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1985ApJS ... 58. .107C brighter membersofmorphologicaltypesScorlater.Also photometric observationsandreductiontechniquesare de- group ofbrightgalaxiesbeyondtheLocalGroup, © 1985.TheAmericanAstronomicalSociety.Allrightsreserved.PrintedinU.S.A. blue pixelprofiles.Afterlooking atthegascontentinthose in §VI.ThecolormapsareusedVIItoconstructred and profiles areanalyzed,whilstthecolordistributionisexamined The AstrophysicalJournalSupplementSeries,58:107-124,1985May absorption isminimal.Ofthesixbrighermembers,three Group (distance=2.5Mpc;deVaucouleurs1978),hasallits scribed. Fromananalysisoftheisophotalmaps,orienta- as atraceroftheluminousmass component.Finallyin§IX, systems, wediscussin§VIII theuseoflightdistribution Sculptor isclosetothesouthgalacticpole,where tion parametersarederivedin§IV.InV,theluminosity the resultsaresummarized. plate andofanHaforeachgalaxy. Figures 1-3(Plates1-3)showprintsofasky-limitedIIIa-J for thisproject.TheirparametersaresummarizedinTable 1. models forthosesystems(Carignan1985;Carignanand little (<2%-3%)tothetotalluminosity.Themainaimis Sd galaxiesNGC7793,247,and300wereselected Freeman 1985). combine thephotometryandkinematicstoconstructmass disk (PDG),i.e.,late-typespirals(Scd-Sd-Sdm)which show noapparentbulgeorinwhichthecontributesvery study (Carignan1983)toderivethegeneralpropertiesofpure The distanceestimatesarediscussedin§II.InIII,the It isfortunateforthisprojectonPDGsthatthenearest The surfacephotometrypresentedhereispartofalarger -2 NGC 300ispresented.Ineachcase,theluminosityprofileshowsanalmostpurelyexponentialdecreaseoutto blue starsfallsoffmoregraduallythanfortheolddisk,aswasalreadyseeninearlier-typespirals(Schweizer intermediate caseatB(0)=22.23.Thecorrespondingscalelengthsare1.1,2.9,and2.1kpcrespectively. color mapsrevealnogradient. the detectionlimit.Thethreegalaxiescoveranexceptionallywiderangeofdisksurfacebrightness,fromNGC of purediskgalaxiesandespeciallytheratiounseenhalomasstoluminousmass. 7793 atZ?(0)=20.33magarcsectothefaintdiskofNGC247Æ(0)23.44,with300an Subject headings:galaxies:individual—photometry suggestion byTalbot,Jensen,andDufour(1979). 1976). TheyalsorevealthatthetypeIIprofileinNGC7793isatruefeatureofolddisk,contraryto c c © American Astronomical Society • Provided by theNASA Astrophysics Data System The luminosityprofilesdecomposedintoredandbluepixelshowthatthesurfacebrightnessofyoung The profileswillbeusedinasubsequentpaper,togetherwithkinematicaldata,tostudythemassdistribution Surface photometryfromSchmidtplatesofthethreenearlypurediskgalaxiesNGC7793,247,and I. INTRODUCTION SURFACE PHOTOMETRYOFTHESCULPTORGROUPGALAXIES: Mount StromloandSidingSpringObservatories;KapteynLaboratorium NGC 7793,247,AND300 Received 1984March19;acceptedOctober18 Claude Carignan ABSTRACT -1 -1 -2 puts NGC300atadistance of1.90Mpc(scale=553 with /i=27.01,corresponding toadistanceof2.52Mpc pc arcmin). between thedifferentphotometricandkinematicalparameters Vaucouleurs 1979û,b)canbefoundinTable2.Therelations close agreementwiththeadoptedvalueoffi=26.39,which CTIO prime-focusplates.Hisdistancemodulusof26.4 is in (1982) recentlypublishedastudyonredgiantsresolved on de VaucouleursandDavoust’s(1980)recentdetermination of (scale =983pcarcmin).Thisagreeswithintheerrors with Bottinelli etal.(1983).ForNGC7793,theadoptedvalue for can befoundindeVaucouleursandDavoust(1980) and 3.13 Mpc. probably onthefarsideofgroupandNGC300 the distancemodulusis27.64,givingaof3.38 Mpc vidual distances. different distanceindicatorsforeachgalaxyandadoptindi- estimate fortheindividualgalaxies.Hencewereview distance modulusforthewholegroupwouldbeaninadequate near side.SincetheSculptorGroupissoclose,amean of ii=25.0magarcsec),itappearsthatNGC7793is H isystemicvelocitiescorrectedforgalacticrotationNGC angular diameters(8'9,14'8,18'2;face-onatalevel 7793, NGC247,and300respectively)atthe 0 0 B -1 Finally, atanintermediate distance, onefindsNGC247 The distanceestimatesusingtertiaryindicators(de For NGC300,asecondaryindicatorisavailable.Graham Looking onlyattheradialvelocities(238,195,102kms; II. DISTANCEESTIMATES 1985ApJS ... 58. .107C Carignan {seepage 107) © American Astronomical Society •Provided bythe NASAAstrophysics Data System Fig. 1.—Printsofasky-limitedIIIa-J plate{top)andofanHa{bottom)NGC7793 PLATE 1 1985ApJS ... 58. .107C Carignan (seepage 107) PLATE 2 © American Astronomical Society •Provided bythe NASAAstrophysics Data System Fig. 2.—Printsofasky-limitedIIIa-J plate(top)andofanHa(bottom)NGC247 1985ApJS ... 58. .107C Carignan {seepage107) © American Astronomical Society •Provided bythe NASAAstrophysics Data System Fig. 3.—Printsofasky-limitedIIIa-J plate{top)andofanHa{bottom)NGC300 PLATE 3 1985ApJS ... 58. .107C -1 -1 -1 o 2-1 (scale =733pcarcmin).However,inthiscasetheuncer- plates kindlytakenbythestaffofUKSTUon1.2 m mm, unvignettedfieldradius=2?7).Thephotoelectric drift tainty onthedistance(0.5Mpc)isaboutafactorof2larger than forthetwopreviousgalaxies. 108 (f/18, 1878mm)inapulse-countingmode.Thephotoelec- scans wereallcarriedoutontheSidingSpring61cmtelescope of calibration.Theplateswere digitizedindensitymodeona Schmidt telescopeatSidingSpringObservatory(scale=67'.T2 Perkin-Elmer PDSmicrodensitometer, usingascanningaper- 5. Thet/-plateofNGC247could notbeusedbecauseoflack tric andphotographicsystemsarepresentedinTables3 4. 1024 X1024arraycoveredapproximately IX. ture of50jam(3736pixel ) with50jamsteps.Theresulting a 0 0 b fto(ß?.A) Basic parameters: The surfacephotometrywasperformedusingsky-limited Log Z) ¿i(red giants) i*o(^.0) Ho(Y,BT) mf A).A) The characteristicsoftheplatesusedcanbefoundinTable Adopted: Distance moduli: A(Mpc) ... A, maximum rotationalvelocity;A:luminosityindex. (^o) c 0 0 0 m c c h Distance Moduli d c a Parameters and fi: distancemodulus. A: distance. (Graham1982). #£: correctedapparentmagnitude;D:face-ondiameter;V 0 0m (kms ‘) hm m ln

NGC 247SAB(s)d04466-21°02:0113795-8375619!90.27165 NGC 7793SA(s)d235526-3252(14753-7771710(10.60233 NGC 300SA(s)d052-3757(4299723-7974219(60.74150 b a HeliocentricradialvelocitiesfromParkesHiobservations. Ratiob/aofminortomajoraxis. Note.—Cols. (2)-(6)fromRC2(deVaucouleurs,deandCorwin1976).Cols.(7)-(9)thisstudy. b a III. OBSERVATIONSANDDATAREDUCTION v Name TypeR.A.(1950)Decl./bD(b/a)(kms~\) ls25 © American Astronomical Society • Provided by theNASA Astrophysics Data System (1) (2)(3)(4)(5)(6)(7)(8)(9) a) PhotographicPlates Distance Estimates NGC 7793 3.38 +0.30 95 27.46 27.82 27.48 27.81 27.64 9.33 1.95 1.34 TABLE 2 1.90 +0.18 NGC 300 C 26.38 26.63 87 26.08 26.48 26.4 26.39 2.26 8.38 1.30 Parameters ofProgramGalaxies 2.52 +0.50 NGC 247 108 26.95 27.57 26.53 27.00 27.01 2.17 9.00 1.40 CARIGNAN TABLE 1 log (intensity)-log(opadtance)plane(deVaucouleurs1968). next stepinthereductionwastomapskybackground in either byathird-orderpolynomialorsplinecurvein the calibration spotsavailable.Thecharacteristiccurvewasfitted The areausedforthepolynomialfitwasanannulusofwidth order tobeableinterpolateitsvalueunderneaththegalaxy. box werereplacedbyinterpolation ofathird-orderpoly- . Thedatausedforthefitweretobeaveragedinboxes the density-to-intensitycalibration.Thiswasdoneusing the value foreachboxwasthemean calculatedafter2arejection nomial fitdonetothesurrounding background.Theadopted galaxies, platedefects)ofsize comparabletotheaveraging fitting regionwasfirstexamined,andallobjects(, faint of typically20x20pixels.Beforedoingthisaveraging, the cycles. 150-200 pixelsattheedgeoffieldandcenteredon the bj IIIa-J2mmGG3854560Â1460À r IIIa-F3mmRG6306690À520 u IIIa-J2mmUG13580Â750 F Bandpass EmulsionFiltersAAX efr The firststepinthephotographicplatedatareductionwas Once thedatawereinformofanintensityarray, ab R 3mmRG630,6660À500Á2 Bj 2mmGG385,4470À1050Â (Coleman, Wu,andWeedman1980). Couch andNewell1980usingEMIS20response. U 1mmUG1,3580Â750Á f Bandpass FiltersAAARef. eff b a Full widthathalf-maximumintensity. CalculatedforthespectralenergydistributionofSdgalaxies References.—(1) Bessell1982usingRCAGaAsresponse.(2) IIIa-J 2mmGG3954570À1460 2 mmBG28 CuS0 cell 3 mmBG20, 1 mmBG38 4 The PhotoelectricSystem The PhotographicSystem TABLES TABLE 4 Vol. 58 1985ApJS ... 58. .107C profiles overawiderangeof magnitudesand,second,acheck by deVaucouleursandCapaccioli (1979)fromvariousauthors. best dataavailableforcomparisonarethoseofthemean 400-600 channels(1or2sintegration).Thesewerecentered proposed asastandardforphotographicphotometry. The per colorgalaxy),itprovides,atthesametime,avery east-west luminosityprofile in theJohnsonBbandcollated of theElgalaxyNGC3379wasreduced.Thisisoften of theUKSTUnorthwedge,whichwasthenrecalibrated. determine thezeropointandslope. de Vaucouleurs,andCorwin1976)toensure on thegalaxyandextendedover10D(asgiveninRC2, drift scanswereobtained,eachconsistingofaseries the density-intensitycalibration bycomparingtheslopeof each galaxy. Between 20and40scanswereobtainedforeachcolor for good checkonthedensity-intensitycalibration.Infact,it was cally around100galaxychannels,whichwassufficientto the driftscanswhichidentifiedaproblemwithcalibration sufficient skychannelsforthesubtraction.Thereweretypi- intensity I(x,y)oftheskyateachpointinarraywas plates (Malin1981),eitherathree-term(plane)orsix-term As notedbyPence(1978),thenormalizationtounitsofI (paraboloid) fitwassufficienttomapthebackground.The then givenby then calculated,andthefinalintensityofgalaxyalonewas takes outmostoftheresiduallocalerrors. No. 1,1985 15 s s NGC 7793 NGC 7793 NGC 7793 NGC 300. NGC 300. NGC 300. NGC 247. NGC 247. As anexternalcheckofthereductiontechniques,aÆyplate Although thistechniqueisverytime-consuming(onenight The twomainobjectiveshere were,first,averificationof In ordertogetthemagnitudezeropoints,photoelectric e d c b a Because oftheuniformitybackgroundonUKSTU Zeropointasdeterminedbythephotoelectricdriftscans. (S/N) =0.4343y/y) = © American Astronomical Society • Provided by theNASA Astrophysics Data System Number BJ 5431 BJ 5425 c) PhotometryofNGC3379 b) PhotoelectricDriftScans R 5432 R 5479 R 5422 U6225 Ö 7245 Plate J 5476 1979 Nov21/22 1979 Nov20/21 1980 Aug8/9 1979 Oct25/26 1979 Oct24/25 1979 Oct24/25 1979 Oct25/26 1981 Oct2/3 Date Emulsion IIIa-J Ilia-F IIIa-F IIIa-J IIIa-J IIIa-J IIIa-F IIIa-J Characteristics oftheUKSTUPlates SCULPTOR GROUPGALAXIES GG 395 UG1 RG 630 RG 630 GG 385 UG1 RG 630 GG 385 Filter TABLE 5 -2 -2 -2 ab indicate someproblemsinthe density-to-intensitycalibration brighter intheinnerpartsand fainterintheouterparts,with for oneofthetwosetsdata. Thegoodagreementbetween differences ofupto0.4mag arcsec.Thisdifferencecould zero-point determinationusingthedriftscansand,second, on Vaucouleurs andDavoustseealargerexcess(A/i«0.2 mag) in theBbandbydeVaucouleursandhiscollaborators(NGC good agreement,inthiscase,confirmsthatthesereduction band. profiles, wherethemagnitudeshavebeentransformedto B Vaucouleurs andPage1962).Thisprovidesanotherexternal the photoelectricandphotographic scanseliminatesthispossi- steps havebeencarriedoutproperly. the transformationbetweenBjandBmagnitudes.The very son provides,thistime,twoadditionalchecks:first,on the above theexponentialfittedtoouterparts.Thecompari- check. Figure5showsthecomparisonbetweenequivalent 7793: deVaucouleursandDavoust1980;NGC300: photometry. Wecansaythatsurfacebrightnessestobetter looking attheagreementlowlightlevels. mag canbederivedfromtheskyleveldownto5below The agreementatalevelofp=27.5magarcsecconfirms mag, whichindicatesthat,atleastthefaintend,thereisno make thetwoprofilescoincide.Theagreementbetween of theskysubtractiontechnique(aplanefitwasusedhere)by sky. than 0.05magarcsecandcolorindicestobetter0.1 tom) canbeusedtoputlowerlimitsontheaccuracyof the goodnessofskysubtractiontechnique.Figure4(bot- significant scaleerrorintroducedbythereductionprocedure. slopes ofthetwoprofilesisexcellentoverfullrange5 sky levelto1%ofthesky,whereazeropointhasbeen subtracted fromdeVaucouleursandCapáccioli’sdatato (min) FogD.S.A.F. fi Time B Exp. 180 240 105 65 90 70 90 70 The situationisdifferentforNGC300.Ourprofile is For NGC7793,theonlydiscrepancyisaround2',wherede Two oftheprogramgalaxieshavebeenpreviouslystudied The twoprofilesarecomparedinFigure4(top)fromthe 0.15 0.22 0.16 0.30 0.54 0.41 0.26 0.44 d) ComparisonwithPreviousPhotometry 0.72 0.76 0.91 0.90 0.75 1.02 1.04 1.04 2.83 2.85 3.14 3.50 3.60 3.09 3.37 3.33 d (S/N) out 61 48 68 70 77 87 54 58 -2 (mag arcsec) Brightness e 21.66 21.10 21.01 22.68 22.62 20.95 21.16 22.66 Sky 109 1985ApJS ... 58. .107C bility inourcase.Becauseofbetterplatematerial,webelieve surface photometry. sufficient tojustifyourconfidenceinthereliabilityof that thegoodagreementforNGC3379and7793is that ourprofileforNGC300ismorereliableandconclude a functionof/a#. Difference betweenourdataanddeVaucouleursCapaccioli’sas 3379 withdeVaucouleursandCapaccioli’s(1979)data{line),{bottom) being affectedbynumerous H nregionsandtheinnerweak The adoptedparametersare given inTable9. The inclinationisdeterminedfollowingBottinellietal.(1983). The resultsaregiveninTables6-8,whereXandY the centers ofthefittedellipsesrelativetoinnermostisophote. 25-point beamisusedforI<0.01/.Thefittingprocedure is used tosmooththepixelswith1.00/>I>0.01/,and a § Ilia.Beforestartingthefitting,a9-pointGaussianbeam is galaxy isophotes:theopticalcenter(x,y)semimajor different orientationthanthe moreregularouterisophotes. spiral structure.Theyaretherefore notveryusefulforde- superposed ontheisophotestoshowgoodnessof fit. Figures 6-8.ForNGC7793,wealsoshowthefittedellipses and semiminoraxislengths(a,b),thepositionangle 0. termining theorientationparameters. Theyalsotendtohavea similar totheoneusedbyCarter(1978). the followingfiveorientationparametersbystudying Stars superposedonthegalaxyimagearefirstremovedas in 110 c G5 5G 0 Fig. 4.—{top)Comparisonoftheeast-westprofile{dots)NGC As canbeseen,theinner isophotes arefairlyirregular, The isophotalmapsderivedfromthe^-platesareshown in Having thefinalgalaxyarrays,nextstepistodetermine © American Astronomical Society • Provided by theNASA Astrophysics Data System IV. ORIENTATIONPARAMETERS CARIGNAN Vaucouleurs andDavoust’s(1980) Bprofile(crasses)forNGC7793. {bottom) Comparisonbetweenour profile{dots)anddeVaucouleurs Page’s (1962)Bprofile{crosses)for NGC300. Fig. 5.—{top)Comparisonbetween theprofile{dots)andde E ro cn 2 22 01 28 24 26 20 n 1r r*(arcmin) 6 810 + deVaucouleurs& • thisstudy NGC 300 Page,1962 12 Vol. 58 1985ApJS ... 58. .107C -2 panel showsthefittedellipsessuperposed ontheisophotesinstepsof1.0 mag. 7793 from21.0to27.0magarcsec instepsof0.5mag.Thebottom No. 1,1985 Fig. 6.—Isophotalmapandfitted ellipsestotheBjdataofNGC © American Astronomical Society • Provided by theNASA Astrophysics Data System (orcmcn) SCULPTOR GROUPGALAXIES -2 -2 2 mag arcsecinstepsof0.5mag. inter-arm region.ForNGC 7793, whichhasnorecognizable pronounced northernspiralarm, thisregioncorrespondstoan level of24.0magarcsec . ForNGC247,whichhasa a truedeparturefromcircular symmetry. spiral pattern,itreflectseither aregionofhigherabsorptionor the eastsideofNGC7793 and northsideofNGC247ata mag arcsecinstepsof0.5mag. Fig. 8.—IsophotalmapinBjforNGC300from22.0to26.0 The mainfeatureinthemapsisakindoffainterplateauon Fig. 7.—IsophotalmapinBjforNGC247from215to270 arcmin 111 1985ApJS ... 58. .107C which weusedthebrightestisophote. isophotes areoffsetbymorethanVtothesoutheast with lopsided galaxy.Thecentersoftheellipsesfittedtoouter level of25fiexceptforthecoordinatescenter, for respect totheinnermostone,withboth0andidecreasing as have beencalculated:major andminoraxisprofiles,equiv- one movesoutward.Wethusarbitrarilyadoptthevalues ata quite uncertainforNGC300,whichisanexampleofa fairly welldefinedforNGC7793and247,theyare to revealstructuraldetailsthat areotherwisesmearedoutin alent profiles,andelliptically averagedprofiles. distribution assumingaconstantM/L.Inthecaseofthese representation ofthelightdistributionandhencemass of luminosityprofileshavetobeusedinorderfindthe best -2 Sculptor Groupsystems(42° <¿75°),threetypesofprofiles B 112 25.50 . 24.00 -17.3 23.50 -10.0 23.00 -2.0 22.00 0 27.00 . 26.50 . 26.00 . 25.00 . 24.50 -10.5 22.50 -4.9 (mag arcsec)(arcsec)(arcmin)b/a(majoraxis) a While theparameters,derivedusingouterisophotes,are The purposeofthemajor'and minoraxisprofilesismainly Depending ontheorientationofgalaxy,differenttypes Eastandnorthpositive. a li XYa% Bjc © American Astronomical Society • Provided by theNASA Astrophysics Data System Ellipse FitstoIsophotesforNGC247 -3.0 -7.8 -5.8 -7.4 4.8 V. LUMINOSITYPROFILES -2 21.0 23.0 22.5 21.5 24.0 23.5 22.0 26.0 25.0 24.5 27.0 26.5 25.5 -13.7 (mag arcsec)(arcsec)(arcmin) -5.5 a 45.9 63.9 67.4 34.7 52.4 15.4 59.6 East andnorthpositive. 0 TABLE 7 3.1 » >7 Bj 11.94 12.88 11.22 10.62 4.12 0.71 9.96 9.34 1.96 8.68 5.91 0.28 0.32 0.57 0.31 0.30 0.30 0.27 0.26 0.24 0.31 0.39 -6.8 -0.1 -4.9 -1.6 23.0 15.4 10.8 0 7.7 1.5 9.2 8.2 8.4 Ellipse FitstoIsophotesforNGC7793 170.9 171.0 171.3 168.3 175.7 171.3 171.1 171.0 171.2 180.2 184.6 -3.0 10.4 12.0 4.5 0 2.7 2.3 2.1 2.3 6.6 9.4 5.9 8.3 73.9 73.9 75.2 75.9 77.9 73.3 72.6 68.1 73.3 76.6 55.9 CARIGNAN TABLEÓ de cde o, hm with previousphotometry. In doingso,wefollowedde major orminoraxis,givesome dynamicalinformationonthe circular symmetry. galaxy, aswellpointingout somepossibledeparturesfrom curves, definedasthedifferencebetweentwosidesof the the twoothertypesofprofiles.Theluminosityasymmetry 0 99.3171.1105.6 / 53.775.442.3 b/a 0.600.280.74 Decl.(1950) ....—32°52Y0"-2002W'-37°5724" R.A.(1950) 2351^2004439?6T.2 0.38 4.78 4.20 2.96 2.36 1.03 6.44 3.42 1.82 5.94 5.69 5.33 5.06 o -2 25.5 41.9-46.010.60.77105.840.0 e 26.0 50.7-67.811.10.81102.636.2 25.0 43.5-38.49.80.74105.642.3 24.5 20.1-21.99.10.65117.050.0 23.5 -12.1-22.35.60.71116.545.2 d c 24.0 21.3-13.37.30.69119.046.8 23.0 8.2-3.64.10.6693.549.2 22.0 01.50.62116.452.2 b a 22.5 12.9-3.13.20.55114.657.3 (mag arcsec)(arcsec)(arcmin)b/a(majoraxis)i ab The equivalentprofileswere mainly derivedforcomparison de VaucouleursandPage1962:z=42?5,0=109?0. de VaucouleursandDavoust1980:z=53°,697?7. For <7o=0.12/ Derivedat/r=25.ö! Derived for24.5