19 96ApJS. .105 . . .93E MD 21218. 970, PortoAlegre,RS,Brazil. Street, MS-27,Cambridge,MA02138. Homewood Campus, Baltimore,MD21218. MD 20742. cular argument.Sincetheformofinputionizingspec- abundance estimatedusingthismethodhaveverylarge material intheactivenucleus,techniqueinvolvesa cir- in nearbyAGNs.Althoughthesedataprovidesignificant emission-line strengthstomatchtheobservationsbyalter- uncertainties. trum isobservationallyverypoorlydeterminedatbest, the new andvaluableconstraintsforthemodelsofionized tially resolvedspectrophotometryofthenarrowlineregion Space Telescopehasprovidedthecapabilitytoobtain spa- siderable popularityoverthelast5years,sinceHubble line regions(LINERs)andSeyfert2galaxiescanreachup concluded thatthenitrogenabundanceofnarrow-line for theionizingspectrumandadjustingpredicted extant AGNphotoionizationmodelsassumethattheele- (in particularoxygen),anaccurateknowledgeoftheele- cooling efficiencyoftheinterstellargas,andtherefore to 5timesthesolarvalue.Thistechniquehasgainedcon- region ofasample177low-ionizationnuclearemission- nique, Storchi-Bergmann&Pastoriza(1990)have ing theelementalabundances.Forexample,usingthistech- dances oftheprincipalelementsbyassumingagivenform mental abundancesareapriorisolar,orverynearlyso. for thepreciseapplicationofthesemodels.Virtuallyall mental abundancespresentinthenearnucleargasiscritical decades, yettheelementalabundancesofnear-nuclear predicted emission-linespectrum,isstronglydependenton gas havenotbeenthoroughlyinvestigated.Sincethe nuclei (AGNs)havebeendevelopedoverthepasttwo Other modelshaveattemptedtoestimatetherelativeabun- the relativeabundancesofelementsheavierthanhelium The AstrophysicalJournalSupplementSeries,105:93-127,1996July © 19%.TheAmericanAstronomicalSociety.Allrightsreserved.PrintedinU.S.A 4 1 2 3 5 UniversityofMaryland,Department ofAstronomy,CollegePark, SpaceTelescopeScienceInstitute, 3700SanMartinDrive,Baltimore, Presentaddress:SmithsonianAstrophysical Observatory,60Garden DepartamentodeAstronomía,IF-UFRGS, CP15051,CEP91501- TheJohnsHopkins University,DepartmentofPhysics &Astronomy, Detailed photoionizationmodelsforactivegalactic Subject headings:atlases—:SeyfertHnregions abundances, abundancegradients,andkinematicsofHnregionsinactivegalaxies,fordetailed studies ofHnregionpopulationsintheseobjects. reference tothegalaxymorphology.Relevantabundancedatafromliteraturearenotedforeach vided. Salientfeaturesofeachgalaxyaredescribed,includingthedistributionHnregionswith object. Theseimageswillfinduseasfindingchartsforfollow-upspectrophotometricinvestigationsof , aninventoryofHnregionsdetectedusingtheCOSMOSimageclassifierandcentroiderispro- brated astrometricallyusingtheHubbleSpaceTelescopeGuideStarCatalogreferenceframe.Foreach Continuum-subtracted Haimagesof17nearbySeyfertgalaxiesarepresented.Thecali- © American Astronomical Society • Provided by theNASA Astrophysics Data System 1. INTRODUCTION 1,234 I. N.Evans,A.P.Koratkar,T.Storchi-Bergmann,H.Kirkpatrick, AN ATLASOFHnREGIONSINNEARBYSEYFERTGALAXIES 1,54 T. M.Heckman,andA.S.Wilson Received 1995August16;acceptedDecembers ABSTRACT abundances, whereas late-typespiralstypically havesteep abundance gradients withlowabundances neartheirHolm- galaxies haveshallowabundance gradientsandhighoverall normal galaxieshaveshown that,statistically,early-type Ardila, &Wilson1996). (e.g., Pageletal.1979;Hawley&Phillips1980;Evans & Bergmann, Wilson,&Baldwin 1995;Storchi-Bergmann, Dopita 1987;Zaritsky,Kennicutt, &Huchra1994;Storchi- regions ingalaxieswithactivenucleiarelimitednumber cited therein).However,detailedstudiesofgiant H n or nonuclearactivity(e.g.,Dinerstein1990,andreferences interstellar medium(ISM)innormalgalaxiesthathavelittle region spectra. intensities ofthestrongestemissionlinesfoundin H n cooling thegasdirectlysolelyfrommeasuredrelative abundances, electrondensity,ionizationtemperature)of the properties andphysicalconditions(forexample,elemental have beenusedextensivelyasobservationalprobesof the abundances oftheprincipalelementsresponsiblefor averaged metallicityarecorrelatedstatistically(Dopita& empirical studiesofgiantextragalacticHnregionshave shown thattheionizationparameterandelement- Evans 1986).Therefore,onecandeterminestatisticallythe “ionization parameter”arefreeparameters.Furthermore, members oftheionizingOBassociation(Shields&Searle well constrainedobservationally.Sincetheexcitingphoton spectrum isdominatedbythehottestandmostluminous number ofparametersinthesemodelsissmall,andtheyare ments otherthanhydrogenarenonzero,numericalsolu- tions totheionizationbalanceequationsarerequired.The within theactivegalaxyformanexcellentchoiceforthis well understood.GiantextragalacticHnregionslocated practical casesinwhichtherelativeabundancesofele- tion fortheionizationequilibriumcanbecomputed.In of apurehydrogenStrömgrensphere,directanalyticsolu- analysis. a muchbetteralternativeistodeterminethemobser- 1978), onlytheelementalabundancesandadimensionless vationally fromstudiesofobjectswhosephysicsisrelatively Strömgren’s photoionizationtheory.Forthesimplestcase Observations ofgiantextragalactic Hnregionsin Because ofthissimplicity,giantextragalacticHnregions The physicsofHnregionsformsasimpleapplication Rather thanassumingsolarratioelementalabundances, 19 96ApJS. .105 . . .93E ing, radialabundance gradients.Strongradial flowsarepre- inflows, thusunexpectedly minimizing,rather thanenhanc- flows (includingenhanced supernova winds)withradial mixing oftheISMthrough theinteractionofnuclearout- cal enrichmentofthegasthrough enhancedsupernovapro- formation ratesandtherefore significantlyincreasedchemi- duction. Suchprocessescould resultinsubstantialradial ways inwhichnuclearactivitymayalterthechemicalevolu- evolution oftheISMinparentgalaxy.Therearemany the localinterstellarmedium, resultinginenhancedstar radio jetsmayprovidesubstantialkineticenergyinput into tion ofthegalaxy.Forexample,nuclearwinds,shocks, and determine justhowthenuclearactivityaffectschemical vations ofthelocalISMwillprovideaverypowerfultool to intrinsic relationshipwiththenuclearactivityratherthan a simple dependenceonmorphologicaltype,thenobser- axies ofsimilarHubbletype,implyingthatthereis an statistically differentfromtheircounterpartsinnormal gal- and applyanappropiatecorrection. (Evans &Dopita1987),itiseasytoidentifywhichHn regions areaffectedbythenuclearionizingradiationfield abundance gradientthatapparentlydecreasesinward elemental abundances.Sincethesignatureofthiseffectisan the emission-linespectrumfromanHnregionwithlower principal coolantswouldbeincreased,andthiscouldmimic were appropriate,theintensitiesoflinesemittedby raising itsionizationparameter.Iftheconditionsingas activity maypartiallyionizethecircumnucleargas,so artificially low.Thisisbecausethecentralsourceofnuclear ionization region,abundancesdeterminedfromsimpleHn region models(assumingnonuclearradiationfield)maybe itself. Acaveattothismethodisthatwithinthenuclear dances usedinphotoionizationmodelsoftheactivenucleus dances typicallytwicesolar. chemical abundancesofHnregionsinfourotheractive dances inthenucleus.Thiswouldthenprovideapowerful stantial radialabundancegradientsandnuclearabun- galaxies (Storchi-Bergmannetal.1995,1996)indicatesub- are shallow(Pageletal.1979;Hawley&Phillips1980; typically solarorhigher,andthattheabundancegradients poorly understood.EarlyobservationsofHnregionsin normal galaxies,thesituationinactivegalaxiesisatpresent observational basisforconstrainingtheelementalabun- dient canbeextrapolatedtoderivetheelementalabun- chemical evolutionmodelstoexplaintheobservedabun- galaxy. Radialinflowsofmaterialarerequiredinmany abundance gradientsarewelldetermined,theobservedgra- and abundancegradientsintheseobjects.Oncetheradial Evans &Dopita1987).Morerecentdeterminationsofthe Seyfert galaxiessuggestthattheelementalabundancesare of elementalabundancesandabundancegradientsin dance gradientsinnormalspiralgalaxies(e.g.,Tinsley& toward thenucleusirrespectiveofHubbletype reach morefirmconclusionsabouttheoverallabundances statistically completesampleofactivegalaxiesisneededto trends arevisible,elementalabundancestendtoincrease Larson 1978;Mayor&Vigroux1981;LaceyFall1985). of irregulargalaxymorphologiesforwhichoftennoclear Walsh 1987,1988;&Roy1989).Withtheexception berg radii(e.g.,Shields&Searle1978;Pagel,Edmunds, Smith 1980;Edmunds&Pagel1984;Evans1986;Roy 94 If theabundancegradientsseeninactivegalaxiesare In contrasttotheextensivestudiesrevealingawiderange A comprehensivestudyofthechemicalabundancesina © American Astronomical Society • Provided by theNASA Astrophysics Data System EVANS ETAL. -1 less than90"andanisophotalratiosmaller2.5:1. diameter asreportedbydeVaucouleursetal.(1991)ofno work, thesampleobjectsarerestrictedtohaveanisophotal atlas ausefulstartingpointforfurtherspectrophotometric Véron-Cetty &Véron(1993)areincluded.Tomakethe from thegalaxy continuumdominates the emission-line Only nearbyactivegalaxieswithradialvelocitieslessthan sample ofgalaxiesselectedonthebasisseveralcriteria. 5000 kmsreportedashavingSeyfertcharacteristicsby galaxies. through thebroadband filter.However, thefluxarising line emissionfromHa+ [N n]contributessomeflux detailed studiesofgiantHnregonsinthissampleactive These datacanbeusedasastartingpointforfurther line, orthroughabroadband redfilter.Inthelattercase, region ofthespectrumredward oftheHa26563emission an interferencefiltercentered onapredominantlyline-free galaxy backgroundcontinuum wasobtainedeitherthrough of thebrightestHnregionsineachgalaxyaremeasured. Catalog (GSC)asthereferenceframe,andcoordinates metrically usingtheHubbleSpaceTelescopeGuideStar from giantextragalacticHnregions.Asindicatedin the nearby activegalaxies.Theimagesarecalibratedastro- observation log(Table1), the imageusedtoremove ponent, sincethe[Nn]linesarealsoanemissionsignature subtracted HaimagesandinventoriesofHnregionsfor17 dances andabundancegradientsinastatisticallysignificant addition totheBalmerfinefluxacomponentfrom the passes. Therefore,the“Ha”imagesactuallyinclude in sample ofAGNs,inthispaperwepresentcontinuum- NGC 1672.Adetailedstatisticalstudyisrequiredtodetect these effectsandtodifferentiatebetweenalternatescenarios. factor of2-3inthestar-formingringsNGC1097and [N n]doublet.Noattemptismadetoremovethiscom- ability offilterspreventedtheusesuchnarrowband- velocities spannedbythesamplegalaxiesandavail- the nearby[Nn]226548,6583doublet,rangeofradial bandwidth isdesirabletoisolatepureBahneremissionfrom al. (1995)findN/Oenhancedabovethesolarvaluebya associated continuumfilterimage.Althoughanarrow interference filterimagecenterednearHa26563and an LINERs andSeyfert2galaxies,Storchi-Bergmannet and possiblyS/O,ratiosinthenarrow-Uneregionsofsome modify thelocalstellarmassfunctionindiskover as partofotherinvestigationsandincludeanarrow-band Bergmann &Pastoriza(1990)findevidenceforhighN/O, timescale ofthenuclearactivity.Onsmallerscales,Storchi- winds maybeenergeticallyinsignificantordonotgreatly rate thathasbeenenhancedbynuclearactivity(Evans& ratios thatwouldbeexpectedfromasupernovaformation exist shownoclearevidenceforabnormalN/OorS/O novae andstarformationtriggeredbynuclearshocks medium asafunctionofradius.Ontheotherhand,few Dopita 1987).Thissuggeststhatenhancementsofsuper- observations ofdiskHnregionsinSeyfertgalaxiesthatdo efficiently mixtheISMandsoeliminatediscontinuitiesin the physicalandchemicalpropertiesofinterstellar dicted bymanygalaxyevolutionarymodelsandactto The observationsreportedherecompriseasubsetof As afirststeptowarddeterminingtheelementalabun- All theCCDimagesincludedinthisatlaswereobtained 2. OBSERVATIONSANDREDUCTIONS Vol. 105 19 96ApJS. .105 . . .93E least-squares polynomial solutionrelating the(x,y)posi- determine bettertheastrometric solution.]Thecoordinates greater numberofforeground starscanbeidentifiedto and theGSCplate scansaremeasuredfrom thelatter,anda of thestarsidentifiedcommon toboththecontinuumimage former isgenerallylargerthan forthelatter.Therefore,a to theHaframesincesignal-to-noise ratio(S/N)ofthe plate scan.[Thecontinuum frame isusedhereinpreference throughout thecontinuumframearevisiblealsoon the common toboththecontinuumimageandplatescan are identified.Typically,oforder20starsdistributed GSC platescansofthesamefield,andforegroundstars reference frame.Thecontinuumframeiscomparedwith the described below. tinuum imageiscomputedtoplacetheonGSC pure Ha(+[Nn])imageofthegalaxies.Thesesteps are are subtractedfromtheemission-lineframestoproduce a frames arecalibratedastrometricallytoplacetheimages on the GSCreferenceframe,andthencontinuumframes since thesearenotavailableforroughly|oftheimages. images. Nophotometriccalibrationsareapplied,however, tion anddetectorflat-fieldcorrections,areappliedtothe between thelineandcontinuumimages. flux, sothattheeffectistodecreaseslightlycontrast Following thestandardCCDcalibrations,individual No. 1,1996HnREGIONSINNEARBYSEYFERTGALAXIES For eachgalaxy,anastrometriccalibrationforthecon- Standard CCDcalibrations,includingbiaslevelsubtrac- NGC 7469., NGC 7314., NGC 7213., NGC 6814. NGC 6300. NGC 5427. NGC 5033. NGC 4939. NGC 4639. NGC 4593. NGC 3081. NGC 4051. NGC 2782. NGC 1672. NGC 1097. NGC 1068. NGC 788.. b * KPNO/CTIOdesignation. SeyfertclassificationfromVéron-Cetty&Véron1993. Object © American Astronomical Society • Provided by theNASA Astrophysics Data System Harris R 6693/76 Harris R 6606/75 7099/80 6606/75 Harris R 6606/75 6586/40 7099/80 Harris R 6606/75 Harris R 6606 7146/80 6649/76 Harris R 6563 Harris R 6606/75 Harris R 6563 6606/75 6606 7099/80 Harris R 7099/80 6606/15 7099/80 6606/75 Harris R 6606 Harris R 6648 Filter* TI no.2 TI no.2 TI no.2 TI no.2 Tek 1024no.1 Tek 1024no.1 TI no.2 TI no.2 Tek 1024no.1 Tek 1024no.1 TI no.2 TI no.2 Tek 2048no.3 Tek 2048no.3 Tek no.2 Tek no.2 RCA no.5 RCA no.5 TI no.2 TI no.2 Tek 1024no.1 Tek 1024no.1 RCA no.5 RCA no.5 Tek 1024no.1 Tek 1024no.1 Tek 1024no.1 RCA no.2 RCA no.2 Tek 1024no.1 TI no.2 TI no.2 TI no.2 TI no.2 Detector* CTIO 1.5m CTIO 1.5m CTIO 1.5m CTIO 1.5m CTIO 1.5m CTIO 1.5m CTIO 1.5m CTIO 1.5m CTIO 1.5m CTIO 1.5m CTIO 1.5m CTIO 1.5m CTIO 1.5m KPNO 2.1m KPNO 2.1m CTIO 1.5m CTIO 1.5m KPNO 2.1m KPNO 2.1m CTIO 1.5m CTIO 1.5m KPNO 2.1m CTIO 1.5m KPNO 2.1m KPNO 2.1m KPNO 2.1m CTIO 1.5m CTIO 1.5m CTIO 1.5m CTIO 1.5m KPNO 2.1m KPNO 2.1m KPNO 2.1m KPNO 2.1m Source Observation Log TABLE 1 scales, whereas thescaleofGSCplate scansissignifi- identified, since thetwoimageshavevery similarplate continuum imageasthereference frameallowsmorefea- tures commontoboththeHa andcontinuumimagestobe they canbealignedwitheach other.Usingthecalibrated racy withwhichtheon-and off-bandimagescanbesub- tracted isdeterminedinpart bytheaccuracywithwhich using theGSCplatescansas areferencebecausetheaccu- This isdoneratherthancomputingaseparatesolution employing thecontinuumimageasreferenceframe. et al.1990). tinuum image,theHaimageiscalibratedastrometrically, inherent intheGSC.Themagnitudeoftheseerrorsdepends Absolute astrometryislimitedbytheastrometricerrors minations inagivenimageislimitedbytheseuncertainties. each of£andrj.Theaccuracydifferentialpositiondeter- on thechoiceofreferencecatalogbutisorder0"5(Russell worst-case solutionshavermsuncertaintiesoforder0"2 in (rms) uncertaintiesofthederivedastrometricsolutionare image. tion formsanaccurateastrometriccalibrationforthe nomial solutionincorporatingbothtranslationandrota- nates iscomputed.ForeachCCDframe,alinearpoly- tions ofthestarsonCCDframetotheirGSCcoordi- Exposure ~0''l ineachaxisrelativetotheGSCreferenceframe.The 225 900 600 300 600 900 600 300 600 900 900 450 After anastrometricsolutionisdeterminedforthecon- 300 600 900 255 600 900 600 For mostofthecontinuumimages,rootmeansquare 300 600 100 600 600 600 150 150 900 300 150 (s) 75 60 20 40 1988 Oct7 1988 Oct7 1988 Oct7 1988 Oct7 1991 Oct8 1991 Oct8 1988 Oct7 1992 Apr9 1992 Apr9 1988 Oct7 1990 Mar21 1990 Mar21 1988 Dec30 1988 Dec30 1994 Apr6 1994 Apr6 1991 Jun7 1991 Jun7 1990 Mar19 1990 Mar19 1989 Jan1 1989 Jan1 1992 Apr9 1992 Apr9 1990 Jan20 1990 Jan20 1991 Oct8 1991 Oct7 1991 Oct7 1991 Oct7 1989 Jan2 1989 Jan2 1989 Jan1 1989 Jan1 Date b Classification Morphology Seyfert 1 Seyfert 1 Seyfert 1 Seyfert 2 Seyfert 1 Seyfert 2 Seyfert 1 Seyfert Seyfert 1 Seyfert 1 Seyfert 1 Seyfert 2 Seyfert 2 Seyfert 2 Seyfert 1 Seyfert 1 Seyfert 2 (R) SAB(rs)a SAB (rs)be SA (s)a SB (rs)b (R) SB(rs)b SAB (rs)be SA (s)cpec SA (s)c (R) SAB(r)0/a SA (s)be SAB (rs)be SAB (rs)be SAB (rs)apec (RS) SA(rs)b SB (s)b SB (s)b SA (s)0/a 95 19 96ApJS. .105 . . .93E measure positionsofsources inthecontinuum-subtracted identified inventory objectsthataredetected atthe95% Ha image.Table 2listsforeachgalaxy all theCOSMOS sky. reader inidentificationand orientationofthefieldon eliminate themmanuallysince(a)theresidualstellar fea- tures arequitedistinctive, and (b)theirpresenceaidsthe subtracted emission-lineimages,wemakenoattempt to profiles arenotcorrectlyremovedinthecontinuum- emission-line andcontinuumimages,produceresidual the fieldofviewCCDframes.Althoughthesestellar image featuresforanyforegroundstarsthatareincluded in small variationsbetweenthepoint-spreadfunctionsfor the tinuum fluxesthroughtheon-andoff-bandfilters, and preting thedata.Thedifferingcontributionsofstellarcon- 1979; MacGillivray&Stobie 1984)isusedtodetectand to distinguishregionsinwhichcareisrequiredwheninter- tures arereadilyapparentintheimages,allowingreader the imagestoremovecosmeticdefects.Ingeneral,such fea- H iiregionmorphology.Wehavechosenfurthernottoedit that iswrappedasnecessarytoenhancethedetailof level, wehavechoseninthesecasestouseanintensityscale faintest objectsandtheskybackgroundtoanunacceptable tion. the point-spreadfunctionsofimagespriortosubtrac- Therefore, nomodificationstoeitheroftheHaorcontin- morphologically smoothonthescaleofafewarcseconds. intensity scale.Ratherthansaturatingthedisplayof brightest Hasourcesorreducingthecontrastbetween larger thancanbeaccommodatedusingasinglelinear uum framesareperformedtocorrectfordifferencesbetween ground detectedinthecontinuumimagesis image. Withtheexceptionofforegroundstars(and,for continuum frameissubtractedfromtheHaaftersuit- metric frames.Followingwarping,theskymodeisdeter- regions neartheskylevelandbrightestHnis cases, thedynamicrangebetweenfaintestvisibleHn uum knotsassociatedwithHnregions),thegalaxyback- observations obtainedusingabroadbandRfilter,contin- result inareasofnegativeresidualfluxthesubtracted the resultingimageandismaximumvaluethatdoesnot able scalingoftheformer.Thefactorbywhichcontin- mined andremovedfromeachimage.Finally,the uum frameisscaleddeterminedbyvisualinspectionof residual differencesbetweentheHaandcontinuumastro- field. light theHiiregionsanddiffuseHaemission.Inmost entation inthisfigureusesalinearintensitydisplaytohigh- same astrometricsolutionastheHaimagetoremoveany tinuum imageiswarpedusingbilinearinterpolationtothe contribute negligiblyinquadraturetothetotaluncer- 96 Ha imageisusedasthefinalastrometriccalibrationfor tainties discussedabove.Theastrometricsolutionforthe hundredths ofanarcsecondineachaxis,andthereforethey metric gridintheGSCreferenceframeoverlain.Thepres- reference frameasthecontinuumimagearetypicallyafew calibration requiredtoplacetheHaimageonsame cantly different.Thermsuncertaintiesoftheastrometric image isshowninFigure1(Plates1-17),withanastro- The COSMOSimageclassifier andcentroider(Lutz Once theastrometriccalibrationsarecomputed,con- For eachofthegalaxies,continuum-subtractedHa © American Astronomical Society • Provided by theNASA Astrophysics Data System 3. THEATLAS EVANS ETAL. measured usingtheCOSMOSclassifieringeneralrepeat identifying sourcesforfurtherstudy.Althoughpositions cantly numbercountsofobjects,buttheyarenotcritical for compact sourcemayornotbeincluded,dependingon surface brightnessfallsoff.Thesebiasesmayaffectsignifi- the choiceofintensitythresholdsandrateatwhich the classifier, andextendedregionsassociatedwithabright emission-line sources. Weestimatethatthis contamination bright componentsarenotwelldetectedbytheCOSMOS detected. Faintcomponentslocatedincloseproximityto determines howeasilyindividualcomponentscanbe identification asanemission-line sourceisambiguous. emission-line complex.We exclude objectsforwhichthe wide rangeofintensitythresholdsettings.Fornoncompact classifier fortheseobjectsisrepeatableto~0''l-0"2overa of thefaintest objectsmaybeerroneously classifiedas However, forfieldswithnumerous foregroundstars,some for thoseobjectswhichthe continuumimageisobtained objects andcrowdedregions,themorphologyofsource using abroadbandRfilter thatincludestheHa-h[Nii] distinguished easilyfromfaintforegroundstars.Thisis par- of-gravity centroidpositiondeterminedbytheCOSMOS to objectsdetectedatthe95%confidencelevel.Thecenter- detected downtoS/N~1.5,withsomeincompleteness. morphology andcrowding.Isolatedcompactobjectscanbe ticularly trueforgalaxiesat lowgalacticlatitude,andalso dependence. crowded orextendedregionsresultsinthecenter-of-gravity However, werestricttheinventoryinformationinTable2 position havinga(possiblystrong)intensitythreshold depends onthelocalS/Nofimage,contrastbetween of symmetrythelocalsurfacebrightnessmorphology for accurately foraspecificintensitythresholdsetting,the lack the sourceandsurroundingbackground, information ismoreimportantthanextendedsourcedata. identify sourcesforfuturemultiobjectfiberspectrograph observations; forthispurpose,small-scalesourceintensity because weexpecttheinventoryinformationtobeused crowded regionoftheframe,anintensitythresholdthatis than simplysummingovertheextendedemissionregion regions. Thisapproachforcrowdedsourcesischosenrather area andintegratedintensityforsourcesincrowded inventory informationinTable2willunderstatethetotal mation forthatobject.However,ifanobjectislocatedina high enoughtoisolatethesourceisused.Therefore, the sourceclearlyisusedtodetermineinventoryinfor- determined byvisualinspection.Foremission-linesources detection thresholdsareexecuted.Theobject that areisolated,thelowestdetectionthresholddefines thresholds foreachcontinuum-subtractedHaimageare sities, severalrunsoftheclassifierwithdifferentobject photometric studies. can beusedasaselectioncriterionforfuturespectro- mate oftherelativemeansurfacebrightnessinemissionand where aisthesemimajoraxisandbsemiminoraxis), integrated intensityandobjectareaprovidesasimpleesti- and theP.A.ofmajoraxis,aregiven.Comparison sities abovetheskybackground,elhpticity(1—b/a, position oftheobjectcentergravity(equinoxJ2000), confidence level.Foreachinventoryobject,theastrometric object area(seebelow),theintegratedandpeakpixelinten- In somecases,isolatedcompactHnregionscannotbe The abilitytoidentifyindividualemission-linesources To identifysourcesspanningawiderangeofpeakinten- 19 9 6Ap JS . .105. . .93: Evans etal.(see105,96) reference frame(J2000).ThedataarescaledlinearlyinDNasshownby theintensitybarbeloweachimage. Fig. 1.—Continuum-subtractedHaimagesforeachofthe17Seyfert galaxiesincludedintheHnregionatlas.CoordinategridoverlaysareGSC Û Ö c c3 q c 0 © American Astronomical Society •Provided bythe NASAAstrophysics Data System 02 012010 02 0100 NGC 788 0 1020 30 Right Ascension Intensity PLATE 1 Evans etal.(see105,96) 19 96ApJS. .105 . . .93E PLATE 2 Q Ö C 03 03 o c -00 0400 -00 0200 +00 00 +00 0200 © American Astronomical Society •Provided bythe NASAAstrophysics Data System 0 100200 300 400500 NGC 1068 02 425040 02 4230 Fig. 1.—Continued Right Ascension Intensity 19 96ApJS. .105 . . .93E Evans etal.(see105,96) © American Astronomical Society •Provided bythe NASAAstrophysics Data System 0 200400600 8001000 02 463015 Fig. 1.—Continued Right Ascension Intensity PLATE 3 Evans etal.(see105,96) 19 9 6Ap JS . .105. . .93: PLATE 4 Û "o _C 0) 03 g c -59 1800 -59 1600 -59 1400 -59 1200 © American Astronomical Society •Provided bythe NASAAstrophysics Data System NGC 1672 ■ .1 JU 04 4600 o, 500 J 1L. WW üX O ^ " aOí Fig. 1.—Continued 1000 1500 Right Ascension i—i tJ -O Intensity 04 4540 o # • * S ■ 2000 04 4520 2500 19 96ApJS. .105 . . .93E Evans etal.(see105,96)

© American Astronomical Society •Provided bythe NASAAstrophysics Data System Declination 13 13451330 13 15 NGC 5033 0 100200300 400500 Fig. 1.—Continued Right Ascension Intensity PLATE 11 Evans etal.(see105,96) 19 96ApJS. .105. . .93 PLATE 12 © American Astronomical Society •Provided bythe NASAAstrophysics Data System 14 033025 14 0320 0 50100150 200250 Fig. 1.—Continued Right Ascension Intensity 19 96ApJS. .105 . . .93E Evans etal.(see105,96) © American Astronomical Society •Provided bythe NASAAstrophysics Data System NGC 6300 0 2040 60 80100 Fig. 1.—Continued Intensity PLATE 13 19 96ApJS. .105. . .93 Evans etal.(see105,96) PLATE 14 13 Û © c c3 o c -10 2100 -10 2000 -10 1900 -10 1800 © American Astronomical Society •Provided bythe NASAAstrophysics Data System NGC 6814 19 424540 19 4235 Fig. 1.—Continued Right Ascension Intensity Evans etal.(see105,96)

© American Astronomical Society •Provided bythe NASAAstrophysics Data System Declination NGC 7213 0 2040 60 Fig. 1.—Continued Right Ascension Intensity PLATE 15 19 96ApJS. .105. . .93 Evans etal.(see105,96) PLATE 16 "5 Û -f—» c co o c 0) -26 0300 -26 0200 -26 0400 © American Astronomical Society •Provided bythe NASAAstrophysics Data System NGC 7314 22 355045 22 3540 Fig. 1.—Continued Right Ascension Intensity 19 96ApJS. .105 . . .93E Evans etal.(see105,96) Q "5 O) c « g c © American Astronomical Society •Provided bythe NASAAstrophysics Data System +08 5100 +08 5200 +08 5300 +08 5400 0 200400600 800 10001200 NGC 7469 23 0320 Fig. 1.—Continued Right Ascension Intensity 23 0315 23 0310 PLATE 17 o O'! 00 LO ^0 a

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TABLE 2—Continued © American Astronomical Society • Provided bythe NASA Astrophysics Data System 122 123

© American Astronomical Society • Provided by the NASA Astrophysics Data System 19 96ApJS. .105 . . .93E timescale short comparedtotheageof galaxy. tends toproduce strongradialflowsinto thenucleusona tions bySchwarz(1981)demonstrated thatsuchapotential the near-infrared(Scovilleet al.1988).Numericalsimula- tional potentialproducedby astellarbarthatisdetectedin radial abundancegradient may berelatedtothegravita- consistent withzeroradial gradient.Thelackofasteep measurements intheinnerdisk byZaritskyetal.(1994)are for aradialabundancegradient.Hnregion abundant comparedtothesolarvalueandfindnoevidence derive ameanoxygenabundancethatisslightlyover- metry of13giantextragalacticHnregionslocatedwithin the innerone-thirdofdisk,Evans&Dopita(1987) complex offainterHnregionsassociatedwiththesouthern ring surroundsthenucleus.Fromopticalspectrophoto- regions isassociatedwiththespiralarms,andastarburst arm. The spiralarmsarebrightesttothenorthwestof the northeastofnucleus.Alargesystembright H n high-excitation gasdistributedinaconelikemorphology to emission-line imaging(Pogge1988)revealthepresence of H iiregionsthattracethespiralarm,togetherwitha nucleus, andFigure1revealsastringofbright,compact with faintspiralarmsvisible~30"radiusfromthenucleus. (Antonucci &Miller1985)revealbroadBalmer-lineemis- tometry (Evans&Dopita1986)andnarrow-band sion associatedwiththenucleus,whileopticalspectropho- Morphologically, thegalaxyisalenticular/early-typespiral optical (e.g.,Hamuy&Maza1987;WagnerKay Wyatt, &Davis(1982),NGC788hasbeenobservedinthe investigated extensively.Spectropolarimetricobservations sources. should notexceedapproximatelyl%-2%forthefaintest 1989), andmillimeter(Heckmanetal.1989)wavebands. 1994; Cruz-Gonzalezetal.1994),radio(Ulvestad&Wilson 124 The prototypicalSeyfert2galaxy,NGC1068,hasbeen Since beingidentifiedasaSeyfertgalaxybyHuchra, 4. NOTESONINDIVIDUALGALAXIES © American Astronomical Society • Provided by theNASA Astrophysics Data System 4.2. NGC1068 4.1. NGC788 Series, Vol.7. No. Note.— Table2ispublishedinitsentiretycomputer-readableformtheAASCD-ROM 18 17 15 14 13 10 16 12 11 4 9 8 6 5 3 7 23 03 23 03 23 03 23 03 23 03 23 03 23 03 23 03 23 03 23 03 23 03 23 03 23 03 23 03 23 03 23 03 (J2000) a 16.95 16.61 16.25 16.24 16.22 16.01 15.61 15.48 15.25 15.10 15.05 14.88 14.73 15.25 15.03 14.91 +085216.6 +08 5218.7 +0852 42.7 +08 5230.8 +0852 07.9 +08 5256.4 +08 5249.2 +0852 29.5 +0852 24.2 +08 5221.2 +08 5249.5 +0852 48.6 +085242.7 +08 5236.2 +0852 27.7 +08 5254.3 (J2000) S EVANS ETAL. TABLE 2—Continued 2 (arcsec) Area 15.7 17.0 4.2 4.8 5.5 4.5 6.1 6.8 3.5 3.5 7.1 7.0 1.9 1.3 1.6 1.9 enhanced throughtheinteractionofradialgasflowsalong the barwithrotationalflows inthespiralstructure. sect. Thestarformationrateinthesecomplexesmay be the regionsinwhichbarandinnerspiralarmsinter- brightest andlargestHnregioncomplexesarelocatednear from wherethearmsconnecttoendsofbar well beyond 3'radius.Outsidethenucleusstarburstring, the readily visibletracersofthestructurespiralarms with thebarbeyond~50"fromnucleus.They are well asthegradientofoxygenabundance,areobtained by regions bothintheringandfurtheroutalongbar,as emission-line knotswithin ~10" radius.Withinthestar- Storchi-Bergmann etal.(1995). energy distributionofthestarburstringthatmetal oxygen abundance thatisapproximately twicethesolar solar values.GaseousabundancesforindividualHn abundances inthegasareenhancedslightlyrelativeto burst region, Storchi-Bergmann etal.(1994) measurean rounded byastarburstregion containingseveralbrightHa & Kinney(1994)determinefromtheUVtonear-IRspectral resonance (e.g.,Hummel,VanDerHulst,&Keel1987; formationthatmayberelatedtotheinnerLindblad Storchi-Bergmann etal.1995).Storchi-Bergmann,Calzetti, nuclear ringofHnregionsdelineatesamassiveburst nucleus (Storchi-Bergmann,Baldwin,&Wilson1993).A blue continuumimpliesthatNGC1097containsaSeyfert1 appearance ofbroadBalmer-lineemissionandafeatureless the opticalemission-linespectrum(Keel1983b),recent regions tracespiralarmstructureouttoadistanceoforder regions anddiffuseHaemissionassociatedwiththeinner rounded byanagglomerationoffainter,compactHn spiral armswithinaradiusofapproximatelyV.GiantHn y fromthenucleus. ~10"-15" inradiusfromthenucleus.Theringissur- Numerous complexesofgiantHnregionsareassociated The nucleusofthisbarredspiral Seyfert2galaxyissur- Although originallyclassifiedasaLINERonthebasisof Figure 1revealsaringofbright,compactHnregions 4380 Total 1220 1200 1140 DN 360 676 297 796 150 125 141 91.2 61.1 62.4 77.0 70.1 Peak 102 114 196 134 DN 22.9 65.0 42.6 43.9 49.2 49.2 36.3 41.3 20.9 87.9 28.1 18.7 4.4. NGC1672 4.3. NGC1097 0.16 0.11 0.52 0.30 0.25 0.08 0.41 0.35 0.42 0.44 0.30 0.59 0.31 0.19 0.19 0.32 P.A. 044 067 008 094 017 029 010 007 002 027 020 075 028 138 160 170 Vol. 105 19 96ApJS. .105 . . .93E with P.A.~60°leadstoaringstructureradius25"- component visibleouttoaradiusof~10",andsuperim- Hoag’s object.Brosch(1985)suggeststhatinthelatter 30". Theouterringstructureissimilartothatobservedin is evidencefor widespread,diffuseHaemission ratherthan posed innerbarlikestructurewithP.A.~120°.Afaintbar Imaging revealsabrightnucleuswithanapparentbulge distinct compact Hasources. regions tracethespiralarms structureoutto~2'radius. from NGC4051by~240kpc. recently obtainedadditionalopticalspectrophotometry. detected fromthenucleus.Cruz-Gonzalezetal.(1994) the nucleus,downto~15"radius. Withinthisradius,there Compact Hnregionsarediscernible individuallycloserto through interactionswithNGC 4013,whichisseparated that theSeyfertactivitymayhavebeentriggeredtidally Ward 1988).Byrd,Sundelius,&Valtonen(1987)suggest and continuumcontourmapsoftheinnerfewarcseconds type ringgalaxyasaSeyfert2onthebasisofspectroscopic surrounding thenucleusareavailable(Haniff,Wilson, & subject ofmanyintensivestudies(e.g.,deRobertis & observations ofnarrow,high-ionizationemission-lines is detectedatlargerradii. Osterbrock 1984;Pogge1989;Veilleux1991;Huntet al. bar/bulge component. possibly faint,diffuseHaemissionassociatedwiththeinner when thebarisstillclearlyvisible.Figure1revealsnumer- represents anearlierstageintheevolutionofsuchobject, visible ~30"Wofthenucleus.FainterdiffuseHaemission emission detectedbyBoeretal.Acomplexofbrightbut entire regionwithin~14"ofthenucleus,inadditionto contour mapofthebrightestHaemission. the nucleus,andastringofbright,compactHnregionsis (Terlevich &Melnick1985).Smith(1994)hasobtained ous Hnregionsassociatedwiththemainstellarring,and result ofanextremebarinstability.Possibly,NGC3081 object theringwasformednomorethanafewGyragoas relatively diffuseHnregionsisvisibleclearly20"-25"Nof high-quality broadbandBVRIimagesandpresentsa 4"-8" Softhecentralstarburst.Theyconcludethatlocal 1992; Kuniedaetal.1992).Detailedopticalemission-line ISM iseithershockheatedorphotoionizedbywarmers & Keel(1992)identifyashellofhighlyionizedmaterial several HnregionsreportedbyHodge&Kennicutt(1983). type spiralgalaxycontaininganuclearstarburstand Using spatiallyresolvedspectrophotometry,Boer,Schulz, inner diskwithin~1'. (1995). BrightHnregioncomplexestracethebarandinner appears colocatedwithfaintcompactHnregionsinthe and outerspiralarms.Additionally,diffuseHaemission determinations, arepresentedbyStorchi-Bergmannetal. No. 1,1996 the ringandfurtherout,withabundancesgradient value. DetailedobservationsofindividualHnregionsin Figure 1demonstratesthat thebrightestgiantHn This nucleusofthisfamousSeyfert1galaxyhasbeenthe Phillips, Charles,&Baldwin(1983)identifiedthisearly- Our data(Fig.1)revealdiffuseHaemissioncoveringthe NGC 2782(Arp215)isawell-studied,peculiar,early- © American Astronomical Society • Provided by theNASA Astrophysics Data System 4.6. NGC3081 4.7. NGC4051 4.5. NGC2782 H ilREGIONSINNEARBYSEYFERTGALAXIES imaging isreportedbyseveral authors(e.g.,Keel1983a; Elmegreen &1983; Pogge1989a). sented byMcAlaryetal.(1983) andRodriguezEspinoza, near (0.35-3.5/un)infrared and IRASphotometryarepre- Rudy, &Jones(1987),respectively. Opticalemission-line photometry isreportedbyKennicutt&Kent(1983),while NGC 5033,and theyconcludethatthere isastrongabun- estimate theabundances ofeightHiiregions inthediskof from thenucleus(Shuder1980;Keel1983c;Filippenko & Sargent 1985).Large(3')apertureHa+[Nn]226548,6583 emission-line strengths. element appearstorequireafactorof~2.5overabundance with respecttooxygenforthemodelsmatchobserved (Zism ~1-2Z©)withtheexceptionofnitrogen.Thelatter models thattheabundancesareapproximatelysolar nucleus isinvestigatedbyStorchi-Bergmann,Bica,&Pas- lation andemission-linegaswithin5kpcoftheactive viously byHodge&Kennicutt(1983).Thestellarpopu- this late-typegalaxy.Haimageshavebeenpublishedpre- toriza (1990a,b).Theyconcludebasedonphotoionization 1 onthebasisofobservationsbroadBalmeremission ends ofthebarthroughmechanicalinteractionsinlocal mation maybeenhancedintheregionsofarmsnear ISM. appears tobelargestinthespiralarmsnearendsof concentration andsurfacebrightnessoftheHnregions bar, althoughnonearevisiblealongthebaritself.Starfor- from thegalaxyat1650Âand2000arepublishedby H iiregionsvisiblydistributedalongthespiralarms.The Inspection ofFigure1revealsnumerousgiantextragalactic Deharveng etal.(1994)andDonas(1987),respectively. Ha +[Nii]226548,6583and[Om]25007CCDimagesof this object.MeasurementsofthetotalUVcontinuumflux narily triggerstarformationisrelativelyweakinthisobject. that theradialgasmixingalongbarwouldordi- tributed alongthebar.Onepossibleexplanationmaybe paper, HnregionsinNGC4593donotappeartobedis- emission. Unlikemostotherbarredspiralsdiscussedinthis compact, withlittleevidenceforthepresenceofdiffuseHa readily visibleinFigure1.MostoftheHnregionsare structure fromaninnerradiusof~30"outto~80"are Gaskell 1991)andX-ray(Ghosh&Soundarajaperumal ultraviolet (e.g.,Claveletal.1983;Koratkar& the opticalnuclearcontinuum,whichisobservedalsoat several epochs.Thesedatashowconsiderablevariabilityof tometry (e.g.,Kollatschny&Fricke1985;Crenshaw1986; Williger 1993;Kotilainen&Ward1994),andspectropho- photometry (e.g.,Winkleretal.1992;Kotilainen,Ward,& spiral havebeeninvestigatedindetail.Opticalandinfrared 1993) wavelengths. Morris &Ward1988)ofthenucleushasbeenobtainedat The late-typeX-ray-brightspiralisclassifiedasaSeyfert Zaritsky etal.(1994)useoptical spectrophotometryto Numerous Hiiregionsdelineatethespiralstructurein Pogge (1989)hasobtainedbothnarrow-band Giant extragalacticHnregionstracingthespiralarm The propertiesoftheSeyfert1nucleusinthisbarred 4.11. NGC5033 4.10. NGC4939 4.9. NGC4639 4.8. NGC4593 125 19 96ApJS. .105 . . .93E inner spiralarms areparticularlycongested. AnHaimage regions tracing boththeinnerandouter spiralarms.The scales. Figure1revealsnumerous giantextragalacticHn tions andcontinuumvariability occurringonshortertime- period ofafewmonthsto fewyears,withsmallervaria- broad nuclearHjßfluxcan vary byfactorsof2-4overa metry (e.g.,Morris&Ward 1988;Sekiguchi&Menzies gated extensively.Opticalphotometryandspectrophoto- interior tothering,althoughthisismostlydiffuse.This is a the nucleus.ThereissomeevidenceforweakHaemission wealth ofcompactHnregionsanddiffuseHaemission, both intheringstructureandextendingouttoover2'from Our continuum-subtractedHaimage(Fig.1)revealsa image oftheobjectispresentedbyRyder&Dopita(1993). enhanced byafactorof~3abovethesolarvalue.AnHa models, theyconcludedthatthenuclearN/Oratiomustbe etry, andonthebasisofcomparisonwithphotoionization (1989), whoconcludethatshockheatingmayplayarolein sources. the ionizationbalanceofnucleus.Storchi-Bergmann& optical spectrawereobtainedbyBonatto,Bica,&Alloin small fractionofthesemaybemisclassifiedasemission-line trophotometry obtainedbyPhillipsetal.(1983).Additional basis ofthenuclearemission-lineprofilesfromopticalspec- location. mation thathasproducedtheHnregioncomplexatthis flows inthelocalISMmayberesponsibleforstarfor- 1990; Winkleretal.1992; Winkler 1992)revealthatthe ous faintforegroundstarsinthefield.Asdiscussed§ 3, a low galacticlatitudeobjectandsuffersfromhavingnumer- located inthewesternarmatpointwhich Pastoriza (1989)obtainedfurtheropticalspectrophotom- nical interactionsduetochangesinthedirectionofgas abruptly changesdirection.Onecanspeculatethatmecha- eastern spiralarm,althoughthereisabrightcomplex from thenucleus.TheHnregionsappearbrightestin complexes tracethedistortedspiralarmsouttoatleastT (Giuricin etal.1990)fluxesareavailableintheliterature. line (Keeletal.1985),infrared(Giuricin1994),andradio been obtainedbyKennicutt&Keel(1984),whosuggest H iiregionswitharadiusof~5".Numerousnregion the galaxy-galaxyinteractions.Opticalnuclearemission- that thenuclearactivitymayhavebeeninducedthrough which isseparatedfromNGC5427by~25kpc(Dahari galaxies Arp271.TheothercomponentisNGC5426, ments. providing anexcellentsampleforabundancemeasure- continuum-subtracted Haimage(Fig.1)revealsthepres- ence ofbrightHnregionsintheinnerspiralarmsdownto regions clearlytracethespiralarmsouttoatleast4'radius, a distanceof~5"fromthenucleus.GiantextragalacticHn oxygen abundancethatisapproximatelytwicesolar.Our dance gradient,withaninferrednuclear(zeroradius) 1984). OpticalspectraofthenucleusNGC5427have 126 The nuclearvariabilityofNGC6814hasbeeninvesti- NGC 6300wasfirstclassifiedasaSeyfert2galaxyonthe NGC 5427isonecomponentoftheinteractingpair Figure 1revealsthepresenceofapossiblenuclearring © American Astronomical Society • Provided by theNASA Astrophysics Data System 4.14. NGC6814 4.13. NGC6300 4.12. NGC5427 EVANS ETAL. from thenucleus. extragalactic Hnregionsare evidentandappeartotrace latter authorsconcludethattheelementalabundances at Wilson etal.(1986)andBonatto&Pastoriza(1990). The obtaining the images ofseveraltheobjects includedin the weakspiralarmstructure outtoadistanceoforder50" laying adiffuseHabackground areclearlyvisiblewithin factor of2overthesolarvalue.CompactHnregionsover- exception ofnitrogen,whichappearstobeenhancedby a nuclear region. al. (1994)presentspecklemaskingimagesoftheinner regions arepublishedbyWilsonetal.(1991),andMauder et (Westin 1985).Additionalopticalemission-lineandcontin- uum images,andradiocontinuumdata,ofthenuclear cumnuclear ring.Thismaybedrivenbycloud-cloudcolli- sions duetotheoutflowofmaterialfromnucleus et al.1982;Keto1992;Miles,Houck,&Hayward and immediatelysurroundingregions(deRobertis&Pogge wave bandsthroughtomedium-IRwavelengths(e.g.,Rudy detail fromX-ray(Brandtetal.1993)andUV(Westin1984) (e.g., Kotilainenetal.1993;&Ward1994). regions hasbeenobtainedbyKotilainenandcoworkers ~10" ofthenucleusinFigure 1.Furtherout,afewgiant 1986) showevidenceforongoingstarformationinthecir- near-infrared photometryofthenucleusandsurrounding 1994). Long-slitspectraandCCDimagingofthenuclear component maybepresentinthenucleus.Opticaland cence line,suggestingthatahigh-density,opticallythick the formerauthorsdetectingOi¿8446Bowenfluores- within ~10"ofthenucleusappearstoberelativelyfree ~8" fromthenucleusareapproximatelysolar,with the published byseveralinvestigators(e.g,Morris8cWard background thatmaytracethespiralstructure.Theregion inclined late-typespiral.Withinthearms,bright,compact Ha emission.Spectrophotometryofthenucleushasbeen H iiregonstypicallyappeartobeembeddedinadiffuseHa regions distributedthroughoutthearmsofthishighly radius fromthenucleus. image revealsthepresenceofbright,compactHnregions broad Balmeremission.Ourcontinuum-subtractedHa 1985, 1988;Schulz,Knake,&Schmidt-Kaler1994),with arranged inaringlikemorphologylocated~20"-40" lips etal.1986),andasaSeyfert1becauseofthepresence nuclear emissionlinessuchas[Oi]/U6300,6364(e.g.,Phil- LINER becauseofthepresencestronglow-ionization is alowgalacticlatitudeobjectwithsomefieldcontami- nation fromforegroundstars. have beenpublishedbyPogge(1989a).LikeNGC6300,this tional Ha+[Nn]/Ü6548,6583and[Oin]>15007images lation frommeasurementsofover700Hnregions.Addi- studied thestatisticalpropertiesofHnregionpopu- of thegalaxywasobtainedbyKnapenetal.(1993),who The authors would liketothankJack Baldwinfor Additional long-slitspectrahavebeenobtainedby This early-typeSeyfert1galaxyhasbeeninvestigatedin Inspection ofFigure1revealsnumerousgiantHn This early-typespiralhasbeenclassifiedvariouslyasa 4.17. 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