198 9ApJS. . .70. .731L © 1989.TheAmericanAstronomicalSociety.Allrightsreserved.PrintedinU.S.A. The AstrophysicalJournalSupplementSeries,70:731-812,1989August ing, systematically,theinterstellarcontentsofyoungopen Westerhout (1968;hereafter GHW) whousedthe21cmline under studyisunknown,andbecauseuncertaintiesexist in molecular cloudsaredestroyedbystarformation.Detailed discussion hascenteredonthequestionofwhetherandhow This approachwasfirstemployed byGordon,Howard,and cumvents ordilutestheimpactofcomplicationsthatarise in clouds. conditions, becausetheexactstateofevolutionsystem one seeksisanunderstandingofthemechanismbywhich studies ofindividual,isolatedregionsareinadequateifwhat cator ofthepresenceionized gasaround41clusters.Bash, cluster environments,consideringclustersofarangeages. stars interactwithnearbyinterstellarmatter(ISM)that cir- appearance ofanindividualregioncanbeaffectedbyinitial stars interactwithcloudsingeneral.Thisisbecausethe as aprobeoftheatomicgas in28clusterneighborhoods. studies ofindividualregions.Themethodconsistsexamin- the positionsandmotionsofnascentstarsrelativeto the the birthplacesofstars,and,inrecentyears,agooddeal Schwartz (1971)soughtradio continuumemissionasanindi- It iswidelyacceptedthatinterstellarmolecularcloudsare Fortunately, thereisawaytoaddressthequestionofhow 1 4 2 -1 12 3 Whenever possible,adistinctionismadebetweeninterstellarmatterthatphysicallyassociatedwithcluster clusters at~10kms',andtheyalsoapparentlyarebeingdestroyedbytheirinteractionwiththestars.Sitesof one molecularcloudmoremassivethan10M\(b)clustersolder~Myrdonothaveassociatedwith ranging from-1to5kpcandages<100Myr.Sampleselectioneffectsarediscussed. uniform samplingintervalof7(5;atypicalregionwas~4deg. radial velocity.Aroundeachcluster,aregionatleast25pcor10clusterangulardiameterswasmappedwith Subject headings:clusters:open—interstellar:moleculesnebulae:Hnregionsstars:formation ongoing starformationarefoundinanumberofthecloudsassociatedwithyoungclusters. and materialthatliesalongthelineofsightbutisotherwisenotrelatedtocluster. enable 3adetectionoflinesasweak1K(7^*)overrangeinvelocity±83kmscenteredonthestellar clusters foremissionfromthe/=1—►0rotationaltransitionofCO.Thesurveysensitivityissufficientto them molecularcloudsmoremassivethanafewtimes10Af;(c)arerecedingfromyoung 0 0 A descriptionisgivenoffeaturestheinterstellarmatterassociatedwitheachsurveyedclusters. The criteriausedtoselectclustersforobservationareoutlined.havewell-determineddistances The Columbia1.2mmillimeter-wavetelescopewasusedtosearchsystematicallyregionsaround34openstar In general,wefindthat(a)allthesurveyedclustersyoungerthan~5Myrhaveassociatedwiththematleast © American Astronomical Society • Provided by theNASA Astrophysics Data System I. introduction A COSURVEYOFREGIONSAROUND34OPENCLUSTERS Laboratory forAstronomyandSolarPhysics,NASAGoddardSpaceFlightCenter; Astronomy Department,TheUniversityofTexasatAustin Received 1988August15;acceptedDecember12 and AstronomyProgram,UniversityofMaryland HarvcU’d-Smithsonian CenterforAstrophysics Patrick Thaddeus David Leisawitz Frank N.Bash ABSTRACT AND 731 is processedintostellarform? Whatphysicalmechanism interaction withthestars?What fractionofthemoleculargas interaction couldbedrawnfromtheirobservations. but notinregionsaroundclustersolderthanA,then one dominates theinteractionbetween ayoungclusterandthe lar cloud.Unfortunately,theBGPspatialresolutionof ~ 2' clouds inwhichtheyform? Dothecloudssurvivetheir BGP. First,simply,whateffect dostarshaveonthemolecular made severeundersamplingoftheirregionsnecessary,and no formation begins)isA.Indeed,theBGPsurveyindicated might concludethatthemolecularcloudlifetime(after star addressed onlywithaCOsurveymorethoroughthanthat of general conclusionsregardingthenatureofcluster-cloud type earlierthanB0showevidenceforanassociatedmolecu- that, onaverage,onlyclustersthatcontainstarsofspectral tected inregionsaroundclustersyoungerthansomeageA, interpreted withtheaidofstellarevolutionmodels,providea line observationsofregionsaround63youngclustersto derive acharacteristicmolecularcloudlifetime.Spectroscopic chronometer withwhichtheclusteragescanbegauged. and photometricobservationsofthestarsinopenclusters, Green, andPeters(1977;hereafterBGP)usedCOspectral It wasclearthatseveralinterestingquestionscouldbe In principle,forexample,ifCOemissionweretobede- 198 9ApJS. . .70. .731L 732 clusters intheGalacticdisk sufficiently unobscuredbyinter- presented elsewhere(Leisawitz1989b,c,hereafterPapers III hoods. OursurveyisalinkbetweentheGalacticplane within whichtoevaluatethesurveyofopenclusterneighbor- nique arepresentedin§III.SectionIVdetailsresultsof the used toselectasampleofclusters,thecharacteristics the large solidanglesandrelativelymassiveclouds. Wilson 1985;Sandersetal1986,andreferencestherein), interaction arethecloud-cloudvelocitydispersionand Paper II).Analysisandinterpretationoftheseresultswill be cluster neighborhoods(alsoseeLeisawitz1989¿z;hereafter open clustersurveycoverageiscomparedtotheof low-resolution survey,notsurprisingly,turnsouttobeespe- mapped, butwithlimitedGalacticlatitudecoverage(Cohen, have beenmade,withtheColumbiatelescopeaswell young openclusterssystematicallyforCOemission. ment sinceBGPinmillimeterreceivertechnologyandbythe molecular cloudsinitsvicinity,thusaffectingthecloudlife- summarized in§V. tion anddiscussionoftheempiricalfacts.Ourfindings are sample, andthesampleselectioneffectsarediscussedin § II. CO surveyoftheregionsaroundthoseclusters.Thecriteria sample ofclustersforobservationandempiricalresultsa the Dameetal.(1987)surveyinFigure1. surveys andstudiesofindividualstar-formingcomplexes.The cially sensitivetodetectionsoflocaldarkcloudsthatsubtend of ourcloudsthataredetectedgenerallynotresolved.The either incompleteorobtainedwithlowspatialresolution.In Dame, andThaddeus1986;Dame1983).Confusionisan (Dame etal.1987,andreferencestherein),orthoroughly detailed informationaboutdistantstar-formingcomplexes covered withaspatialresolvingpowertoolowtoprovide reasons, theydonotprovidethedatathatweseek.Theinner molecular gascontentoftheGalaxyand,foranumber and IV,respectively);theobjectiveofthispaperisapresenta- survey andincludesdescriptionsoftheISMin34young Observational parametersandourCOdataacquisitiontech- the molecularGalaxyandthusprovideanaturalframework Galaxy eitherhasbeenundersampled(Knapp,Stark,and others, thesesurveyswereintendedtoshowthelarge-scale Milky WayconductedwiththeColumbiamillimeter-wave angular areas,wedecidedtomapregionsaroundanumberof availability ofatelescopedesignedspecificallytosurveylarge cluster environments,andspurredonbyamajorimprove- stellar initialmassfunction(IMF). spiral galaxies?Alsopossiblyinfluencedbythecluster-cloud the low-angular-resolutionsurveyofDameetal.(1987),those a relativelylargepartofthesky,coveragetherehasbeen additional majorcomplicationintheinnerGalaxy. telescope. AlthoughCOsurveysoftheentireGalacticplane time andthearm-interarmcontrastofmolecularcloudsin Within 6kpcoftheSun,there areabout1200openstar To learnmoreaboutthemoleculargascontentofyoung Two majortopicsaretreatedinthispaper:selectionofa The Galacticplanesurveysdoshowusthelargepictureof The presentsurveyisoneofseveralCOsurveysthe Because themolecularcomponentofouterGalaxyfills II. thesample:selection,characteristics, © American Astronomical Society • Provided by theNASA Astrophysics Data System AND SELECTIONEFFECTS LEISAWITZ, BASH,ANDTHADDEUS just fillthebeamoftelescope.Fewopenclustersmore likely thanolderonestobe found neartheirparentalclouds. increase therelativeprobabifitythatmolecularclouds with whichobservedclustersarefoundtobeinteracting younger thanatypicalcluster-cloudcollisiontime,r* , to The Pleiades,forexample,are behevedtobeinteractingwith opposed tostraycloudspresentbychance.Clustersofall ages (Breger 1987).Althoughempirically r*shouldnotbea chance encounter,butyounger clustersarearguablymore generally arethecloudsthatgavebirthtoclusters as distant than5kpcarewell-studiedoptically. with thissamplingwouldrequire400spectraormore,and The samplingintervalchosenforourCOobservationswas a cloudthatisnottheonefrom whichthestarclusterformed are equallylikelytobeinteracting withamolecularcloudin one atadistanceof5kpcwouldrequireabout20spectra.To independent pubhshedestimatesofthedistanceandagea be <100Myr,and(d)itsdeclinationmust>-20°.By begin thissectionwithadiscussionofselectioncriteriaand by Lyngâ(1982)andJanes,Tilley,(1988). physical characteristicsof1180openclustersarecontainedin at 5kpc,whichdistancea12.5pcdiametercloudwould severe beamdilutioneffects,anouterdistancecutoffwas set able toresolvemolecularcloudsadequatelyandavoid away wereselectedforobservation.Ontheotherhand,to be avoid biasingthesamplebyspendingexcessivetimemapping Liszt, Xiang,andBurton1981;Sanders,ScoviUe,Solomon dimension thatexceeds50pc(see,e.g.,Dameetal.1986; distance mustHeintherangelOPEN CLUSTER CO SURVEY 737 ° The galactocentric distance and distance from the Galactic Although there is fairly good agreement among optical equatorial plane, the linear diameter, visual extinction, and observers on the distances to open clusters, the discrepancies Í age of each of the clusters are in Table 2. The solar galacto- between observers are often significantly larger than their < centric distance is assumed to be 8.5 kpc (Kerr and Lynden- internal measurement errors (Fenkart and Binggeli 1979). ^ Bell 1986). Whenever possible, visual extinction values are Therefore, uncertainties are assigned to cluster distances based ^ from Becker and Fenkart (1971). Extinction values in brack- on the scatter among different authors’ measurements. To ets were derived from the published color excess assuming a calculate a typical external error, those clusters in the data normal interstellar reddening law with Av = 31 E(B-V). base of Leisawitz (1988) for which multiple distance estimates The spectral type, an indicator of cluster age, refers to the star are available were considered. For each cluster, alog(J), the of earliest spectral type on the main sequence (lower case standard deviation of the logarithms of the tabulated dis- letters refer to “photometric type”). Most of the B - F colors tances was determined; since not all of the published dis- of the main-sequence turnoff points are from the compilation tances represent independent measurements, the true uncer- of Janes and Adler (1982). Numerical values for the ages of tainty will be slightly underestimated by this calculation. The clusters are the ones reported by Lyngâ (1987) or, in the cases average standard deviation for the 95 clusters considered is of values shown in parentheses, are derived in § IV(6) from (aiog(¿)) = 0.054 + 0.006. Thus, typically, the distance of a published data. cluster can be self-consistently estimated to within 15% (dis- Next we compare the composition of the sample of 34 tances to 80 of the 95 clusters are known to within 26%). observed clusters (referred to below as “our sample”) with that of the sample of all known clusters (referred to below as ii) Distribution of Clusters in the Galactic Plane the “Lyngâ sample”). In Figure 3 we show distributions of three samples of clusters in the Galactic plane. Figure 3 a shows the distribu- i) Cluster Distances tion of all the photometrically observed clusters in the Lynga sample, and Figure 3 b shows those whose ages are estimated The distribution of open cluster distances for all clusters to be <5 Myr, i.e., those beheved to he in or near the for which information is available in the compilation of Galaxy’s spiral arms (see Fig. 1 of Fenkart and Binggeli Lyngâ (1987) is shown in Figure 2. Because only photometri- 1979). In Figure 3c we show the distribution of the clusters in cally observed clusters have tabulated distances, and since the our sample. As a result of our tendency to select regions in clusters are obscured by intervening dust which contributes relatively unconfused parts of the Galaxy, most of the ob- an average of ~ 0.75 mag of visual extinction per kiloparsec served clusters are in longitude quadrant II and many are in (Lyngâ 1982; see § IV), there is a decrease in the number of or near the Perseus arm. clusters with increasing distance for J > 1.5 kpc. Relative to the Lyngâ cluster sample, the clusters in our iii) Cluster z Distribution sample have a flatter distribution in d, and clusters with d>1.5 kpc are disproportionately represented. Thus, the sam- Distributions of the clusters with respect to the Galactic ple of observed clusters is not as heliocentrically biased as the plane {b = 0°) are shown in Figure 4. Lyngâ clusters with Lyngâ sample. known distances are distributed approximately symmetrically about z = 20 pc, which suggests (Lyngâ 1982) that the Sun is located approximately 20 pc above the Galactic plane. Figure 5 shows that only very old clusters ( > 500 Myr) are displaced by more than -150 pc from the z = 0 plane. The z distribution of the clusters we observed is less sharply peaked than the Lyngâ cluster z distribution. Since heavily obscured clusters remain undiscovered or tend not to be well-studied, we have undoubtedly selected against clusters that he very near the Galactic equator (Fig. 6). Furthermore, to minimize blending of clouds, some preference was given to observing high-Galactic latitude clusters. The full width at half-maximum (FWHM) of the open cluster layer (Fig. 4, solid line) is ~ 120 pc, which is fairly close to the FWHM of the molecular cloud layer (Dame 1983). This agreement is not surprising since open clusters form from the present molecular cloud disk. For comparison, the atomic hydrogen disk thickness of the Galaxy is about 250 pc near the solar circle, and greater outside (see, e.g., Baker and Burton 1975; Henderson, Jackson, and Kerr 1982). Since all clusters as young as the ones that we have observed he within the Galactic molecular cloud layer (Fig. 5), the fact Fig. 2.—Frequency distributions of the distances to open clusters. that we have selected against clusters narrowly confined to the Solid line: clusters whose distances are tabulated by Lyngâ (1987); plane of symmetry should not represent a serious source of hatched area: observed clusters. bias.

© American Astronomical Society • Provided by the NASA Astrophysics Data System 198 9ApJS. . .70. .731L low-declination clustersfrom oursample(§IIû);thefourth is largelyattributabletothe factthatwehaveexcluded sample ofobjectsthathewithin thesolarcircle(Æ=8.5kpc) hatched area:observedclusters. Figure 7.Theunderrepresentation intheobservedcluster the Lyngâclustersandthose inoursampleareshown clusters (filledcirclesmarkpositionsofyoungerthan5Myr). (x, y)=(0,-8.5kpc).(a)AllclusterscatalogedbyLyngâ(1987)for whichdistancesareknown;{b)Lyngâclustersyoungerthan5Myr;(c)observed 738 The distributionswithdistance fromtheGalacticcenterof Fig. 4.—Frequencydistributionsofopenclusterdistancesfromthe Galacticplane.Solidline:clusterswhosedistancesaretabulatedbyLyngâ(1987); Fig. 3.—Galacticplanedistributionsofopenclustersinacoordinate systemwiththesolarneighborhoodatoriginandGalacticcenter © American Astronomical Society • Provided by theNASA Astrophysics Data System iv) ClusterRDistribution Fig. 3c Fig. 3a x (kpc) x (kpc) LEISAWITZ, BASH,ANDTHADDEUS confusion ininterpretation of themolecularlineemission, quadrant ofGalacticlongitudeisinaccessiblefromthe lati- preference wasgiventoobservation ofouter-Galaxyclusters tude oftheColumbiatelescope. Furthermore,tominimize emission inthelongitude-velocity planeforthesecondand (see Figs.1and2ofCohen etal1980,whichshowCO first quadrants,respectively). Fig. 3b Fig. 4 x (kpc) Vol. 70 198 9ApJS. . .70. .731L ure 8.Thediameterofaclusteristypically1-5pc.Because there issomewhatofatendencyforyoungclusterstobelarge No. 4,1989 distances andextinctionsaretabulatedbyLyngâ(1987). very youngclustersmakesmeasurement ofarehablecluster (see Fig.3ofLyngâ1982),oursamplecontainsadispropor- dynamical relaxationexpected intheepochfollowingdissipa- diameter difficult,butifvery youngclustersare,infact,larger than average,thenthisobservation couldbeexplainedbythe tionate numberoflargeclusters. by Lyngâ(1987). Cluster lineardiameterdistributionsareillustratedinFig- Fig. 6.—Thevisualextinctionsmeasuredtowardopenclustersasa function oftheirabsolutedistancesfromtheGalacticplaneforclusterswhose The opticalemissionnebulosity thatgenerallyaccompanies Fig. 5.—AbsolutedistancesofopenclustersfromtheGalacticplaneasafunctiontheiragesforwhoseand aretabulated © American Astronomical Society • Provided by theNASA Astrophysics Data System v) ClusterSizeDistribution OPEN CLUSTERCOSURVEY enced bycompetingobservational selectioneffects.Young clusters aremorelikelythan olderonestobeenvelopedby clusters intheLyngâsample isapparentlysomewhatinflu- (Lada, Margulis,andDearborn1984;seealsoBurki1978). 1988; Lyngâ1982;Widen1971). Thenumberofveryyoung order of100Myrhasbeendeduced (Janes,Tilley,andLyngâ cluster ages,fromwhichacharacteristic clusterlifetimeofthe tion orexpulsionofthecloudthatgavebirthtocluster In Figure9a,thesolidlineshowsdistributionofLyngâ vi) ClusterAgeDistribution 739 \—I 00 0 740 LEISAWITZ, BASH, AND THADDEUS Vol. 70

Fig. 8 Fig. 7.—Frequency distributions of the galactocentric radii of open clusters. Solid line: clusters whose distances are tabulated by Lyngâ (1987); hatched area: observed clusters. Fig. 8.—Frequency distributions of the linear diameters of open clusters. Solid line: clusters whose sizes are tabulated by Lyngâ (1987); hatched area: observed clusters.

Fig. 9.—Frequency distributions of open cluster ages. In (a), the solid line is for clusters whose ages are tabulated by Lyngâ (1987) and the hatched area is for observed clusters, (b) Distribution of the 5 - F main-sequence turnoff colors of observed clusters. the material from which they formed, but also are more Since we will want to look for similarities in the molecular popular as candidates for study (Lyngâ 1982). contents of the neighborhoods of clusters of a similar age, and For the clusters we studied, the net bias is probably in for systematic differences between neighborhoods of clusters favor of the young clusters for several reasons. Related to our whose ages differ, the accuracy with which cluster ages can be sample selection criteria, few clusters were observed whose measured will affect how we are able to analyze our data. ages are greater than -100 Myr, and a relatively large Analogously to our estimation of the average cluster distance fraction of the known young clusters were selected for obser- uncertainty (§ IIZ?[i]), we calculate the mean author-to-author vation because there is a tendency for them to have been dispersion in age estimates (^log (age) )== 0.54 + 0.05 for 60 “well-studied.” Furthermore, our sample was deliberately bi- clusters for which multiple age estimates are tabulated by ased in favor of younger objects because it was possible to Leisawitz (1988). According to this calculation, cluster ages anticipate from the results of BGP and by considering plausi- typically are uncertain by a factor - 3. However, some com- ble interaction mechanisms that clusters and the molecular ponent of the measured dispersion in age estimates is system- clouds from which they form should interact on a relatively atic in nature: stellar evolution models and photometric in- short time scale. A number of older clusters were, however, strumentation and techniques have improved over the past 20 observed as a control group. or so years and now yield better cluster age calibrations.

© American Astronomical Society • Provided by the NASA Astrophysics Data System \J 1 R No. 4,1989 OPEN CLUSTER CO SURVEY 741 ° Thus, the factor of 3 calculated can be regarded as a useful main-sequence turnoff colors for 434 clusters, show in their upper limit to the real age uncertainty. The ages adopted for Figure 4 (see Lyngâ 1982) the conversion from turnoff color ^ clusters in our sample (Table 2) generally are modem esti- to cluster age. ré mates. œ More readily available in the literature than a numerical ^ value for the age of an open cluster is the B — V color of the vii) Visual Extinction of Clusters main-sequence turnoff point or the spectral type of the most Well-studied clusters are not in general very heavily ob- massive star on the main sequence, both of which are indices scured. The distributions of visual extinction, Av, toward of cluster age. Moreover, one or the other of these parameters clusters in the Lynga sample and the sample that we observed is often the source of a numerical age value when one is are shown in Figure 10. The distribution oi A v with cluster published. The turnoff color distribution for observed clusters age in Figure 11 shows that very few clusters with less than is shown in Figure 9b. Janes and Adler (1982), who tabulated 1 mag of extinction are less than 10 Myr old, which explains why in our sample there are few low-obscuration clusters. Relatively few clusters have been studied for which Av ex- ceeds 2.5 mag. Despite the large scatter of the points in Figure 11 (much of which may be due to differences in the distances and Galactic latitudes of the clusters and the inhomogeneity of intervening interstellar material) there is evidently a tendency for young clusters to be more heavily obscured than old ones, suggesting that at least part of the obscuration seen toward young clusters is caused by material with which they are associated.

c) Selection Effects As we have shown, the sample of all well-studied clusters (the “Lynga sample”) is afflicted with a few relevant selection effects. First, the Sun’s location in the disk of a dusty galaxy exacerbates a natural heliocentric bias and results in our knowing little about clusters that are more distant than a few kpc. Second, some very young star clusters must not have Fig. 10.—Frequency distributions of the visual extinctions of clusters. been discovered or cataloged because they remain concealed Solid line: clusters whose extinctions are tabulated by Lyngâ (1987); by the opaque molecular clouds in which they formed. Re- hatched area: observed clusters. lated to this, there is a greater probability that a cluster found

4

CDo) 3 E > < 2

1

0 6 7 8 9 loglAge (yr)] Fig. 11.—The visual extinctions measured toward open clusters as a function of their ages for the clusters whose ages and extinctions are tabulated by Lyngâ (1987).

© American Astronomical Society • Provided by the NASA Astrophysics Data System 198 9ApJS. . .70. .731L 1216 7 9 isotopic speciesC0. with theColumbiamillimeter-wavetelescopeinNewYork veyed clustersfortheyoungestonestodifferinmassfrom points areworthnotinghere,however:(1)5-20Myrold This isasubjectthatwillbeaddressedwhenweinterpretthe number ofunboundobjects.Butthereremainsthepossibility and thatthisinfluencesthecluster-cloudinteraction. narrow rangeofgalactocentricradius,thepresentCOsurvey older ones(seeTable8). massive stars”;theygenerallydocontainstars,albeit clusters cannotsimplybewrittenoffas“clusterswithout survey resultssummarizedin§V(seePaperFV).Tworelated characteristics andundoubtedlycontainssomeindeterminate § llb[v]).Statistically,oursampleof34clustershasthese 742 City. AllofourobservationsweretheJ=rotational approximately 9000COspectrawereobtainedforthissurvey star formationiscoordinatedonalargescaleintheGalaxy alone cannotbeusedtoconfirmordenythehypothesis that evolved ones;and(2)thereisnotendencyamongthesur- are greaterthan—20Myr,boundPopulationIobjects. early Bstars.Theunboundclustersare,ofcourse,short-lived; made onlyiftheclusterstellarvelocitydispersionisknown (see, e.g.,Mathieu1986).Suchinformationgenerallyishard which Janesetal.referhaveabroadzdistribution(seeFig. which COemissionwassurveyedisprobablymorerepresen- marized inTable3.The telescope wasequippedwitha transition (restfrequency= 115.271201 GHz)ofthenormal that someofthesurveyedclusters,especiallythosewhoseages 10 yrandarecharacterizedbytheirrelativelylargesizes(see they canbeexpectedtoremainintactforaboutafewtimes veyed clustersallofthesametype?Theoldboundto older boundclusters.Thisraisesthequestion:Aresur- cataloged clustersis. distant andrelativelyyoungclusters,thesetofclustersnear posed toexplainCOobservationsofthesurveyedopenclus- to comebyandisevenrarerincasesofclusterswithO ters issubtleand,inthecaseofanindividualcluster,canbe unbound clusters,boundclustersofPopulationIstars,and remember theseselectioneffectswhenhypothesesarepro- effects inherentintheLyngâsampleofclustersextendto any, ofthesurveyedclustersshouldbethistype. 5) andacharacteristiclifetimeoffewtimes10yr.Few,if that thereareasmanythreetypesofopenclusters: tative oftheGalacticpopulationclustersthansetall faces theSunthanthatitformedonfarsideofcloud. ter regions.Nevertheless,becausewefocusedonrelatively then tothesampleofclustersactuallyobserved.Onemust sample ofclustersselectedascandidatesforobservationand near itsparentalcloudformedonthesideofthat In theperiodfrom1983Novemberto1984 Important parametersofthe Columbiatelescopearesum- Because wehaveconcentratedonclustersthatliein a Janes, Tilley,andLyngâ(1988)suggestedthepossibility The distinctionbetweenyoungboundandunboundclus- So arewecomparing“apples”with“oranges”?Maybe. Of course,itcannotbepreventedthatmostoftheselection HI. INSTRUMENTATIONANDOBSERVINGTECHNIQUE © American Astronomical Society • Provided by theNASA Astrophysics Data System a) Instrumentation LEISAWITZ, BASH,ANDTHADDEUS -1 per channelwasreducedto0.28 Kin7^*.Thissensitivitywas within a6%rmsdeviation(Dame 1988,privatecommunica- observed atleastonceduring each6-8hrobservingsession. when theirelevationsexceeded30°,andaneffortwasmade to were stableandthewateropacity,t,was<0.25perunit air pattern, forsourcesthatarelargerthantheprimarybeamitis At 115GHz,thevelocityresolutionandbandwidthwere0.65 were considerednecessaryonlyafewtimesperobserving mately biweekly,butcorrectionstothepointingconstants mass. Typically,rwas~0.10.Sourceswereobserved only reasonable toassumethatt]~1,inwhichcaseT-. perature, =T*/y,wheretheefficiencyfactortjfs> tion). It wasdeterminedthatour measurements arerepeatableto calibration constants,astandardsource(SI56orOriA) was observe eachsourcenearitstimeoftransit. feed hornpowerbeyondtheprincipalforwardlobeof corrected foratmosphericattenuation,resistivelosses,and gested byKutnerandUlich(1981),usingthetwo-layeratmo- (1986). season. azimuth andelevation.Thisprocedurewasfollowedapproxi- accuracy wascheckedbyscanningthelimbofSuninboth scribes thecouplingofsourcetoantennapower antenna diffractionpattern.Althoughanotherfactor,tj,de- rearward spilloverandscattering.Inturn,theradiationtem- results ina“measurement”of7^*,theantennatemperature and 166kms,respectively. et al.1983),butwasotherwiseessentiallythesameas sensitive, single-sidebandSISjunctionmixerreceiver(Pan shown inTable3,adjustsforspilloverandscatteringofthe assumptions thatmustbemadeabouttheEarth’satmosphere calibration temperaturescalefordataobtainedwithasingle- sphere modelofKutner(1978).Determinationthe system describedindetailbyCohen,Dame,andThaddeus and relativesidebandgainswhenworkingwithaninstrument sideband receivercanbedonereliablyandisindependentof that doesnotrejectimagefrequencyradiation.Calibration w w cR AFSSS c As acheckontelescopepointing,receivertuning,and Integrations weregenerallyterminated whenthermsnoise The telescopepointinguncertaintyis~1'. The spectrometerwasa256channel,250kHzfilterbank. Observations weremadeonlywhenweatherconditions Survey datawerecalibratedaccordingtotheschemesug- 4 -1 1 Antenna resolution8Í7 Velocity resolution0.65kms Beam efficiency,tj0.82 Receiver noise Integration timeperscan-45s Spectrometer range166kms~ Pointing uncertainty[v]). to theclusterangularsize.Althoughaminority(14/34)of other wastheanglesubtendedby25pcatcluster’s angular sizes:onewas5clusterdiametersandthe simple algorithm.Themapradiiwerethemaximaoftwo Each mapwastobecircular,centeredontheclusterposition and tohavearadiusdeterminedinadvanceaccording CO inregionsaroundalargenumberofyoungstarclusters. were usedinthepresentsurvey,thoughregionsathigh no linecouldbedetectedinaspectrumwithrmsnoiseper Galactic latitudesnewcleanoffpositionshadtobefound. computer. Manysuchpositionsdiscoveredbyotherobservers frequency switchingandthenstoredinthetelescopecontrol channel oflessthan0.2K.Thesepositionswerediscoveredby measured inthedirectionofonpositionwasnearlyequal to theaveragetotalpowermeasuredtowardemission-freesky. tions fromtheonposition.Thus,averagetotalpower gration time.Inadditiontothis,allobservationswereposi- times usingeachoftheoffpositionsweightedbytheirsepara- surrounding the“onposition”inelevation,withintegration of theSISreceiverandtofrequenton-source-off-source No. 4,1989 tion-switched withtwoorthreeemission-free“offpositions” switching asrequiredtoaccommodatetheoverallshortinte- excellent flatbaselinesarelargelyattributabletothestability radiation temperatureisatleast6.6K. and thosewithcurvatureweregenerallyreobserved.The distance ofourmostremotecluster,shouldbedetectableat detect a5pcdiametercloudatdistanceofkpcifits chosen sothatevenaverycold,smallmolecularcloud,atthe the 3alevel;specifically,surveyissufficientlysensitiveto Table 4showsthediameterand degreeofcompleteness,in Within theboundaryofeachcircularmap,oursampling The 256-channelfilterbankwascenteredonthevelocityof Our objectivewastoobtainuniformlysampledmapsof Off positionswereconsideredacceptablyemission-freeif Nearly allofthespectrahadonlylinearbaselinesremoved, © American Astronomical Society • Provided by theNASA Astrophysics Data System c) MappingStrategy OPEN CLUSTERCOSURVEY in theregionssurveyed. motions, sizes,andmorphology ofthemolecularclouds.The ment ofa“typical”young cluster. Trendsarefoundinthe spatial distributionandkinematics ofionizedandatomicgas apparently areinfluencedby the presenceofmolecularclouds § V),collectivelydescribethe changinginterstellarenviron- describe themolecularclouds. contains anoutlineoftheprocedureusedtoidentify and size featuresofthedatathat,whenviewedinhindsight(as in maps, andreviewobservationsofthesurveyedopenclusters associated, orpossiblywiththem.Section IVû and oftheionized,atomic,molecularinterstellarmatter observed propertiesofthemolecularcloudsfoundin our In ourdiscussionsofindividualregions(§IVb),weempha- In thissectionwepresenttheCOsurveydata,catalog 3 Cluster Identification pled uniformlybutwithabeamspacingof15'. region. Ruprecht, andVanysek1970. Number c b a NGC 654andNGC659arewithinthe663 The relativelylargeregionaroundIC1396wassam- 406 208 205 Open clusternumberfromthecatalogofAlter, 467 441 439 429 404 403 291 286 244 236 224 222 124 476 339 333 330 321 319 314 313 138 100 394 362 345 332 320 364 OCL 67 c c b NGC 6823 NGC 7160 NGC 7067 NGC 7062 NGC 6709 NGC 6694 NGC 663 NGC 457 NGC 433 NGC 281 NGC 103 NGC 7380 NGC 1778 NGC 1624 NGC 957 NGC 659 NGC 654 NGC 436 Bk 59 IC 1442 IC 1396 Roslund 4 NGC 2129 NGC 1931 NGC 1893 NGC 1605 NGC 1444 NGC 744 Bk 62 NGC 2175 IC 1848 Bk 11 Stock 5 Monoceros Common Name Survey Completeness IV. RESULTS TABLE 4 Diameter 2?625 2.125 3.125 2.125 2.625 2.625 2.125 3.125 2.125 3.125 3.625 1.125 1.625 Map 2.125 2.125 3.125 2.125 2.125 1.125 1.625 1.625 1.125 1.625 1.625 3.125 1.625 1.125 1.625 1.125 1.625 1.125 1.625 Beam Spacing Completeness AT T.5 (%) 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 63 30 743 198 9ApJS. . .70. .731L -1 velocity. Allvelocitiesquotedinthispaperarewithrespectto maps ofCOintensitysuperposedonreproductionsthe presented inAppendixA(alsoFig.12)theformof profile shapeandoccasionallyindicatethepresenceofemis- information. TheyenableinspectionoftheCOlinewidthand of catalogedcloudsintheplaneskyandradial 744 different purpose.The“spectrummaps”containthemost Palomar ObservatorySkySurvey(POSS)prints. CO surveydata.Rawdataforafewselectedregionsare of Hcolumndensity(Bloemenetai1986,andreferences from thatofthetargetedcluster.Such“high-velocity”emis- CO lineintensity(fT*dv)arepresented.Alsoin§TVb spatial “maps”ofCOspectra.In§TVbcontourmapsthe tables andschematicillustrationsthatindicatethelocations sion isnotdiscussedinthispaper. sion ataradialvelocitythatdiffersbymanytensofkms the LSR.Forafewregions,weshowinAppendixBcontour 2 A Table 5isadirectoryoftablesandfiguresthatdescribethe Each oftheseveralmodesdatapresentationservesa Contour mapsofCOlineintensityindicatethedistribution © American Astronomical Society • Provided by theNASA Astrophysics Data System a Cluster Identification Number b a 439 441 403 476 364 244 222 286 406 404 467 236 208 330 319 314 339 313 124 NGC 654andNGC659arewithin theNGC663region. Open clusternumberfromthecatalog ofAlter,Ruprecht,andVanysek1970. 429 394 333 332 138 291 321 362 OCL 224 205 345 320 100 67 b b NGC 6823 NGC 1893 NGC 654 NGC 1931 NGC 1624 NGC 7380 NGC 281 NGC 2175 NGC 2129 NGC 957 NGC 1444 NGC 663 NGC 659 NGC 7160 NGC 7067 NGC 433 Bk 59 IC 1848 NGC 103 NGC 1605 NGC 457 Bk 62 Roslund 4 Monoceros IC 1396 NGC 7062 NGC 1778 NGC 6694 NGC 436 NGC 6709 NGC 744 Stock 5 Bk 11 IC 1442 Common Name Cluster (Myr) Age 500 500 158 10 10 10 15 15 13 13 11 78 30 30 18 16 16 15 91 79 39 38 4 4 2 6 2 2 1 1 9 5 5 3 CO SurveyResults:GuidetoFiguresandTables LEISAWITZ, BASH,ANDTHADDEUS JT/dv (Figure Number) Contour Maps 25 24 23 22 21 20 28 28 29 28 27 26 18 16 15 14 40 30 12 19 17 42 41 33 32 31 37 36 35 34 39 38 TABLE 5 (Table Number) -1 integrated intensitytomeasuretheCOlinefluxesandlumi- nosities ofthecatalogedcloudsandtomeasuretheirmasses. described in§TVa),and,IVc,weusethespatially both coordinateandvelocityspace.Whencontourlinesof fore, weuseCOintensitymapstolocatemolecularclouds(as integrated COintensitysuggestthatacrescent-shapedstruc- resolved) entityshowingCOemission,whichiscontinuousin therein; DameandThaddeus1985;Strongetal.1988).There- clouds. regions, however,COemissionisnearlyubiquitousandisola- nearly allcases,thisisthe1Kkmscontour.Inafew to outlineacloudwecallitsboundaryincoordinatespace.In ture canbesubdivided,itistreatedasifweretwoormore tion ofindividualcloudsiscomplicated;inthesecases(noted Parameters Location We defineamolecularcloudassomewhatextended(i.e., Cloud The lowestlyingCOintensitylevelthatcanbeconsidered 6P 6C 6B 6A 6P 6R 6Q 6P 60 6N 6M 6L 6K 6J 61 6H 6G 6F 6E 6D 6W 6U 6T 6S 6DD 6CC 6BB 6AA 6Z 6Y 6X 6V a) MolecularCloudIdentification (Figure Number) Spectrum POSS Map Print 49 48 12 51 50 53 55 54 54 56 61 61 57 58 60 59 61 Vol. 70 198 9ApJS. . .70. .731L _1 -1 -1 _1 _1 -1 positions. Stripesindicatethatthe cloudradialvelocitiesareatleast10kmsmorenegativethanthose ofthecluster;solidshadingindicatesthat intersections betweenlinesthroughordinatetickmarksparallelto thex-axisandabscissatickmarksparalleltoy-axiscorrespondobserved (see text)arein(c),(<7),(e),and(/).Heresubsequentanalogous contourdiagrams,rangesofvelocityintegrationareindicatedandlevels coordinates, relativetothecoordinatesofcentralstarcluster (Table1),areindicated.A60kmsportionofbasehneisdisplayed,centered km smorepositivethanthose of thecluster,andunshadedellipsessymbolizecloudswithradial velocities within10kmsoftheclustervelocity.) cloud isalocaldarkseenon thePOSSprints.(Insubsequentanalogousfigures,dashedstripesare usedtohighlightcloudswithvelocitiesatleast10 (FWHM) andtheclusterangulardiameter(AD)areshownforcomparison. Thelargecircleshowstheapproximateboundaryofsurveyedregion; are 1,2,3,4,5,6,8,10,12,14,16,18,20,25,30,35,40,45,and50K kms.Inpanels(c),(d),(e),and(/),respectively,1Kcorrespondsto1.5, approximately ontheradialvelocityofcluster,(b)COintegrated incontiguous,2kmswidebins(seetext);thesecontourdiagrams,1K, as anexample,(a)Spectraobtainedtomaptheregion.Locations of thespectraonpagecorrespondtopositionsinplanesky;Galactic 1.6, 1.5,and1.3a.(g)Schematicillustrationofthepositionsorientations ofcatalogedmolecularclouds(seeTable6H).Thetelescopebeamwidth the lowestcontourlevel,correspondsto3.2a.ContourmapsofCO intensity integratedoverthevelocityrangesinwhichmolecularcloudsshowemission No. 4,1989 Fig. 12.—Illustrationofdataprocessingstepsfollowedtolocateand catalogmolecularclouds.ObservationsoftheregionaroundNGC7380areused © American Astronomical Society • Provided by theNASA Astrophysics Data System NGC 7380(io,bo)=107°.08,-0°.90 OPEN CLUSTERCOSURVEY Al (degrees) Fig. 12a 745 198 9ApJS. . .70. .731L 746 © American Astronomical Society • Provided by theNASA Astrophysics Data System -46.6 km/s-44.6 -58.3 km/s LEISAWITZ, BASH,ANDTHADDEUS -56.3 km/s Fig. Ub -36.8 km/s -42.7 km/s -48.5 km/s -54.4 km/s Vol. 70 198 9ApJS. . .70. .731L No. 4,1989 -0.5 -1.0 0.0 0.5 1.0 1.0 0.50.0-0.5-1.0 1.0 0.50.0-0.5-1.0 © American Astronomical Society • Provided by theNASA Astrophysics Data System OPEN CLUSTERCOSURVEY Fig. 12—Continued 1.0 0.50.0-0.5-1.0 747 198 9ApJS. . .70. .731L -1 -1 -1 velocities canbefoundinTable6.Thevelocitytabulated for ping intervals(Fig.126).Thelowestcontourplottedwasthe below) highercontourlevelsareusedtodefinecloudbound- represent cloudsasellipses and defineacloud’smajor-axis cloud velocitiesgenerallyare between0.1and0.3kms.We ( fvTj*du/jT*dvwithintegration restrictedtotherangeof cloud wasdetected,oftheintensity-weightedmeanvelocity each cloudistheaverage,overlinesofsighttowardwhich the little difficultydistinguishingmolecularclouds. nels (~2kms)inasequenceofcontiguous,nonoverlap- length (a)astheof achordthatstretchesfromone region. molecular cloudscatalogedfromthesurveyofNGC 7380 clouds’ emission,werecreated(asinFigs.12c-12/).Figure clouds wereidentifiedandthennewcontourmaps,showing approximate radialvelocityextremaoftheCOemission.In our surveyisasfollows(seeFig.12).The“spectrummap”of the cloud’semission).Thestandard errorsassociatedwiththe tations ofthecatalogedmolecularcloudsandtheirradial exception ofthoseourregionsintheinnerGalaxy,we had cally thelocations,angularsizes,andorientationsof the 1 Kkms(3.2a)level.Inthesethree-channelmaps,the CO intensity(fT*dv)integratedoverthreefilterbankchan- aries. 12 g,basedonthefinalcontourmaps,summarizesschemati- the COintensityintegratedoverfullvelocityrangesof this velocityrange,contourmapswereproducedshowingthe a region(e.g.,Fig.Via)wasexaminedtodeterminethe 748 to alloftheregionssurveyed.Ingeneral,withnotable maj A The procedureemployedtolocatethemolecularcloudsin The proceduredescribedabovewasappliedsystematically Quantitative informationabouttheshapes,sizes,andorien- © American Astronomical Society • Provided by theNASA Astrophysics Data System LEISAWITZ, BASH,ANDTHADDEUS _1 2012 1 -1 measured towardeachofoursurveyedclusters.Wederive the where theCOintensityisinunitsofKkms.Equation (2) observed reddeningfromtheextinction(Table2)and a gas ratioisthesameinmolecularcloudsasdiffuse contains theimplicitassumptionthat,onaverage,dust-to- zero. BasedontheassumptionthatcolumndensityofH in thecloud;otherwisekE{B—V)shouldbeapproximately toward someofthesurveyed clusters—especiallyNGC6823, selective extinctionratio3.1.TheCOintensitymeasured (1978) betweengascolumndensityandreddening,wederive molecules percm,AT(H)=1.9xl0/T/(CO¿/y(Strong lar cloudtiesinfrontofacluster,kE(B-V)isapproxi- atomic interstellargas. for thecloudcomponent et al1988),andontherelationofBohlin,Savage,Drake mately equaltoE(B-F),thereddeningcausedbydust where eisthemeanreddeningperkiloparsecandd E(B-V)~ ■^diffuse—V)canbecalculated.Ifamolecu- reddening, E(B-V),isthesumof(1)acomponentdueto (§ IV6).Sincedustinthesecloudsreddensthetightofcluster Lyngâ 1982),isameasureofe. reddening toclusterdistance,0.2135+0.0013magkpc(see diffuse gasreddeningcomponentcanberepresentedas component (2)isnotnecessarilypresentinallcases.The dust associatedwithmolecularclouds.Unlikecomponent(1), dust associatedwithdiffusegasuniformlydistributedalong of theclustersfromcloudsthatmustbebehindclusters. Evidence forthisispresentedonacase-by-casebasisbelow complete (C)or,apparently,incomplete(I). points towarddecreasingGalacticlongitude.Weindicate coefficient tocompensateforthefact thatourcalibrationofrjdiffers emission wasdetected,themeanratioofobservedcluster cluster distance.ForsevenclusterstowardwhichnoCO stars, itisoftenpossibletodistinguishcloudsthatareinfront symbolically inthetableswhethermapofacloudis corresponding toavectorparalleltheGalacticplanethat cloud isthepositionangleofmajoraxiswithrespectto from thatassumedintheStronget al.(1988)derivation. coordinates ofwhicharetabulated.Alsotabulatedforeach cloud edges.Thepointofintersectionthemajorandminor of theperpendicularbisectormajor-axischordbetween extent. Theminor-axislength(tf^)isdefinedasthe the tineofsighttostarsand(2)acomponentcausedby the Galacticplane,measuredcounterclockwisewithP.A.=0 graphic center,”andliesinthedirectionofitsmaximum end ofits“boundary”totheother,passesclose“geo- axes ofacloudisthenominalcenterposition, 2 2 cXouá kpc ohs ohs FSS 1 In Figure13weshowkE(B-V)andtheCOintensity Then, withequation(1),thedifferencekE(B-V)= To demonstratethis,weassumethattheobservedcluster For consistency,asmallcorrection wasappliedtothepublished Molecular cloudsheinfrontofsomeourclusters. 21 £cioud(5- F)(mag)=8.0X10-/r/(CO)dv,(2) v £diffuse(£ -)(mag)=«/,(1) kpc Vol. 70 198 9ApJS. . .70. .731L No. 4,1989 © American Astronomical Society • Provided by theNASA Astrophysics Data System NGC2175F 18cCL-0.5190.9-00.60.311.300 NGC281B 19cCa-44.0122.7 -06.30.440.86-64 NGC281A 19bCA-30.4123.4-06.40.741.116 NGC2175G 18dCA7.2191.1+00.41.072.0149 NGC2175E 18cIa0.3190.3+01.40.370.94-81 NGC2175D 18cIa-0.6191.6+01.30.370.6058 NGC2175C 18bCa6.7189.7-00.70.310.7267 NGC2175B 18bCA7.4190.0-00.11.021.6063 NGC2175A 18bIU4.2189.1+01.11.151.3060 Bk 59E17fIA-8.1119.2+05.41.632.4853 Bk 59D17eCA-0.8118.0+04.80.741.20-18 Bk 59C17dIA-6.6118.0+04.01.053.1024 Bk 59B17cIa-17.8118.2+03.30.460.570 Bk 59A17bCA-13.6117.5+05.20.791.8112 NGC6823A 16bCA25.3059.3-00.30.621.83-35 NGC 1893B15bCa-5.7173.4-02.60.150.2535 NGC7380E 12eC A-41.4107.1-01.00.301.20-27 NGC7380D 12dI a-50.2107.5-00.10.571.08 21 NGC6823E 16fCa23.7059.8-00.80.530.6656 NGC6823D 16eIa28.8060.2-00.50.530.8230 NGC6823C 16dIa34.8058.5+00.50.610.83-48 NGC6823B 16cCa32.0059.1-00.30.631.48-5 NGC 1893E15bCa-7.2173.9-01.00.250.5426 NGC 1893D15bIa-8.2172.6-01.40.360.50-67 NGC 1893C15bCa-3.6173.2-01.30.210.45-57 NGC 1893A15bCA-6.0174.0-01.90.571.5024 NGC7380F 12fI L-3.5107.2-00.10.530.73 90 NGC7380C 12cC a-54.3106.3-00.90.320.49 22 NGC7380B 12cIa-53.5107.8 -01.40.331.01-46 NGC7380A 12cIa-55.3106.6 -00.10.540.84-47 IC 1396F20eCL7.6098.1 +03.21.311.6059 IC 1396E20dCA-0.3100.0 +04.50.871.78-50 IC 1396D20dIa-1.0099.3 +05.30.681.2621 IC 1396C20cIa-0.7098.3 -05.00.611.01-82 IC 1396B20cCA-2.2100.3 +03.20.871.58-37 IC 1396A20bCA-6.8098.9 +04.20.520.9048 IC1848G 14bIa-34.7136.9+00.20.150.6072 IC 1848F14eCL-10.9137.1+00.50.30 IC 1848E14bCA-38.2137.4+00.70.300.4745 IC 1848D14eIL-12.6136.2+00.50.260.66-46 IC 1848C14dCA-38.1138.1+00.80.290.4317 IC 1848B14cCA-39.0137.7+01.40.440.78-61 IC 1848A14bCA-38.2136?7+01?30?851?56-42° -1 Cloud FigureI/CClass(kms)/bûP.A. maj Classifications, Locations,andOrientationsofMolecularClouds Map in(V)CenterPosmoN OPEN CLUSTERCOSURVEY H. COCloudsnearNGC7380 E. COCloudsnearNGC2175 C. COCloudsnearNGC6823 B. COCloudsnearNGC1893 F. COCloudsnearNGC281 G. COCloudsnearIC1396 A. COCloudsnearIC1848 D. COCloudsnearBk59 TABLEÓ 749 198 9ApJS. . .70. .731L 750 LEISAWITZ,BASH,ANDTHADDEUS © American Astronomical Society NGC 1624D21cIL0.0154.9+02.60.451.1675 NGC 1624B21bCA-36.7155.5+02.60.360.77-68 NGC 1624A21bIU-37.0154.9+02.60.440.5990 NGC 433C26dCa-10.9126.3-02.60.320.800 NGC 433B26cIa-21.6126.0-02.10.320.61-43 NGC 433A26bIa-22.8125.4-02.60.430.5928 NGC 1624C21cIL0.6155.6+03.00.320.544 NGC7067D 29dI L4.3091.2-02.10.370.67 25 NGC7067C 29cCL4.5091.3 -01.90.20 NGC 7067A29bCL0.2091.1 -01.50.310.6353 NGC 663G28hIL3.3128.2 -00.80.691.4174 NGC 663D28eCL-10.9129.3 -01.60.441.19-43 NGC 663B28cIa-32.9130.7 -00.90.600.8822 NGC 1931A27bIa-18.4174.3+00.90.260.6690 NGC 433D26dIa-10.7125.8-02.20.310.83-78 Stock 5A23bCa-6.6130.6+03.30.330.84-18 MonocerosA ....22bCA27.3218.0-00.30.451.0034° NGC7067E 29eI a-19.9090.8-01.40.190.33-67 NGC7067B 29cIL4.9090.7 -01.50.480.89-65 NGC 663H28hCL3.5129.6 -00.20.500.9974 NGC 663F28gIL-10.5130.5 -00.90.430.8528 NGC 663E28fIL-13.2129.7 -02.20.310.71-26 NGC 663C28dIa-13.6128.9 -00.31.412.26-38 NGC 663A28bIa-34.9129.1 -00.00.981.4834 NGC1931C 27dIA-3.3174.3-00.10.411.1847 NGC1931B 27cCU-13.9173.5+00.00.340.61-62 Bk 62C25cCa-12.5124.0+00.70.410.7661 Bk 62A25bIa-45.1124.3+00.50.46 Roslund 4B24cIa13.0066.6-01.10.781.92-87 Roslund 4A24bCL4.3066.9-01.30.701.030 Stock 5123dIa1.1129.9+02.21.051.54-4 Stock 5H23dCa0.8131.4+02.20.501.52-37 Stock 5F23cCa-4.4130.3+02.20.230.31-45 Stock 5E23cCa-4.8130.2+02.80.340.3974 Stock 5D23cIa-1.7130.1+03.80.791.73-17 Stock 5C23bIa-7.4131.7+02.80.711.12-42 Stock 5B23bCa-8.1130.7+02.90.190.5687 Bk 62B25cIL-8.7124.2+01.80.750.84-22 Stock 5G23cCa-3.1129.8+02.10.290.47-66 -1 Cloud FigureI/CClass(kms)/baPA. maj Map in(V)CenterPosition O. COCloudsnearNGC1931 Q. COCloudsnearNGC7067 J. COCloudsnearMonoceros L. COCloudsnearRoslund4 I. COCloudsnearNGC1624 N. COCloudsnearNGC433 P. COCloudsnearNGC663 K. COCloudsnearStock5 M. COCloudsnearBk62 TABLE 6—Continued Provided bythe NASA Astrophysics Data System Vol. 70 198 9ApJS. . .70. .731L No. 4,1989 © American Astronomical Society • Provided by theNASA Astrophysics Data System NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC NGC 103A. NGC 1605B. NGC 1605A. NGC 2129C. NGC 2129B. NGC 2129A. Bk 11G. BkllF.. Bk HE.. Bk 11C. Bk 11A. NGC 957A. Bk 11D. BkllB.. Cloud 7160A.. 7160C. 7160B . 7160R. 7160Q. 7160P . 71600. 7160N. 7160M. 7160L . 7160K. 7160J.. 71601.. 7160H. 7160G. 7160F . 7160E . 7160D. 1444L . 1444J.. 14441.. 1444G. 1444F . 1444E . 1444D. 1444C . 1444B . 1444A. 1444K. 1444H. Figure Map in 30b 30e 30e 30d 31h 31g 31e 31d 31c 31c 31c 31c 31b 31b 30e 30e 30e 30e 30c 30c 30c 30c 30d 30d 30d 30d 30d 30c 31g 31f 36b 34c 34b 34b 33d 33c 33b 35c 35b 34d 34e 34e 34d 32b I/C Class C c C C C C C C C c c C c c c c c c c c C C C C C C C C I I I I I OPEN CLUSTERCOSURVEY I I I I I I I W. COCloudsnearNGC1605 R. COCloudsnearNGC7160 U. COCloudsnearNGC2129 S. COCloudsnearNGC1444 X. COCloudsnearNGC103 T. COCloudsnearNGC957 V. COCloudsnearBk11 TABLE 6—Continued u U U L L L L L L a a a L L L a a a a a a x (V) (km s) -25.9 -23.6 -19.9 -20.6 -20.2 -24.3 -24.6 -12.5 -11.4 -10.9 -25.4 -34.9 -30.6 -22.1 -31.6 -26.0 -4.3 -9.7 -2.9 -6.8 -2.4 -5.9 -0.9 -5.3 -0.0 -0.9 -0.4 -4.5 -3.7 -7.1 -6.2 -8.1 -8.8 -10.8 -3.4 -9.1 -1.1 -0.9 -8.0 0.2 5.5 4.3 6.3 1.3 Center Position 104.9 148.8 104.3 103.3 146.9 147.3 148.3 149.2 103.3 104.6 104.9 104.0 105.4 104.4 102.8 102.9 103.2 103.4 103.9 103.2 103.8 104.4 104.2 147.6 149.2 147.5 147.9 149.6 147.0 148.2 119.4 158.5 157.1 158.6 157.3 157.8 157.2 156.8 157.3 156.9 186.0 186.7 187.1 136.3 / + 07.3 + 06.6 -01.4 -01.3 -05.7 -06.7 + 05.8 + 06.8 + 07.6 + 06.1 + 07.8 + 05.4 + 07.3 + 07.0 + 06.4 + 05.1 + 05.8 + 05.7 + 06.4 + 07.3 -02.5 -01.2 -00.4 -00.3 -00.4 -01.8 -01.1 -02.1 -01.5 -01.5 -00.1 + 00.2 -00.2 -02.0 1.161.55-56 -01.6 0.26 -01.1 -01.9 -04.3 -04.0 -03.0 -02.9 -03.1 -04.0 -03.0 b 0.33 0.35 0.30 0.45 0.16 0.25 0.24 0.19 0.30 0.19 0.17 0.12 0.26 0.23 0.65 0.25 0.49 0.21 0.33 0.21 0.45 0.40 0.74 0.33 0.88 0.43 0.32 0.53 0.57 0.44 0.38 0.56 0.21 0.23 0.62 0.26 0.14 0.62 0.51 0.61 0.36 0.78 0.87 0.39 0.37 0.63 0.48 0.30 0.54 0.93 0.88 0.51 0.82 0.47 0.79 0.50 0.77 0.26 0.56 0.52 0.21 0.58 0.23 0.60 0.62 0.48 0.48 1.43 1.25 1.14 1.03 1.76 0.70 0.49 0.25 0.35 0.69 0.38 0.91 0.67 0.93 1.04 1.11 1.21 1.32 P.A. -31 -76 -15 -44 -77 -45 -89 -35 -37 -44 -67 -89 -65 -84 -79 -71 -65 -41 -49 -42 -6 4 49 28 29 23 66 30 70 78 54 84 41 87 70 67 77 37 81 9 1 3 751 198 9ApJS. . .70. .731L lar cloud.Thefactthatthisdoesnotoccurmoreoftenin our Roslund 4,NGC654,and1624—issignificantlygreater clouds thatarelocatedbehindtheclusters. 752 it isfound.Weclassifytheclouds accordingly.Ifwearefairly whether itisphysicallyassociatedwiththeclusternearwhich (e.g., IC1848;seeAppendixB)individuallyin§TVb. H iiregionionizedbytheclusterstars.Wediscussthesecases determined tolie“infrontof’theclusterwithwhich it is at leastsomeoftheCOemissionmustariseinmolecular than theintensitypredictedfromequation(2);inthesecases, be consideredassociatedwith acluster,wetabulate“L”;if associated becauseitobscurestheopticalnebulosityfrom the Other casesexist,however,inwhichamolecularcloudcan be sample canbeattributedtoaselectioneffect(see§ lie). strong COemissionthatmaybeduetoaforegroundmolecu- certain thatacloudisassociated withacluster,weshow“A” all evidenceavailableandattempttodetermineforeachcloud dark cloud,andthusistooclose tothesolarneighborhood as thecloud’sclassification in Table6;ifacloudislocal Only onecluster(Berkeley59)liesinadirectionwith In ourdiscussionsofindividualclusterregions,weconsider © American Astronomical Society • Provided by theNASA Astrophysics Data System NGC 6709A38bIU27.5041.4+03.80.792.0145 NGC744D 37dCa-4.3131.6-06.00.430.5479 NGC744C 37cCa-10.4132.6-06.00.320.99-34 NGC744B 37cCa-10.4132.1-05.70.531.19-53 NGC6709C 38dIa5.7042.1+03.30.200.4538 NGC6709B 38cCU31.1042.9+03.80.291.04-30 NGC744A 37bCa-18.0132.0-06.10.210.23-57 NGC 1778D40dIL5.7169.3-02.80.250.3845 NGC 6694G39bIL8.8023.7-04.20.35 NGC6694E 39bCL7.8022.9-02.90.890.96-4 NGC6694D 39bCL8.2023.2-02.40.410.5578 NGC6694C 39bIL8.3023.8-02.00.971.242 NGC6694B 39bCL8.7024.1-03.30.461.30-4 NGC 6694A39bCL9.5024.4-02.50.530.84-12 NGC7062B 41bIL3.8089.9-02.20.561.3632 NGC 7062A41bIL3.6090.7-02.40.430.5451 NGC 1778C40cIL-10.7168.8-01.20.681.56-44 NGC 1778B40cIL-8.5169.7-01.50.720.9363 NGC 1778A40bIL-15.2168.4-01.10.520.90-41 NGC6694F 39bCL10.1023.4-03.70.190.65-15 NGC7062C 41bIL1.4089.3-02.70.350.79-31 IC1442A 42bCU-29.8101.4-02.60.25 l Cloud FigureI/CClass(kms)lba¿zP.A. minaj LEISAWITZ, BASH,ANDTHADDEUS AA. COCloudsnearNGC6694 CC. COCloudsnearNGC7062 BB. COCloudsnearNGC1778 Z. COCloudsnearNGC6709 DD. COCloudsnearIC1442 Y. COCloudsnearNGC744 TABLE 6—Continued linear sizesofthecloudsandtheirCOlinefluxes,luminosi- mane toadiscussionoftheinteractionyoungclusters with of thenonmoleculargasto the molecularmaterial.Regions gas associatedwiththeclusters andparticularlytherelation contains supplementaryinformation aboutionizedandatomic found inoursurveyareconsidered inthissection;PaperII class a. cloud isconsideredtobepossiblyassociatedwiththecluster, cluster weregister“U”for“unassociated”;otherwisethe cloud isarguablyassociatedwithanobjectotherthanthe ties, andmassesaregiveninTable7. are adoptedforthecatalogedmolecularcloudsin§IVc. The are ofclassL,9U,andtheremaining77 of a conditionwhichwedenoteby“a.”Ourcatalogcontains their surroundinginterstellar matter.Themolecularclouds total of148molecularclouds,20whichareclassA,42 We nowsummarizefeaturesofthesurveyedregionsger- On thebasisoftheirassociationclassifications,distances Center Position b) MolecularCloudsFoundintheSurvey Vol. 70 198 9ApJS. . .70. .731L cluster (i.e.,“behind”thecluster). The COintensity-reddeningrelation(eq.[2])isshownasasolidline(dashedUnescorrespondto20%uncertaintyinslope).Pointsthat hesignificantly above thelinecorrespondtosituationsinwhichatleastsomeofCOemissionarisesamolecularcloudlocateddistancegreater thanthatofthe No. 4,1989 Fig. 13.—TheCOlineintensityasafunctionof“corrected”clusterreddening(seetext)forlinessighttoward33openclusters.Error barsare1ct. American Astronomical Society •Provided bythe NASA Astrophysics Data System o O co NGC 1893E NGC 1893B NGC 2175F NGC 6823E NGC 6823D NGC 6823A NGC 1893D NGC 1893C NGC 1893A NGC 281B NGC 2175G NGC 2175C NGC 2175B NGC 2175A NGC 6823C NGC 6823B IC 1848G. IC 1848F. IC 1848E. IC 1848D. IC 1848C. IC 1848B. IC 1848A. NGC 281A NGC 2175E NGC 2175D Bk 59E. Bk 59D. Bk 59B. IC 1396C. Bk 59C. Bk 59A. IC 1396B. IC 1396A. 12 Identification (Kkms~deg)(kpc) Derived CharacteristicsoftheObservedMolecularClouds 271. (0.15) 23.5 (0.16) 11.7 (0.11) 11.1 (0.11) 14.3 (0.15) 15.5 (0.13) 19.7 (0.17) 0.14(0.02)’ 0.35(0.02) 0.61(0.02) 0.26(0.03) 0.24(0.03) 0.28(0.03) 0.090(0.02) 0.23(0.04) 0.28(0.05) 0.51(0.03) OPEN CLUSTERCOSURVEY 0.73(0.07) 0.72(0.03) 0.21(0.02) 2.6 (0.08) 2.3 (0.06) 2.1 (0.07) 7.6 (0.08) 1.8 (0.07) 9.9 (0.13) 2.9 (0.06) 2.7 (0.08) 7.4 (0.11) 1.2 (0.04) 5.6 (0.09) 1.8 (0.07) 1.3 (0.05) 1.3 (0.06) *Sco d AE(B-V) (mag) TABLET <1.00 <1.00 <1.00 4.00 4.00 4.00 4.00 4.00 2.31 2.31 0.80 0.80 2.70 2.70 2.70 2.70 2.70 2.31 2.31 2.31 0.80 2.20 2.20 1.95 1.95 1.95 3.50 1.00 1.00 1.00 1.00 1.00 1.95 1.95 (pc) <5 <5 <5 40 29 28 25 25 29 25 11 12 12 34 28 11 35 70 18 30 18 15 18 17 36 13 13 13 14 12 6 9 7 8 <23 (PC) <12 105 <5 maj 43 21 24 31 63 43 68 20 25 32 39 38 31 18 19 17 22 33 55 79 54 10 31 39 70 86 35 14 13 32 < 0.0021 < 0.0076 < 0.019 15. (L) q Leo 0.028 0.039 0.0091 0.83 0.062 0.067 0.022 0.43 0.018 0.022 0.18 0.79 0.053 0.012 0.12 0.29 0.35 0.11 0.14 0.13 0.057 0.028 0.053 0.017 0.20 0.81 0.041 2.8 1.2 1.3 3 (10 M) Q 1300. ^cloud 240. no. 100. <0.18 <0.64 <1.6 69. 66. 68. 25. 29. 11. 36. 15. 10. 12. 16. 0.76 4.5 4.8 2.3 4.5 1.8 2.3 3.3 9.3 5.2 5.6 1.5 1.9 1.4 3.4 1.0 753 198 9ApJS. . .70. .731L 754 American Astronomical Society •Provided bythe NASA Astrophysics Data System NGC 7160J NGC 7160B NGC 7067D NGC 7067A NGC 663E.. NGC 663D.. NGC 663C.. NGC 663B.. NGC 663A.. NGC 1931C NGC 1931B NGC 1931A NGC 433D. NGC 433C NGC 433B NGC 7160R NGC 7160N NGC 7160M NGC 7160L NGC 7160K NGC 71601 NGC 7160G NGC 7160F NGC 7160D NGC 7160A NGC 7067E NGC 7067C NGC 7067B NGC 663H.. NGC 663G.. NGC 663F.. NGC 433A NGC 1624D NGC 1624C NGC 1624B NGC 1624À NGC 7380F NGC 7380E NGC 1444B NGC 1444A NGC 7160Q NGC 7160P NGC 71600 NGC 7160H NGC 7160E NGC 7160C NGC 7380D NGC 7380C NGC 7380B NGC 7380A Bk 62C Bk 62B Bk 62A Roslund 4B Roslund 4A Stock 5E. Stock 5D Stock 5C. Stock 5B. Stock 5A. Monoceros A Stock 51. Stock 5H Stock 5G Stock 5F. IC 1396F... IC 1396E... IC 1396D... Identification -12 LEISAWITZ, BASH,ANDTHADDEUS (K kmsdeg) 13.4 (0.16) 0.16(0.03) 0.34(0.03) 0.12(0.02) 0.97(0.04) 0.46(0.02) 0.82(0.04) 0.24(0.01) 0.99(0.05) 0.75(0.04) 4.7 (0.13) 0.51(0.03) 0.35(0.02) 0.43(0.03) 0.36(0.03) 0.26(0.01) 0.44(0.03) 0.15(0.02) 0.24(0.03) 0.89(0.04) 0.19(0.02) 0.65(0.03) 4.9 (0.10) 0.71(0.03) 0.70(0.05) 0.33(0.05) 0.21(0.04) 0.13(0.03) 0.33(0.05) 0.56(0.07) 0.20(0.04) 0.067(0.03) 0.33(0.04) 0.16(0.04) 0.99(0.08) 0.53(0.06) 0.53(0.05) 0.21(0.04) 0.43(0.05) 0.53(0.04) 0.86(0.05) 0.59(0.04) 0.27(0.03) 0.47(0.04) 0.93(0.05) 0.38(0.04) 0.93(0.05) 0.73(0.05) 0.57(0.03) 0.34(0.02) 0.22(0.05) 3.7 (0.08) 1.1 (0.08) 1.0 (0.06) 1.3 (0.06) 1.8 (0.07) 1.7 (0.05) 9.0 (0.13) 3.4 (0.07) 3.9 (0.07) 3.1 (0.06) 3.6 (0.06) 9.2 (0.16) 6.9 (0.09) 2.2 (0.06) 1.0 (0.08) 1.6 (0.11) 1.7 (0.06) Sco TABLE 7—Continued (kpc) (pc) <1.00 <1.00 <1.00 <1.00 <1.00 <1.00 <1.00 0.70 0.70 0.70 0.70 0.70 0.30 0.30 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.83 0.83 0.83 0.83 4.50 4.50 4.50 4.50 0.40 6.00 2.53 2.13 2.53 2.30 2.40 6.00 0.40 0.80 0.80 1.00 3.50 2.05 2.05 2.90 1.60 1.60 1.60 1.60 1.60 1.60 1.60 3.60 1.00 1.80 1.80 1.60 1.60 3.60 3.60 3.60 3.60 <12 <13 <9 <9 <8 <5 <8 43 46 22 20 40 62 22 24 25 40 29 12 13 14 25 34 19 38 36 20 21 15 17 14 19 12 10 4 4 4 4 4 6 6 2 2 2 2 2 6 6 6 2 2 3 3 3 3 3 5 3 7 9 5 9 8 8 8 5 8 9 “maj (pc) <25 <21 <17 <15 <12 <13 <15 100 48 42 48 46 43 42 23 20 65 24 21 65 63 31 62 68 64 11 11 14 13 11 10 33 37 27 13 11 16 81 75 25 10 13 17 97 31 53 11 18 6 4 6 6 6 7 7 3 7 3 7 6 7 9 3 5 8 3 9 8 3 < 0.019 < 0.027 < 0.012 < 0.0036 < 0.015 < 0.013 < 0.025 (Lo) (10Mq) ^CO ^cloud 0.14 0.034 0.0073 0.025 0.42 0.0048 0.00095 0.38 0.25 0.00095 0.0024 0.0041 0.0015 0.00049 0.0024 0.0012 0.0072 0.0039 0.0039 0.0015 0.0031 0.0073 0.029 0.0012 0.0047 0.051 0.45 0.082 0.040 0.017 0.13 0.11 0.033 0.0082 0.15 0.12 0.010 0.0058 0.0092 0.18 0.33 0.073 0.18 0.14 0.022 0.066 0.021 0.0085 0.0051 0.0016 0.0024 0.0015 0.0073 0.0080 0.0035 0.010 0.078 0.13 0.037 1.3 1.1 110. <2.1 <2.3 <0.30 <1.2 <1.6 <1.0 <1.1 21. 28. 12. 35. 32. 38. 11. 11. 95. 13. 10. 15. 15. 12. 0.87 0.77 0.61 0.41 0.080 0.20 0.098 0.33 0.29 4.3 0.69 0.48 2.9 2.1 0.20 0.13 0.080 0.20 0.34 0.12 0.041 0.61 0.33 0.13 0.26 0.61 0.68 0.61 0.10 0.84 0.40 6.9 6.6 6.2 0.71 0.43 0.14 2.5 3.4 9.1 2.8 1.9 5.5 1.4 3.1 1.8 Vol. 70 198 9ApJS. . .70. .731L Vazquez, andBenvenuto1986; Harris1976;Moffat1972; radio sourceW5). a prominentPerseusarmH n region(emissionnebulaSI99; Sharpless 1954;Vallée,Hughes, andViner1979)thationizes illustrations ofthecatalogedmolecularclouds,analogous to detected (32ofthe34surveyedclusterregions). each ofthesurveyedregionsinwhichCOemission was analogous tothoseinFigures12c-12/,areshownbelow for the oneinFigure12g,andcontourdiagramsofjT/(CO) dv, ally, inorderofincreasingclusterage(seeTable5).Schematic around eachofthesurveyedclustersareconsideredindividu- No. 4,1989 This isanextremelyyoung ( -1Myr)cluster(Feinstein, © American Astronomical Society • Provided by theNASA Astrophysics Data System i) IC1848 NGC 2129A NGC 1444J NGC 1444H NGC 1444G NGC 1444E NGC 1444D NGC 1444C NGC 2129C NGC 2129B NGC 957A.. NGC 1444L NGC 1444K NGC 14441 NGC 1444F NGC 6694F NGC 6694D NGC 6694A NGC 744D.. NGC 744C.. NGC 744B.. NGC 103A.. NGC 1605B NGC 1605A BkllA NGC 7062B NGC 1778D NGC 1778B NGC 1778A NGC 6694G NGC 6694E NGC 6694C NGC 6694B NGC 6709C NGC 6709B NGC 6709A NGC 744A.. BkllG BkllF Bk HE BkllD Bk 11C BkllB NGC 7062C NGC 7062A NGC 1778C IC 1442A... Identification -12 (K kmsdeg) 0.27(0.02) 0.27(0.02) 0.21(0.03) 0.10(0.02) 0.44(0.03) 0.58(0.03) 0.61(0.03) 0.40(0.05) 0.37(0.03) 0.21(0.04) 0.71(0.04) 0.27(0.04) 0.72(0.05) 6.2 (0.10) 0.21(0.03) 0.49(0.04) 0.58(0.05) 0.39(0.04) 0.27(0.02) 0.25(0.05) 0.25(0.04) 0.37(0.04) 0.70(0.06) 0.13(0.01) 2.4 (0.06) 6.6 (0.14) 2.8 (0.06) 7.4 (0.11) 2.9 (0.06) 0.97(0.05) 2.0 (0.06) 2.9 (0.07) 2.2 (0.08) 1.6 (0.04) 1.3 (0.06) 1.6 (0.06) 1.1 (0.05) 1.2 (0.10) 2.3 (0.14) 1.2 (0.06) 1.4 (0.06) 1.2 (0.06) 5.6 (0.08) 1.9 (0.07) 1.2 (0.05) 3.2 (0.08) OPEN CLUSTERCOSURVEY Sco TABLE 7—Continued (kpc) (pc) <1.00 <1.00 <1.00 <1.00 <1.00 <1.00 <1.00 (3.00) 0.30 0.30 0.80 2.00 2.00 0.20 0.20 2.20 2.20 2.20 2.00 1.00 1.00 1.00 1.00 0.83 0.80 0.80 0.80 0.20 0.20 0.20 0.20 0.20 0.93 2.72 2.20 2.20 0.83 0.83 0.30 2.20 2.20 3.03 1.50 1.50 1.50 1.50 like localdarkcloudsonthe POSSprints,andhavemuch interaction withanHIIregiontodeterminewhichclouds are hand, cloudsDandFdonot havethesecharacteristics,look with positionsofenhancedradiocontinuumemission or B, C,andEareassociatedwith IC1848andthat1848D more positiveradialvelocities thantheothermolecularclouds Viner 1979),andarebrightInfraredAstronomicalSatellite distorted radiocontinuumcontours(Vallée,Hughes, and B, C,andEhaveopticalemission-line“brightrims”(Pot- (see Table6A).Therefore,we behevethatcloudsIC1848A, (IRAS) sources(LeisawitzandHauser1988).Ontheother tasch 1956;seeWilkingetal1984;AppendixB),coincide associated withtheyoungcluster.MolecularcloudsIC1848A, (Table 6A;Fig.14)andlookedforindicationsofcloud M <20 <13 <10 min maj < 4 <6 <9 <6 (13) We foundsevenmolecularcloudsintheIC1848region 27 24 20 21 27 15 14 10 13 14 11 30 11 10 4 7 8 6 2 1 9 5 6 3 2 2 8 9 7 1 3 1 3 1 1 8 5 8 <22 <27 <25 <13 <9 <5 <8 (13) 46 47 49 23 33 31 14 15 35 14 40 26 37 10 15 22 77 13 20 13 14 31 13 11 4 9 4 6 3 2 3 2 3 7 2 1 5 8 <0.0040 < 0.024 < 0.0031 < 0.098 <0.042 < 0.0091 <0.043 (1),(c),(d), Table 6Aareusedin(a),which is analogoustoFig.12g.Thecontour and (c),respectively,thelowestcontour level,1Kkms,corresponds may betransientsurvivorsofthecloudsurfaceerosion. nebulosity aroundIC1848.Theglobules,whichrangeinsize to 1.2,1.4,2.1,and1.6a. from -0TtoIT(0.060.7pcatthedistanceofIC 1848), Heneartheedgesofmuchlargermolecularcloudsand At leastonemolecularcloud,NGC1893A(seeBlitz,Fich, All fiveofthemolecularcloudsfoundinthisregion(Table Photometric observations(Cuffey1973;Hagen1970;Hoag Fig. 14.—Surveyresultsforthe region aroundIC1848.Datafrom Sim (1968)foundseveralBokglobulesinfrontofthe ii) NGC1893 Vol. 70 198 9ApJS. . .70. .731L No. 4,1989 -0.5 -1.0 0.5 0.0 1.0 1.0 0.50.0-0.5-1.0 © American Astronomical Society • Provided by theNASA Astrophysics Data System OPEN CLUSTERCOSURVEY Fig. 14—Continued 757 198 9ApJS. . .70. .731L 1 -1 km s",themolecularcloud may berecedingfromthecluster, kilometers persecond(muchgreaterthantheinternalmea- because thebrightstarstendtobeinbinaryormultiple by theirappearanceinIRASco-addeddata,suggeststhat but theclustervelocityistoo uncertainforustobesureof Johnson andSvolopoulos1961; Wilson1953;Wramdemark nately, theradialvelocityofclusterisnotwellknown NGC 1893isthatthemolecularcloudastrongsourceof (1972) tovarywithtimeanddifferfromeachotherbytens of (ranging fromB2to05inspectraltype)wereshownbyJones one can,inprinciple,compareradialvelocitiesofthecloud extended infraredemission(LeisawitzandHauser1988).The NGC 1893A,theclusterstarlightispolarizedwithvectors interacting withtheHuregion.Perhapsasaresultofdustin presence of“brightrims”onthesurfacessome this. surement error)withameanvelocity—4+8kms (see systems (Sharpless1954)withunknowncenter-of-mass mo- and theclustertodeterminetheirrelativemotion.Unfortu- fact thatcloudsCandEalsocontainwarmdust,asimplied faint, marginallyresolvedemissionfeatureinthelow-resolu- dusty clumps(seeJohnsonandWhite1980),especiallythose 1982). Sincetheradialvelocity ofNGC1893Ais—6.0 tions. Forexample,theradialvelocitiesofeightmassive stars these cloudstooareinthevicinityofluminouscluster. aligned andtiltedatapositionangle-20°withrespectto Inspection ofIC410onthePOSSredplatereveals tion GalacticplaneCOsurveyofDameetal.(1987). the Galacticplane(Serkowski1965).CloudAappearsasa to thesouthofionizingcluster,indicatingthatcloudAis -1 758 (b) isanalogoustoFigs.12c,12and12/.Thelowestcontourlevel,1Kkms,corresponds1.6o. A furtherindicationthatNGC1893Aisassociatedwith Since NGC1893Aisinfrontof1893(seeabove), Fig. 15.—SurveyresultsfortheregionaroundNGC1893.DatafromTable6Bareusedin(a),whichisanalogousto12g.Thecontour diagram © American Astronomical Society • Provided by theNASA Astrophysics Data System Ai (degrees) LEISAWITZ, BASH,ANDTHADDEUS 20 -2 -1 intensity ofthisCOfeaturecorresponds,accordingtoequa- reddening. Theabsorptionline at21cmmeasuredbyGHW measurements ofthereddeningclustermemberscan be sity V(Hi)^1.3xl0cm , butthiscorrespondstoa (see TovmassianandNersessian 1973)impliesacolumnden- reddening producedbydust inforegrounddiffusegas(eq. our dataatavelocity-10kms(seeAppendixA); the rift molecularcloud(DameandThaddeus1985)isfound in used todistinguishbetweenforegroundandbackground ma- [1]), theVulpéculacloudalone canaccountfortheresidual nonmolecular gasassociatedwithit,thereaderisreferredto tion (2),toareddeningof0.20+0.06mag.Afterallowing for 1970; Starikova1969).EmissionfromthenearbyVulpécula 1970; HoagandApplequist1965;Moffat1972;Polishchuk terial. Theclusterreddening,£(2?-F)0.80mag(Hagen against theNGC6823Hnregion,ourCOobservations, and Paper II. B0.5Ib (Harris1976;HoagandApplequist1965;Moffat (Feinstein, Vazquez,andBenvenuto1986;Walbom1972) evolved massivemembershavespectraltypes07.5111(f) most massivemain-sequencestarisan07star,andtheonly contracting ontothezero-agemainsequence(ZAMS).The (1972) indicatethatlow-massclustermembersmaystillbe 1987; Moffat1972). 1972). Theageoftheclusterthereforeisestimatedtobe UBV photometricstudiesofHoagetal(1961)andMoffat — 1-2Myr(Feinstein,Vázquez,andBenvenuto1986;Lyngâ Observations oftheHI21cmlineseeninabsorption For furtherdiscussionoftheNGC1893cluster,and This clusteralsoisamongtheyoungestinoursurvey.The -10 TO-3km/s iii) NGC6823 Vol. 70 198 9ApJS. . .70. .731L -1 -1 -1 1- -1 intensity fromthiscloudinthedirectionofclusteris NGC 6823Bislocatedbehind6823thattheCO No. 4,1989 nebula andisrecedingfromtheclusterat-4kms. optical nebulosity.CloudA,therefore,isinfrontofthe uncertainty fromtheclustervelocity.Persuasiveevidencethat blueshifted withrespectto+25kmsisseparatedfromthe hereafter PGK),isoneinwhichCOemissionthat by theVulpéculacloudoccursatavelocitywithin-10 any, fromNGC6823A,andthisclouddoesobscurethe [2]) muchgreaterthantheobservedstellarreddening(seeFig. 29.9 +0.8Kkms,towhichcorrespondsareddening(eq. velocity ofNGC6823Bdiffersbylessthantheobservational relatively redshiftedemission.Thisdivisionresultsinthe clouds, suggestedbycomparisonofthethree-channelintegra- (Wramdemark 1982).Thekinematicandmorphologicalstruc- km s'ofthatthecluster(seeBPS),29s presence ofdustintheionizedgas,wouldbetoosmallto 13). catalog entriesNGC6823Aand6823B(Table6c).Theradial optical emissionlines(Parker,Gull,andKirschner1979, difficult. Areasonabledivisionoftheemissionintodiscrete the directionofNGC6823containsonlyweakemission,if ture ofthisemissionisexceptionallycomplicated(seeFig. reddening ofonly0.02mag(Bohlin,Savage,andDrake1978), tion maps(seeFig.12)withthespatialbrightnessdistribu- 16), andthetaskofcatalogingmolecularcloudsistherefore affect thisargument. tions ofradiocontinuumemission(Altenhoffetal1978)and and anadditionalreddeningcorrection,toaccountforthe 0.94,2.1, and1.3a. ^ , are analogoustoFigs.12c,I2d, and12/.In(6),(c),(J),(/),respectively,thelowest contour level,1Kkms,correspondsto513 On theotherhand,COspectrallineprofileobtainedin Nearly alloftheCOemissionotherthanthatcontributed Fig. 16.—Surveyresultsfortheregion aroundNGC6823.DatafromTable6Careusedin(a),which isanalogoustoFig.12g.Thecontourdiagrams © American Astronomical Society • Provided by theNASA Astrophysics Data System OPEN CLUSTERCOSURVEY -1 5 line fluxfromcloudCmayhavebeenoverlookedforthis were used,respectively),andasignificantfractionoftheCO intensity contourlevelsareusedtodefinetheboundariesof latter cloudispartofthesamecomplex.CloudsAandB radio sourceW1(diameter-3°;ChurchwellandFelli1970; rounded bythenebulaS171(diameter-40'),alsoknownas reason. lack ofacleardistinctionbetweenNGC6823Aand6823Bin NGC 6823,thenthegreatestconcentrationofmassnear intensity andcomplexityonlybytheemissionfoundnear and Williams1959;MacConnell1968).Theclusterissur- clouds NGC6823Band6823C(the720Kkmslevels region, ~3X10M(seeTable7).RelativelyhighCO our three-channelCOintensitymaps,onemightinferthatthe NGC 6823and2175(seeAppendixA;cf.Rydbeck age ofBk59arediscussedinPaperII. Rossano, Angerhofer,andGrayzeck1980).Constraintsonthe opaque materialthatcoincidesspatiallywithNGC6823A cluster isintheformofmolecularclouds(seediscussion 1987) intheCepheusOB4association(diameter-5°;Blanco alone contain—70%ofthetotalmolecularmassthis suggests thatthecloud,atleast,isnearcluster.Given the ionizedandatomicgasinPaperII).A“brightrim”on et al1976).Thus,high-levelcontoursofCOintensitywere emission foundinoursurveyofthisregionisequaledits of radius-30pcaroundBk59(Fig.17).TheCOline 0 Berkeley 59isthecentralcluster(diameter-10;Lyngâ If thecloudsthatwecatalogactuallyareassociatedwith Carbon monoxideemissionisnearlyubiquitousinaregion 1.0 0.50.0-0.5-1.0 J I1L 18 TO26km/s iv) Berkeley59 759 198 9ApJS. . .70. .731L 760 LEISAWITZ,BASH.ANDTHADDEUSVol.70 -1.0 -0.5 0.0 0.5 1.0 1.0 0.50.0-0.5-1.0 © American Astronomical Society • Provided by theNASA Astrophysics Data System 24 TO35km/s 27 TO31km/s Fig. 16—Continued -0.5 0.0 0.5 1.0 1.0 0.50.0-0.5-1.0 18 TO29km/s 22 TO43km/s 198 9ApJS. . .70. .731L -1 -1 -1 1213 -1 analogous toFigs.12c,124, and 12/.In(h),(c),(4),(/),respectively,thelowestcontour level,1Kkms,correspondsto1.4,1.8, 1.5, and1.3a. No. 4,1989 4.8 andG118.5+4.6foundlinevelocities,respectively,of line brightrimsarefoundtowardtheclouds,butalsofrom velocities. Forexample,CCGobservedHatowardG118.4+ km s,coincidentwiththeHIdepletionnotedbyGrayzeck relative minimaintheoverallCOemissionfromregion. ently isassociatedwithmolecularcloudsurfaces.Supportfor of fourmajorconcentrationsionizedgas:atabout—19, Pedlar andDavies1972;Rossano,Angerhofer,Grayzeck (1980). Radiorecombinationline(DownesandWilson1974; There isarelativedeficiencyofCOemissionat10 multiple velocitycomponentsintherange(—20,+2kms). liar. TheCOspectrallines(seeAppendixA)typicallyhave vicinity ofBk59ismorphologicallyandkinematicallypecu- beyond theboundaryofourmap(seeDameetal.1987). the locallycoincidentmolecularcloudandionizedgasradial 1980) andHaline(CCG)observationsindicatethepresence mapped emissionfromtheCOandCOisotopestomea- The strongestCOemissionoccursincloudAataposition Bk 59D,andperhaps59A,liesentirelywithintheregion used todefinetheboundariesofcloudsBk59CandE.Only this ideacomesnotonlyfromthefactthatopticalemission- cate thattheyareassociatedwiththeyoungclusterand Bright rimsonthemolecularclouds(seeAppendixB)indi- CO sourceincloudD. sure thedensityandtemperaturestructureofasecondstrong adjacent toBk59.Elmegreen,Dickinson,andLada(1978) suggest thattheyaredissolvinginthehotintercloudmedium. surveyed; thethreeothercatalogedcloudsapparentlyextend — 14,—10,and—4kms.Atthesevelocities,wefind Fig. 17.—Surveyresultsfortheregion aroundBk59.DatafromTable6Dareusedin(a),whichisanalogous toFig.12g.Thecontourdiagramsare On theotherhand,atleastsomeofionizedgasappar- Ionized, atomic,andmolecularinterstellarmatterinthe © American Astronomical Society • Provided by theNASA Astrophysics Data System 1.5 1.00.50.0-0.5-1.0-1.5 AÍ (degrees) OPEN CLUSTERCOSURVEY 5 -3 -1 ionization fillsa35pcdiametersphere,thenitcontains ionized gasareessentiallycomoving. molecular cloudsis~10M. directions ofcloudsDandA,respectively,the NGC 2175Band2175Gweresomewhatarbitrarilydistin- Appendix A).Sevenmolecularcloudswerefound,but pc radiusregionmappedaroundNGC2175(seeFig.18and implied bythemain-sequencelifetimeofexcitingstar (see §IVc)thatthetotalmassinformofassociated density intheregionas/z^-lOcm.Ifof OBI molecularcloudcomplex. heated bythestarsinNGC2175(LeisawitzandHauser1988) gether, thesecloudsconstitutethestrongestCOsourcenear guished frommoreextendedemissionbyreferringtohigh-level Pismis 1970)inferaclusterageof2Myr. data andisochronefitting,GrasdalenCarrasco(1975;cf. (see, e.g.,Maeder1981),and,fromtheirspectrophotometric nous memberofthisclusterandisresponsiblefortheioniza- the Galacticanticenter(see,e.g.,Dameetal.1987),Gem CO intensitycontours(6and3Kkms,respectively).To- tion ofS252.A7Myrupperlimittotheageclusteris and thusareassociatedwiththecluster.Analogously,cloudA 0 -1.8 and-13.4kms.TheseCCGpositionsareinthe - 5500Mofionizedhydrogen.Forcomparison,weestimate 0 Pedlar andDavies(1972)estimatedtheaverageelectron An 06.5main-sequencestar,HD42088,isthemostlumi- Carbon monoxideemissionisnearlyubiquitousinthe50 Clouds BandGaresourcesofextendedinfraredemission _i i 1.5 1.00.50.0-0.5-1.0-1.5 -18 TO-8km/s v) NGC2175 761 198 9ApJS. . .70. .731L 762 -1.0 -1.5 -0.5 0.0 0.5 h 1.0 1.5 1.5 1.00.50.0-0.5-1.0-1.5 1.5 1.00.50.0-0.5-1.0-1.5 i r © American Astronomical Society • Provided by theNASA Astrophysics Data System (0 -20 TO-15km/s -5 TO3km/s n 1\r LEISAWITZ, BASH,ANDTHADDEUS Fig. 17—Continued 1.5 1.00.50.0-0.5-1.0-1.5 1.5 1.00.50.0-0.5-1.0-1.5 -14 TO-3km/s -10 TO-1km/s Vol.'70 198 9ApJS. . .70. .731L No. 4,1989 are analogoustoFigs.12c,124,12c,and12/.In(b),(c),(4), respectively, thelowestcontourlevel,1Kkms,correspondsto1.1,1.9,and1.3o. -1.0 -0.5 -1.5 Fig 18-SurveyresultsfortheregionaroundNGC2175.Datafrom Table6Eareusedin(a),whichisanalogoustoFig.12gThecontourdiagrams 0.5 0.0 1.0 1.5 1.5 1.00.50.0-0.5-1.0-1.5 © American Astronomical Society • Provided by theNASA Astrophysics Data System OPEN CLUSTERCOSURVEY -1.0 -0.5 -1.5 0.0 0.5 1.0 1.5 1.5 1.00.50.0-0.5-1.0-1.5 1.5 1.00.50.0-0.5-1.0-1.5 -3 TO12km/s 3 TO14km/s 763 198 9ApJS. . .70. .731L -1 -1 Wooden (1979)supportstheideathathigh-densitymolecular is justtheamountbywhichCOintensityoverestimates young clusters(Leisawitz1985;PaperIII),butthedifference in thedirectionofNGC2175s,-8.5±0.9Kkms,can be intervening molecularcloud,thentheCOintensitymeasured molecular cloud(albeitnot exceptionally massivecompared cloud Bisindeedgreaterthaninothercloudsassociated with compared withthenominalCO-to-reddeningratio(eq.[2]) to is moreheavilyreddenedthanNGC2175,whichnearby of NGC2175B(see§IVc) indicates thatthisisamassive gas ispresentthere.Hence,the relativelylargeCOluminosity the columndensity.Furthermore,detectionofCS / = Eg_ j/[NGC2175]-0.5mag;Pismis1970)isattributedto the of NGC2175sversus2175(£_[2175s]- present case.WeargueasfollowsthattheCOlineintensity to thecloudsdiscussedbyDame etal1986). 3 2emissionfromthewesterncloudfragmentbyLada and show thattheCOlineisbiasedbyheatingafactorof only only inprojection.Ifmostofthedifferencereddening Fortuitously, thesmallstarclusterNGC2175s,studiedpho- from thisparticularcloudisanestimatorofcolumndensity. density, butthelatterconditionevidentlyisdominantin enhanced gaskinetictemperatureorfromalargeCOcolumn found inoursurvey.AhighCOluminositycanresultfrom order ofmagnitudethanthatanyothermolecularcloud matter associatedwithNGC2175,thereaderisreferredto nearly thesameasthatofadjacentmolecularcloudNGC velocity ofthenearbyHnregionS247,fromHaobserva- with thespatialdistributionofCOemission.Theradial tometrically byPismis(1970),islocatedbehindcloudBand 2175A. Forfurtherdiscussionofnonmolecularinterstellar model proposedbyFountain,Gary,andO’Dell(seetheirFig. bination linesfromthegasionizedbyNGC2175havebeen NGC 2175B. near theprojectededgesofclouds.Theseclouds,referred (Lada andWooden1979;cf.Fountain,Gary,O’Dell region S252issurroundedontwosidesbymolecularclouds molecular cloudssubtendalargesolidangleasseenfromthe Paper II. cloud Bcanexplaintheseobservationsinamannerconsistent used tostudythekinematicsofHnregion.Theschematic features (Felli,Habing,andIsrael1977,referencestherein) central cluster(LeisawitzandHauser1988).Indeed,theHn The otherthreecatalogedcloudsinTable6Eare“possibly is alocaldarkcloudclearlyvisibleonthePOSSblueprint. tions ofGeorgelinand(1970),is~7kms, fragments, aresubsetsofthemuchlargermolecularcloud a largefractionoftheclusterluminosity,suggestingthat can beshowntoassociatedwithS247(seeBFS).CloudF associated” withNGC2175becausenoevidenceisfoundto tain, Gary,andO’Dell1983)observationsofhydrogenrecom- to byLadaandWoodenastheeasternwesterncloud 1983) andincludeshigh-surface-brightnessradiooptical the contrary. 8) inwhichionizedgasflowsfromtheilluminatedsurfaceof 764 — 2(seeLeisawitzandKlinglesmith1988).ThepeakT/ in 5K Cloud BhasaCOspectrallineluminositygreaterbyan The infraredluminosityoftheregionaroundNGC2175is Radio (Falchi,Felli,andTofani1980)optical(Foun- © American Astronomical Society • Provided by theNASA Astrophysics Data System LEISAWITZ, BASH,ANDTHADDEUS 13 12 Wooden (1979)tocoincidewithradiocontinuumpeaks, dio peakB),thenain thenearinfraredemission,and encounters thesoutheastern concentration ofionizedgas(ra- from theionizingstarsto easterncloudfragment,onefirst Johnson, White,andPedlar1981).Aperturesynthesis 1.4 region ofstarformation. optical emission“knots,”andanH0maser,suggestingthat frared signature.Following a vectorintheplaneofsky cloud fragment,andthehasanextended,warm in- ferred tointheliteratureasradiopeakA,isslightlyoffset (in other tothesouthwest.Thesouthwesternconcentration, re- Pedlar 1981)showtwoconcentrationsofionizedgas, each find thationization-dissociationfrontsarepresenton the nebula (seeAppendixB). ment” obscuresasmallpartofthesoutheasternedge molecular cloud“fragment”containsthedustthatobscures in alargeareaaroundthecentralclusterisexposedto offset by~4'fromHD5005,onetothesoutheastand the surfaces ofbothcloudfragments(seeFelliandHarten1981; the directionofHD5005)fromcenterwestern GHz maps(FelliandHarten1981;Israel1977;Roger and and inCO(Leisawitz,Chin,Bally1988).Thewestern (1981), andbyinfraredemissiondetectedIRAS(Leisawitz map (Fig.19),byHifeaturesobservedRogerandPedlar interstellar environments. biguous spatialarrangementofinterstellarmatterwithrespect high Galacticlatitude(-6?24)ofNGC281andtheunam- the interstellarenvironmentofNGC2175isstillanactive the southwesternquadrantofSI84;easterncloud“frag- stellar radiation. Klinglesmith 1988)indicatesthatalllinesofsightwithmea- covering a2°X2°areacenteredonNGC281(Leisawitzand two componentsbothinCO(ElmegreenandLada1978) and Hauser1988).Theinfraredemissionindicatesthatdust nature oftheinteractionbetweenyoungclustersandtheir radio source(diameter-40'),observationsofwhichare surable extinctionarematchedbyCOfeaturesinoursurvey 6), observationsofthisregionoffervaluablecluestothe cal nebulosityS184(Sharpless1953).Thesizeofthe lived, theageofNGC281cannotbemuchgreaterthanafew bom (1973)asspectraltypes06.5V(f)and08V(seeWalker same asthatofthevisiblenebula.Becauserelatively summarized inTable4ofIsrael(1977),isapproximatelythe conclusion. IonizingphotonsfromNGC281excitetheopti- (Sharpless 1954).TheseOstarshavebeenclassifiedbyWal- cluster dominatedbythebinaryOstarsystemHD5005 to thestarcluster(Johnson,White,andPedlar1981,theirFig. and Lada1978,referencestherein;Sharpless1954) Myr; estimatesofthedynamicalagecluster(Elmegreen the region(Johnson,White,andPedlar1981)supportthis and Hodge1968).Sincestarsasmassivetheseareshort- 2 By superposingradio,millimeter,andinfraredimageswe The peanut-shapedmolecularcloudNGC281Aconsistsof Bright spotsintheCOemissionwereshownbyLadaand A mapofthestardensity(fromPOSSblueplate) NGC 281(alsoknownasADS719;Aitken1932)isapoor vi) NGC281 Vol. 70 198 9ApJS. . .70. .731L -1 diagrams areanalogoustoFigs.12c, Yld,12c,and12/.In(b)(c), Table 6Fareusedin(a),which is analogoustoFig.12g.Thecontour respectively, thelowestcontourlevel, 1Kkms,correspondsto1.3and No. 4,1989 1.8 a. Fig. 19.—Surveyresultsfortheregion aroundNGC281.Datafrom 0.8 0.40.0-0.4-0.8 © American Astronomical Society • Provided by theNASA Astrophysics Data System -46 TO-41km/s Ai (degrees) OPEN CLUSTERCOSURVEY -1 -1 _1 is morenearlyperpendiculartotheplaneofskythan An H0maser,generallyconsideredtobeanindicatorofstar warm Hii/Hinterfaceonthewesterncloud.Kinematic Williams (1973)thatNGC281isinsideanexpandingHi phenomenon. location suggeststhepossibilitythatmaserisasurface molecular cloudwasfoundbyElmegreenandMoran(1979). evidence forthepassageofashockthroughwestern formation, existsattheprojectedionizationboundaryon front onthesurfaceofeasternmolecularcloudapparently be explainedbyamodelin whichthemolecularcloudsare clouds onthefarsideofshell;NGC281Ais near (see AppendixA)ofemissionthatcouldariseinmolecular HD 5005(Cruz-Gonzalesetal.1974),andtheshellexpands Pedlar 1981).Thevelocitycentroidoftheexpansionisabout finally COemissionfromthemolecularcloud.Theionization at ~10kms.WefindnoevidenceintheCOspectral lines shell, theinneredgeofwhichisionized(Johnson,White,and Pedlar (1981)andinthelarge-scalesurveyofWeaver surface ofthewesternmolecularcloud(ElmegreenandLada direction oftheionizingstars. Mostoftheatomichydrogen Pedlar 1981;Williamson1970),atomic(Rogerand son, White,andPedlar1981;Reynolds1985;Roger and side ofthecluster(seeabove)andisapproachingusrelative 1978). Theabsenceofacompactinfraredsourceatthemaser from thesurfacesofclouds (seeMiller1968)inthe 1978; Leisawitz,Chin,andBally1988)gascomponents can to theionizingstarsat~8kms. the sourceoffreshlydissociated andionizedgaswhichflows 1981), andmolecular(Table6F;also,ElmegreenLada 2 2 — 20kms,ingoodagreementwiththeradialvelocity of Evidence existsintheaperturesynthesismapofRogerand Radial velocitymeasurementsoftheionized(CCG;John- -36 TO-26km/s 765 198 9ApJS. . .70. .731L 1 2 4 km s“,whichdiffersfromthe COvelocityofcloudF,the21 van SomerenGreve(1976). Although the21cmabsorption we believethatIC1396Fis notassociatedwiththecluster. is anomalous,wefindnoevidencethationizingphotonsfrom between themolecularcloudsandionizingstar’sradiation feature attributedtoKh141 occurs atavelocityofabout—2 Kh 141,at—400pc,observed inHibySimonsonand density initsdirectionisexceedinglylow;forthesereasons, by IRAS—isfoundinthecasesofIC1396A,B,C,D,and E. Cloud Fmaybepartofthe edgeofthe15degdarkcloud (Matthews etal1980),andbrightinfraredemissiondetected —“bright rims”(Pottasch1956),enhancedradioemission located attheedgeofnebula.Evidenceinteraction offset fromtheionizingstarby~1?5andappearto be clouds arelocatedinfrontofthenebula.CloudsCandD are visible wavelengthsbycloudsIC1396A(seeLoren,Peters, photographs oftheIC1396region.Thenebulaisobscuredat the IC1396clusterreachitssurface,andforeground star and VandenBout1975),B,E,F,indicatingthatthese comparing theMatthewsetal(1980)radiomapwithoptical 6G; Fig.20)aredeterminedwithrespecttothestarclusterby no morethanafewmillionyears(Feinstein,Vazquez,and its spectraltype,weinferthatitisaslightlyevolvedstarof mass -60MandthusconcludethattheageofIC1396is rounded byanHnregionexcitedasinglemassivestarof vicinity ofNGC281andthatthedustyarcisallremains 1982). Benvenuto 1986;Maeder1981;alsoseeJanesandAdler observations oftheionizingstar(Humphreys1978)andfrom NGC 281islarge(seePaperII). of anolderexpandedshell. Although thekinematicdistanceofcloudBis~3.5kpc, infrared images,andasaveryfaintfeatureinthe1.4GHz between theHIandnmolecularclouds,from with CO-emittingregions(Johnson,White,andPedlar1981; spectral type06.5V(f)(Buscombe1977).Fromphotometric ratio ofnonmoleculartomoleculargasintheregionaround gas mass<2X10M(see§IVc;seeElmegreenandLada to itbyinteractionwithstarsofanearliergenerationinthe 281. Itispossiblethatthemotionofcloudwasimparted star densitydeficiencyinthedirectionofcloudisconsis- observations ofCondonandBroderick(1985,hereafterCB). extinction mapofLeisawitzandKlinglesmith(1988),inIRAS from thesouthwesternedgeofSI84.Thearcisseenin (1981) correspondstothemolecularcloudNGC281Binour from thestarsismadebyrocketacceleration. CO map.Thiscloudliesalonganarcofdustthatextends a minorcontributiontotherecessionofmolecularclouds Roger andPedlar1981).Fromthesmallvelocitydifferences 1978). ComparedwithotherHnregionsinoursurvey,the tent withitshavingadistancecomparabletothatofNGC the relativemassesofgascomponents,weinferthatonly around NGC281isspatiallyandkinematicallycoincident 166 0 0 -1 Relative totheotherclouds,radialvelocityofIC1396F Locations ofthemolecularcloudsthatwecatalog(Table The -44kmsHIclouddiscussedbyRogerandPedlar This nearbycluster,alsoknownasTrumpler37,issur- From ourCOobservations,weestimateatotalmolecular © American Astronomical Society • Provided by theNASA Astrophysics Data System vn IC1396 LEISAWITZ, BASH,ANDTHADDEUS 1- -1 -1 -1 by its“local”radialvelocityandcorrespondencetoa region S212.An06.5star(Georgelin 1975;Mayer1973)on (see Table7)ismorethananorderofmagnitudegreater than cause thevelocityofionizedgas(seePaperII)isessen- receding fromthecluster.Thismotioncannotbereadily negative thanthatofthecluster,molecularcloud is bright rimsandpatchyobscurationduetotheinteractionof being inthePerseusspiralarm(see,e.g.,Cohenetal1980)at velocities ofcloudsA,B,C,andDareconsistentwiththeir NGC 7380region(seeFig.12andTable6H),butonlyoneof Allowing forthefactthatwemeasureonlyline-of-sight density oftheionizedregion measuredbyMcCutcheonetal explained intermsofarocketaccelerationmechanism be- cluster (seeAppendixBandBFS). cloud EwithSI42implythatthisisassociatedthe region oflowstardensityonthePOSSprints.Theradial nonmolecular gasassociatedwithIC1396anditsrelationto km s",andthevelocityofIC1396Aisabout-7s. (1986). Theshortmain-sequence lifetimeofsuchastarand cloud FismuchclosertotheSunthanclustersuggested region S142.Theclustercontainsalargernumberofmassive D (seeFig.20). of the“ring”COemissionthatcomprisescloudsB,C,and component ofthecloudrecessionvelocities,weestimatethat unwarranted here. the clustermainsequence(Moffat, FitzGerald,andJackson that oftheionizedmaterialinregion. tially thesameasthatofcloudandmass S142 (seeFig.13ofIsrael1977),is-14kmsmore any case,noclosertoitthan-40pc.Ontheotherhand, angular separationsfromtheclusterindicatethattheyare,in a distancegreaterthanthatofNGC7380(3.60kpc;Moffat ods, theageofNGC7380hasbeenestimatedtobe-2-4 Humphreys 1978;Mermilliod1981Z>).Byanumberofmeth- stars haveevolvedawayfromtheZAMS(Harris1976; stars thanmostotherclustersofasimilarage.Somethese Myr, consistentwiththeageofIC1396,isimpliedbysize from theclusterat-10kms.Adynamicalageof-2 from cloudsIC1396B,C,D,andEiscenteredatabout-1 from thestarcluster.Theradialvelocityofclusteris cm backgroundisexceptionallycomplicatedinthisregion,so 1979) suppliestheionizingflux andaccountsforthesize 1971; seeBeckerandFenkartHagen1970),their to beassociatedwiththestarcluster.Theconclusionthat Myr (Harris1976;Moffat1971;Sandage1963). the moleculargas. all themolecularcloudsassociatedwithIC1396arereceding about +4kms(Wramdemark1982),whereasCOemission an attempttoassessthesignificanceofthisdifferenceis them (NGC7380E)canbeconsideredwithsomeconfidence This distantouterGalaxycluster issurroundedbytheHn We findseveralmolecularcloudsinourCOmapofthe NGC 7380isaveryyoungclustersurroundedbytheHn Since theradialvelocityofcloudE,whichisinfront of The readerisreferredtoPaperIIforadiscussionof The molecularcloudsassociatedwithIC1396arereceding viii) NGC7380 ix) NGC1624 Vol. 70 198 9ApJS. . .70. .731L -1 a. analogous toFigs.12c,12and 12/.In(b),(c),(d),andrespectively,thelowestcontourlevel, 1Kkms,correspondsto1.4,1.5,1.7,and1.3 No. 4,1989 Fig. 20.—SurveyresultsfortheregionaroundIC1396.DatafromTable 6Gareusedin(a),whichisanalogoustoFig.12g.Thecontourdiagrams 1.5 1.00.50.0-0.5-1.0-1.5 © American Astronomical Society • Provided by theNASA Astrophysics Data System -5 TO2km/s Ai (degrees) OPEN CLUSTERCOSURVEY -0.5 -1.5 -1.0 0.0 0.5 1.0 1.5 T5 TO0^5(LO-0.5-1.0-1.5 1.5 1.00.50.0-0.5-1.0-1.5 i \1r -11 TO-1km/s -3 TO2km/s 767 198 9ApJS. . .70. .731L -1 -1 -1 be locatedbehindthecluster.Thelocationofpointin which onlyNGC1624Bwascompletelymapped.CloudsB intensity inthiscloudpeaksatthepositionofHuregion region S211(seePaperII).ThereddeningofstarsinNGC with NGC1624andthestarsthationizenearbyHu not comoving,theionizedgas maybeflowingawayfromthe velocity isgiveninTable61. Even ifS212andNGC1624are mately 300pcfromtheSun(KieferandBaker1941) and (see BFS),becausethestarsaresoheavilyobscured by Myr. foreground material. tion ofcloudAwithrespecttoS211,eventhoughtheCO the ideathatcloudBisbehindcluster.Unfortunately,a Figure 13correspondingtoNGC1624isalsoconsistentwith Harris 1976)bothimplythatNGC1624isnotolderthan~5 Georgelin and(1970) is-39kmsandthecloud etal. 1987)intheLindbladringCOemissionfeature. tion ofS211.QoudsNGC1624CandDhaveradialvelocities similar argumentcannotbeappliedtodeterminetheorienta- 1624 isuniform(Moffat,FitzGerald,andJackson1979), 1988) presumablybecausetheyareassociated,respectively, and Aarebrightinfraredsources(LeisawitzHauser the CMDofMoffat,FitzGerald,andJackson(1979),(see at afewkms.TheH n regionvelocitymeasuredby Cloud Dispartofamuchlargermolecularcloud(seeDame therefore arenotassociatedwithNGC1624orS211. the POSSprints;thesearelocalmolecularclouds,approxi- S212 isundistortedinitsopticalappearance,socloudBmust then cloudB,situatedbehind thecluster,isrecedingfromit 768 — 0kmsandcoincidewithregionsofhighobscuration on Indeed, cloudDcontributessubstantiallytotheobscura- In ourCOmap(Fig.21)wefoundfourmolecularcloudsof If thegasionizedbyNGC1624iscomovingwithstars, © American Astronomical Society • Provided by theNASA Astrophysics Data System 1.5 1.00.50.0-0.5-1.0-1.5 0 TO12km/s Fig. 20—Continued LEISAWITZ, BASH,ANDTHADDEUS -1 -1 have beguntoevolveawayfrom theZAMSbutarenoolder members, severalearlyBgiant stars(Schmidt-Kaler1961), (Schmidt-Kaler 1961;Stock 1956). Themostmassivecluster than ~10Myr(Doom,deGrève, anddeLoore1985;Maeder judgment, basedonacomparisonoftheMonocerosCMDto 1981). Theabsenceofradiocontinuum emissionatthecluster by McCutcheonetal(1986;alsoseeBFS).Bothcloudswere receding fromtheclusterat>10kms. IRAS. TheshapeofcloudA(seeFig.22)mayhaveresulted Table 7)thanthehigh-resolutionobservationsimply.Asis M andsizesoftheorder20pc.Ourobservationsindicate stellar radialvelocityis+40±5kms(Graham1971), and cloud, andradialvelocityinformationcanbeusedtomeasure red POSSprint),theclusterislocatedbehindmolecular cloud isasourceofextendedinfraredemissiondetectedby distinguishable onthePOSSredplate,indicatethatstars cluster (seeBFS).First,brightrimsintheS287nebula,barely found inoursurveyofthisregionisassociatedwiththe of thisclusteris<5Myr. using thebluest-staragecalibrationofHarris(1976), by thisstar.UsingthedataofGraham(1971),wegrapheda The spectraltypeofthemostmassiveclustermemberis ham (1971)andbyMoffat,FitzGerald,Jackson(1979). 1624 ismuchgreaterthanthemassofionizedgasand estimated bytheseauthorstohavemassesofseveralthousand from itserosionoraccelerationbythecluster. are interactingwithdenseinterstellarmatter.Second,the cluster studiedphotometricallyandspectroscopicallybyGra- 1985; PaperIV). total massinstars(McCutcheonetal1986;seeLeisawitz typically thecaseinregionsaroundveryyoungopenclusters, that thecloudsmaybeslightlylargerandmoremassive(see ated withS211andS212(NGC1624),spatialresolution cloud surface.Unfortunately,nospectroscopicmeasurement the cloudvelocityisgiveninTable6J.Evidently, A is the relativemotionofcloudandcluster.Themean CMD inwhichthestarswereindividuallydereddened.Inour Georgelin, andRoux1973).Radiocontinuumobservationsof the massinneutralinterstellarmaterialassociatedwithNGC cluster (seeJacksonandSewall1982).Thecircularvelocityof determine withconfidencethatcloudBisrecedingfromthe of theradialvelocityNGC1624isavailable,sowecannot the standardclusterisochronesofMermilliod(1981û),orby are consistentwithamodelinwhichionizationisdominated 09.5 VorB0IV(Crampton1971;Georgelin1975;Georgelin, sured velocityofthecloud. the Hiiregion(FelliandHarten1981,referencestherein) the cluster(Table1)isapproximatelysameasmea- 0 ~T, havebeenobtainedbyJacksonandSewall(1982) This isthecentralclusterinagroupofmassivestars Compelling evidenceexiststhatthesinglemolecularcloud The faintnebulaS287surroundsasparselypopulatedopen Maps oftheCOemissionfrommolecularcloudsassoci- Since S287ispartiallyobscuredbycloudA(see,e.g.,the x) MonocerosCluster xi) Stock5 Vol. 70 198 9ApJS. . .70. .731L -1 _1 ionizing Ostarsarepresent. All oftheCOemissionoccurs inarangeofradialvelocities coordinates inthe1400MHzsurveyofCBconfirmsthat no are uniqueintheirspatialdistribution andintheirproperties. from -10to4-3kms. three-dimensional expanding molecularshellcenteredinpro- No. 4,1989 respectively, thelowestcontourlevel,1Kkms,correspondsto1.5 and Table 61areusedin(a),whichisanalogoustoFig.12g.Thecontour diagrams areanalogoustoFigs.12c,12d,lie,and12/.In(b) (c), 1.7 a. The molecularcloudsaroundStock5(Table6K;Fig.23) Clouds A,B,D,andEcanbe construedtobeelementsofa Fig. 21.—SurveyresultsfortheregionaroundNGC1624.Datafrom -0.2 -0.6 -0.4 0.6 0.2 0.0 0.4 © American Astronomical Society • Provided by theNASA Astrophysics Data System 0.6 0.40.20.0-0.2-0.4-0.6 i 1r » «i,i—ilJ -4 TO2km/s Ai (degrees) OPEN CLUSTERCOSURVEY _1 -1 jection onthesupernovaremnant3C58.Wepursuethisline ing thesupernovaremnant 3C 58.Analternativeinterpreta- prises cloudsA,B,D,andE; thenthisstarexploded,produc- most massivedenizensofthe Stock5regionhollowedoutand ing PerseusarmHnregionsIC1805and1848.Oneof the visual wavelengths,sothefactthattheydonotcoincidewith well beyondtheregionsurveyedaroundStock5(seeDame its truthbytheavailableevidence.Apossibledifficultyfor began tobreakaparttheedgeofGMC,producing the nearby massivestarsformednearthelowGalacticlatitude in cloudsHandIindicatethattheyshouldbeopaqueat because ofitsextraordinarilylowinfraredluminosity- km s(seeDameetal.1986).CloudIalsoispeculiar expanding molecularshellhypothesisisthatcloudDextends tion isthatStock5Dalocal darkcloudwithanedgethat accelerated ashellofmolecular materialthatpresentlycom- sive stars,theregionaroundStock5resembledneighbor- fragments thatwepresentlyobserveascloudsStock5A to I. surface ofthegiantmolecularcloud(GMC)whichStock seem equallyplausible.OneinterpretationisthatStock5 and evidence thatcloudsHandIareassociatedwithStock5is cates thattheyarenotlocalclouds.Unfortunately,theonly clouds haveexceptionallynarrowCOlinewidths,-0.70 dark cloud,perhapsmuchclosertotheSunthan1.6kpc. et al.1987)andisresponsibleforobscurationdetectableon of argumentinPaperIIbecauseitssignificanceifsubstan- 5D isapart.Themassivestarsformed~10Myrago and tiated byfutureobservations,notbecauseweareconvincedof Several millionyearsago,priortotheevolutionofmas- their morphology.Theradialvelocitiesofthecloudsdiffer by a heavilyobscuredregiononthePOSSprintsprobablyindi- to-molecular massratio(Leisawitz1987).TheCOintensities structure centeredinprojectionontheStock5cluster.These the POSSprints,factswhichsuggestthatStock5Disalocal -14 kmsfromthatofthecluster. Two hypotheses,eachconsistentwithourobservations, Molecular cloudsHandIconnecttoformasemicircular 0.6 0.40.20.0-0.2-0.4-0.6 -39 TO-32km/s 769 198 9ApJS. . .70. .731L -1 -1 4954 (RoslundI960).InPaperIIwearguethattheageof produce areddeningofabout0.9mag.Theleastreddened we estimatethatthesamelineofsightthroughcloudBcould produce £(R-F)=0.35+0.07mag(eq.[2]);analogously, The COintensityinthedirectionofclusterdue to lies behindtheclusterandotherisaforegroundcloud. mately centeredon3C58. coincidentally mimicstheshapeofanillusoryshellapproxi- emission fromcloudAis4.4±0.5Kkms,sufficient to Fig. 24). (see AppendixA),therearetwomajoremissioncomponents. Roslund 4is<10Myr. not bereddenedbyaslittle0.9magifcloudBwerein the cloud arereddenedbyasmuch-1.2mag(Racine1969). stars inRoslund4haveE(2?-F)>0.90mag,while stars cloud notassociatedwiththe cluster,isthecoincidenceofits foreground. associated withanyforegroundmolecularclouds,must con- Since dustembeddedindiffusegas,additionto dust Hence, theemissionisdividedintotwoclouds(Table6L; CO brightnesscontourswith regionsofobscurationonthe tent withthisidea,andsuggesting thatcloudAisalocaldark tribute tothereddening(seeeq.[1]),starsinclustercould that appeartobepartiallyembeddedinthereflecting dust topped, whileothersshowatleasttwovelocitycomponents diagram isanalogoustoFigs.12c,lid,and12/.Thelowestcontourlevel,1Kkms,corresponds1.3a. Though manyoftheindividualCOlineprofilesareflat- This clusterisresponsibleforthereflectionnebulosityIC Figure 13canbeusedtodeterminethatoneoftheseclouds Cloud A,however,couldlie in frontofthecluster.Consis- Fig. 22.—SurveyresultsfortheregionaroundMonoceroscluster.DatafromTable6Jareusedin(a),whichisanalogousto12g. Thecontour © American Astronomical Society • Provided by theNASA Astrophysics Data System xii) Roslund4 Ai (degrees) LEISAWITZ, BASH,ANDTHADDEUS 1 evidence thatcloudCisnot associatedwithBerkeley62,we member of,theCasOB7association(Forbes1981). was detectedbyBFS,whoreportedaCOradialvelocityof POSS prints.Weconclude,therefore,thatcloudAisa cloud werelocal.However, sincethereisnocompelling balance ofthereddeningcould beexplainedbycloudCifthe ing (E(B-F)0.86mag;Forbes1981)canbeattributed to more, onlyabouthalfoftherelativelystrongclusterredden- velocity ofcloudCissimilartothatB,theformer is alocalcloud,notassociatedwiththecluster.Since the heavily obscuredregiononthePOSSprints,suggestingthat it locations oftwothethreecloudsfoundinourCO map derived atthebeginningof § IVisapplicablehere,andthe dust associatedwithdiffuse interstellar gasifthevalueofe maximum visualextinctionofonly0.7±0.2mag).Further- could accountforitstransparency(usingeq.[2],weestimate a of Forbes(1981),andthepresenceaBlVstar(Hiltner dark cloudsinVulpécula(d~400pc;DameandThaddeus foreground molecularcloud,probablypartofthegreatrift cloud mayalsobelocal.AlthoughCisnotresponsible (Table 6M;Fig.25).CloudB,theexception,coincideswith a approximately spatiallycoincidentwith,andthusmaybea 1956) indicatesthattheageofthisclusteris<10Myr.It associated withthesmallHnregion.EmissionfromcloudB for strongobscuration,itsrelativelylowpeakCOintensity 11.6 kms". 1985), andthatcloudBreflectstheclusterstarlightis No main-sequenceturnoffisfoundintheUBVphotometry We arenotabletodeterminewithanyconfidencethe -0.4 -0.6 -0.2 0.0 0.4 0.6 0.2 0.6 0.40.20.0-0.2-0.4-0.6 J 1iL T 1r 22 TO34km/s xiii) Berkeley62 Vol. 70 198 9ApJS. . .70. .731L -1 No. 4,1989 analogous toFigs.12c,12d, and12/.In(b),(c),(d),respectively,thelowestcontourlevel, 1Kkms,correspondsto1.9,1.7,and2.1a. Fig. 23.—SurveyresultsfortheregionaroundStock5.DatafromTable 6Kareusedin(a),whichisanalogoustoFig.12g.Thecontourdiagrams © American Astronomical Society • Provided by theNASA Astrophysics Data System 1.0 0.50.0-0.5-1.0 Ai (degrees) OPEN CLUSTERCOSURVEY __l IL_ 1.0 0.50.0-0.5-1.0 1.0 0.50.0-0.5-1.0 -10 TO-6km/s -1 TO3km/s 771 198 9ApJS. . .70. .731L -1 kpc; Forbes1981).Butitis possiblethatthevelocityof kpc, muchgreaterthanthe distancetothecluster(-2.05 cloud includesalargepeculiar componentpreciselybecause classify thecloudas“possibly associated,”andthesameis true ofcloudA.Thekinematic distanceofcloudAis>4 Table 6Lareusedin(a),whichisanalogoustoFig.12g.Thecontour the cloudisassociatedwith, andacceleratedby,aninterac- respectively, thelowestcontourlevel,1Kkms,correspondsto1.8 and diagrams areanalogoustoFigs.12c,\2d,and12/.In(A) (c), 1.2 a. 772 Fig. 24.—SurveyresultsfortheregionaroundRoslund4.Datafrom 0.8 0.40.0-0.4-0.8 © American Astronomical Society • Provided by theNASA Astrophysics Data System » 1«IL 6 TO19km/s i 1r Ai (degrees) LEISAWITZ, BASH,ANDTHADDEUS loged molecularcloudsisassociatedwithNGC433,but no metric andspectroscopicobservations oftheclusteraremade. cannot dismissthepossibilitythatsomesubsetofcata- (kinematic) distancetocloudsCandDis~1±0.2kpc and not beenstudiedphotometrically.Aweakcontinuumsource statement moredefinitivethanthiscanbemadeuntilphoto- clouds areprimarilyduetoGalacticrotation,then the closer totheSunthan-1kpc).Ifradialvelocitiesof the POSS prints,thecloudsarenotlocal(i.e.,theymuch (Table 6N;Fig.26)producesapparentobscurationon the (Reinmuth 1926;seeLyngâ1987),weestimateanupperlimit consistent withthepresenceofamain-sequencestarspec- the distancetocloudsAandBisinrange1.8-2.8kpc. We Myr, butthatitsageisnotgreaterthanthisifaBOmain- apparent magnitudeofthebrighteststarinclusteris9.0 straint, wedrawtootentativeconclusions.First,sincethe “OB” clusterofsmallangulardiameter,butthishas Ruprecht, andVanysek(1970),classifiedNGC433asan sequence starisinfactaclustermember. tral typelaterthanoraboutBO.Onthebasisofthiscon- at thepositionofclusterin1400MHzsurveyCBis Second, weestimatethattheclustercouldbeasold~10 S237. Fromanopticalemission-line spectrum,Glushkov, information unreliable. tion withthecluster;wegenerallyconsiderkinematicdistance - 3.2kpc(seeAlter1944)forthedistancetocluster. This isapoorclusterthat ionizes thesmallHnregion Since noneofthemolecularcloudsfoundinthisregion Stock (1957),inaprivatecommunicationtoAlter, 0.8 0.40.0-0.4-0.8 j iL T 1r 2 TO7km/s xv) NGC1931 xiv) NGC433 Vol. 70 198 9ApJS. . .70. .731L -1 1 -2 Table 6Mareusedin{a),whichisanalogoustoFig.12g.Thecontour diagrams areanalogoustoFigs.12c,12*/,and12/.In(6) (c), respectively, thelowestcontourlevel,1Kkms,correspondsto1.4 and No. 4,1989 1.7 a. by astarofspectraltypeB0.5. TheGlushkovetalconclusion km s“(GeorgelinandGeorgelin 1970;Georgelin, is consistentwiththe1400 MHz continuumfluxdensityof derive anexcitationparameter ~15pccm(seePanagia Denisyuk, andKaryagina(1975)deducedthatS237isexcited 1973). Theradialvelocityof theHalineinS237is~2.9 the Hiiregion,0.6Jy(seeCB), anditssize,fromwhichwe Fig. 25.—SurveyresultsfortheregionaroundBk62.Datafrom © American Astronomical Society • Provided by theNASA Astrophysics Data System -15 TO-10km/s OPEN CLUSTERCOSURVEY -1 which appearstobealocaldarkcloud,werefoundinthis NGC 1931canbefoundinPaperII. bright-rimmed dustfeaturesintheHnregionsuggestthat ionized byan09.5VstarandaB0atdistanceof were detectedintheBFSCOsurveyofHnregionsandas region (Table60;Fig.27).Thenearlycoincidentpositions line ofsighttothestars(seeFig.13).Usingequation(2), we part totheedgeofcloudCifintervenesalong our moderately highB-VreddeningofNGC1931,~0.70 mag molecular cloudswithwhichthesenebulaeareassociated, the cloud andtheHnregionarephysicallyrelated.Ananalogous (Georgelin andGeorgelin1970;Miller1968). and Roux1973).Afewcommentsonthedistanceageof ies ofHagen1970;Mermilliod 1976,andreferencestherein; 0.06 maginthisdirection. (Moffat, FitzGerald,andJackson1979),canbeattributed in from, theHiiregionsandstarsthatexcitethem. The clouds areinfrontof,albeitapparentlytangentiallyoffset faint, unresolvedfeaturesinthelow-resolutionGalacticplane and radialvelocitiesofS234cloudBthepresence Roux 1973).TheHaradialvelocityofS234is-18kms estimate thatthecloudshouldproduceareddeningof0.21 ± survey ofDameetal(1987). and hencewiththeclusterNGC1931.CloudsBCboth set ofevidenceimpliesthatcloudCisassociatedwithS237 and Moffat1972)suggests a clusterage-10Myr(Harris Schwartz (1971)detectedno 2.7GHzcontinuumemission, 1976; JanesandAdler1982; Lindoff1968;Lyngà1987). ~ 2.3kpc(Georgelin1975;Georgelin,and Three spatiallynonoverlappingmolecularclouds,noneof The surveyedregionalsoincludesS234,asmallHn The bluestmain-sequencestar (fromthephotometricstud- Since portionsofS234andS237areobscuredbythe -49 TO-39km/s xvi) NGC654 773 198 9ApJS. . .70. .731L 774 -1 are analogoustoFigs.12c,12d,and12/.In(A),(c),(d), respectively, thelowestcontourlevel,1Kkms,correspondsto1.7,2.8,and2.2a. Fig. 26.—SurveyresultsfortheregionaroundNGC433.Datafrom Table6Nareusedin(a),whichisanalogoustoFig.12g.Thecontourdiagrams © American Astronomical Society • Provided by theNASA Astrophysics Data System 0.6 0.40.20.0-0.2-0.4-0.6 0.6 0.40.20.0-0.2-0.4-0.6 -23 TO-21km/s-12TO-9 Ai (degrees) LEISAWITZ, BASH,ANDTHADDEUS -0.4 -0.2 -0.6 0.4 0.6 0.2 0.0 0.6 0.40.20.0-0.2-0.4-0.6 -26 TO-21km/s Vol. 70 198 9ApJS. . .70. .731L -1 are analogoustoFigs.12c,Yld, and12f.In(h),(c),(d),respectively,thelowestcontourlevel, 1Kkms,correspondsto1.9,1.7,and1.7a. No. 4,1989 Fig. 27.—SurveyresultsfortheregionaroundNGC1931.Datafrom Table60areusedin(a),whichisanalogoustoFig.12g.Thecontourdiagrams © American Astronomical Society • Provided by theNASA Astrophysics Data System -17 TO-11km/s Ai (degrees) OPEN CLUSTERCOSURVEY -0.2 -0.8 -0.6 -0.4 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.8 0.4 0.6 0.2 0.4 0.0 0.6 0.8 —i—i—i—i i» 0.8 0.40.0-0.4-0.8 0.8 0.40.0-0.4-0.8 T 1 (d) -6 TO0km/s r 775 198 9ApJS. . .70. .731L -1 are analogoustoFigs.12c,1212c, and12/.In(Z>),(c),(d),(/),(g),(/*),respectively,the lowestcontourlevel,1Kkms,correspondsto 1.1, 1.7,1.3,2.8,1.5,and1.4 10Myr(Hassan near thecluster(seePGK)despitemodestextinction(see, (Conti andvandeHeuvel1970;JanesAdler1982; and spectroscopic(ContivandenHeuvel1970)observa- trary. Table 6Qareusedin(û),which is analogoustoFig.12g.Thecontour e.g., Mermilliod19816),sonosubstantialLymancontinuum Lindoff 1968;Mermilliod19816).NoHaemissionisfound tions suggestanagefortheclusterbetween10and18Myr diagrams areanalogoustoFigs.12c, 12

0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6

4 TO 7 km/s -21 TO -17 km/s T 0.6 (d) 0.4

0.2

0.0

-0.2

-0.4

-0.6 J I I L 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6

Fig. 29—Continued

© American Astronomical Society • Provided by the NASA Astrophysics Data System 198 9ApJS. . .70. .731L -1 780 which mightbeexpectedtolessentheconfusionproblem,is van denHeuvel1970;HagenLyngâ1987;Mermilliod with theclusteristhatnearlyallCOemissionoccursata not particularlyhelpfulinthisregardsincetheGalacticplane dence thatthecloudsactuallyareassociatedwithNGC7160. (Table 6R;Fig.30;comparewiththeregionaroundNGC present. ZAMS hasoccurred.TheradioobservationsofSchwartz curves towardpositivelatitudesandbroadensinthesecond Even therelativelyhighGalacticlatitudeofthisregion(-6°), 19816), thentheirsizesaretypically-5pc. the cluster,-750pc(BeckerandFenkart1971;Conti 1444, showninFig.31).Ifthecloudsareatdistanceof vicinity ofthecluster(seeFig.28),butseveralfactorsindicate been estimatedbyanumberofauthorstolieintherange radial velocitywithin~12kmsofthatNGC7160. only evidencethatthecatalogedcloudsmaybeassociated quadrant (see,e.g.,Henderson,Jackson,andKerr1982).The (1971) implythatnostarofspectraltypeB0orearlieris reddening (^(5—K)-0.59mag;Hagen1970;Polishchuk sequence turnoffcolor(seeJanesandAdler1982),probably Steppe 1974);apparently,someevolutionawayfromthe the resultofscatterinCMD,agethisclusterhas by Wallenquist(1975)iswhatonemightexpectfrom a low POSSplatestardensityinthedirectionsofCOintensity line intensitymeasuredinthedirectionofclustercorre- ing canbeexplained,however,ifcloudDintervenes:theCO that thisisaforegroundcloudandnotoneassociatedwith within —20pcofaclusterasluminousthisone. is notfarfromtheSim.Third,patchyobscurationfound maxima incloudD(seeAppendixB)suggeststhatthe contribution ofonly0.45magtotheclusterreddening;based equation (1)andthedatainTables12,adiffuseISM the cluster.First,itmaybedifficulttoexplaincluster (1973), thereddeningexpectedfromdustinforegrounddif- on the21cmlineobservationsofWeaverandWilliams 1970) ifthecloudisbehindcluster.Weestimate,using Tosi 1979),butthecolorofbluestmain-sequence stars fuse gasmaybeevenlower(<0.30mag).Theclusterredden- of thiscluster(seePanagiaandTosi1980;Sandage1963; foreground molecularcloud.Finally,cloudDisnotanIRAS giants intheH-Rdiagram (Humphreys1978;Mermilliod (Hagen 1970;Hoagetal.1961; JanesandAdler1982;Moffat source of100/imemission,aswouldbeexpectedforacloud sponds toareddening(eq.[2])of0.16+0.03mag.Second,the 1981tf), theabsenceofradio continuumemission(Schwartz 1972; vandenBerghandde Roux1978),thelocationof 1971), andotherindicatorsall pointtoanage-10-20Myr. -10-20 Myr(seeHagen1970;Lindofif1968;Lyngà1987; This regioncontainsnumeroussmallmolecularclouds Unfortunately, itisnotpossibletodeterminewithconfi- Despite inconsistentestimatesoftheNGC659main- Only onemolecularcloud,NGC663D,isintheimmediate Widely varyingestimateshavebeenpublishedfortheage © American Astronomical Society • Provided by theNASA Astrophysics Data System xix) NGC659 xx) NGC663 LEISAWITZ, BASH,ANDTHADDEUS _1 -1 1 lowest contourlevel,1Kkms, correspondsto1.2a. Table 6Rareusedin(a),which is analogoustoFig.12g.Thecontour diagrams areanalogoustoFigs.12c, I2d,12c,and12/.Inallcases,the be explicableintermsofidentifiableinterstellarclouds.We Applequist 1965;Mermilliod19816;Moffat1972;Polishchuk intermediate betweenthatofthecluster(about—27kms; ing andthediffusegasreddeningcontribution,anecessary, less thanthe0.3magdifferencebetweenobservedredden- reveal anincreaseintheextinctiontonorthwestof dust associatedwithforegrounddiffusegasandthenattempt with reddeningfromforegrounddiffusematerialandcloudA. line parameterstabulatedbyGHWis-0.12mag,nearly mag. Thus,thereddeningproducedbycloudAissomewhat cloud Ameasuredinthedirectionofcluster,weestimate foreground cloud(see§IV6[xvi]).FromtheCOintensityof cluster (seeAppendixB),aneffectthatcouldbeproducedby Moffat (1972)andthestarcountsofWallenquist(1975) estimate (eq.[1])thatareddeningof-0.45magiscausedby The massofatomicgaswasestimatedbyGHWtobe—1900 Hagen 1970;Humphreys1978;Sanford1949;Wramdemark Indeed, GHWdetectedHiat-29kms“,avelocity e.g., dustmixedwithdissociatedmoleculargasfromcloudA. contributed bydustinaforegroundatomichydrogencloud, (eq. [2])thatthecloudcanreddenstarlightby0.10+0.07 to accountforthebalance,-0.3mag.Thephotometryof 1970; Starikova1969;vandenBerghanddeRoux1978),may enough toaccountfortheclusterreddeningwhencombined (Bohlin, Savage,andDrake1978)onthebasisof21cm the edgeofmolecularcloudNGC663A(Fig.28)ifitisa the cluster(Fig.13).Someadditionalreddeningcouldbe though notsufficient,conditionforthecloudtolieinfrontof 1982) andcloudA(seeTable6P).Thereddeningexpected Fig. 30.—Surveyresultsfortheregion aroundNGC7160.Datafrom The clusterreddening,-0.78mag(Hagen1970;Hoagand Ai (degrees) Vol. 70 198 9ApJS. . .70. .731L No. 4,1989 1.5 1.00.50.0-0.5-1.0-1.5 © American Astronomical Society • Provided by theNASA Astrophysics Data System -19 TO-6km/s -8 TO5km/s OPEN CLUSTERCOSURVEY Fig. 30—Continued -29 TO-16km/s -14 TO-1km/s 781 198 9ApJS. . .70. .731 3 -1 J 0.0 "m 0.5 <-0.5 782 1.9, 1.6,1.4,2.2,2.1,and2.Fà. are analogoustoFigs.12c,12d12e,and12f.In(b),(c),(d), (/),(g),and(A),respectively,thelowestcontourlevel,1Kkms,correspondsto 03 03 y -1.0 -0.5 -1.5 Fig. 31.—SurveyresultsfortheregionaroundNGC1444.Datafrom Table6Sareusedin(a),whichisanalogoustoFig.12g.Thecontourdiagrams -1.0 -1.5 0.0 0.5 1.0 1.5 1.0 1.5 1.5 1.00.50.0-0.5-1.0-1.5 1.5 1.00.50.0-0.5-1.0-1.5 © American Astronomical Society • Provided by theNASA Astrophysics Data System Al (degrees) LEISAWITZ, BASH,ANDTHADDEUS -1.0 -1.5 -0.5 0.0 0.5 1.0 1.5 1.5 1.00.50.0-0.5-1.0-1.5 -28 TO-24km/s -10 TO-3km/s Vol. 70 198 9ApJS. . .70. .731L No. 4,1989 1.5 1.00.50.0-0.5-1.0-1.5 1.5 1.00.50.0-0.5-1.0-1.5 © American Astronomical Society • Provided by theNASA Astrophysics Data System -2 TO2km/s -8 TO2km/s OPEN CLUSTERCOSURVEY Fig. 31—Continued -6 TO-3km/s 4 TO7km/s 783 198 9ApJS. . .70. .731L -1 -1 -1 based onthephotometricmeasurementsofHoagetal(1961; overestimates theageofthisclusterbecauseis IRAS throughoutmuchofthisregion.Amaptheinfrared M ifthe21cmemissionarisesinacloudatdistanceof B giantstars,whichsuggeststhat15Myrisabetterage see Hagen1970),buthisunconventionalmethodprobably material betweenthem)areexternallyheatedbyluminous ( —41,—26kms)(Fig.28b),suggestingthatthemolecular within 1?5oftheclusterisfilledwithfaint,patchyHa plane COsurveyofDameetal(1987).Muchtheregion estimate. and Applequist(1965)classifiedasclustermemberstwoearly sparsely populated(Ruprecht1966;Trumpier1930).Hoag km s;Humphreys1978)isthesameasthatofheated km srecessionofthecloudfromcluster.Notethat clouds atthisradialvelocity(cloudsAandBabridgeof emission matchesthedistributionofCOinvelocityrange 784 ionized gasisalsoinhomogeneous.A1.4GHzmapof the (see Table7),wasdetectedinthelow-resolutionGalactic (see Fig.31).OnlycloudH,themostmassivepresent molecular clouds.Ifthesecloudsareremnantsofthematerial radial velocityofthesupergiantstarsinCasOB8(—36+9 measured radialvelocities(Tables1and6P)implyan8 stars intheCasOB8association,ofwhichclustersNGC the cluster. bility thattheseclustersexemplifyaphasethroughwhich NGC 7160region(see§IV7>[xviii]),whichsuggeststhepossi- numerous smallmolecularcloudsmayaccountforsomeof emission (seePGK)knownasS205.Extinctionfromthe one mightinferfromthekinematicstructureofthisregion from whichNGC663anditsneighboringclustersformed, same regionofspace;seeSchmidt-Kaler1961). 581, NGC654,659,and663aremembers(i.e., region fromtheCBsurveycontainsmanydiscrete,weakradio § IVZ>[xvi]). quired theirpeculiarvelocityrelativetotheclusters(see that therelativelydiffusecollectionofhigh-massstars(the the clustersandassociationstarsoccupyapproximately sources, mostofwhichareresolved(i.e.,theygreater than the patchiness,butunattenuatedradioemissionfrom supergiants) formedinthemolecularcloudsaftertheyac- offer acluetowhetherornotthemolecularcloudsfound in cluster environmentspass. 12'). ClumpinessoftheISMisalsoastrikingfeature the (/, b)=(147?8,-0?6),whichmaybeexcitedbythenearby our COsurveyareassociatedwithNGC1444.Thesource at elongated 1.4GHzsourcecentered at(148?8,-0?9)doesnot clouds GandH.Optical nebulosity correspondingtoan B1 IIIstarHD24094,isencircledbyCOemissionfrom cloud. The1.4and2.7GHz sourceconsideredbySchwartz (possibly the09IIIstarHD 24431)mustbeinfrontofthe appear tobeobscuredby cloud E,sotheionizingstar 0 Lindoff (1968)derivedanageof-160Myrforthiscluster Extended emissionat60and100fimwasdetectedbythe Morphologically, theCOemissioninthisregionisunusual Since cloudAprobablyliesinfrontofthecluster, Several radiosourcesareparticularlyinterestingandmay © American Astronomical Society • Provided by theNASA Astrophysics Data System xxi) NGC1444 LEISAWITZ, BASH,ANDTHADDEUS -1 -1 -1 -1 _1 -1 -1 however, whetheranypartofthecloudfromwhichNGC in therange-10-0kms(seeTable6S).Theradial in radialvelocity.MajorcomponentsoftheCOemissionare members oftheOBassociation;itcannotbedetermined, velocity ofthestarclusterisabout+1kms(Wramdemark evidence thatatleastsomeofthemolecularcloudsarenear Humphreys 1978).Thesequalitativeobservationsconstitute conform totheshapeofedgecloudJ.Theionizing cluster members.Thissourceandanothernearbyradio (1971) tobeassociatedwithNGC1444actuallylies~10' region ispresentedinPaperII. clouds areassociatedwithCamOBI(seeBFS). occurs atabout—26kms.Itisnotclearwhetherthese OBI associationandso,apparently,isNGC1444(see stars (e.g.,HD24431and24094)aremembersoftheCam the southandwestofclustermaynotbeproducedby (Humphreys 1978)areintherange—13to+4kms. 1444, isthatthecloudsandstarsareapproximatelycomoving associated withtheCamOBIstars,andperhapsNGC 1444 formedstillexists. 1982), andthevelocitiesofmostassociationmembers have tobeenatleast - 3kmstoaccountforthe by Neckel(1967)andGiménezGarcia-Pelayo(1980) was found.Thevariablereddeningofclusterstarsdiscussed believe isaforegroundcloudnotassociatedwiththecluster, kinematic distance-0.8+0.2kpc,whereasthe to and clusterdriftedapart;the relativepropermotionwould 957 formedonly16Myrago? Onepossibilityisthatthecloud low-resolution Galacticplane COsurveyofDameetal(1987). kpc. CloudAhadbeendetected,butnotresolved,in the radial velocityofthecloud,—10.8kms,corresponds to a radial velocityis—33kms(Hagen1970;Wramdemark direction oftheclustercanbeusedtoshowthatsurface of foreground starssuggeststhatthecloudismuchcloserthan 2 obscuration onthePOSSprints;apparentpaucity of fact thattheIRASdetectednoexcessinfraredemissionin surveyed areaandcorrespondstoalargeregionofheavy and Garcia-Pelayo1980;Hagen1970;Lyngà1987) its the clusteris—2200pc(BeckerandFenkart1971;Giménez the cloudisatleast20pcfromcluster.Furthermore, the 957 canbeexplainedifcloudAisinfrontofthecluster.The models discussedbyDoom,DeGrève,anddeLoore(1985). ments ofthestarsconsistentlyleadtoanageestimateforthis 1982). Finally,thecloudextendsbeyondedgeof our the locationofpointinFigure13correspondingtoNGC (Schwartz 1971).Themostmassiveclustermember,aB1.5lb cluster of—16Myr(seeLyngâ1987).NoHaemissionis seen (PGK),noris2.7GHzcontinuumemissiondetected troscopic (Harris1976;HoagandApplequist1965)measure- 1961; Mermilliod1976;alsosee19816)andspec- star, isa13Myrold,22A^,staraccordingtothestellar Another factorthatindicatesthemolecularcloudsare An additionalsmallamountofemission(cloudsAandB) Evidence thatmassivestarshaveceasedtoforminthis A singlemolecularcloud(Table6T;Fig.32),whichwe So whathappenedtothemolecular cloudfromwhichNGC Photometric (GiménezandGarcia-Pelayo1980;Hoagetal xxii) NGC957 Vol. 70 198 9ApJS. . .70. .731L -1 contour level,1Kkms,corresponds to1.3o. diagram (A)isanalogoustoFigs. 12c,12d,and12/.Thelowest Table 6Tareusedin(a),which is analogoustoFig.12g.Thecontour No. 4,1989 Fig. 32.—Surveyresultsfortheregion aroundNGC957.Datafrom © American Astronomical Society • Provided by theNASA Astrophysics Data System 1.0 0.50.0-0.5-1.0 -17 TO-6km/s Ai (degrees) OPEN CLUSTERCOSURVEY -1 -1 o -1 _1 1 with, butdoesnotsignificantly substantiate,ahypothesisthat cloud Bliesinfrontofthecluster. cloud andclusterarephysically associated.Theclusterextinc- ity thattheyarelocaldarkcloudsisruledout.Thecluster in thelow-resolutionGalacticplanesurveyofDame etal indicated byamapoftheIRAS60/xm/100/imintensity velocity betweenNGC957anditsparentcloudwasasgreat beyond oursurveyedregion,thenonemightargue,basedon tion (BeckerandFenkart1971; Neckel1967)isconsistent Galactic anticentermakesthis likelyregardlessofwhetherthe radial velocity,-2kms(Hagen1970;Johnson and if anymolecularmaterialisassociatedwiththiscluster.Faint, photometric (BeckerandStock1958;Hagen197Ö;Hoagetal velocity range—36to—41kmsarefoundinseveralof same asthatofcloudB,butvelocitycrowdingnear the (1987) and,sinceonlyamodestdiminutionofthePOSSprint Myr. Harris 1976;JanesandAdler1982;Lindoff1968;Mermilliod cluster datingmethods(Doom,deGrève,andLoore1985; ratio, appearstocoincidewithanotherweak,elongatedCO extended atthe3alevelofCOintensity;however,theydo clouds correspondingtotheselinesbecausetheyarenot our spectra(seeAppendixA).Wedonotcatalogmolecular complexes. Thus,itisimprobablethattheinitialseparation cloud fromwhichtheclusterformedisstillintact,but star densityoccursinthedirectionsofclouds,possibil- unresolved COemissionisseeninthevicinityofNGC 2129 giant (HD236979;seeHumphreys1978forstellarparame- feature neartheinfraredpointsourceYZPer,anMsuper- source inthisregion,AFGL341.Amodestwarmingofdust, found inthedirectionofstrongestcompactinfrared appear toberealemissionfeatures.OneweakCOfeaturewas (cloud fragmented;COdissociated).Wefindevidencethat observations, iftheinitialvelocitywasarandomsampleof absence ofthecloudwithinIcluster.Ifmolecular Svolopoulos 1961;Wramdemark1982),isapproximately the 1981a) consistentlyleadtoageestimatesintherange~15-20 that itcontainsseveralearlyBsupergiantstars.Various 1961; Mermilliod1981Z>)studiesofthisclusterhaveshown therein; HoagandApplequist1965;Humphreys1978) this mayhaveoccurred.WeakCOlines(T/<0.8K)inthe that producedNGC957isthecloudwasdestroyed as 3Ions,theminimummeanvelocityimpliedbyour are greaterthan5kms(FWHM)onlyinthelargestcloud thought tomeasuretheinternalturbulentmotionsofclouds, the cloudwasaccelerated.ThewidthsofCOlines,whichare the impliedrelativemotionbetweencloudandcluster,that are atbestweaklyconstrained,soweunabletodetermine ters), at~2kpc.Theseobservationssuggestthattheweak the internalmotionofcloud. molecular cloudsatthedistanceofNGC957(see§§IV¿>[xviii] from whichtheclusterformed. and rV7>[xxi]).Thesecloudsmayberemnantsofthecloud CO linesat—38±2kms“ariseinsmall(<5pcdiameter) A secondpossibleexplanationfortheabsenceofcloud The distancesofthreenearbyclouds(Table6U;Fig.33) Thorough spectroscopic(Harris1976,andreferences xxiii) NGC2129 785 198 9ApJS. . .70. .731L -1 are analogoustoFigs.12c,lid,and12/.In(h),(c),(d), respectively, thelowestcontourlevel,1Kkms,correspondsto1.7,2.1,and2.1a. 786 Fig. 33.—SurveyresultsfortheregionaroundNGC2129.Datafrom Table6Uareusedin(a),whichisanalogoustoFig.12g.Thecontourdiagrams © American Astronomical Society • Provided by theNASA Astrophysics Data System LEISAWITZ, BASH,ANDTHADDEUS Vol. 70 198 9ApJS. . .70. .731L -1 -1 -1 -1 local. CloudsDandEwere detected (thoughnotresolved)in cloud velocities(Table6V)we tentativelyconcludethatclouds if thecloudisinfrontofcluster. (1987). Basedonitsvelocity, cloudEisconsideredtobepart D andEarelocalclouds thatcloudAprobablyisnot distinct inradialvelocity.Inthedirectionoftheseclouds is cluster (Table1),cloudBisrecedingfromitat~16km s half oftheobservedreddening(E(B-V)-0.96mag;Jack- be explainedifcloudBisinfrontofBk11.Inthiscase,about be accountedforbyforegrounddiffuseinterstellarmattercan A andB. peculiar (noncircularGalactic)motionsofthesecloudsdonot the low-resolutionGalactic plane COsurveyofDameetal. that atleastoneofthecloudsislocal.Onbasis the an areaofobscurationonthePOSSblueprint,whichsuggests direction ofthecluster.Basedoncircularvelocity the high Galacticlatitudessuggestthattheirdistancesarecloser possibility thatatleastsomeofthecatalogedcloudsare the molecularcloud,whichproducesaweakCOlinein the son, FitzGerald,andMoffat1980)isattributabletodust in exceed 10kmswederiveakinematicdistanceintherange radial velocityofcloudsAandBtheassumptionthat (Jackson, FitzGerald,andMoffat1980).Fromthecommon and correspondinglysmallerkinematicdistancesthanclouds the clusterhavelessnegativeradialvelocities(seeTable6V) to 2.5than10kpc.Theothermolecularcloudsfoundnear associated withthecluster.ThedistancetoBk11is2.2kpc existing datathatmaybeusefulinthisrespect. of themareassociatedwiththecluster.Belowwediscuss Further observationsofthestarsinthisregionareneededto which thecharacteristicsofmostmassiveclustermember No. 4,1989 constrain thedistancesofcloudsandtodetermineifany other regionsinoursample,confusionisaproblemhere. exceptionally complicated(seeFig.34);unlikemostofthe could begaugedmorereliablyisavailable. cluster withapossibleredgiantmemberandbluestmain- km softhecluster(radialvelocityequalsapproximately ald, andMoffat(1980)concludedthatthisisa30Myrold sequence starofphotometrictypeb4.Nospectroscopywith associated atomicgasispresentedinPaperII. emission wasfoundwithin1?06(52pc)andatleast30 (Sim 1968;Wallenquist1975)and,asFigure54shows,noCO mated tobe~25Myr(Hagen1970;JanesandAdler1982; (1971) of2.7GHzemissionconfirmstheabsencestars earhest spectraltypeinthiscluster,thecluster’sageisesti- Lyngâ 1987;Moffat1972).ThenondetectionbySchwartz spectral typeearlierthanBO. — 2.5-10kpc.Thelargeangularsizesofthecloudsandtheir — 28kms;Wramdemark1982).Inconclusiveevidencefor Clouds A,D,andEliealongthesamelineofsightbutare From Figure13,itappearsthatthereddeningcannot Kinematic informationcannotbeusedtoruleoutthe The distributionofmolecularmaterialaroundtheclusteris Based ontheirphotometricobservations,Jackson,FitzGer- No clumpyobscuringmatterliesinfrontofthecluster From UBVphotometryandthelifetimesofstars © American Astronomical Society • Provided by theNASA Astrophysics Data System xxv) Berkeley11 xxiv) NGC457 OPEN CLUSTERCOSURVEY -1 -1 -1 diagrams areanalogoustoFigs.12c, lid,12c,and12f.In(h),(c),(d), Table 6Vareusedin(u),which is analogoustoFig.12g.Thecontour and (c),respectively,thelowestcontour level,1Kkms,corresponds to 1.4,2.5,1.8,and2.2a. We estimatefromthenondetectionofS213inCB1400 it isnotknownwhetherS213ionizedbyaclustermember projected boundaryofBk11(seeJackson,FitzGerald,and observations oftheionizingstarscouldbeusedtoestimate centered approximatelyonS214.IfcloudBispartoftheshell or whetherthedistanceofS214issameasthatBk11. cloud Dcanbeassociatedwiththe“—12kmsCOemis- IRAS pointsourceswithspectralenergydistributionsthat found (e.g.,withadeepHaimage)thenspectrophotometric for theinteractionofS214withmolecularcloudscouldbe and thedynamicaltimescaleforexpansionmustbeonly POSS platethattheionizingfluxcannotcomefromamain- MHz surveyandthebrightnessofnebulaonred region, S214,islocatedinthesurveyedregion.Unfortunately, Moffat 1980,theirFig.1),andanotherfaintSharplessHn of theLindbladringemissionfeatureat~300pc.Likewise, rise towardlongerinfraredwavelengthsarefoundinthe the distancetoshell. then theexpansionvelocitymaybeashigh-20kms sequence starofspectraltypeearlierthanB2. the starsthatexcitethesenebulaehavenotbeenidentified,so sion feature”at-800pc. direction ofthecloud.Theinfraredsourcesareatleastan Extended radiocontinuumemission(seeCB)andseveral to befragmentsofanexpandingmolecularshell(seeFig.34) — 0.2dMyr,wheredisthedistanceinkpc.Ifdirectevidence Fig. 34.—Surveyresultsforthe regionaroundBk11.Datafrom An extremelyfaint,smallHnregion,S213,lieswithinthe Clouds FandGmorphologicallykinematicallyappear Cloud Amaybeassociatedwitharegionofstarformation. 787 788 LEISAWITZ, BASH, AND THADDEUS Vol. 70

-36 TO -26 km/s -23 TO -21 km/s T 1 1 1 1 1 1 r i 1 1 1 1 1 1 r 0.8 0.8 (0 0.6 0.6

0.4 0.4

0.2 0.2

0.0 0.0

■0.2 -0.2

-0.4 -0.4

-0.6 -0.6

-0.8 -0.8 i i i i i—i—i—i—i— J I I I I I I L 0.8 0.4 0.0 -0.4 -0.8 0.8 0.4 0.0 -0.4 -0.8

-10 TO -5 km/s

© American Astronomical Society • Provided by the NASA Astrophysics Data System 198 9ApJS. . .70. .731L -1 3 2 4 believe thatitisassociated. we confirmthefindingofFang(1970)thatnostarspectral cloud Awiththecluster,but findnocompellingreasonto possibility. Thus,weareunabletoruleoutanassociation of not soapparent.IfcloudAweremoredistantthanthecluster of CBorintheopticalemission-linesurveyPGK,andthus (1961) andFang(1970)suggeststhatthisclusterisofinterme- presented inPaperII. (d^2J5 kpc;Fang1970;cf.BeckerandFenkart1971; distance is~300pc. discovered cloudBbystarcountingandestimatedthat its Fig. 35).CloudBcoincideswitharegionofobscurationon diate age(seeBeckerandFenkart1971;JanesAdler from theGalacticplaneinouterGalaxy,anunlikely Lyngâ 1982),andtheobscurationproducedbythiscloud is greater thanorapproximatelyequaltothatofthecluster so itisanearby,foregroundcloud.KieferandBaker(1941) the POSSprintsandhasavelocityclosetothatofLSR, then itwouldbealargemolecularcloudmorethan-100 pc type earlierthanB3isaclustermember. 1982). Wefindnoevidenceofionizationintheradiosurvey No. 4,1989 Appendix A).TheIRsourcehasanopticalcounterparton limeter observationsareneededtoconfirmthenatureof if itsdistanceis-3kpc.High-resolutioninfraredandmil- IRAS far-infraredpointsource04173+4524,at(l,b)= hypotheses shouldbeconsidered:(¿z)thefar-infraredpoint cloud CandtheIRASpointsource. (156?70, -3?17),isacandidateCO“outflow”powersource. point sourcesandtheabsenceofemissionnebulosityimply of cloudAcouldbeusedtotestthevariouspossibilities. optically thickmaterial.AmoredetailedHa/IR/radiostudy may beembeddedincloudAbutnotsurroundedbyvery low-density intercloudmaterial,thenonlyasmallfractionof molecular cloudwhosedistanceislessthan3kpc,soconsider ionizing stars(Panagia1973)iftheyareembeddedina about —31kmsandanarrowfeatureat—22(see Our COspectrumfromthesurveypositionclosesttothatof sion ofcloudA.BecauseitscoincidencewithC,the the infraredsourceshowsabroademissionlinecenteredat sources maynotbetheionizingstars;and(b)IR that thebacksideofcloudisionized.Twoalternative early Bstar.ThemissingopticalcounterpartsoftheseIR cloud. IftheIRsourcesareoutsidecloud,surroundedby for theradioemission,butthattheyarelocatedbehind order ofmagnitudetooweaktobeevenmodest10L the POSSprints,anditsluminosityisoforder10L source fluxesisafewtimes10L,theenergyradiatedbyan stellar luminosityrequiredtoaccountfortheIRASpoint the stellarradiationisabsorbedbydustnearstarsand the hypothesisthatsourcesareionizingstars,responsible 0 0 0 The kinematicdistanceofcloudA,ontheotherhand, is The photographicphotometryofBarkhatovaandChentsov Two molecularcloudswerefoundinthisregion(Table6W; Evidence foraforeground cloud ofatomichydrogenis The small,elongatedcloudCmaybeahigh-velocityexten- © American Astronomical Society • Provided by theNASA Astrophysics Data System xxvi) NGC1605 OPEN CLUSTERCOSURVEY 1 -1 o _1 -1 No radiocontinuumemissionwasdetectedinthedirectionof which isprobablycausedby dustmixedwithforeground less impressiveiftheyarecloser. is consideredtobe-40Myrold(Lindoff1968;Lyngâ1987). implied bythespectralline intensity isonly0.12±0.05mag moderately smallandoflowmass(seeTable7);theyare even molecular cloudlayeriftheyweremoredistantthan the located beyondthecluster{a)becausekinematicdis- km s"wasfoundinfourdistinctclouds(Table6Y;Fig.37). be presentinafewspectraadjacenttotheclusteratabout diffuse gas(eq.[1]).Sinceonly weakCOemissionfromcloud dark clouds,”theyareclassifiedas“possiblyassociated” with cluster (allowingforthewarpofGalaxywouldstrengthen more likelythattheyareforegroundcloudsthan (Hagen 1970;JanesandAdler1982).Accordingly,thecluster northwest ofthecluster(seePGK).WeakCOemissionmay of cloudA(Table6X;Fig.36)isthesameasdistanceto occurs atthemeasuredclustervelocity,kinematicdistance velocity quotedbyLyngâ(1987)is—3.0kms,avalueso Buscombe 1963;Hagen1970;Lyngâ1987)and(Z>)because of If thesecloudsarenotassociatedwiththecluster,thenitis the clusterbySchwartz(1971). Fenkart 1971;Neckel1967),todustindiffuseinterstellargas extinction ofstarsinNGC103,-1.5mag(Beckerand detected inthedirectionofcluster,weattributevisual classification criteria(see§IVa).Sincenoemissionwas emission areunresolvedandthusdonotsatisfyourcloud associated withthesourceofHaemissionthatlies-I sion foundinthisregion.Althoughnoneoftheemission Lyngâ 1987;Neckel1967)thatwequestionthereliabilityof cluster (3.0kpc;BeckerandFenkart1971;Lindoff1968; rotation (3kms)foranobjectatthedistanceof C wasfoundinthedirection ofthecluster(thereddening 1970; HoagandApplequist1965;Polishchuk1970),most of the cluster.Ifcloudsareasdistantcluster,they are this argument).Sincethecloudscannotbedescribedas“local tic plane(z160pc),thecloudswouldbewelloutside the the relativelylargedisplacementofNGC744fromGalac- sequence turnoffintheCMDoccursat(2?-V)0.1mag are severalA0Vstars(Mermilliod1976)andthemain- the measurement. discordant withtheradialvelocityexpectedfromGalactic the clusterdistanceof1.5kpc(BeckerandFenkart1971; tances ofthecloudsrangefrom0.2to1.6kpc,compared that Mesalongthelineofsight. the cluster.However,emissioncouldjustaswellbe that itsageis-38Myr(Lynga1987).Theclusterradial sequence ofthiscluster(BeckerandFenkart1971),suggesting 0 —15 to-20kms(seeAppendixA),butthesourcesofthis Weak COemission(J)f<1.5K)at-18,-10,and-4 The clusterreddening,E(B-V),is<0.4mag(Hagen No clearlinkexistsbetweentheclusterandCOemis- No starofspectraltypeearlierthanB3existsonthemain The mostluminousmain-sequencemembersofthiscluster xxviii) NGC744 xxvii) NGC103 789 198 9ApJS. . .70. .731L -1 Table 6Wareusedin(a),which isanalogoustoFig.12g.Thecontour diagrams areanalogoustoFigs.12c, 12d,12c,and12/.In(b)(c), respectively, thelowestcontourlevel, 1Kkms,correspondsto1.5and 1.7 a. 790 Fig. 35.—Surveyresultsfortheregion aroundNGC1605.Datafrom © American Astronomical Society • Provided by theNASA Astrophysics Data System 0.6 0.40.20.0-0.2-0.4-0.6 -6 TO-1km/s Al (degrees) LEISAWITZ, BASH,ANDTHADDEUS -1 latitude (4?70). with theclusterisfacilitatedbyitsrelativelyhighGalactic Wramdemark 1982).Cloud C maybepartoftheAquilarift (Table 6Z),onlyoneofwhich, NGC6709C,hasavelocity 6709 (seePaperII),andverylittleCOemissionisfound in (Becker andFenkart1971;Hagen1970;Lyngà1987). An molecular cloudfromwhichtheclusterformedisnotnearby. region aremodestinsizeandmasseveniftheyatthe whether anyoftheinterstellarmaterialfromwhichNGC744 remains thatitisaremoteclustermember. needed tomeasureaccuratelytheabsolutemagnitudeof close tothatofthecluster, ~6kms(Hagen1970; the morethan500spectraobtainedtomapregionaround assessment ofwhatinterstellarmattermightbeassociated Lyngà 1987;Mermilliod19816),anditsdistanceis<1 kpc distance ofthecluster,however,soitislikelythatmost formed remainsintheneighborhoodofcluster.The respect tothecluster. at about200pc(Dameand Thaddeus1985).Wecannot, this cluster(Fig.38).Wecatalog threesmallmolecularclouds atomic (seePaperII)andmolecularcloudsformedinthis star; onthebasisofexistingobservationspossibility center ofNGC744is-4.5clusterradii,and,assumingthat orientation ofthecloud(foregroundvs.background)with 1971; Hagen1970;Harris1976;HoagandApplequist1965; the sameasthatofcluster.Spectroscopicobservationsare and C.Theangularseparationofthestarfromnominal according toeq.[2]),itisnotpossibledeterminethe the starisonmainsequence,itsdistanceapproximately the middleofa“ring”COemissionformedbycloudsB To summarize,weareunabletodeterminewithconfidence Little, ifany,atomichydrogenisassociatedwithNGC The ageofthisclusteris<80Myr(BeckerandFenkart The 9.7magB3starSAO022812islocatedinprojection -0.6 -0.2 -0.4 0.2 0.0 0.6 0.4 0.6 0.40.20.0-0.2-0.4-0.6 -30 TO-23km/s xxix) NGC6709 Vol. 70 198 9ApJS. . .70. .731L -1 -1 -1 -1 is atleast1.5kpcaway(Becker andFenkart1971;Hagen extinction (BeckerandFenkart 1971;Neckel1967)canbe attributed tounrelatedforeground material. few inoursamplewithinthe solarcircle.Becausethiscluster 1969; Harris1976;Lindoff1968;Lyngà1987)isoneof the 1970; Lyngà1987),muchof its2magormoreofvisual km s,>1°closertotheGalacticplanethancluster. however, ruleoutthepossibilitythatNGC6709Cisassoci- Dame etal(1986)atanestimateddistanceof2.2kpc. edge ofthelargemolecularcloud(39,32)incatalog This emission,fromcloudsAandB,probablycomesthe No. 4,1989 tion fromthecluster,cloudisatleast25pcstars. ated withNGC6709;ifso,fromitsprojectedangularsepara- velocity (about-28kms;AbtandBiggs1972;Wilson 0?8 (30pc)oftheclusterandwithinatleast30kms its ent. Figure54showsthatnoCOemissionwasfoundwithin Janes andAdler(1982)tabulatedamain-sequenceturnoff (b) isanalogoustoFigs.12c,12d,and12/.Thelowestcontourlevel,1Kkms,corresponds1.3a. Ha emission(seePGK);nomassive,ionizingstarsarepres- Lyngâ 1987).Notsurprisingly,Schwartz(1971)foundno2.7 1953). GHz emissioninthedirectionofcluster,andthereis no color, (B-V)=-0.12fromthephotometryofBeckerand ally lowforaclusteratitsdistance(2.2kpc;Lyngà1987). and Fenkart1971;Neckel1967;Wallenquist1975),isunusu- Stock (1958),implyinganageforthecluster<100Myr(see to This 90Myroldcluster(Barbaro,Dallaporta,andFabris Weak butsignificantCOemissionwasfoundat-25-32 The visualextinctiontowardNGC436,0.47mag(Becker Fig. 36.—SurveyresultsfortheregionaroundNGC103.DatafromTable6Xareusedin(a),whichisanalogousto12g.Thecontour diagram © American Astronomical Society • Provided by theNASA Astrophysics Data System xxxi) NGC6694 xxx) NGC436 Ai (degrees) OPEN CLUSTERCOSURVEY -1 clouds aremuchclosertotheSunthanclusterand dence oftheCOintensitycontourswithareasstrong cluster by~10kmsandisprobablylocal.Thecoinci- B isaforegroundobject. obscuration onthePOSSprintssuggeststhatmolecular the clusterinFigure13isconsistentwithideathatcloud the Aquilariftat200pc(DameandThaddeus1985). 39), butthisisataradialvelocitythatdiffersfromofthe plequist 1965)andphotometric(BarbonHassan1973; therefore notrelatedtoit.Thesecloudsapparentlyarepartof was derivedbyanumberofinvestigators(e.g.,Barbon and the reddeningofNGC6694,andpointcorrespondingto clouds A,B,andCcorrespond totheKieferandBakercloud material discussedbyKiefer andBaker(1941).Specifically, members, andthemain-sequenceturnoffoccursat(B-V) No starofspectraltypeearlierthanB7ispresentonthemain consistently indicatethatthisisarelativelyoldopencluster. Hoag etal1961;Joshi,Sagar,andPandey1974)observations (see, e.g.,Humphreys1978). Clouds BandCweredetectedas POSS printsandcanbeidentified withthenearbyobscuring of whichcoincidewithregionslowstardensityon the Hassan 1973;Joshi,Sagar,andPandey1974;Lyngà1987; cf. sequence (BeckerandFenkart1971),severalgiantstars are at 800pcandprobablyareassociated withstarsinAurOBI Lindoff 1968). 0 -0.4 -0.6 -0.2 There ismuchCOemissioninitsvicinity(Table6AA;Fig. Dust inthemolecularcloudNGC6694Bmaycontributeto Four molecularcloudswerefound(Table6BB;Fig.40),all Spectroscopic (BarbonandHassan1973;HoagAp- -0.10 mag(JanesandAdler1982).Anageof-150Myr 0.0 0.2 0.6 0.4 0.6 0.40.20.0-0.2-0.4-0.6 -41 TO-30km/s xxxii) NGC1778 791 198 9ApJS. . .70. .731L _1 are analogoustoFigs.12c,12d,12e, and12/.In(6),(c),(d),respectively,thelowestcontourlevel, 1Kkms,correspondsto2.1,1.5,and1.7a. 792 Fig. 37.—SurveyresultsfortheregionaroundNGC744.Datafrom Table6Yareusedin(a),whichisanalogoustoFig.12g.Thecontourdiagrams © American Astronomical Society • Provided by theNASA Astrophysics Data System -14 TO-6km/s LEISAWITZ, BASH,ANDTHADDEUS -19 TO-16km/s -6 TO-1km/s Vol. 70 198 9ApJS. . .70. .731L -1 are analogoustoFigs.12c,lid, and12f.Inboth(b)(c),thelowestcontourlevel,1Kkm s, correspondsto1.6a. No. 4,1989 Fig. 38.—Surveyresultsfortheregion aroundNGC6709.DatafromTable6Zareusedin{a),which isanalogoustoFig.12g.Thecontourdiagrams © American Astronomical Society • Provided by theNASA Astrophysics Data System 27 TO34km/s Ai (degrees) OPEN CLUSTERCOSURVEY 1.5 1.00.50.0-0.5-1.0-1.5 23 TO30km/s 5 TO7km/s 793 198 9ApJS. . .70. .731L -1 -1 indeed associatedwithit.Untilsuchobservationsareavail- e.g., Georgelin,and Roux1973),whichhasaless (see BFS).ProbablyS226is behind thenearbycloudA(see, required todemonstrateconclusivelythatNGC1778C is because itsmotionmaybeaffectedbylocal-scale,aswell as be evidencethattheyareassociated.Inprinciple,then,the associated COemissionata radialvelocityof-33kms edge oftheregionthatwesurveyed aroundNGC1778,has able, thedistanceestimateofKieferandBaker(1941), ob- stars thationizeS228areneededtodeterminethedistance of Galactic-scale, forces.Spectrophotometricobservationsof the (Georgelin, Georgelin,andRoux1973),isunreliablebecause distance ofS228couldbeusedasanestimatorthe region, butthefactthatcloudandHnregionhavea tained bythemethodofstarcounting,probablyismost common radialvelocity(GeorgelinandGeorgelin1970)may Encrenaz impliesonlythatthecloudisinfrontofHn detection asa6cmHCOabsorptionsourcebyLucasand relatively faintCOemissionfeaturesintheGalacticplane trustworthy oneforcloudC. the Hiiregionreliably,andadditionalobservationsmay be the HiiregionislocatednearGalacticanticenter and to thecloud.ThekinematicdistanceofS228,-2.6 kpc (Dickinson, Frogel,andPersson1974;LucasEncrenaz Baker objectat300pc.SincethedistancetoNGC1778is survey ofDameetal.(1987).CloudDmatchestheKieferand 1975) and,ifso,thecloud’sdistancemaybedeterminable.Its the cluster. 1974) ,noneofthecloudsinourcatalogareassociatedwith 2 ~ 1.7kpc(BarbonandHassan1973;Joshi,Sagar,Pandey (b) isanalogoustoFigs.12c,12d,and12/.Thelowestcontourlevel,1Kkms,corresponds1.4a. 794 Another smallHnregion,S226, whichislocatednearthe Cloud CmaybeassociatedwiththeHnregionS228 Fig. 39.—Surveyresultsfortheregion.aroundNGC6694.DatafromTable6AAareusedin(a),whichisanalogousto12g.Thecontour diagram © American Astronomical Society • Provided by theNASA Astrophysics Data System 1.0 0.50.0—0.5-1.0I1ii_ Ai (degrees)1.00.50.0-0.5-1.0 LEISAWITZ, BASH,ANDTHADDEUS -1 NGC 7062is-1900pc(Becker andFenkart1971;Hagen nearby cloudrelatedtotheCygOB7association(Dame and Adler 1982). Thaddeus 1985;seediscussionofNGC7067in§IVZ>[xvii]) at POSS printsindicates,however,thattheemissionarises in a cluster. Onemightbetemptedtoconcludefromthishighly 1987). Wallenquist(1975)noted aheavilyobscuredregion 1970; Hassan1973;Lindoff 1968;Lohmann1971;Lyngâ suggestive morphologythatthemolecularcloudsproduce appears tobeapartialringofCOemissioncenteredon the (Hagen 1970;Hassan1973;Hoagetal.1961)implyanage of giant-branch starsandthecolorofmain-sequenceturnoff derived withanunconventionalmethod(Lindoff1968)to this emissionareassociatedwiththecluster.Inspectionof the of estimateshavebeenpublishedforitsage,from-100Myr This mayindicatethatthesecloudsareintheprocessof We foundweakCOemissionat—33kmsinonlyone forming low-massstars. found bytheIRASindirectionsofcloudsA,B,andC. negative radialvelocitythantheemissiondetectedbyBFS. sources, withnodistinguishableopticalcounterparts,were spectrum, inthedirection(/,b)=(168?38,-1?00). >10' east-northeastofthe cluster, positionallycoincident - 830pc(Humphreys1978). For comparison,thedistanceto - 500Myr(Hassan1973;seeHarris1976andJanes and -1800 Myr(Fenkart1965).Thelocationofaclump In ourincompleteCOmapofthisregion,wefindwhat A relativelyhighconcentrationofweakfar-infraredpoint This clusterisamongtheoldestinoursurvey.Awiderange xxxiii) NGC7062 Vol. 70 198 9ApJS. . .70. .731L 1 diagrams areanalogoustoFigs.12c, 124,12c,and12/.In(b),(c),(4),respectively,thelowest contour level,1Kkms',correspondsto1.6,1.7, and 2.2a. No. 4,1989 -0.5 -1.0 Fig. 40.—SurveyresultsfortheregionaroundNGC1778.Data from Table6BBareusedin(a),whichisanalogoustoFig.12g.Thecontour 0.0 0.5 1.0 © American Astronomical Society • Provided by theNASA Astrophysics Data System -1 2TO-6km/s AÍ (degrees)1-00-50.0-0.5-1.0 OPEN CLUSTERCOSURVEY 4 TO7km/s 795 198 9ApJS. . .70. .731L 12 20-1 1 -12 -1 -1 discussed in§TVb.TheCOfluxisequaltotheintensity, of thesolarluminosity,fromequation extents (Table6).TheCOlineluminosityisobtained,inunits the cloud.Cloudlinearsizesarederivedfromtheirangular /7]f (CO)du,integratedoverthesolidanglesubtendedby an adopteddistance(seebelow)foreachofthe148clouds cluster neighborhoods.WetabulatetheintegratedCOspec- describe themolecularcloudsfoundinoursurveyof34open where bothLandAfareexpressedinsolarunits. In preceding eq.[2]),thenthemolecularcloudmass, tral lineflux,*^co(16errorsareshowninparentheses),and presence ofhelium.TheCO luminositiesofthecataloged (Dame andThaddeus1985;Strongetal1988;seefootnote 1, where distheclouddistanceinkpcand*Scounitsof Table 7. clouds andthemassestowhich theycorrespondaregivenin 2.72 amuperHmolecule (Allen1973)toallowforthe equation (4),themeanmolecularweighthasbeentakento be and fT£dvis1.9XlOHmoleculescmKkm s column density.However,onemightwishtomakethis as- sumption. IftheconstantofproportionalitybetweenY(H ) the assumptionthatCOlineintensityisatracerof H K kmsdeg. implies aclusterage>500Myr. Janes andAdler(1982)convertedtheRGUmagnitudesto main-sequence turnoff(photometric)“spectraltype”isb5. rotation curve,weestimatefromtheradialvelocityof equivalent UBVmagnitudesandtabulatedthemain-sequence cated inthePerseusarm(seeCohenetal1980)andisnot molecular cloudcanbeassociatedwiththeclusteronlyifits the clusterphotometricallyinRGUsystem,foundthat in PaperII. with theCOemissionalongtruncatededgeofourmap associated withIC1442. galactocentric azimuthaldirectionorabout+40kmsin distance totheclusteris-1.80kpc(Yilmaz1970), cloud thatitsdistanceisintherange2.8-3.8kpc.Since 6DD; Fig.42).AllowingforuncertaintyintheGalactic turnoff color,2?—=—0.10,whichwiththeircalibration (see Fig.41). the cloudwouldhavetobeabout+17kmsin Galactic orbitishighlynoncircular(thepeculiarvelocityof the galactocentricradialdirection).CloudAprobablyislo- cocloud 2 2 2 2 796 Table 7summarizesobservedandderivedparametersthat None oftheconclusionsthispaperdependsensitivelyon IC 1442isaveryoldcluster.Yilmaz(1970),whostudied Atomic gaspossiblyassociatedwiththisclusterisdiscussed One smallmolecularcloudisfoundinourCOmap(Table c) ACatalogofMolecularCloudProperties © American Astronomical Society • Provided by theNASA Astrophysics Data System 1 4 L =1.5X10dSQ,(3) M=8.4Xl0L (4) co0 cloudCO) xxxiv) IC1442 LEISAWITZ, BASH,ANDTHADDEUS -1 km s,correspondsto1.4a. used in(a),whichisanalogousto Fig.12g.Thecontourdiagram(A)is cated, oursurveyofthisregionwas incomplete.DatafromTable6CCare analogous toFigs.12c,lid, and 12/.Thelowestcontourlevel,1K -0.6 -0.4 -0.2 -0.8 Fig. 41.—Surveyresultsforthe region aroundNGC7062.Asindi- 0.6 0.0 0.2 0.4 0.8 0.8 0.40.0-0.4-0.8 j—i i i 1r -2 TO8km/s OBSERVED REGION NOT Ai (degrees) Vol. 70 198 9ApJS. . .70. .731L -1 Table 6DDareusedin(a),which isanalogoustoFig.12g.Thecontour contour level,1Kkms,corresponds to1.9a. diagram (b)isanalogoustoFigs. 12c,lid,and12/.Thelowest No. 4,1989 Fig. 42.—Surveyresultsforthe region aroundIC1442.Datafrom _J IL_ 0.8 0.40.0-0.4-0.8 © American Astronomical Society • Provided by theNASA Astrophysics Data System i 1r -32 TO-28km/s Al (degrees) OPEN CLUSTERCOSURVEY which allclusterspassastheyage. intermediate ageclustershaveassociatedwiththemnumerous with themmoremassivemolecularcloudsthanclustersof were foundtocorrespondCOemissionfeaturesinthe with increasingclusterage.Thiscanbeseenbycomparingthe ize moremassiveclouds.Thetendencyfor molecular materialassociatedwiththem.Thistrendisunmis- intermediate agewhilestillolderclustershavelittleorno Dame etal.(1987);insuchcases,thedistancesofthese discovered becauseitappearstobeassociatedwithanother cloud hasbeenclassifiedasalocaldark(L)then,inthe cannot beconfidentthattheyrepresentabriefstagethrough diagrams forNGC7160and1444,bothofwhichare one inFigure12g,arrangedaccordingtoclusterage.Only cloud sizes,luminosities,masses,anddensities(PaperIII). the clusterdistancesareknown(see§IIh[i]).Hence,uncer- cluster canbeestablishedarereasonablywellknownbecause features wereadoptedastheclouddistances. complex forthatofthecloud.Manylocaldarkclouds star-forming complex,thenweadoptthedistanceoflatter ered tobeunassociated(U)withtheclusternearwhichitwas absence ofinformationtothecontrary,weadopt1kpcasan associated (A)orpossibly(a)withanopencluster, small molecularclouds,whereastheveryyoungclusters tend about 15Myrold,withtheyoungerclusters.Bothofthese quantitatively in§V. clouds tobeassociatedwithyoungerclustersisdescribed shown inthemontage,anddarkershadingisusedtosymbol- than uncertaintiescustomarilyassociatedwithinterstellar Galactic planesurveysofDameandThaddeus(1985)or approximate upperlimittoitsdistance;ifacloudwasconsid- the distanceisassumedtobethatofcluster(Table1);ifa to asimplerule.Ifcloudisclassified(§IVb,Table6)as clouds, includingmeandensity,COlinewidth,peak/7}fdv, mass ofinterstellarmatterwithin ~25pcofaclusterisnot not balancedbyanincreasein thenonmoleculargas;total Table 8wesummarizethedataforthoseclusterswithmea- to haveafewmassivecloudsassociatedwiththem.Since only there isapparentlyachangeofmolecularcloudmorphology “possibly associated”withthesurveyedopenclustersare takable inFigure43,whichisamontageofdiagrams,likethe trend existsinwhichtheyoungestclustershaveassociated tainties inthephysicalparametersofthesecloudsaresmaller and peak7^*,aretabulatedinPaperIII. dation andionizationof the moleculargasisoccurring. conserved. of interstellargasassociatedwithclusters,mostwhich is in two ofthesurveyedregionsshowthisbehavior,however, we those cloudsthatareconsideredeithertobe“associated”or sured atomicorionizedgascomponents.Clearly,thediminu- tion ofthemolecularcomponentwithincreasingclusterage is the molecularphase,decreaseswithincreasingclusterage. In Among themostsignificantresultsofthissurveyisthata Distances areadoptedforthemolecularcloudsaccording Distances tothecloudsforwhichanassociationwitha Regardless ofthenumbercloudspresent,totalmass Somewhat lessquantifiable,butstillinteresting,isthat In otherwords,someprocess otherthansimplyphotodisso- Some additionalcharacteristicsofthecatalogedmolecular 797 O'! 00 (T) o oo r" r- \—i ft younger clustersatthetopof page andolderonesatthebottom.Darkershadingisusedtosymbolize moremassiveclouds. Fig. 43.—Montageofschematicdiagrams showingcatalogedmolecularcloudsassociatedorpossibly associated withopenclusterssortedbyage ' r INCREASING CLUSTER AGE © American Astronomical Society • Provided by theNASA Astrophysics Data System NGC 281 IC 1848 1 NGC1893 IC 1396 1 NGC6823 NGC 7380 798 10 NGC433 2 Berk59 NGC 1624 Monoc. NGC 2175 198 9ApJS. . .70. .731L mass fortheNGC2175regionislessthan0.1%. which molecularcloudsareconvertedtostars(seeLarson veyed, weconsiderthisanupperlimittotheefficiencywith lar) massistypicallyaboutl%-2%fortheyoungestclusters. independent chronometerwithwhichonemightgauge the of theclusterstarsmaybe“missing”fromregionssur- gas masses;theratioofstellartototal(stellarplusinterstel- molecular cloudsassociatedwithyoungclustersarereceding rate atwhichaclusterinteractswithitsenvironment.Using not significantlyimpactourmainfindings. from theclusters.Theseresultsaresummarizedbelow. Indeed, wehavefoundalargenumberofcasesinwhichthe conclusions: our observations,wedrawthefollowingstrictlyempirical young openclustersintheouterGalaxy.Theprimarysample Since someoftheinterstellargasinvolvedinproduction the stellarmassesaremuchlowerthantotalinterstellar selection effect,abiasagainstheavilyobscuredclusters, does regions largerthan~25pcinradiuscenteredon34young 1988; Myersetal.1986);infact,theratioofstellartototal tion modelsandspectrophotometricdata,canbeusedas an open starclusters.Theclustersampleisrepresentative of NGC 436,457, 659,NGC957,and regions aroundNGC6694, 6709,NGC7062,103, emission. Nineofthesurveyed openclusterregions—the considered toariseinmolecular cloudsassociatedwiththe 1778—show littleornoCOemission thatcouldreasonablybe Also showninTable8areclusterstellarmasses.Notethat Information abouttheclusterages,basedonstellarevolu- We havesystematicallysearchedforCOemissionfrom 1. SomemoderatelyyoungclustershavenoassociatedCO © American Astronomical Society • Provided by theNASA Astrophysics Data System V. SUMMARYANDCONCLUSIONS NGC 7062. NGC 6709. NGC 744... associated withcluster. as thoseofclassA.ZeroimpliesnoCOdetectedfromcloudsthatcouldbe NGC 1624. NGC 457... NGC 1444. NGC 663... NGC 7380. NGC 281... NGC 6823. IC 1396.... NGC 2175. NGC 1893. Bk 59 IC 1848.... Identification c b a NondetectionreportedbySchwartz1971. Molecular massesinparenthesesincludeall“possiblyassociated”cloudsaswell StellarmassesarefromBruchandSanders1983. Stellar andInterstellarMassesAssociatedwithClusters Cluster (Myr) Age 500 78 39 18 15 15 4 4 5 3 2 2 2 1 1 OPEN CLUSTERCOSURVEY 3 (10 Mo) a Mass 0.34 0.24 0.35 0.59 0.26 0.80 0.47 0.61 0.65 0.72 0.28 TABLE 8 15 Ionized AtomicMolecular 0.01 0.45 4.0 2.9 0.22 2.0 4.6 5.2 5.5 3.0 4 which massivestarsformin a cluster,theamountofmolecu- interaction betweentheionizedgasandmolecularclouds, in thisagegroupareNGC6823,7380,Bk59, c lar materialthatremainswithin -25pcexceeds,oftenbyan order ofmagnitude,thecombined stellar(seeBruchand one canarguepersuasivelythat thecloudsactuallyareassoci- region and,inmostcases,byappealingtoevidenceof the Monoceros cluster.EachoftheseclustersionizesanH n best, weak. luminosity andmassthantheabovenumberswouldindicate. possibly associatedwithclustersinthissubsampleactually line luminosities(<0.04L)andcorrespondinglylowmasses 281, IC1848,NGC1624,1893,2175,and the molecular cloud(>40pcindiameter;COluminosity which arelessthan—5Myrold,eachcontainatleastonelarge ( <3000M).Ifanyofthecloudsthatweconsidertobe NGC 1444aresmall(<15pcindiameter)andhavelowCO associated withthemmolecularcloudsmoremassivethanafew ated withtheclusters.Thus, within5Myrofthetimeat 2129 arepossibleexceptionstothisrule,andtheevidence that a massivecloudisassociatedwitheachoftheseclustersis, at than -15Myr.OnlyNGC654,Bk11,1605,and Myr, butfourofthefiveclustersarebelievedtobeyounger Clusters inthissubsamplerangeagefrom-10to—40 associated maybeevensmallerinsizeandmoremodest are notassociatedwiththeclusters,thencloudsthat associated withNGC7067,7160,Bk62,744,and thousand solarmasses.Themolecularcloudsthatmaybe clusters. Alloftheseclustersareolderthan-15Myr,but only —15-20Myrold. three ofthem—NGC457,NGC659,and957—are 0 g >0.2 L;andequivalentmass>2xl0Af).Theclusters 0 3. Regionsaroundtheyoungestclustersobserved,all of 2. Asarule,clustersolderthan-10Myrdonothave 3 Associated GasMass(10M) 0 20.0 2o'o 10.0 0.02 0.03 0.75 1.2 0.3 1.9 1.3 3.0 1.8 1400 (1400) 100 (300) 67 (67) 32 (32) 15 (76) 16 (21) 36 (53) 11 (16) 85 (87) 0 (0.2) 0(0) 0(7) 0(0) 0(4) 0(2) >1405 Total >90 105 22 48 34 34 36 73 0 0 0 1 2 1 799 LEISAWITZ, BASH, AND THADDEUS Vol. 70 ° Sanders 1983), ionized (see Schwartz 1971), and atomic (see rV7?[ii], IYZ?[vi], and IV7>[xx]). Large numbers of small molecu- GHW) mass in the region. The amount of material in the lar clouds were found in the vicinities of the intermediate age ^ latter three states typically is a few thousand solar masses. clusters NGC 7160 and 1444; these could be described as < 4. Molecular clouds are receding from young clusters at ~ 10 clumps left over from the once more massive clouds from S km s~l. Eighteen molecular clouds—NGC 6823A, IC 1396A, which the clusters formed. The much smaller “globules” ^ IC 1396B, IC 1396C, IC 1396D, IC 1396E, NGC 7380E, Bk found by Sim (1968) near the edges of the molecular clouds 59A, NGC 281A, NGC 663A, NGC 663C, IC 1848A, IC IC 1848A and IC 1848B may be minute pieces of these 1848B, IC 1848C, IC 1848E, IC 1848G, NGC 1893A, and eroding massive clouds. Monoceros A—can be determined to be either in front of or 6. Star formation appears to be continuing or to have begun behind clusters with measured stellar radial velocities. With in the molecular clouds associated with some young clusters. only one exception (Bk 59A), these clouds are receding from Water masers, CO outflow sources, radio continuum emission the clusters; the relative radial velocities range from - 4 to peaks, and infrared hot spots occur in the directions of clouds ~ 20 km s~l with a mean value 10.7 + 1.6 km s-1 (see Fig. associated with NGC 281, IC 1848, NGC 1444, Bk 11, NGC 44). Strong evidence exists that 13 of the 18 clouds are 1778, and NGC 2175, suggesting that the clouds are heated associated with the open clusters from which they are reced- internally by nascent stars. ing; the other five clouds are “possibly associated.” Theoreti- 7. The ratio of stellar mass to total (stellar plus interstellar cally, the recession velocities should be larger than their gas) mass measured in regions around the youngest clusters is measured radial components, but these clouds were selected ~l%-2%. This can be thought of as an estimate of the star because they are either “in front of’ or “behind” clusters, so formation efficiency (SFE), but, strictly, it is only an upper their tangential components of recession are assumed to be limit to the SFE if some of the gas involved in the formation small. A consequence of this recession is that clouds with of the stars has departed from the regions observed. proper motions can move beyond our 25 pc survey “window” Conclusions (1), (2), and (3), illustrated in Figures 45, 46, in as short a time as ~ 3 Myr. and 47, imply that the typical interstellar environment of a 5. As the molecular clouds recede from the clusters, the cluster containing massive stars changes drastically during the clouds at least partially dissolve (i.e., clumps are dispersed and first 5 Myr. Ten million years after a cluster containing O molecules are dissociated). Bright rims are found on the stars forms in a molecular cloud, little remains within 25 pc of 5 molecular clouds in nine regions (NGC 6823, IC 1396, NGC the stars of what once was, perhaps typically, a 10 Af0 cloud. 7380, Bk 59, NGC 281, IC 1848, NGC 1893, NGC 2175, and the Monoceros cluster). Ionized gas motions appear to be perturbed along lines of sight that intersect molecular clouds (see, e.g., §§ JVb[i\, IVh[iv], IVh[v], and rV7>[vii]); generally, radio recombination-line and optical emission-line observa- tions can be interpreted with a model in which dense, freshly ionized gas streams away from the illuminated surfaces of the clouds at a few km s-1. Atomic hydrogen also is found to be concentrated, in both position and radial velocity, near the molecular clouds associated with young clusters (see, e.g., §§

Fig. 45.—Distributions of the masses of molecular clouds confidently (class A) or possibly (class a) associated with clusters, (a) Masses of the Fig. 44.—Distribution of the velocities of recession of 18 molecular most massive clouds associated with clusters younger than ~ 5 Myr. clouds from young clusters. The cluster radial velocity uncertainty (see (b) Masses of the most massive clouds associated with clusters older than § Tib) contributes significantly to the dispersion in the distribution. ~ 10 Myr.

© American Astronomical Society • Provided by the NASA Astrophysics Data System ^ No. 4,1989 OPEN CLUSTER CO SURVEY 801

Fig. 47.—Molecular mass associated with clusters as a function of their age. All molecular clouds associated with confidence (class A) or possibly associated (class a) with the clusters are included. At most -10 A/q of molecular gas is associated with clusters near which no CO emission was detected.

We have compiled a data base (see Leisawitz 1988) which Fig. 46.—Same as Fig. 45, but for the diameters of the largest clouds contains information about the 128 well-studied open clusters associated with clusters. The cloud diameter used is the geometric mean that satisfy our selection criteria with respect to distance (1-5 of “mm and tfmaj from Table 7. kpc), age ( < 100 Myr), and declination (greater than - 20°). Photometrically and spectroscopically derived cluster parame- ters and data that characterize the interstellar environments Conclusions (4) and (5) suggest that the molecular cloud’s of the clusters are tabulated. The data base and a set of dissappearance can be attributed to a combination of cluster- Fortran programs that enable the user to operate on it in an cloud relative motion and destruction of the cloud by frag- interactive fashion can be obtained from the National Space mentation and dissociation. Observations of the molecular gas Science Data Center (NSSDÇ). associated with nearby clusters, such as the very young X Ori (Maddalena et al. 1986) and the relatively old Pleiades (Breger People too numerous to mention, but who are not forgot- 1987), are consistent with our findings. ten, contributed significantly to various aspects of this re- Some implications of the cluster-cloud environment modi- search. We are most grateful to A. Kerr and S.-K. Pan for fication for the redistribution of OB star luminosity in the developing a truly state-of-the-art receiver, to S. Palmer for interstellar medium were addressed by Leisawitz and Hauser keeping it on the air, and to D. Bazell, T. Dame, N. Evans, (1988). K. Janes, J. Scalo, F. Verter, and J. Vrtilek for helpful Additional analyses and interpretations of our findings will conversations and comments on the manuscript. We thank be the subjects of future papers in this series. The empirical our referee, C. Lada, for a careful reading and for comments conclusions drawn in this paper will be used to discuss that led to an improved organization of the paper and a more plausible mechanisms for the dynamical interaction of mas- thorough discussion of selection effects. Partial funding sup- sive stars with their interstellar environments (Paper TV). port was provided by the National Science Foundation under Properties of the molecular clouds cataloged in § TV will be grants AST 816403 and AST 8312332. Also, at various times discussed (Paper III); the present catalog is, to the best of our during the course of this study, DL derived financial support knowledge, the largest systematically observed sample of from the National Research Council as a Resident Research molecular clouds for which reasonably rehable distances are Associate at the NASA Goddard Space Flight Center and available. from NASA SADAP grant R033-87.

APPENDIX A

RAW SURVEY DATA To embellish arguments or highlight features of the data discussed in § TV, we present in Figures 48-56 spatial “maps” of CO spectra obtained to survey the regions around NGC 6823, Roslund 4, Bk 59, NGC 103, NGC 281, NGC 436, NGC 457, NGC 957, Bk 11, and NGC 2175. These “maps” are analogous to the one shown for the NGC 7380 region in Figure 12a.

© American Astronomical Society • Provided by the NASA Astrophysics Data System 198 9ApJS. . .70. .731L -1 Vulpécula riftcloudat10kms. on theradialvelocityofcluster.NoteextremelybroadCO linesinthemolecularcloudNGC6823Candrelativelyweakfrom 802 -1 Fig. 48.—SurveydatafortheregionaroundNGC6823displayedas inFig.12a.A60kmsportionofbaselineisdisplayed,centeredapproximately T3 0) <1> CA 0 Ö5 © American Astronomical Society • Provided by theNASA Astrophysics Data System -1.0- 0.5- OE^ ^J»*ÀJ.^mAA^J.>L./w14à^ÀtâJii M 1.0- ,p * ■•»ni^'jvfp 0- 1.0 NGC 6823U/b)=59°.41,-0°.15 0 Jb K V1w 4 4â.AA/\>,.^>éAui«Mft hk ■ '*i"pip*T^1’fWrI LEISAWITZ, BASH,ANDTHADDEUS 0.5 aJL. Vr%t A^^jî JU JL. ■ A, «¿Mr* A£ (degrees) vwJii J.. -A, i¿AÍ 0 uU A Au W\r ijiv. fT— 1 J4 ^ *tip•■i -0.5 1 1 ^^pjjA^frAi-A^j^4j-Ai*« 1 ■rf'Vn4|p r *▼"v■“% 44 ,11 *^L^iUb 4.Aj^j¿iift Am^ *ifA»\i^ yAH* JUrv if '■•“*^i"ir?T ^ ifk,AvAyv/S,« J -10 55km/s V|_SR ^LSR |^ -1.0 a, Vol. 70 198 9ApJS. . .70. .731L No. 4,1989 many. the radialvelocityofcluster.Notethatsomeemissionispresent innearlyallofthespectraandthatmultipleemissioncomponentsarepresent -1 Fig. 49.—SurveydatafortheregionaroundBk59displayedasin 12a.A30kmsportionofbaselineisdisplayed,centeredapproximatelyon ■O 0 0) 0) CO Ö) k_ © American Astronomical Society • Provided by theNASA Astrophysics Data System -1.5- -1.0- -0.5- 0.5- 1.5- 1.0- 0- BERKELEY 59(l,b)=118°.25+4°.95 0f Airn 1,l,l w1ii,t ujT M , ,i,r ,w1 1,,m 1H ,A i -^A^^^^j^y^yi-^-iA^Uj^f[~~*>^S.^yt|rr*ir[ij-u*rV.[ri~A|»*~VLrj|_n.^^j|.>*iA*^|**-^K|.~‘*^>-|T^At^l*.^~j.|_iJi<^|>j^rAA4.[j'A~~ T W"t*wFmPT—T•”l1>ITITTftl'Ifl'^rll|''riIT*T’PI•I"I•!!•T'I'nPHr“II* i 1>ul1.^..«jl..L^aA^jJIA/I^I.jIWa^LA^».flAl.L>A^.I-|AL**--1-j-^.-.-‘rA*T.lrV*^yl-lfV-r it 'l'T"P'rr^rr"i“F"»^-rT^l-Vl">tHi^Mlrri“^P*f^F1r*!rrit^—r^r’P'T“P*^♦'PP*! l IU.Íja..I.JA.IAa.LMLAa^[¿A.L/A1aA,.[a/I.[JW>^j./Ai.,/Ai/L.LJL.Jk.i.A*iln^»fi*i-/ l•“^ p^“rir^pTf<^‘»rr•r'T''ir*ir^ri“™rnn““—“fi■n’r^^fi"n I A.-1Jv1.Aj.I.Aaj\k-1„AiI„aa.L-a,L^a_^L..a.^1..L.^a...lj*a.I^Mi1Vi-IAA.Li.aKl.i.nL...[^aA..i.iK^.L./^.*i~La.*... p'f *rnr»u*t"it^'T’in"rnr^rpt^rTPr^'(n“r^r“imr'~f*ir^*^•r"^*»ap.'■»•fi»»*— LAu. L.^^.L^AmmL^d^am4u^a»larf^Lb. f I«nrP'TI'T^F1I"!'FP»!!lF*ri■l"1'»FT»M'l’’ll“»F*"T™1'•F'^^i-~I'l'r" 1- .aaa»-L-aa>I.*iaI.ma.LaA^-A^*a*+L^a.^.L.#^a.l^aA..IAw.L^bk.L^Lju-LJLLJuL^L^LJLLAaLJLLJLLJL rnr r^n^pt’*p'i*r^rr—ri•f^v'r'“i■•pi*wtmii™tii'^‘ii'i'tri"T'l L.^i. 1.v*a.1ím.Lkal/Vc.i.j^á.[~y*-ALv«.a,Ij.I.A.^[■/^M^.|4pv.LaAl.Ju.l^jA^L^l..[jA„Í-t«A4.LjTv.-A^L^A.LiA... PI *i^rr"?FTT^Ptit'ITrT^*P"rr’TnT^^r“~r^'rPtt'*1*^1Ft“•'*F^r"P'r’—Fr^r'"»P'Ft^F L» Imy^A-LivpA_il.I—it■*-\l-it^-lfT*-V^Laj*~^*•I.V^*1.r.^^Lrx*^V1^~ji1^AjInr^L'i0^~j.Lc*^-LriAl-lyu'^—flj^-jIr\riLfil^i-11_«A 1.5 u1rtT StrvT 11f r1 t v,r>1 1,taNr¥Fw I ..A*kÁ.Í■.A-ft.i.>4.1^A±AI.A^A1.^llA.1^1.^iO.1.-.^JV.-AA..1._.Art.b1LbAbbAlAlAb^A^bL1^.. Mr'^'Pir ^r't^^'r'“^ppt''P'nP'i«ri"*pT^ir“—ry*P“»“F^r■FI•"“nr'^ip— I ..AJk.Lb^A^bWb^U4B^LJLRb^JL^v TP“»*PíX tr'i'^'IT■Fr^r'P^*r’^rtF'r"'^r^I'r^r'•Hrrr^I!•Htt^P•nT^ At 1 .AA1.^.a.1b»LilIftilI>1^I-m/^Lnj-^l-r^-^\.LwAfL-AvJHu*^LL-A»--A-L.*“.-*rrL»nrm^i.- l h1w |rlj>J1T, | FF“■lf•i"rI^.p*[~”r'."I*»T*’'ïP i ~|.'Vu|i1~^l*A^|r-bJ^‘f|“'T‘^\|jl^\r|rj|'‘'*^L.l‘t'|.r*^r[nJ^~/|^riA^J^V^V-l-*f^~^lj~'^i.l'^"*v|P^*~~|~if-'1/. t,<f|r.ir**^-!|i r ti J OPEN CLUSTERCOSURVEY |^.Jb^.|^^l^-|^jA^.|-**^*(.[‘l A,j.^.A^|_^.À1.^^ Jlftj 0.5 |yL,L ^J/V^^[/L\[A^[>b>bJ^.[^K. Al (degrees) 0 -0.5 -1.0-1.5 |gà^^A* |iMn^MW 803 198 9ApJS. . .70. .731L 804 on theradialvelocityofcluster.Notethatemissionisrelatively strongandthatCOwasdetectedinalargefractionofthepositionsobserved. 1 Fïg. 50.—SurveydatafortheregionaroundNGC2175displayedas inFig.12a.A30kmsportionofbaselineisdisplayed,centeredapproximately < _ 0.5H -g OH _Q d) © American Astronomical Society • Provided by theNASA Astrophysics Data System -1.5- -1.0- -0.5- 1.0- 1.5 1.5 1.00.50-0.5-1.0 NGC 2175Uo,bo)=190°.20,+0°.42 L-L.L-L.ULí-L-LuL.LL.L.LUIaU.ÜlUUUL-L-L-L-L j*. *■«.L-^<'[»«^—■■Í^A'»Í'—L-^AÍ-»«^V.L»*j.^.^j,V\^.[.A..,l..^/*L..|^^W.[s»A^,..l^^u.|,i*i.,l..*... I -1^[,j—A..1A■—-J-A[_-A.A—[-A-JJLA-L\-j-juA^jfiA.,[-iV«l-- L U_1^.U1-^L-Al1.Í-1-^--l-^l-.^wUKULA.Ul^l^UU-1.-11-1*, L^l..^. L***'■!..■■»'1-*»».La..1jiLa^.1^Ai...l».a^.i.La—[.jv.>**.L~»-.1...i.-<^ 1-1 -A-.[M.J.^|,.-A[-I-J-W[j-A.[^ArA,,[--/1j-A-_1^-At.1A.-A-|.LJJ-A^jAa^I^fL-J.-[-.| Í—l Ll...^*»1^,.>.1-4».»l.,^..».,[..^i.,1,fcfc ;r r 1^- r*-n.-1.ir**ii.Íi_*-l_|^rW~j•l-1,^i..,-|-^\--|-|A.7^—A./V..|_^A_,-|AAj.A/s.-_|.A-A-...„I.j l^.a. ly»^,..[»..^11..»*.»11.■«1«J»«*>.i.»1.»«.«i».L.^.i.L»*.»I**«--!.*-»«'.I.«—*.1^.L.L...LJ,ifc. t|Jfr T* JlO K l. i..a.—»-l..■—-—Í...»--.i.•~ÍÍ—.**.....1i..—«Í.-|—^---.[^W-l^/V..{-/V.l^-. ru j.iMt [>.^..L..b.w1..^«^iL»i•..1.B^v«I.»L.li.M.t.Ul^I^l^L^L,. l_L_L_L_L-L_l_L_L_Ll_LL_L LEISAWITZ, BASH,ANDTHADDEUS 11 »■.^L».*<'»*>!«*1»E (degrees) rw ^Srvr / aJvVjyi i /Via|i , &^(mW\JVíí 'HIT ^“ »ji.s ^ “I"FW nfT ff 0 ; -i»r-Pf : j^AJkijD^LjL4biL^^^IaIVí^^Li,■»¿il.i_â. nnr Jl^. * 'TT'T^”#r»ry»|^-r^/■—t'•*•y“fHt“p▼TpW ÏW^T ^"1*•*W*T* wvk-. ». >>Aâ>JLkiJ. . aaí*Vj-iiii^iJva T • ^»ffT prP I ,B +i ' “[ï i JV-^A|ax 1f, fr i vyj«^^ k i* ’ A , AujvvV^fV wtv pv“wyfVpVTn f^i'! *(“ rp- 'fy•"1*1 |^F 'll“wy^r^Jßfrpr - AU-hi^rujá.■baMVJLa.j-L *1é l_L»JM.,.a.i_/ -0.5 wr 1f 11,1 ^uJULuà ^ rMi. 1 AjL^Wé,uu^âjyyiBAilL r V«prPTrWf’'*fi“ ^ rrVT¥“ V" 1*'"'^•pf ± -20 40km/s V I LSR Vol. 70 198 9ApJS. . .70. .731L on theradialvelocityofcluster.Weakemissionfromunresolved sourcescanbeseeninafewspectrathevelocityrange-36to—41kms. No. 4,1989 1 Fig. 53.—SurveydatafortheregionaroundNGC957displayedas in Fig.12a.A60kmsportionofbaselineisdisplayed,centeredapproximately © American Astronomical Society • Provided by theNASA Astrophysics Data System NGC 957ü,b)=136°.34,-2°.66 0 OPEN CLUSTERCOSURVEY 807 198 9ApJS. . .70. .731L approximately ontheradialvelocityofcluster. 808 1 Fig. 54.—SurveydatafortheregionsaroundNGC436and457 displayedasinFig.12a.A60kmsportionofbaselineisdisplayed,centered © American Astronomical Society • Provided by theNASA Astrophysics Data System NGC 457(IQ,b)=126°.56,-4°.35 0 LEISAWITZ, BASH,ANDTHADDEUS Vol. 70 198 9ApJS. . .70. .731L spectrum containsbothbroad-lineandnarrow-linecomponents. the radialvelocityofcluster.Acandidatemolecularoutflowsource (seetext)canbeseenneartheupperright-handcomerofmapwhereCO No. 4,1989 -1 Fig. 55.—SurveydatafortheregionaroundBk11displayedasin Fig. 12a.A60kmsportionofbaselineisdisplayed,centeredapproximatelyon © American Astronomical Society • Provided by theNASA Astrophysics Data System o BERKELEY 11U,b)=157.08,-3°.65 0 OPEN CLUSTERCOSURVEY Ai (degrees) 809 198 9ApJS. . .70. .731L on theradialvelocityofcluster. 810 LEISAWITZ,BASH,ANDTHADDEUSVol.70 1 Fig. 56.—SurveydatafortheregionaroundNGC103displayedas inFig.Via.A60kmsportionofbaselineisdisplayed,centeredapproximately © American Astronomical Society • Provided by theNASA Astrophysics Data System NGC 103U,bo)=119°.80,-1°.38 0 198 9ApJS. . .70. .731L Conti, P.S.,andvandenHeuvel,E.J.1970,Astr.Ap.,9,466. 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Formation, ed.R.S.RogerandP.E.Dewdney(Dordrecht:Reidel), Suppl, 41,211. 223. 103 (GHW). 811 198 9ApJS. . .70. .731L 1_ _1 _1 km scontoursareshownforIC1848D;andonly1K areshownforIC1848E,1848F,and1848G.Dashed-linecontours used forIC1848Dand1848F(seeFig.14). confusion, 3,10,and16KkmscontoursareshownforcloudsIC 1848A andIC1848B;14Kkmscontoursareshownfor1848C;5 Leisawitz, Bash,andThaddeus(see70,811) PLATE 148 Fig. 57.—ContoursofCOintensitysuperposedonareproduction of thePOSSredprintshowingregionsurveyedaroundIC1848.Tominimize © American Astronomical Society •Provided bythe NASAAstrophysics Data System IC 1848Uo,b)=137°.19,+0°.92 0 Al (degrees! 198 9ApJS. . .70. .731L -1 1 1 1 confusion, 3and8Kkmscontoursareshownwithsolidlinesfor cloud Bk59A;the2Kkmscontourisshownwithasolidlinefor59B;8and14 contours areshownwithsolidlinesforBk59E(seeFig.17). K kmscontoursareshownwithdashedlinesforBk59C;3and5 K kmslevelsareshownwithdot-dashedUnesforBk59D;and610 Leisawitz, Bash,andThaddeus(see70,811) Fig. 58.—ContoursofCOintensitysuperposedonareproduction ofthePOSSredprintshowingregionsurveyedaroundBk59.Tominimize © American Astronomical Society •Provided bythe NASAAstrophysics Data System BERKELEY 59(i,bo)=118°.25,+4°.95 0 Ai (degrees) PLATE 149 198 9ApJS ... 70. T" -1 -1 Leisawitz, Bash,andThaddeus(see70,811) contours, atlevelsof3,6,and9Kkms,areusedtoshowthemolecular cloudNGC281A;dashedlinecontoursatlevelsof1and3Kkmsareused to showNGC281B(seeFig.19). PLATE 150 Fig. 59.—ContoursofCOintensitysuperposedonareproduction of thePOSSblueprintshowingregionsurveyedaroundNGC281.Solidline © American Astronomical Society •Provided bythe NASAAstrophysics Data System 3 < CD CD CD CO Ö) -0.50 0.50 0 NGC 281Uo,bo)=123°.13,-6°.24 0.50 0-0.50 AI (degrees) 198 9ApJS. . .70. .731L _1 Leisawitz, Bash,andThaddeus(see70,811) levels are1and5Kkms;themolecularcloudNGC7380Fisshown withdashedlinecontoursforclarity(seeFig.12). Fig. 60.—ContoursofCOintensitysuperposedonareproduction ofthePOSSredprintshowingregionsurveyedaroundNGC7380.Contour © American Astronomical Society •Provided bythe NASAAstrophysics Data System 1.00 0.500--1.00 1 IiL—^i—S«*■ Al (degrees) PLATE 151 198 9ApJS. . .70. .731L 1 _1 1 -1 1 _1 663G (seeFig.28). Leisawitz, Bash,andThaddeus(see70,811) 663E; the1and4Kkms“contoursareshownwithdot-dashedlines forNGC663Gand663H,the8Kkmscontourisalsoshown dashed UnesforNGC663F;the4Kkmscontourisshownwitha solidlineforNGC663C;the1Kkmscontourisshownwitha contours areshownwithdashedUnesforcloudNGC663A;1and 3 Kkms“contoursareshownwithsolidlinesforNGC663Band663D also includestheclustersNGC654and659,asindicated inFig.28«.Tominimizeconfusion,2,6,10,and20Kkms PLATE 152 Fig. 61.—ContoursofCOintensitysuperposedonareproduction of thePOSSredprintshowingregionsurveyedaroundNGC663.This © American Astronomical Society •Provided bythe NASAAstrophysics Data System NGC 663(i,b)=129°.46,-0°.94 0 1 h yi y A ¿(degrees) 198 9ApJS. . .70. .731L Patrick Thaddeus:Harvard-SmithsonianCenterforAstrophysics, 60GardenStreet,Cambridge,MA02138 David Leisawitz:InfraredAstrophysicsBranch,Code685, NASAGoddardSpaceFlightCenter,Greenbelt,MD20771 .1972,Astr.Ap.Suppl.,1,355. .19816,Astr.Ap.Suppl.,44,467. .1981a,Astr.Ap.,97,235. 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