 0.065 0.160 0.120 0.100 0.085 0.190 0.140 r*(*) p{5(Pn)*Pc-PoPc 0.430 0.255 0.300 0.215 0.500 0.360 e T Tr T r T By integrationofequation(1),thetotalluminosity 0 0.125 0.081 0.2000 0.150 0.106 0.237 0.175 0.625 0.450 0.319 0.269 0.537 0.375 Mt. StromloData(a*»2"4) 0.5946 0.5706 0.5335 0 0.6687 0,6468 0.6223 0.6977 0.8891 0.8190 0.7825 0.7515 0.7202 L' =126&nlr*. 0.8560 te 0.00 6.26 4.95 4.44 6.82 6.00 4.75 6.51 5.81 5.18 5.57 5.38 7.13 7.40 5 5 -0.10 -0.06 -0.05 -0.09 -0.04 -0.06 -0.08 -0.01 -0.02 -0.02 -0.03 -0.01 -o•o1 5 5 3.86 ♦0.2: ♦0.6 ♦ 0.06 ♦ 0.09 ♦0.1 -0.05 ♦ 0.09 -0.02 -0.03 -0.07 ♦ 0.11 ♦ 0.02 -0.04 -0.06 0-C 197 5ApJS. . .29. .193D ponent becomessignificant,anditmaybeisolatedby subtracting fromtheobservedluminositycontrib- ution ofthespheroidalcomponentgivenbyequation Beyond r*æ0.'5thecontributionofflatcom- © American Astronomical Society •Provided by theNASA Astrophysics DataSystem X. THEFLATCOMPONENTOFNGC1291 effective radiusofspheriodalcomponent (Table8). from observedbrightnessJ(Table 5B);=r*/r*(N)r*/0!8, 6.82 6.36 6.12 6.62 5.62 4.78 7.06 5.86 5.36 5.08 4.32 3.32 2.18 7.32 1.96 2.58 1.80 1.54 1.24 1.07 0.91 0.71 0.50 1.65 1.40 0.59 0*43 * J,ftpbrightnessofflatcomponent aftersubtractionof F 0.0200 0.100 0.0398 0.0631 0.159 0.200 0.251 0.0159 0.126 0.316 0.398 0.501 6.31 0.0251 0.0316 0.0795 0.631 2.00 2.51 1.00 1.26 3.16 3.98 5.01 0.795 1.59 0.0501 1.7392 1.7236 1.7087 1.6961 1.6792 1.6451 1.6631 1.6280 1.6089 1.5874 1.5635 1.5244 1.3401 1.4273 1.2848 1.2511 1.2038 1.0754 1.2247 1.1779 1.1502 1.1158 1.0327 0.9706 0.9267 0.8891 0.8562 1 cp*)/* Flat ComponentofNGC1291 SOUTHERN GALAXIES 27.94 27.81 27.44 27.01 26.86 27.69 27.31 27.16 26.68 26.48 26.15 25.34 24.62 27.58 24.16 23.27 22.41 22.06 20.58 23.88 23.66 23.48 23.04 21.54 22.75 21.18 20.86 TABLE 9 0.0069 0.0087 0.0110 0.0078 0.0096 0.0124 0.0142 0.0163 0.0187 0.0221 0.0266 0.036 0.076 0.147 0.225 0.291 0.356 0.421 0.825 6.09 0.510 0.631 1.13 1.56 3.50 4.70 2.51 (1). TheresultsofthisoperationaregiveninTable9 and ring.Atentativedecompositionoftheluminosity outer oneoflowerdensitycorrespondingtothedisk higher densitycorrespondingtothelens(r*<2'), component hastwomainregions,theinneroneof and displayedinFigure18.Itappearsthattheflat spheroidal componentJ,fi(eq. [1]) s reduced equivalentradiusinunits of 0.0090 0.0122 0.0220 0.0164 0.0288 0.0377 0.0489 0.1039 0.1324 0.164 0.0632 0.0813 0.175 0.169 0.173 0.210 0.490 0.48 0.22 J-J 0.275 0.374 0.629 0.87 0.95 0.65 0.765 0.31 -2.046 -1.914 -1.785 -1.657 -1.541 -1.311 -1.199 -0.878 -1.424 -1.089 -0.983 -0.785 -0.757 -0.772 -0.022 -0.762 -0.678 -0.561 -0.060 -0.187 -0.319 -0.427 -0.310 -0.201 -0.116 -0.508 -0.66: log J r 27.66 27.32 26.68 26.39 26.10 25.82 25.54 25.26 25.00 27.00 24.73 24.50 24.43 24.47 24.44 24.23 22.60 23.61 22.69 23.33 23.94 23.31 23.01 23.04 22.83 24.19 23.81 213 197 5ApJS. . .29. .193D -2 -2 -2 -2 -1 -2 Two mainregions(lensanddisk+ring)areidentified;notethatJ-+0whenr*0. (dashed line)fromobservedluminosity.OrdinatesnareinBmagarcsec(above)andnormalizedfluxdensityunitsJ (below). pc). Onlytheouterenvelope(r*>5')seemsto luminosity Jæ0.95(fi&22.6magsor60 age æ0.17(ji24.5magsor£10 over abroadannularregion(2'

Fig. 19.—Computer-processed, filtered, and smoothed tracing of composite of Mount Stromlo spectrogram of NGC 1291. Abscissae are rest wæ identified. Original dispersion: 4-12 /¿Â-1.

© American Astronomical Society • Provided by the NASA Astrophysics Data System 197 5ApJS. . .29. .193D îngths correctedforprismaticdispersion.Ordinatesareonanarbitrary scaleandnonlinearinintensity.Mainlinesblendsare © American Astronomical Society •Provided by theNASA Astrophysics DataSystem- SOUTHERN GALAXIES 217 E,E+ L* L° L+ SoM So Sab Sb Sbc Se 50

100 f

40

30

20

10

O -4-2 O 2 4 t 6 Fig. 20.—Relative frequency / of outer ring structures as a function of stage t along the Hubble morphological sequence. Half height of error box at each t is standard error. High frequency at i = 0, low frequency at í = 1 may be due to classification bias. Dashed line shows probable trend of true frequencies.

Also, it will be most important to discover whether percent is not significantly greater than is indicated the 21-cm emission observed in NGC 1291 arises by Table 11 for galaxies in the same range of morpho- preferentially from the outer ring or not. logical types. There is nothing unusual, therefore, in The apparent relative deficiency of (R) structures at the presence of outer ring structures in some Seyfert type Sa (f = +1) and excess at type SO/a (t = 0) are galaxies, and this statistic does not support the sug- rather larger than the expected statistical fluctuations gestion that such structures might be somehow a result shown by the heights (&2f/^/N) of the calculated of nuclear activity. error boxes ; but this may reflect a classification bias On the other hand, it is perhaps noteworthy that (say, a tendency to assign Sa galaxies with outer rings the range of morphological types which exhibit outer to the SO/a stage). Otherwise the relative frequency ring structures (L to Sbc) coincides precisely with the of outer ring structures is seen to increase rapidly range of types in which the Seyfert phenomenon along the from ~ 0 in the earliest occurs. Among the 1500 galaxies with the best revised lenticulars to a maximum of ~ 30 percent at SO/a, types (de Vaucouleurs 1963), 750 or 50 percent fall in dropping back to 0 at Sc. the range L to Sbc (—2 ^ ^ 4-4), and of those, 10 It is of some interest that out of the dozen classical or 1.4 percent are classical Seyfert objects (G. and A. Seyfert galaxies listed in the Reference Catalogue, de Vaucouleurs 1968). This may be compared with three or four—NGC 1068 (Sb), 4151 (Sbc), 7469 (Sa), the relative frequency of outer ring structures, 4.1 and possibly NGC 3516 (L°)—have (R) or (R') struc- percent of all classified galaxies or 8.2 percent of those tures. The relative frequency of ~ 25 (or perhaps 33) in the same restricted range of types (—2 to +4).

Abies, H. D. 1971, Pub. U.S. Naval Obs., 20, Part IV, p. 15. de Vaucouleurs, G. 1948, Ann. d?Ap. 11, 247. Balkowski, C. 1973, Astr. and Ap., 29, 43. . 1953, M.N.R.A.S., 113, 134. Bottinelli, L., Gouguenheim, L., Heidmann, J., and Heidmann, N. . 1956<2, Occ. Notes R.A.S., Vol. 3, No. 18, p. 118. 1968, Ann. ¿Ap., 31, 205. . 1956b, Mem. Com. Obs. Canberra, No. 13. Danby, J. M. A. 1965, A.J., 70, 501. . 1958, Ap. J., 128, 463.

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