1989AJ 98. .7663 10 THE ASTRONOMICALJOURNAL brightest extragalacticsourcesintheIRASsurvey.Thesam- accurate reductionsoftheIRASobservationspresently al. (1986)derivedthefar-infraredluminosityfunctionfor galaxies relatetotheiropticalmorphology isthesubjectofa densities forallthegalaxiesinBGsample,usingmost the infraredpropertiesofbrightgalaxies. criterion, andtherebyshouldpresentawell-definedviewof IRAS observedpropertiesoftheBGsample. at 60pm,inanareaofskyhighGalacticlatitude.Soiferet ple consistsofallextragalacticsourcesbrighterthan5.24Jy the BGsample)waschosenasarepresentativesampleof Paper I.Briefly, theoriginalcriteriawere:any extragalactic subsequent paper(Sanderscía/. 1989). available. Thestudyofhowthe infraredpropertiesofthese straints andaflux-densitylimitat60pm.Thissamplethus thermore, theonlyselectioncriteriaappliedwereareacon- lactic sourcesat60pm,itpresentsthebestopportunityto entire sample.Thispapercompletesourexaminationofthe and thefar-infraredluminosityfunctionwasderivedfor Paper I(Soifereta/.1987),thefullsamplewasdescribed,60 the BGsampleforfar-infraredluminositiesZ,>10L.In should beunbiasedexceptforthespecific60pmselection study theinfraredpropertiesofbrightgalaxies.Fur- and 100pmfluxdensitieswerereportedforthesegalaxies, 766 Astron.J.98 (3),September1989 0 The selectioncriteriafortheBG sampleweredescribedin In thispaperwereportthe12,25,60,and100pmflux The IRASBrightGalaxySample(hereafterreferredtoas Because theBGsamplerepresentsbrightestextraga- © American Astronomical Society • Provided by the NASA Astrophysics Data System S{25 pm)correlatewithinfraredluminosity,andmoresignificantlytheratioofinfrared-to- densities at25and60pmcanbedistinguishedinseveraloftheinfraredproperties.Forgalaxies a galaxy’sinfraredproperties.Galaxiesselectedtobe“warm”and“cold”intheobservedratioofflux tions thatarefoundshowsignificantdispersion,sonosinglemeasuredparameteruniquelydefines in theBrightGalaxysampleshowsignificantrangesallparametersmeasuredbyIRAS.Allcorrela- and fluxdensityshowthattheBrightGalaxysamplecontainssignificantsubsamplesofgalaxiesare have lessdustmassatagiveninfraredluminositythandothecoldgalaxies. holds forthesample,withdifferentslopesappearingtoexistwarmerandcoldergalaxiesin the BrightGalaxysamplebothratiooffluxdensities^(60pm)/S(\0Dpm)and5^(12pm)/ complete to0.8,and16Jyat12,25,100pm,respectively.Thesecutoffsaredeterminedbythe the 313aredetected.At100pm,allgalaxiesTherelationshipsbetweennumbercounts revised BrightGalaxysample.At12/¿m,300ofthe313galaxiesaredetected,whileat25pm,312 of theinfraredpropertiesbrightgalaxiesobservedinIRASsurvey.Datafor330 all sourcesintheIRASBrightGalaxySample.Thissamplerepresentsbrightestexamplesofgalaxies depth effectsappeartoaltertheemergentradiationat12and25pm.Thewarmergalaxiesgenerally 25 pmradiationfromgalaxies,significantlyaffectstheemissionofsomegalaxiesat60pm,whileoptical visible flux.Therelationbetweenthesetworatiosoffluxdensities,foundpreviouslybyseveralworkers, 60 pmselectioncriterionandthedistributionofinfraredcolorsbrightgalaxies.Thegalaxies are reportedhere,with313galaxieshaving60fimfluxdensities>5.24Jy,thecompletenesslimitofthis selected byastrictlyinfraredflux-densitycriterion,andassuchpresentsthemostcompletedescription Total fluxdensities,peakandspatialextents,arereportedat12,25,60,100/¿mfor sample. Itissuggestedthatsinglephotonheatingofsmallgrains,oftenthedominantsource12and v v IL THESAMPLEANDDATAREDUCTION THE IRASBRIGHTGALAXYSAMPLE.IV.COMPLETEOBSERVATIONS Division ofPhysics,Mathematics,andAstronomy,CaliforniaInstituteTechnology,Pasadena,91125 I. INTRODUCTION B. T.Soifer,L.Boehmer,G.Neugebauer,andD.Sanders Received 15March1989;revisedMay1989 0004-6256/89/030766-32$00.90 VOLUME 98,NUMBER3 ABSTRACT Optical Galaxies(Riceetal.1988).Forallothergalaxiesin the BGsampleIRASdata werereprocessedbythe were takenfromtheCatalogofIRASObservationsLarge axies withlargeangulardiameters,theIRASfluxdensities frared ProcessingandAnalysis Center.Allthemeasure- addscan/scanpi processing(Helou etal.1988)attheIn- for theBGsamplewereobtainedfromtwosources.Forgal- and 100pmfluxestimates,improvedIRASmeasurements Version 2.0. ments werebroughtontothecalibration scaleofthePSC, the BGsampleat12and25pm,aswelltoimprove60 IRAS PointSourceCatalogat60pm)inanareaof tions werereportedintheaforementionedIRAScatalogs. extended atthesewavelengths,andinmanycasesnodetec- number countsandfluxdensity,hereaftercalledthe“logN- the CatalogofIRASObservationsLargeOpticalGalaxies tude, I>30°.SourcesweretakenfromtheIRASPoint “mean track” for thesource,addscan processing to reportdataat12and25pmbecausetheobjectswereoften Small ScaleStructures(SSS),andapreliminaryversionof Source CatalogVersion1.0(PSC),theIRASof were reportedinPaperI.Noattemptwasmadethatpaper BG sampletakenfromthePSC,SSS,andRiceetal.(1988) complete tothefluxdensitycutoffof5.4Jy. logS” relation,forthissampleindicatedthattheis source withcolorcorrected60pmfluxdensity>5.4Jy (Rice etal.1988).Analysisoftherelationshipbetween (roughly tentimesthelowestmeasurablefluxdensityof —14,500° sq.withdeclination,<5>—30°,andGalacticlati- After projectingtheindividual detectortracksontoa In ordertoprovidefluxmeasurementsforthesourcesin The bestfluxdensityestimatesat60and100pmforthe © 1989Am.Astron. Soc.766 SEPTEMBER 1989 1989AJ 98. .7663 sources, NGC838and839,previously confusedwithNGC completeness limitof5.24Jy at 60[im(seebelow).Two tion oftheVersion2.0PSC,are abovethenewBGsample ple becausetheirfluxdensities, based ontherevisedcalibra- addition, threesourceswereadded totheoriginalBGsam- oughness, butarenotconsidered furtherinthispaper.In this limit.ThesesourcesareincludedinTable1(a)forthor- ed) selectionlimitoftheBGsampleat60yumis5.24Jy. ments. 835, havebeenincluded, ashasNGC4699,agalaxy thatwas Seventeen sourcesfromtheoriginalBGsamplefallbelow scanpi estimateshasresultedinchangessomemeasure- tion ofthefluxdensitiesusingimprovedaddscan/ determined completenesslimit.Furthermore,therecalcula- brought tothecalibrationscaleofPSCVersion2.0,so by 5%-7%overthe“rawfluxdensity”asgiveninvar- some ofthetabulatedfluxdensitiesfallbelowpreviously The colorcorrectionfactordependeduponboththeas- ious IRAScatalogs.ThefluxdensitieslistedinTableIhave sumed formoftheenergydistributionandratio60- not beencolorcorrected,andtheentiresamplehas sensitivity limitin“color-corrected”fluxdensityof5.4Jy. Appendix A. the BGsample,whilecontentsofTableIaredescribedin and sourcesizeat50%25%ofpeakfluxdensitywereall total fluxdensity,peaktemplate retained forthesource. plate fluxdensitydidnotadequatelyfitthedata,then estimator oftheIRASfluxdensity.Ifpoint-sourcetem- from thepoint-sourcetemplatefitwasretainedasbest to determineifthesourcewasadequatelyfitbypoint- four IRASbandsforallsources.Afterprocessingthedata, integrating thefluxdensityversuspositiondata.Thepoint- source template.Ifthiswasadequate,onlythefluxdensity the outputwasinspectedforeachsourceatallwavelengths source fluxdensityandtotalwerederivedforall sity within+4'ofthesourcepositionwasdeterminedby relation coefficientofthefit.Inaddition,totalfluxden- source template”wasfittedtothesource,deriveboth ways basedonthecoaddedone-dimensionaldata.A“point- measured directlybyIRAS. “Point SourceCatalog”equivalentfluxdensityandthecor- the infraredemissionfromgalaxiesdetectedarethose 100 fj,mfluxdensities,buttypicallyincreaseddensities tory Supplement1988)suggeststhatthebestpositionsfor positional uncertaintiesofknownsources(IRASExplana- assumed. ForthethreesourcesaddedfromPSCVersion 2.0, thepositionwastakenfromthatcatalog.Analysisof I. Forthelargegalaxies,opticalpositionofgalaxy tion takenforthesourcewaspositionreportedinPaper the meantrack.ForallsourcesincludedinPaperI,posi- mensional “driftscan”offluxdensityversuspositionalong within +4min).Theresultofthiscoadditionisaonedi- within +ofthecentralposition(butexcludingdata 767 SOIFERETAL.:IRASBRIGHTGALAXYSAMPLE after subtractingasecond-orderbaselinefittedtothedata crossing thepositionofsource.Thedataarecoadded coadds inone-dimensionaldatafromallIRASdetectors (de Vaucouleurs,deandCorwin1976)was The resultofthesechangesisthatthe(noncolorcorrect- As describedinPaperI,theBGsamplewasselectedtoa Table 1(a)containsthesummarydataforallsourcesin The fluxdensityofthesourcewasestimatedinseveral © American Astronomical Society • Provided by the NASA Astrophysics Data System III. THEDATA 0 0 /zm thereisonlyonelimitfor asourceintheBGsample. /zm (Fig.1)givesapowerlawfitof—1.30.Thisnon-Eu- in theminisurveyfield. icantly loweridentificationrateofIRASsourceswithgalaxy tude oftheIRASminisurveymightbecausesignif- ment withtheminisurveyresultsisdifficulttounderstand. /zm, withadetectorwidthofmorethanhalfthesources bands for72galaxies with(60/zm)>2.0Jy. Ofthese,all Extinction andenhancedconfusionatthelowergalacticlati- results ofSmithetal.issatisfactory,however,thedisagree- bright galaxiesintheVirgosupercluster.Extrapolating Smith etal.(1987)reportedmeasurements inallfourIRAS BG sourcesforwhichonlylimits wereobtained,whileat25 M51 andNGC5195at100/zm. ]At12/zmthereareonly13 and Rice,privatecommunication) wereusedtoseparate sured at100/zm.[Imagereconstruction techniques(Levine wavelengths otherthan60/zm.Allthesourcesweremea- the sampleofSmithetal.(1987).Theagreementwith higher thanthesurfacedensityof60/zmbrightgalaxiesin found inthe//L4S'minisurvey(Soiferetal.1984),and20% This isapproximatelytwicethesurfacedensityofgalaxies sq.at0.6Jy.TakingintoaccounttheVirgoClusterwould ness limitofthePSCgivesasurfacedensity0.55galaxies/ numbers ofsourcesintheBGsampleto60/zmcomplete- clidean valueisareflectionoftheenhancednumbers reduce thisnumberby~10%,toroughly0.5galaxies/sq. counts athighfluxdensitycanbeattributedtotheVirgo tion limitof5.24Jy,whiletheflatteningnumber Cluster beingasignificantcontributortothesample. shows thatat60/zmtheBGsampleiscompletetoselec- of sourcesversusfluxdensityat60/zmtotheselectionlimit and Sisthefluxdensity.Theconstantslopeofnumber flux densitiesgiveninTable1(a);iVisthenumberofsources relations foreachIRASwavebandbasedontheobserved detector widthof3'(IRASExplanatorySupplement1988). more than|ofthesourcesareunresolvedat100/zmwith are unresolvedat60/zmwithadetectorwidthof1.5',and BG sampleareresolvedormarginallyat12and25 function ofwavelength.Whilenearly§thesourcesin changing angularresolutionoftheIRASinstrumentasa for thesourcesateachwavelength.TableIVreflects private communication). length foranunresolvedsource(HelouandKopan1988, peak fluxdensityaregiveninTableIIIasafunctionofwave- ence, theaveragevaluesoffullwidthsat25%and50% Jy inthestatisticallycompleteBGsample. contents ofthistablearedescribedinAppendixB.Forrefer- resolved (R),additionaldataareincludedinTableII.The are 313sourceswithfluxdensityat60/zmS(60/zm)>5.24 the newselectionlimitarelistedinTable1(b).Thusthere tios ofS(60i¿m)/S(100/¿m).Thesourcesthatfallbelow sion, i.e.,thoseclassifiedasmarginallyresolved(U+)or extended emissionwhilesearchingforgalaxieswithlowra- found tomeetthe60/zmflux-densitycriterionbasedonits v v v Nearly alltheBGsourcesaredetectedatIRAS The formalfittothenumberversusfluxdensityplotat60 Figure 1showstheintegralanddifferentiallogA-logS Table IVshowsthedistributionamongextentcodes For thosesourcesthatshowevidenceofextendedemis- v a) CompletenessoftheBrightGalaxySample IV. RESULTS 767 1989AJ 98. .7663 768 NAME NGC23 NGC 157 NGC34 NGC 150 NGC 174 MCG-02-01-051 NGC 232 NGC 253 NGC 247 UGC 556 NGC 337 NGC 470 IC 1623 UGC 903 MCG-03-04-014 NGC 520 MCG+02-04-025 NGC 598 NGC 578 NGC 628 NGC 613 NGC 660 NGC693 IR 0136-10 NGC 697 NGC 695 © American Astronomical Society NGC 701 III ZW035 NGC 835 NGC 772 UGC 1451 UGC 1351 NGC 873 UGC 1720 NGC 839 NGC 838 NGC 1068 NGC 992 NGC 958 NGC 922 NGC 877 NGC 1083 NGC 1055 NGC 1022 NGC 908 SOIFER ETAL.:IRASBRIGHTGALAXYSAMPLE H MS 0 7 0 32 0 16 0 8 0 34 0 31 0 40 0 45 0 44 0 52 0 5719.9 1 518.0 1 742.0 1 1722.8 1 179.6 1 196.5 1 3159.0 1 3103.0 1 2803.7 1 2159.5 1 3624.0 1 341.0 2 407.2-0133001125 2 364.6-6533101498 2 3435.8+2053604119 1 4754.2 1 4148.0 1 4021.6 2 4318.7-1534505040 2 3911.8+0135201005 1 4831.1 1 4828.1 1 5018.7 1 4835.0 1 5541.5 56 34.6 28 11.8 22 49.4 20 46.6 11 28.3 14 5.3 15 15.1 RA 7 15.0 7 11.0 6 56.6 47.3 -28 33.4 -12 40.0 -21 31.4 -29 19.4 +25 18.0 -10 13.9 -8 17.5 -23 7.7 +28 5.0 -25 +14 5 +17 19 +30 23 +22 2010 +16 517 +13 2342 +12 2743 +22 0641 +25 75 +18 45 +14 -17 46 -17 7 -22 55 -29 40 -10 4225 -10 25 -10 23 -10 22 -11 -25 -21 +3 8 +3 31 +5 53 +4 56 15 3136 -7 50 -9 570 -3 0 /// DEC czDm z 40 23 45 11 23 10 38 46 39 14 50 2 33 47 58 26 4 44 2 0 Table 1(a).Integratedfluxdensitiesof//LIS'brightgalaxies. 53 01651 37 05550 40 01696 53 09337 52 02320 53 02374 54 52 02261 34 01487 00 03870 23 04066 28 08940 52 55 03450 54 03086 36 03866 32 05750 36 01508 12 03811 1 10040 km/s Mpc 04536 01651 07513 05931 03471 01593 06250 04567 00655 01593 08215 00862 03109 09769 04916 04597 14250 33.1 18.9 13.0 3.6 3.6 0.8 11.5 13.0 12.5 12.5 14.0 14.0 15.3 12.5 15.0 15.5 14.5 14.7 12.4 11.5 12.4 10.5 11.0 13.5 13.5 15.8 12.8 14.0 12.7 14.3 13.8 11.3 13.0 14.4 13.4 13.5 12.5 13.5 11.5 12.5 11.0 12.5 14.0 7.5 9.8 6.5 9.7 Provided bythe NASA Astrophysics Data System <1.20* <0.15 36.58 <0.10 32.69* 36.10 0.23 0.36 0.36 0.39 0.40 0.59 0.33 0.73 0.27 0.41 0.36 0.98 0.47 1.57 0.91 0.49 0.28 2.33 0.36 0.25 2.07* 0.33 0.26 0.55 0.71 0.35 0.73 0.56 0.20 0.42 0.69 2.88 0.52 0.70 0.59 2.20 0.87 Jy mJySize 1.12 1.83 S|/ (Ty 12^m 40 U 42 U 45 U 44 R 42 R 49 R 62 U+ 38 U 78 R 41 R 24 U 48 U 44 U 43 U 49 R 39 R 48 U 42 U 64 R 35 R 31 U+ 64 U 42 U 43 R 45 R 64 R 30 U 26 U 29 U 57 U 39 U 28 R 30 R 33 U 37 U 36 U 39 R 38 R 50 R 36 R U R R U U 137.89 194R <1.70* 40.26* 84.25 191U 2.38 2.08 Jy mJySize 0.44 45U 1.64 1.24 1.22 1.18 0.88 0.75 1.28 0.52 3.43 7.71 Sj/ Rom Rice et al. 780 781 © American Astronomical Society • SOIFER ETAL.:IRASBRIGHTGALAXYSAMPLE Table II. (continued) l* 1 O 00 £>i&C*(*ÈÈ£c*t4C*t4(*c4Oç<0ï(40iC6&&i>&È(i6t*èèèttp4ptièÈctcziDKÈÈ ©oor-ioNddoo cSrHod»n©d»-!inddr-'cs'ddo'^Noddd ctuuoectctÈèètiioioiêiçiicicteièctitiitxuciuccuéèBeceÈiiot&asoiciciêè ^ CS'• sassassasaasasaassassaasgaasgaassiassaasaiQ mi r-'O^ © NOCO cnp Rom Rice et al. 781 O'! 00 UD UD r" C/} 782 © American Astronomical Society SOIFER ETAL.:IRASBRIGHTGALAXYSAMPLE Table II. (continued) s < : , : S 8 2aS82!Q8882a2a2a2a28S8288828882S82SS82a82 *h' o¿dr-*oó«dr*esoÑ\ovo-h’ vod ssssîïsçîîissssüsssssâisssiBssaçsiRiissisæîsæsçspa ddrt^dd'S-'Tj-’dddd^OO—iS-oovoriorioovjdd^-'íd^inddoÑoóddoód RssKSSfcSSSfcPiisssxsiRgsiissassssssssiia&sass co Tf"»neseoio^i-î>-î«-iri<ô«ies’rr»-itt»hes*^-îtí-’es' o U esescoco*-^des Table II. (continued) ),0oov Table II. (continued) •I I * : <: èèetxeeèeioieiÈoteieiiiiiixèèuaieixèèoiKeiBteiXeieiaixoièeieeeiiee 2as82a82as82a88sasaas82as8sa$82aa2|82a2as P40ÎP4P4P4P4Êxp4P4ix{4P4èiDèè&PÎP4êp4Q4P4P4P4P4P4P4ÈÈ£èp4P4&èc*il*P6 ©o»r>c[jdd»nd»-J^vrj^H^4e^ood<-4o\ddTfendi- NGC 4419 12 R 0.72 0.50 0.61 1.18 0.76 25 R 0.76 0.31 0.41 2.15 1.53 25 U+ 1.69 1.47 1.54 1.14 0.84 60 R 5.85 4.34 4.40 2.66 1.89 100 U+ 20.86 18.44 19.04 4.34 3.14 784 785 SOIFERETAL.:IRASBRIGHTGALAXYSAMPLE © American Astronomical Society Table II. (continued) 4,,,—l etiÍDKt>séÍDÉ£oíéxoíoíoí£éeieíotéaíÉocctiiíiaíaí&e¿ééoíQíe¿í*o¿cíc6£c6e6 -<©covo©-»^©OTi-co«o^gggdd«dd©'vn^'-H'codddM'cdcdp^csdcddddcj©©invod»q 8RS3SS5?9S|S^!88SS2S22!S25:8?3!î2P;2SS38S38S3S!2pç8S2aa ©O co©oco-if^cO'-ioôdd’Tt'ddindi-H'ciddcidi-îi-îdcodcs'dd’crooddcicdoc)© © corfdci^-i cs«s\otnr^«noico^HfH\p RS???»S» 22îJS^28ÇÏ!S!S?86?S8S2g:Sîag8S?g5RS8S«©SiSS? «n«n-H»qvooovr)cscs^sF CS^CSxf-H^cS-HCS'cOTf vn oocovqescO cooioo^csinoi©^^ •-—CO'—!•-*>—Il—ii-^CSCO g gg Z 2zz 2as2sss2a282a2ssa28ssa82as8sias8a2s¡as82asa2a ©©r^-^'-Hcsvo©'«tcsco©©©©vo-< —cscs^oin-H-Hvodior^dc^'—«d^r-iosoo^cs©^©--^ ^r>. oq^vq^osONC^coo^in^SKoTr.rjcoco^dfor^OiTr.oo»n©ô(2.io^)2îpiS5Soit^23Ç ©—ioococooscs^©t^coiOO\»©woCN‘ncs©vovoa\«no\»n—ivoQr^'íj-t^in©oooTí-Tí-inr-(cocsr' d r^^»-íco»-Íes"©wñ•-<’*-íoópott»-!»-Î^h’rjgÑ^h"oí-f»-i^<’r''r-¡ d <-î-h'dcocs'cs©vri^h'ö-h’os>n^^h’Tfin © -**dC>*-i^-*'-h'*-<*CÓ«-H*-H*-H*cñ ^ Rom Rice et al. 785 786 SOIFERETAL.:IRASBRIGHTGALAXYSAMPLE © American Astronomical Society Table II. (continued) •I I - ,> 1 xuièÈuèeietütiipttitèitèasèaiaiuÈiittxoioi&BècitièaitïiotèüoièBitii&è ONOor^»no\Kcot^oopc^o\Ti; ONoqwSr^aiPoqvqoora\oor~r>; a»’«->-H'^-vo^00C'OSpHfri From Rice et al. 786 1989AJ 98. .7663 787 © American Astronomical Society • Provided by the NASA Astrophysics Data System SOIFER ETAL.:IRASBRIGHTGALAXYSAMPLE R -Resolved U+ -MarginallyResolved U -UNRESOLVED Wavelength FWHM Width at25%PK. Wavelength NGC 6070 Object NGC 6285/6 NGC 6217 NGC 6090 NGC 6181 NGC 6503 NGC 7448 NGC 7465 NGC 7469 NGC 7479 NGC 7541 ZW 475.050 NGC 7591 NGC 7678 NGC 7625 NGC 7771 UGC 12915/4 MKN331 Table IV.DistributionofextentcodesforBGsample. Band 100 25 25 25 60 60 25 25 60 25 60 25 60 25 12 12 60 12 12 12 25 60 12 12 25 12 60 12 25 12 25 60 25 60 12 60 25 25 60 25 60 25 25 12 12 12 12 12 ¿¿m 0.77' 1.00' Table III.Sizeofunresolvedsource. R R R Res. R R R u+ U+ R U+ R U+ R R R R u+ R R R R R R R U+ R U+ R R R R U+ U+ R R R U+ R R R R R U+ U+ R U+ U+ Table II.(continued) 12 ¡xm 126 169 11.27 10.16 27.68 Total 20.59 15.35 20.46 35 0.51 0.77 0.29 0.74 0.64 0.50 2.03 0.65 9.87 5.07 0.35 0.84 0.50 0.83 8.32 8.44 5.50 1.35 1.22 1.06 5.84 1.13 1.60 3.92 1.40 7.82 0.32 0.59 7.01 0.97 1.49 6.27 0.88 0.43 2.18 0.87 2.56 1.99 1.23 1.88 1.10 Jy 25 ¡im 0.78' 1.04' Tempi 11.01 26.15 13.27 18.54 19.34 4.69 0.34 0.40 0.23 0.50 0.60 7.88 0.51 0.35 7.35 0.47 0.43 0.40 7.64 0.36 0.25 0.60 8.09 1.10 1.13 3.23 1.68 0.80 5.84 3.38 1.26 0.90 7.04 0.23 0.66 0.59 0.89 0.38 0.99 0.27 0.69 6.59 2.34 1.65 5.86 1.75 1.72 Jy 25 ¡xm 155 114 61 10.69 27.00 Peak 13.60 19.01 19.58 0.35 4.22 0.43 0.25 0.60 0.53 0.42 0.58 7.52 0.54 0.50 0.28 7.44 0.42 8.35 7.43 0.45 0.65 1.11 1.17 3.86 1.68 6.04 0.95 3.48 1.36 7.64 0.27 0.77 0.90 0.45 6.03 0.67 6.71 1.06 0.35 0.75 2.43 1.83 1.67 1.06 1.77 jy 60 ¡im. W25 W50 2.42 2.07 2.30 1.74 2.74 2.33 2.34 1.80 1.35 1.06 1.07 4.74 2.25 1.57 1.33 1.12 1.09 1.33 3.46 1.22 1.21 1.57 1.44' 1.31 1.95' 2.22 1.14 1.03 1.79 1.99 2.13 1.17 2.02 2.06 1.43 2.01 1.33 2.02 1.03 1.45 1.13 1.13 1.24 1.47 1.17 1.41 1.06 1.37 1.07 60 /¿m Arcminutes 179 107 44 0.90 0.80 0.80 0.78 0.89 0.85 0.85 0.97 1.09 0.83 1.38 0.92 1.73 1.07 0.81 1.53 1.56 1.51 0.76 3.48 1.95 1.68 0.99 1.60 1.14 0.84 1.49 0.95 0.96 1.44 0.77 0.95 0.92 0.75 0.86 0.81 1.59 0.96 0.94 0.88 0.78 0.80 1.54 1.45 1.49 1.54 1.50 100 /im 100 /im 2.94' 3.83' 254 39 37 787 788 SOIFER ETAL. : IRAS BRIGHT GALAXY SAMPLE 788 10.0 1.7 2.2 LOG S (60/xm) LOG SAMixm) LOG Sl/(25/¿m) LOG 5^(1 00/um) Fig. 1. The number versus flux-density relations plotted for the galaxies in the IRAS Bright Galaxy Sample. The data are for the 313 galaxies with ^ (60 /zm) >5.24 ¡im, and all panels show both integral [ACS',, > 5) ] and differential N(SV + ds) counts. The bins have width ¿/(log 5) =0.1. The errors shown are statistical errors only, i.e., 4Ñ. Only those galaxies with measured flux densities, i.e., 300 at 12/zm, 312 at 25 //m, and 313 galaxies at 100 /tzm are included in the plots. were detected at 25 ¡im, while only 58 were detected at 12 of 0.4 Jy at 12 /mi (IRAS Explanatory Supplement 1988). //m. This latter low detection rate is clearly attributed to the Thus the BG sample represents a sample that is virtually lower 60 //m flux-density limit of their sample. complete and unbiased (except for such biases as are intro- At 12, 25, and 100 //m, there is a portion of the log N- duced by the 60 /zm selection criterion) for the study of the 3/2 log5'v plot that follows the relation N~S ~ , suggesting infrared properties of far-infrared bright galaxies. that the BG sample contains a complete flux-density-limited sample at those wavelengths to the break point in the log N- b) Infrared Colors 3/2 log Sv plots. The departures from the S ~ power law show where a significant population of sources is being lost as a The histograms showing the range of the flux-density ra- result of the 60 ¡um selection criterion. At 100//m, the depar- tios (i.e., colors) 5^(12 /zm)/^(60/zm), 5^(25 /zm)/ 3/2 ture from the S ~ power law occurs at 5^(100 jum) S 16 S^öO/zm), 5^(60 /zmí/S^OOO /zm), and 5V(12 /zm)/ Jy. The completeness limit of the IRAS Point Source Catalog Sv(25 ¡im) are plotted in Fig. 2. The distributions of the is 1.5 Jy at 100/mi (IRAS Explanatory Supplement 1988), colors in Fig. 2 do, of course, reflect the primary selection so that this departure is a result of the 60 jum selection crite- effect of a 60 /zm flux-limited sample. Because the sample is rion. This is consistent with the rare occurrence of galaxies flux limited at 60 /zm, and nearly all sources are detected at with Sv(100/Ltm)/Sv(60¡um) >3.5, and increasing fraction all the IRAS wavelengths, these distributions represent the of infrared bright galaxies with lower values of this ratio. true distribution of the IRAS colors of galaxies selected at 60 At 25 jum, the departure from a S'“3/2 power law occurs /zm. at 0.8 Jy, as compared to the Point Source Catalog complete- The distributions of flux-density ratios are quite broad, ness limit of 0.38 Jy for sources detected at multiple wave- immediately suggesting that a variety of physical environ- lengths (Sanders et al. 1988 ). Thus the departure from the f ments are important in producing the infrared emission in power law is again a result of the 60 /¿m selection of the BG galaxies. The ratio 5^(60¡j,m)/Sv ( 100 /zm) shows the nar- sample. The population of galaxies that is being lost by the 60 rowest distribution, but still ranges from 0.2 to 1.6, a total /¿m selection are the systems with S'v(25 /¿m)/S'v(60 /¿m) span of a factor of 8, while the ratio 5^(12 /zm)/^ (25 /zm) >0.15. At S^ (25 /mi) <0.8 Jy, sources with larger values of shows the broadest distribution, ranging from 0.07 to 2, a Sv ( 25 //m ) /Sv ( 60/zm ), i.e., the “warm” IRAS galaxies ( see total span of a factor of 25. The upper limits on ^ ( 12 /zm)/ below ), are excluded from the BG sample. A similar effect is ^ (25 /zm) for the sources with 12/zm upper limits span the seen at 12/zm, with the incompleteness beginning at 0.8 Jy as entire range of observed values, and are not biased toward compared with the Point Source Catalog completeness level the low end of the observed range. © American Astronomical Society • Provided by the NASA Astrophysics Data System C/} UD r" 00 789 SOIFER ETAL. : IRAS BRIGHT GALAXY SAMPLE 789 ^0 (S\ 00 LOG [Sly(60yum)/Sl/(100/um)] LOG [Sl/( 1 2^.m)/Sl/(60/u-m)] LOG [S1/(25Mm)/Sv(60yunn)] LOG [S¡y(12Mm)/SI/(25/am)] Fig. 2. Histograms of the distribution of infrared colors for the galaxies in the Bright Galaxy Sample. The histograms use only those galaxies with measured flux densities at both wavelengths. For the histograms of the £„(12 tim)/Sv{25 //m) ratio, the limits are fairly uniform spread over the observed range of ratios, while for the histogram of the 5v(12//m)/5'v(60//m) ratio, the limits are dominated by values of log [Sv(\2¡im)/ SV(6Q¡im) ] < 1.6. V. DISCUSSION is dismissed since in nearby infrared bright galaxies, the strongest line, [C ll] at 158/2m, contributes less than 1% of a) Emission Mechanisms in Infrared Bright Galaxies the total luminosity (Crawford ^0/. 1985). In this section we describe the observed properties of in- frared bright galaxies as derived from the BG sample. We b) Response of Dust to the Heating Radiation Field adopt as our starting point the viewpoint that the infrared emission from galaxies is predominantly thermal emission The mean radiation field in which the grains are embed- from dust heated either by a central luminosity source of a ded is best characterized by the longest-wavelength emis- diffuse radiation field. The infrared emission from galaxies is sion. This is illustrated in Fig. 3, which examines the relation thus a process by which the interstellar dust converts the between the mean radiation field responsible for heating the incident radiation field from higher-energy photons to in- large dust grains and the far-infrared luminosity (see Paper frared photons, and the goal of inferring the primary mecha- I ) of the galaxy. We have assumed that the far-infrared emis- nisms for producing the infrared luminosity must follow sion is dominated by the emission from large grains (radius from an understanding of the reprocessing mechanism. a—0.1 pm ), and that the ratio of60-100 pm flux densities is In this picture, the dust grains should reach a steady state determined by the temperature T% of the grains emitting when the absorption of short-wavelength radiation is bal- with a emissivity proportional to frequency. The total power anced by long-wavelength emission. Thus the infrared emis- radiated by these grains (proportional to must equal the sion measures the intensity and spectrum of the radiation energy absorbed; this is proportional to the intensity of the field in which the dust grains are embedded. In general, the short-wavelength radiation field convolved with the grain- emission observed at 60 and 100 /¿m appears to agree with absorption cross section, often assumed to be constant at the this premise, although Helou (1986), among others, has relevant wavelengths. Since the absolute intensity of the ra- shown that the 12 and 25 /¿m radiation from galaxies is con- diation field that heats the dust cannot be determined unless sistent with the combined effects of this effect plus the tran- the filling factor of the dust responsible for the far-infrared sient heating of small grains by single UV/optical photons. emission is known, we have arbitrarily normalized the inten- Nonthermal processes are dismissed because many of the sity to unity at a grain temperature of 25 K. Figure 3 is sources are spatially resolved, and none of the objects shows equivalent to the plot of >SV (60pm)/Sv ( 100pm) versus lu- evidence for nonthermal processes producing significantly minosity, as in, e.g., Paper I, but is cast into the more phys- luminosity at the shortest radio wavelengths. Line emission ical, although model dependent, form of intensity of the radi- © American Astronomical Society • Provided by the NASA Astrophysics Data System C/} UD r" 00 790 SOIFER ETAL. : IRAS BRIGHT GALAXY SAMPLE 790 ^0 (S\ 00 c 13 X Ö _Q O KV (/) Fig. 3. The intensity of the radiation heating the far-infrared emitting dust grains plotted versus the far- 5 infrared luminosity of the galaxies in the BG sample. The intensity is derived as / = ( Tg/T0) where Tg is the dust grain temperature determined from the equation 5(60//m,!^) 60 w Sv(60/im) 5(100/^1,7;) ~ 100 X ^(100//m) ’ and T0 is arbitrarily taken as 25 K (effectively taking grains with emissivity proportional to frequency). In this plot, as in all subsequent plots, the BG sample is separated into “warm” galaxies, with 5V ( 25 yum )/Sv ( 60 /¿m ) >0.17, and “cold” galaxies with ^ ( 25 /¿m ) /Sv ( 60 yum ) < 0.17. The lines shown are best fits to the separate subsamples of warm and cold galaxies assuming the form log I = A log Lfir + B. ation field that heats the dust as the ordinate versus infrared et al. 1987; Rowan-Robinson, Helou, and Walker 1987). luminosity. This figure also shows that there is a significant spread in In Fig. 3, and the subsequent figures, galaxies are separat- mean radiation field, more than an order of magnitude, at ed by the ratio of their 25-60 ¡im flux densities into warm any luminosity, for the entire sample. If the subsamples of and cold systems. This separation is made for ^(25 ¡im)/ warm and cold galaxies are viewed individually, the disper- Sv ( 60 //m) = 0.17, which is nearly the value found by Miley sion is lessened for each subsample. At large luminosities, et ah (1985) to be the demarcation between warm the warm galaxies have a higher mean radiation field intensi- (25/zm)/^(60/zm) >0.2] “infrared selected” Seyfert ty than the cold galaxies for a given total infrared luminosity. 11 galaxies, and cold infrared bright non-Seyfert galaxies. For Above Lfir ~ 10 Z,0, the spread in the radiation field inten- uniformity, we will subsequently refer to those galaxies with sity of the two subsamples are about equal, about a factor of Sv (25 yizm)/Sv (60 /zm) > 0.17 as the “warm” galaxies, with 6, with the mean level for the warm galaxies being larger by a the others as the “cold” galaxies. The separation at 0.17 factor of—3. places 51 galaxies, or \ of the total BG sample, in the “warm” At lower far-infrared luminosities, the spread in the radi- category. We note that the ratio ASv(25ytzm)/5v(60ytzm) ation field intensity for the warm galaxies becomes signifi- 10 shows no significant correlations with any of the quantities cantly larger, reaching a factor of —20 at Lfir ~10 Lo, discussed in this paper, so that those relations that distin- while the spread for the cold galaxies remains roughly con- guish between the warm and cold infrared galaxies based on stant at a factor of 6. The mean radiation field intensity re- the ratio Sv ( 25 /zm ) /Sv ( 60 /zm ) cannot be due to such cor- mains roughly constant for galaxies with luminosities L 10 relations. Further, Smith et al. ( 1987) found no correlation < 10 Z,o. If interpreted literally, this means that below this of the ratio *5^(25 /znO/S^bO/zm) with either luminosity luminosity there is no systematic change in radiation field at 60 /zm, or Sv ( 60 /zm ) /Sv ( 100 /zm ), again suggesting that with infrared luminosity, so the quantity that is changing is this criterion for dividing the BG sample is not obviously the amount of radiating dust. While such an effect could be a biased. consequence of the 60/zm selection criterion, the bolometri- The grain temperature inferred from the ratio cally selected subsample of the BG sample shows a quite , *S v(60/zm)/5v(100/zm) is the (dust) mass-weighted grain similar distribution of intensities (Soifer et al. 1989) arguing temperature, or, effectively, the mass-weighted intensity of against such a selection effect. Alternatively, Boulanger et the radiation field that heats the dust. Figure 3 shows qual- a/. ( 1988) have suggested that at the lowest luminosities the itatively that, as expected, the mean radiation field increases nonsteady state emission of small grains begins to contribute as the infrared luminosity increases. This has been seen in significantly to the observed 60 /zm flux density, thereby in- several other samples of 60/zm selected galaxies (e.g., Smith creasing the inferred dust temperature. © American Astronomical Society • Provided by the NASA Astrophysics Data System C/} UD r- 791 SOIFER ETAL. : IRAS BRIGHT GALAXY SAMPLE 791 O'!00 While the radiation field intensities inferred from the 60 source of the changing infrared luminosity is only weakly ^0 and 100 /zm flux ratios vary in the expected manner with seen in the optical luminosities of these galaxies. infrared luminosity, the same cannot be said for the Figures 3-5 show that while there are significant trends in 00 Sv(\2^m)/Sv(25fim). Figure 4 shows a decrease of the variation of the infrared properties with the infrared lu- Sv ( 12 fim)/Sv (25 ,um), i.e., decreasing color temperature, minosity of galaxies, there is a significant dispersion of the with increasing infrared luminosity. This variation of mean radiation field and ratio of infrared to optical light at a given infrared luminosity. The properties of galaxies in the 5v(12/zm)/iSv(25ium) with luminosity is counter to the expected behavior of steady-state dust heating, where in- infrared thus cannot be thought of as a sequence described creasing luminosity would result in increased dust tempera- by the single parameter of the infrared luminosity. ture. A measure of the infrared luminosity per unit galaxy There is a distinction between the warm and cold galaxies mass, might more properly parametrize the infrared proper- in Fig. 4, in the sense that the warm galaxies have a lower ties of galaxies, since the infrared luminosity measures both the mean radiation field heating the dust and the mass of value 0^(12 ¿zm )/Sv ( 25 ytzm ) at a given value of Lfir. This distinction is consistent with the measure of the radiation dust in the galaxy. In Fig. 6, the radiation field intensity field intensity as shown in Fig. 3, i.e., at a given luminosity derived from the ratio SV{6Qtim)/Sv(\0D¡zm) is plotted against the infrared-to-visible light ratio in these galaxies. To the intensity determined from Sv ( 60 /zm ) /Sv ( 100 (im ) is higher in the warm galaxies than in the cold galaxies. Taken the extent that in these galaxies the mass-to-(visible) light purely as phenomenology, the behavior of the ratio ratio is constant, the infrared-to-visible light ratio is a mea- sure of the infrared luminosity per unit mass of the galaxy. Sv ( 12 yUm)/*Sv (25 /zm) with infrared luminosity, although not physically reasonable, is consistent with the ratio The trend of increasing radiation field intensity with increas- ing infrared to visible light ratio is seen for both the warm 5v(60yizm)/5'v(100ytzm) being a measure of the radiation field intensity. and cold galaxy subsamples. Again, the warm galaxies have As discussed in Paper I, in Feigelson et al. ( 1987) and in a higher mean radiation field at a given infrared-to-visible Smith et al. ( 1987), there is a reasonably tight correlation ratio than do the cold galaxies. between the ratio of infrared to visible flux and the infrared In Fig. 5 the loci of the warm and cold galaxies are virtual- ly indistinguishable. In contrast, the warm and cold galaxies luminosity. This relation has been refined with the new data, and the results are plotted in Fig. 5. The visible magnitudes, are easily distinguished in Fig. 6. Furthermore, the spread in taken predominantly from the Zwicky catalogs, have uncer- the intensities for the warm galaxies in Fig. 6 is significantly tainties of at least 0.5 mag, and so half the spread in infrared- less than the spread in Fig. 3. In Fig. 6 the spread in radiation to-visible flux ratio at a given infrared luminosity could be field intensity is roughly a factor of 3 at a given infrared-to- due simply to the uncertainties in the visible magnitudes visible light ratio for the warm galaxies, while in Fig. 3 the used to calculate the infrared-to-visible flux ratio. As dis- spread in radiation field intensity is a factor of 5 over the entire range in infrared luminosity, and a factor of —20 at cussed in Paper I, the nearly linear slope between infrared- to-visible flux ratio and L suggests that the source of the low infrared luminosities. fir The significant reduction in the scatter of the relation infrared luminosity is decoupled from that producing the between the radiation field and infrared-to-visible flux ratio observed optical radiation, i.e., the highest luminosity in- (Fig. 6), as compared to the relation between radiation field frared galaxies are only slightly more luminous in the visible and infrared luminosity (Fig. 3) for the warm galaxies, but than the typical galaxies in the sample. As the infrared lumi- not the cold galaxies, is surprising. This tightening of the nosities of galaxies vary by a factor of ~ 3000, the visible correlation is made more significant by noting that the visi- luminosities change by roughly a factor of 20. Thus the ble magnitudes for the galaxies, taken predominantly from Fig. 4. The ratio of SVC 12/mi)/ Sv(25 /¿m) plotted versus far-infrared luminosity for the warm and cold sub- samples of the BG sample. © American Astronomical Society • Provided by the NASA Astrophysics Data System C/} UD r" 00 792 SOIFER ETAL. : IRAS BRIGHT GALAXY SAMPLE 792 ^0 Fig. 5. The ratio of far-infrared flux F (S\ lK 00 to visible flux, plotted versus far-in- frared luminosity for the warm and cold subsamples of the BG sample. The far- infrared flux is determined using the measured 60 and 100 //m flux densities, and the algorithm described in Appen- dix B of Cataloged Galaxiesand Quasars Observed in the IRAS Survey (1985). The visible flux is i/v(0.44//m), where /v (0.44 fim) is derived from the Zwicky magnitude mz using the conversion to mB described in Kirschner, Oemler, and Schechter (1978). The lines are best fits of the form logiF^/F^ ) = A log(LFIR ) + 2? to the warm and cold subsamples separately. LOG [Lfir/Le] the Zwicky catalogs, have large ( > 0.5 mag) uncertainties, The emission of galaxies at 12 and 25 //m shows the ex- significantly larger than the measurement error in the in- pected qualitative behavior in relation to the infrared-to-visi- frared fluxes of the galaxies. ble flux ratio. The correlation between the Sv{\2fim)/ In summary, the mean radiation field viewed by the dust Sv{25 yum) ratio and the infrared-to-visible flux ratio in Fig. and the infrared luminosity per unit visible luminosity ap- 7 is substantially tighter for the warm galaxies than for the pear to be coupled for the warm galaxies. The slope of the cold galaxies; the total spread in ^ ( 12 ¡jLm)/Sv (25 fim) ra- relation suggests that for the warm galaxies the variation in tio at a given infrared-to-visible ratio is a factor of 10 for the luminosity is dominated by the variation in the radiation cold galaxies and a factor of 4 for the warm galaxies. There is field intensity, rather than by the variation in the dust con- a clear difference in the relation between the warm and cold tent of the galaxies. This is consistent with the much weaker galaxies, with the warm systems having a significantly lower correlation between dust mass and luminosity for the warm value of ( 12 fim)/Sv{25 fim) at given infrared-to-visible galaxies than for the cold galaxies (see below). flux ratio than the cold systems. Again, as in Fig. 6, a large Perhaps as surprising as the comparatively tight relation contribution to the spread of infrared to visible flux ratio for between the radiation field intensity and infrared-to-visible the warm galaxies can be attributed to the uncertainties in light ratio in the warm galaxies is the lack of any substantial- the visible magnitudes of the galaxies. ly improved correlation between these quantities as com- The warm galaxies appear to have a significant reduction pared to the intensity versus luminosity relation in the cold in spread in Sv ( 12 Jam)/»SV (25 /¿m) at a given infrared-to- galaxy sample. It is puzzling that there is an apparently clear visible flux ratio as compared to the spread as seen in Fig. 4, distinction between warm and cold galaxies in Fig. 6, par- where Sv ( 12 (im)/Sv (25 fim) is compared to the infrared ticularly given the comparatively minor distinction between luminosity. The behavior of the Sv ( 12 iim)/Sv (25 ¿¿m) ra- the two subsamples in most properties. tio versus infrared-to-visible flux ratio is counter to the phy- c =3 O _Q Fig. 6. The intensity of radiation heating O the far-infrared emitting grains plotted versus the ratio of FXK /Fvis. The lines are > best linear fits to the warm and cold sub- 00 samples of the BG sample. © American Astronomical Society • Provided by the NASA Astrophysics Data System C/} UD r" 00 793 SOIFER ETAL. : IRAS BRIGHT GALAXY SAMPLE 793 ^0 (S\ 00 Fig. 7. The ratio 5^(25/4111) plotted versus the ratio of Fir /Fvis for the warm and cold galaxies of the BG sample galaxies. sically intuitive one, i.e., as the infrared-to-visible flux ratio cantly affected by the requirement of being detected and , increases, the ratio of *S'v(12//m)/5 v(25yam) decreases unresolved at all four IRAS wavelengths. Because of the sub- (the grains get colder). This effect has been attributed to a stantially higher 60 pm flux-density threshold of the BG manifestation of small grains in the radiation field of the sample, and the detection of virtually the entire sample at all galaxies ( see below ). wavelengths, the BG sample is not affected by such implicit selection effects. c) Infrared Colors and Systematic Variations in Galaxy Qualitatively the differences in slope between the warm Properties and cold samples seen in Fig. 8(a) can be explained as a Because the BG sample is virtually complete in all IRAS result of the combined effects of the small dust grains in the colors, these data are ideal for studying the systematic varia- radiation field and radiative transfer effects. At the lowest tions of the infrared colors of infrared bright galaxies. The values of ^(bO/imJ/^ilOO/zm) (i.e., lowest radiation Sv(60 iim)/Sv(\00 pm) ratio is plotted versus the field intensities), the cold galaxies show larger values of r 5'v(12/am)/*Sv(25//m) ratio in Fig. 8(a). Helou (1986) ( 12 pm)/Sv (25 pm) than do the warm galaxies. At these has found that for galaxies in the IRAS survey, the 12-25 pm low radiation field intensities, the ^ (60pm)/Sv ( 100pm) color temperature appears to increase as the 60-100 pm col- ratio is most sensitive to a non-steady-state contribution of or temperature decreases. Figure 8(a) shows that this rela- small grains to the 60 pm flux as suggested by Boulanger et tion holds for both the warm and cold galaxies in the BG al. (1988). Thus the ratio *5^(12/zm)/^ (25 ¿¿m) could be sample. This relation reflects the correlations between ob- dominated by the small grain, non-steady-state emission served colors and luminosity found in Figs. 3 and 4. While processes. In contrast, the 60 pm emission is a combination Helou and others have interpreted this color-color plot as an of steady-state emission from large grains and non-steady- activity sequence in galaxies, where the higher infrared ac- state emission in small grains and in the coldest galaxies the tivity is reflected in a systematic increase of the value of ^(bOz/mV^VOOO/mi) is larger than would be *S'v(60//m)/5v(100^m) ratio and decrease of the determined purely by steady-state emission of large grains. *5^ ( 12 pm)/Sv (25 pm) ratio, the properties derived above Qualitatively this behavior is consistent with the lack of vari- for the BG sample demonstrate that the underlying measure ation of intensity with infrared luminosity at low infrared of “infrared activity” is not simply infrared luminosity or luminosity as seen in Fig. 3. infrared-to-visible flux ratio. Rather, these results show that At the highest radiation field intensities, the cold galaxies the systematic variations in infrared colors seen in Fig. 8(a) show a lower ratio of 5'v(12//m)/5'v(25//m) than do the have a more complex origin. warm galaxies for a given value of Sv ( 60 pm ) /Sv ( 100 pm ). Helou (1986) found a distinction between the warm and The reduced ratio of Sv ( 12 ^m)/5v (25 pm) can be under- cold systems where the warm systems had a great deal more stood as the effects of radiation transfer on the 12 and 25 pm scatter than the colder systems when the ratio ( 12pm)/ radiation as it escapes the infrared-emitting region. For ex- Sv(25 pm) is plotted versus Sv (60 pm)/Sv ( 100 pm). Such ample, Arp 220 is a high-luminosity “cold” galaxy that has an increased scatter is not seen in Fig. 8(a). Instead, the the smallest observed 5V ( 12//m)/5'v(25//m) ratio. It is © American Astronomical Society • Provided by the NASA Astrophysics Data System O'! 00 CD CD r" CO 794 LOG [S¡,(12¿¿m)/Sj,(i oo¿¿m)] Z LOG [5^(12/^m)/S[/(60/xm)] £ LOG [Sj.C 12^m)/S¡/(25//m)] © American Astronomical Society • Provided by the NASA Astrophysics Data System -1.0 -0.5 -2.0 -1.5 -2.5 SOIFER ETAL.:IRASBRIGHTGALAXYSAMPLE -0.8 -0.4 0.0 LOG [S(60am)/SlOO/zm)] LOG [S(60L¿m)/S1OO/xm)] LOG [S(60^m)/S1xm)J ¡y/ iy/l zyi/ sample. SV(60¿mi)/SV(100¿mi) fortheBG SV(100¿mi) plottedversustheratio separately, (c)TheratioSV(12¿mi)/ the formlog[S'(12¿¿m)/S'60¿ím)] SVC60¿mi)/SVC 100¿mi)fortheBG sample. Thelinesarebestlinearfitsof 5'(60wm)/*S'10//m) fortheBG separately, (b)TheratioS{\2fim)/ the formlog12¿/m)/^25¿mi)] sample. Thelinesarebestlinearfitsof S(25fim) plottedversustheratio Fig. 8.(a)TheratioS(\2tim)/ v vi v v + 2?tothewarmandcoldsubsamples v = ,4log[SV(60¿/m)/SV(100¿/m)] + ^tothewarmandcoldsubsamples =/Hog^tóO^m)/^ 100/mi)] 60¿mi) plottedversustheratio 794 1989AJ 98. .7663 log5(60/im)/*S'100^m) =—0.4,of—7.5magis This isbecausetherequiredmeanAevenat fuse interstellarradiationfieldrecycledintotheinfrared. nosity sourcesarehighlylocalized,ratherthanbeingadif- by —0.25at12//mlogAS(60//m)/S100/mi) is correct,itdirectlydemonstratesthattheinfrared-lumi- crudely to30magofvisibleextinctiony4.Ifthisexplanation between thewarmandcoldsystemsisduetodifferentmean for thedistinctionincolorsofwarmandcoldgalaxies difference inmean12¡imopticaldepthis1,corresponding mean opticaldepththatislargerthaninthewarmgalaxies optical depths,thenthecoldgalaxiesareviewedthrougha optical depthbetween12and60/¿m.Iftheentireseparation tioned above,whichareenhancedbythelargerratioofdust explained astheresultsofradiative-transfereffectsmen- similar behaviorisseenwhenthe(12^m)/S100¡im) luminosity foundbySmithetal.(1987).Aqualitatively that betweentheratio^(12/¿m)/S(60//m)andinfrared seen inFig.8(c). ratio isplottedagainstthe^(60fj,m)/S(100/¿m),as correlated intheinfraredluminosity,thiseffectissimilarto ^(óO^mJ/^í lOO/zm)correspondstoadecreaseinthe tems. TotheextentthatratioS(60fim)/S100//mis of S{\2fim)/S60fim)thanfoundinthewarmersys- cold galaxiesshowanextensiontosubstantiallylowervalues more scatter,isseeninthewarmgalaxies.Inaddition, ratio *S(12//m)/560//m).Asimilareffect,withmuch v vi v plotted versusS(\2fim)/S6Qnm),asshowninFig. distinguishable whentheratio^(óO/mO/SVOOO^m)is v lower observedvaluesof^(12¡im)/S(25¡¿m). value ofS{\2tim)/S(‘5pm)issignificantlyalteredby be concentratedtothegalaxynuclei(Scovilleetal.1986; O 8(b). Forthecoldgalaxies,anincreaseinratio radiation-transfer effectsinthecoldgalaxies,producing Sargent étal.1987),itisentirelyplausiblethattheobserved the gasbelievedtobeassociatedwithdustisobserved of coldmaterialatagivenluminosity(seeFig.9below),and 795 SOIFERETAL.:IRASBRIGHTGALAXYSAMPLE luminosities, thecoldsystemshavesignificantlymoremass O v v v v v v = —0.4,whileatlog^ibO^ml/^ilOO/zm)0,the v v v ~o 00 D © Part oftheseparationwarmandcoldgalaxiescanbe The warmandcoldgalaxiesintheBGsampleareclearly © American Astronomical Society • Provided by the NASA Astrophysics Data System L0G [LfirAJ 91 5 -^gas >5X10forL3.Furthermore, higher luminositygalaxies. sion, theprocessmustbeanincreasinglytransientonein massive starscontributesubstantiallytotheinfraredemis- creasing withincreasinginfraredluminosity,thenifyoung tion thatwehavetaken^—L/T,sotheabscissa therefore themeanradiationfieldmustbelargertoproduce have systematicallylessdustmassatagivenluminosity,and nosity, i.e,themeanradiationfieldheatingdustisin- galaxies withthelargestamountsofinterstellardust,i.e.,if ty forthe“cold”and“warm”galaxiesinFig.9.Theappear- since theratioofdecreaseswithincreasinglumi- the gastodustmassratiois150,thenof ly requiresthatthemostluminoussourcesoccurwithin ation fieldincreaseswithincreasingluminosity,asseenin dust mass,atagiveninfraredluminosity.Themeanradi- this plotshowsthatthereisonlyafactorof—4spreadin and ordinatearenotindependentquantities.Nonetheless, ance ofatightcorrelationmustbetemperedwiththerealiza- ing dustemissivity—vbetweenthesetwowavelengths. Fig. 3.Theincreaseofdustmasswithluminosityimmediate- from theobservedratioofS(bO/zm)/^(100/¿m),assum- perature approximation,withthedusttemperaturederived dust massfortheBrightGalaxies,usingsingledust-tem- the dustparametersofDraineandLee,wehavederived reasonably wellknown(e.g.,DraineandLee1984).Using particles responsibleforthe60and100fimemissionare sion. Ontheotherhand,opticalpropertiesoflarge meaningfully derivethemassrequiredtoproducethisemis- cal propertiesareatthispointonlypoorlyknown,wecannot icantly affectedbyemissionfromsmallparticleswhoseopti- firQ dustfir not observed. ral galaxies.Further,suchlargeaverageAwouldrequire v visible luminositiesthanopticallyselectedspirals,whichis the infraredbrightspiralstohavedrasticallylowerapparent much largerthanfoundonaverageforeventhedustiestspi- v The deriveddustmassisplottedversusinfraredluminosi- Figure 9mostclearlyillustratesthatthewarmgalaxies Because theradiationat12and25/¿misapparentlysignif- d) MassofDustinInfraredBrightGalaxies 5 independent. two parameters^and£arenot relation -#aL/Tsothatthe ple. Thedustmassiscalculatedfromthe far-infrared luminosityfortheBGsam- Fig. 9.Themassofdustplottedversus dustFIR dustrxKd 795 1989AJ 98. .7663 1 best and,moretypically,afactorof5. ^(óO/jml/^OOO/zm) and5'(12um)//S5//m),first served ratioofS(25¡im)/S60¡im)showqualitatively temperature inferredfromtheratioof60-100¡imflux that heatstheradiatingdust,measuredbyresultantdust the infraredemissioninBGsample.Theradiationfield mines othermeasurablepropertiestowithinafactorof2at sured globalpropertyoftheinfraredbrightgalaxiesdeter- properties bymanyordersofmagnitude.Nochoicemea- of S{\2fim)/S(60¡im)and S{\2¡im)/SQO¡im) and coldsubsamplesoftheBGsample.Thewarm galaxies. Thestronginverserelationbetween by theemissionfromlargedustgrainswhichradiatein to-visible light. ation fieldwithinfraredluminosityortheratioofinfrared- samples oftheBGsample,selectedonbasisob- obscured bythedustinthesesystems.Warmandcoldsub- the starspoweringinfraredluminosityaresignificantly infrared tovisiblefluxratiointheBGsample,implyingthat densities, isproportionaltotheinfraredluminosityand and coldgalaxies. observed distinctionsbetweenthe IRAScolorsofthewarm ed thatsignificantopticaldepth effectscausesomeofthe when plottedversusS(60fim)/S (100/zm).Itissuggest- galaxies alsoshowdistinctions between theobservedvalues found byHelou(1986),istoholdforboththewarm nosity, demonstratingthattheinfrared-luminositysources ing radiationfield.TheBGsampleshowsastrongcorrela- transiently heatedtohightemperaturesbytheabsorptionof taken asevidenceforasubstantialcontributiontotheemis- similar, butquantitativelydifferent,variationsoftheradi- are onlyweaklyseeninthevisibleoutputofinfraredbright tion oftheinfrared-to-visiblefluxratiowithinfraredlumi- steady stateandreflectthemeanenergydensityofheat- single UVphotons.Thisemissioncontributionismodulated sion ingalaxiesatwavelengthsA<25/¿mfromsmallgrains opposite senseastheratioS(60/¿m)/S(100fim).Thisis luminosity andwiththeinfrared-to-visiblefluxratioin IRAS BrightGalaxysampleof313extragalacticsources and appearstocontainsignificantcompletesubsamplesat The BGsampleisstatisticallycompleteat60[¿mto5.24Jy, between thewarmandcoldsystems.Furthermore, the sameluminosity.Ataninfraredluminosityof10L, frared brightgalaxiesinthelocalUniverse. available atthistimetodefinetheinfraredpropertiesofin- infrared brightgalaxiesobservedintheIRASall-skysurvey. the mostcompletedescriptionofinfraredproperties with S(60fim)>5.24Jy.Becausethesegalaxiesarenearly between dustmassandinfraredtovisiblefluxratioissignifi- this representsalmostafactorof2differenceindustmass v/ v all detectedatIRASwavelengths,thissamplerepresents minosity. cantly poorerthanthatbetweendustmassandinfraredlu- ies. ForbothsubsamplesoftheBGsamplecorrelation dust massandinfraredluminositythandothewarmgalax- galaxies showasignificantlytightercorrelationbetween v v v v 796 SOIFERETAL.:IRASBRIGHTGALAXYSAMPLE v 12, 25,and100fimaswell.Thissampleisthereforethebest 0 v Thermal emissionfromdustgrainsistakentodominate The ratioS(12//m)/Y25¡im)isfoundtovarywith Infrared brightgalaxiesarefoundtovaryintheirinfrared The massofinterstellar dustrequiredtoproduce theob- © American Astronomical Society • Provided by the NASA Astrophysics Data System In thispaperwecompilecompleteIRASdataforthe v VI. SUMMARY 1-1 Extended MissionProgram. Carrah Wrightinpreparingthemanuscriptandtables. formed tobluemagnitudesusing thepreceptsofKirschner, Zwicky magnitudes(Zwickyetal.1961-1968),trans- km s~Mpcatlargedistances). tance of17.6Mpc(correspondingtoaHubbleconstant75 Aaronson andMould(1983),adjustedtoaVirgodis- Tully distancesaretakenfromAaronsonetal.(1982),or taken fromSandageandTammann(1981),whileFisher- ence totheradialvelocitydistance.Primarydistancesare graph (OkeandGunn1982)onthe5mHaletelescope(see Bright Galaxies(deVaucouleurs,deandCor- columns included.Thefirstcolumn givesthebestestimate scope, andreportedinPaperI. Oemler, andSchechter(1978). Allotherobservationsare Fisher-Tully distancewasavailablethisisgiveninprefer- able. Forthosegalaxieswheretheredshiftwasnotavailable ing ofinfraredcolorsgalaxies. of thetotalIRAS fluxdensityinJanskysmeasured at\2fim. CCD bmagnitudesobtainedusing thePalomar1.5mtele- Paper Ifordetails). in thesecatalogs,itwasmeasuredusingtheDoubleSpectro- ity ifavailable,oropticalredshiftnoHIvelocityisavail- private list),andselectedinorderofpriorityastheHIveloc- position wastakenfromtheSecondReferenceCatalogof the nameistakenindecreasingpriorityorderfrom the BGsource.TheconventionissameasinPaperI,i.e., vided manyhoursofstimulatingconversationsonthemean- addscan/scanpi processingwithgreatpatience,andpro- tion. GeorgeHelouguidedusthroughtheintricaciesof the IRASLargeGalaxyCatalogwellinadvanceofpublica- zella-Nitta, andVettalani1983;Huchraetal.Rood, this wastakenfromamajorredshiftcatalog(Palumbo,Tan- win, 1976). except forthoselargegalaxiesfromRiceetal.wherethe per Iandarenotlistedhere. mon names)suchasMessierorArpnamesaregiveninPa- karian, andIRAScatalogs.Alternate(andoftenmorecom- NGC, UGC,IC,MCG,Zwickycatalog,lists,Mar- puter outputsintoamostusefulform.WalterRiceprovided dez, LarryLloyd,andCynthiaBennetorganizedthecom- fully andquickly,whiletheLibrarystaff,RosanneHernan- support ingatheringthedatausedhere.Inparticular, infrared luminosity,thereisarangeoffactor—4inthe decreases withincreasinginfraredluminosity.Atagiven frared luminosityingalaxies,whiletheratioof^/L served far-infraredluminosityincreaseswithincreasingin- Data ManagementTeamprocessedthedatarequestscheer- frared luminositythanthewarmgalaxies. BG samplehavingsystematicallymoredustatagivenin- amount ofdustmassobserved,withthecoldgalaxiesin dustfir This researchwassupportedbyNASAthroughtheIRAS Finally, itisagreatpleasuretoacknowledgetheeffortsof The entriesinTable1(a)areasfollows: It isapleasuretothankmanypeopleatIPACfortheir (5) m(fromPaperI).Inmostcasestheseareobserved (4) Distance(fromPaperI).Wherea“primarydistance (6) IRASmeasurementsat 12 jxm.Therearethree (3) Radialvelocity,cz(fromPaperI).Whereavailable (2) 1950position.AllpositionsaretakenfromthePSC ( 1)Objectname.Thisisthecommoncatalognamefor z APPENDIX A 796 1989AJ 98. .7663 1 / ~v~powerlawspectrum.Anegativenumberindicates IRAS CatalogsandAtlases:PointSourceCatalog(1988)(U.S.GPO, Miley, G.K.,Neugebauer,G.,andSoifer,B.T.(1985).Astrophys.J.Lett. Aaronson, M.,andMould,J.(1983).Astrophys.265,1. Lonsdale, C.J.,Helou,G.,Good,J.C.,andRice,W.,compilers(1985). Kirschner, R.P.,Oemler,A.,andSchechter,P.L.(1978).Astron.J.83, Huchra, J.,Davis,M.,Latham,D.,andTonry,J.(1983).Astrophys. de Vaucouleurs,G.,A.,andCorwin,H.Jr.(1976). Crawford, M.K.,Genzel,R.,Townes,C.H.,andWatson,D.(1985). Becklin, E.E.,andWynn-Williams,C.G.(1987).InStarFormationin Aaronson, M.,etal.(1982).Astrophys.J.Suppl.50,241. Helou, G.,andWalker,D.,Eds.(1988).CatalogsAtlases:Small Helou, G.,Khan,I.R.,Malek,L.,andBoehmer,L.(1988).Astrophys.J. Helou, G.(1986).Astrophys.J.Lett.311,L33. Feigelson,E. D.,Isobe,T.,andWeedman,D.W.(1987).Astrophys.J.319, Draine, B.T.,andLee,H.M.(1984).Astrophys.J.285,89. Boulanger, F.,Beichman,C,Désert,F.X.,Helou,G.,Pérault,M.,and 797 SOIFERETAL.:IRASBRIGHTGALAXYSAMPLE same asforthe12/umfluxdensities. same asforthe12/imfluxdensities. integrated fluxforthesource. v plate fitforthesource.U+indicatesthatsourceismar- same asforthe12/umfluxdensities. clearly resolved.Again,thefluxdensityinthiscaseis the integratedfluxforsource.Rindicatessourceis ginally resolved.Inthiscasethefluxdensityreportedhereis this casethefluxdensityistakentobepoint-sourcetem- gives theextentcode.C/indicatessourceisunresolved.In mJy, measuredawayfromthesource.Thethirdcolumn data. Anasteriskbyanumberindicatesthatthefluxdensity in theIRAScatalogsisbasedonassumptionofan second columngivesthermsnoiseforcoaddedscan,in an upperlimit,whichis3timesthermsnoiseofcoadded Because ofthebroadbandpass,fluxdensityasreported (or limit)wastakendirectlyfromRiceetal.(1988).The Scale StructureCatalog(U.S.GPO,Washington,DC)(SSS). No. D-1932. Washington, DC)(PSC). Second ReferenceCatalogueofBrightGalaxies(UniversityTexas, Suppl. 52,89. Austin). Astrophys. J.291,755. 2466, p.643. 193, LI1. Cataloged GalaxiesandQuasarsObservedintheIRASSurvey,JPLPubl. Suppl. 68,151. L51. Ryter, C.(1988).Astrophys.J.332,328. Galaxies, editedbyC.J.Lonsdale,NASAConferencePublicationNo. 1549. The entriesinTableIIareasfollows: ( 1)NameofsourcefromTableI. (9) IRASmeasurementsat100pm.Thedetailsarethe © American Astronomical Society • Provided by the NASA Astrophysics Data System (8) IRASmeasurementsat60|xm.Thedetailsarethe (7) IRASmeasurementsat25\im.Thedetailsarethe APPENDIX B Zwicky, F.,etal(1961-1968).CatalogofGalaxiesandClusters Soifer, B.T.,Sanders,D.B.,Neugebauer,G.,Danielson,G.E.,Lonsdale, Soifer, B.T.,Sanders,D.B.,andNeugebauer,G.(1989).Inpreparation. Soifer, B.T.,Sanders,D.B.,Madore,F.,Neugebauer,G.,Danielson, Palumbo, G.C,Tanzella-Nitta,G.,andVettolani,(1983).Catalog Oke, J.B.,andGunn,E.(1982).Publ.Astron.Soc.Pac.94,586. Soifer, B.T.,etal.(1984).Astrophys.J.Lett.278,L71. Smith, B.J.,Kleinmann,S.G.,Huchra,J.P.,andLow,F.(1987). Sanders, D.B.,Soifer,B.T,Madore,andNeugebauer,G.(1989).In Sanders, D.B.,Soifer,B.T,Elias,J.H.,Neugebauer,G.,andMatthews,K. Sandage, A.,andTammann,G.A.(1981).ARevisedShapely-AmesCata- Rowan-Robinson, M.,Helou,G.,andWalker,D.(1987).Mon.Not.R. Rice, W.L.,Lonsdale,C.J.,Soifer,B.T.,Neugebauer,G.,Kopan,E. Scoville, N.Z.,Sanders,D.B.,Sargent,A.I.,Soifer,B.T.,Scott,S.L.,and Sargent, A.I.,Sanders,D.B.,Scoville,N.Z.,andSoifer,B.T.(1987). entry isgiven,andthesourceofdatanoted. some oftheentriesarenotappropriate.Inthesecases,no point-source width. sity. Again,noattempthasbeenmadetodeconvolvethe source width. sity. Noattempthasbeenmadetodeconvolvethepoint- the source. while thepeakfluxissimplymaximumdensityof described intheIRASExplanatorySupplement(1988), density becausethetemplatefitsabaselinetodataas age scanofthesource.Thiscandifferfromtemplateflux the bestfittoaveragedscandata. sity fromtheamplitudeofapoint-sourcetemplatethatwas unresolved. source atanywavelengthwherethewasclassifiedas U +orR.Noadditionalinformationisprovidedfora 320, 238(PaperI). L41. C. J.,Madore,B.F.,andPersson,S.E.(1986).Astrophys.J.Lett.303, G. E.,Elias,J.H.,Lonsdale,C.J.,andRice,W.L.(1987).Astrophys. Astrophys. J.318,161. preparation. log ofBrightGalaxies(CarnegieInstitute,Washington,DC). Astron. Soc.227,589. 68,91. of RadialVelocitiesGalaxies(GordonandBreach,NewYork). Lo, K.Y.(1986).Astrophys.J.Lett.311,L47. Astrophys. J.Lett.312,L35. Lloyd, L.A.,deJong,T.,andHabing,H.(1988).Astrophys.J.Suppl. (California InstituteofTechnology,Pasadena). (1988). Astrophys.J.Lett.328,L35. In somecases,wherethedataaretakenfromRiceetal. ( 8)ObservedsourcewidthW50at50%ofpeakfluxden- (7) ObservedsourcewidthW25at25%ofpeakfluxden- (6) Peakfluxdensity—thepeakdensityintheaver- (5) Templatefluxdensity—theestimateoftheden- (4) Totalfluxdensity—fromTableI. (3) Resolutioncode—fromTableI.Thiswillbeeither (2) Wavelengthforfollowingdata. 797 o©>n©»noorN)»n-<»nr-;n¿mo r^o-iooc^ooi-i ,vfr0 dcóe^od^r’Vodddv-Íod^eoooincQOes’r^^do^-'vndrH’vdddodr^’ddoeid es-í-Tí-