1992Aj 103.1987B the Astronomical Journal

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1992AJ 103.1987B 2 THE ASTRONOMICALJOURNAL is operatedbytheAssociationofUniversities forResearchinAstronomy, contract totheNationalScienceFoundation. by theAssociationofUniversitiesfor ResearchinAstronomy,under tribution ofelementswithintheGalaxy(Pagel&Patchett els ofchemicalevolutionandontimescalesfortheredis- long-lived stars,forexample,providesconstraintsonmod- The metallicitydistributionfunction(MDF)oflow-mass, only betestedwithalargesampleofmetal-deficientstars. tion andevolutionofstarsinthehaloourGalaxycan under contracttotheNationalScience Foundation. Visiting Astronomer,CerroTololoInter-American Observatory,which 'Visiting Astronomer,KittPeakNational Observatory,whichisoperated 1975; Hartwick1976;Pagel1989).Untilveryrecently, 1987 Astron.J. 103 (6),June1992 A hostoflongstandingproblemsconcerningtheforma- © American Astronomical Society • Provided by the NASA Astrophysics Data System _1 with accuraciesontheorderof10kms,areobtainedforallourprogramstars.Distanceestimates, with aninferred[Fe/H]>—2.0),weobtainestimateddereddened(B—V)colorsfromempirical one-third ofthepresentsample.Formajoritystarswithoutavailablephotometry(primarily published calibrationofthevariationinequivalentwidthCailKabsorptionline(A3933A) survey. Metalabundancesfortheprogramstars,on[Fe/H]scale,areobtainedfromapreviously hemisphere, chosenfromalistofcandidatemetal-deficientstarsdiscoveredintheHKobjective-prism We reportonspectroscopicobservationsfor1044stars,locatedprimarilyinthesouthernGalactic accurate distancesareobtainedfortheremainingstarsbyacalibrationofapparentmagnitudewith calibration ofthevariationBalmerlineequivalentwidthwithbroadbandcolor.Radialvelocities, as afunctionofbroadband(B—V)color.BroadbandUBVphotometryisavailableforroughly with [Fe/H]<—1.0,446stars—2.0,703.0,andatleastthree crude brightnessestimatesfromtheoriginalsurveyplates.Thesamplereportedhereincludes734stars accurate to10%-15%,arereportedforthesubsampleofprogramstarswithavailablephotometry.Less of 5-10.FiftystarsinoursampleexhibitanomalouslystrongGbands,characteristicthesubgiantCH late-type stars,theactualnumberofstarswith[Fe/H]<—4.0inpresentsamplemaybeonorder with [Fe/H]<—4.0.Duetouncertaintiesinthecalibrationofourmetal-abundancedeterminationsfor seven timesthenumberofpreviouslyidentifiedstarswithspectroscopicallydeterminedabundances form thebasisforaddressingawiderangeofquestionsconcerningformationandevolution stars discussedbyBond.Amongthemostmetal-deficientobjects(asinferredfromtheirCanK universe. Thenumberofextremelymetal-poorstars([Fe/H]<—2.0)reportedinthepresentsampleis equivalent widths),weidentifysixstarswithmoderatetostrongCNbands.Thepresentprogram follow-up spectroscopyandphotometryofmetal-deficientcandidatesidentifiedinourongoing which arethislow.Weemphasize,however,thatthepresentsampleonlyrepresentsonorderof regime whenallsourcesareincluded.Thenumberofstarswith[Fe/H]<—3.0inthepresentsampleis ported bypreviousworkers,andisontheorderoftotalsamplesstarsinthisabundance roughly quadruplethesamplesizeofnonkinematicallyselectedstarssimilarmetalabundancere- Galactic halopopulation,and,byinference,thenatureoffirstgenerationsstarformationin objective-prism survey. 0 0 10% ofthenumbersuchextremeobjectsthatremaintobediscovereduponcompletion Department ofPhysicsandAstronomy,MichiganStateUniversity,EastLansing,48824 1. INTRODUCTION A SEARCHFORSTARSOFVERYLOWMETALABUNDANCE.II The Observatories,CarnegieInstitutionofWashington,Pasadena,California91101 2 George W.PrestonandStephenA.Shectman Received 27November1991;revised19February1992 VOLUME 103,NUMBER6 1 2 0004-6256/92/061987-48$00.90 Timothy C.Beers ABSTRACT dz, whichwasflatdowntothelowestmeasurableabun- least [Fe/H]=—3.0(Lairdet al.1988;Ryan&Norris modified byHartwick1976)and observationdowntoat cellent agreementbetweensimple modelpredictions(as of kinematicallyselectedhalo stars haveconfirmedtheex- dance, aspeculationsupportedbytheanalysisofBeers licities mightbeconsistentwithadifferentialMDF,dN/ speculated thattherelativenumbersofstarsatlowmetal- Beers etal.(1985,hereafterreferredtoasBPSI)identified even relativelycrudemodels.Inthefirstpaperinthisseries anything butthemostgenerallimitsonapplicabilityof however, samplesofstarshavebeentoosmalltoplace 1991). (1987). Recently,analysesoftheMDFforlargesamples 134 starswithinferredabundances[Fe/H]<—2.0,and Other importantproblemsof current interestinclude: © 1992Am.Astron. Soc.1987 JUNE 1992 1992AJ 103.1987B -1 0 bang cosmologicalmodels(Malaney&Alcock1990; metal-poor stars,onemightattempttounravelthemass have takenplaceinourGalaxy(Gilroyetal.1988;Grat- vide sensitivetestsofstandardandinhomogeneousbig extremely metal-deficientstars(Gilmoreetal.1991; above. InSec.2wesummarizethepresentstatusofHK sample aresufficientlylargenumbersofstarswithextreme interference-filter surveyofBeersetal.Includedinthis poor starsselectedfromtheHKobjective-prism/ distance estimatesforasampleof1044candidatemetal- early chemicalhistoryoftheGalaxy. nucleosynthesis siteswhichareexpectedtodominatethe time. Thielemann,etal.(1990),andMathews&Cowan function ofchemicaltime,andperhaps,eventually,real spectrum ofstarformationandevolutionprocessesasa Norris etal.1992).Withasufficientlylargesampleof Castelli 1990;Zhao&MagainRyanetal.1991; ton &Sneden1990;MolaroBonafacio tion, stellarevolution,andnucleosynthesisprocesseswhich summarize aspectsofthecumulativehistorystarforma- dances ofheavyelementsinmetal-deficientstars,which lar metallicity.(3)Measurementoftherelativeabun- studies isthedependenceofCNOabundancesonstel- therein; Sneden1990).Ofparticularimportancetosuch references therein;Wheeleretal.1989,and of theCNOelementsinfieldstars(seeSneden1985,and Walker etal.1991).(2)Measurementoftheabundances Hobbs etal.1991;Molaro1991),whichpotentiallypro- abundances toaddressmanyoftheproblemsoutlined indices forstarspresentlywithoutphotometry.InSec.5 and discussestheestimationof(B—V)qfromBalmerline available forroughlyone-thirdofthestarsinsample, Section 4summarizesthebroadbandUBVphotometry spectroscopic observationsforstarsinthepresentsample. survey. InSec.3wediscussmoderate-resolution(1Â) low-metallicity stars.Briefly,candidate starsinthepresent which alsoexhibitmoderatetostrongCNfeatures. with recenthigh-resolutionobservationanalyses.Inthis for ahandfulofthemostextremelymetal-deficientstars from observedequivalentwidthsoftheCailKlineinour estimates of[Fe/H](accurateto<$[Fe/H]~0.15-0.20dex we applythecalibrationofBeersetal.(1990)toobtain sion ofroughly 180AmmatCailHand K. Allexpo- American Observatory.The4° prismproducedadisper- tained witha4°objectiveprism mountedonthe24V36" sample areidentifiedfromwide-field (5°X5)platesob- the pasttodiscoveralimitednumberofrelativelybright ification ofthetraditionalobjective-prismmethodsusedin field starswithanomalouslystrongGbands,afewof section wealsodrawattentiontoasubsetofmetal-poor stars. InSec.6wecompareourabundancedeterminations Curtis-Schmidt telescopeat the CerroTololoInter- 1988 BEERSETAL:STARSOFVERYLOWMETALABUNDANCE (1) ObservationsofthelightelementsLi,Be,andBin (1990) conciselysummarizeatheoreticaloutlineofthe © American Astronomical Society • Provided by the NASA Astrophysics Data System In thispaperwereportradialvelocities,metallicity,and As discussedinBPSI,oursurveytechniqueisamod- 2. THEOBJECTIVE-PRISMSURVEY—ANUPDATE coverage of6750squaredeg.TheplatesinTables1(b)for been obtainedtodate.Intotal,thesurveynowcontains the arealcoveragefromsouth. northern hemispherewiththe24V26"Burrell-Schmidtat magnitude 2?^16.0,severalmagnitudesfainterthanthe reduced. Thefainteststarsinoursurveyreachapparent plane restrictsthebandpassofoursurveytoapproximately the guidetelescope.Thespectralresolutionvarieswithsee- means ofasingletrailproducedbyninediscreteoffsets forming gas.Thespectrawerewidenedto0.2mmby objective-prism platedrawnroughlytoscale.Thedark are indicatedinboldfacetype.Figure1showsthelocations which wehaveatleastpartialspectroscopicdataavailable 289 plates,270ofwhichareunique,forapresentsky similar observingstrategy),andarecontinuingtoexpand MacConnell (1973).TheprismspectrasaturateatB surveys ofBond(1970),(1980),orBidelman& filter, skybackgroundissuppressedandspectraloverlap A FWHM.Aninterferencefilterplacednearthefocal ing andfocusqualityfromplatetoplate,butistypically5 sures were90minlong,using103a-Oemulsionbakedin age within20°oftheGalacticpoles. are discussedinthispaper.Asseenthefigure,wepres- some (butnotnecessarilyall)low-metallicitycandidates squares representplatesforwhichdetailedobservationsof Galactic hemispheres.Eachsquarerepresentsasingle of thesurveyplatesonpolarplotsnorthandsouth Kitt PeakNationalObservatory(usingIla-Oplates,anda strong CailHandKabsorptiontypicalofnormalG ently havesufficientplatestoprovideexcellentskycover- hot sdO,sdB,ordegeneratestars(seeBeersetal.1992a). division betweentheAandMPcategories,areas- stars (Beersetal.1992a).Numerousstraddlethe include main-sequenceAstarsandothermiscellaneoushot et al.1991,hereafterreferredtoasFHBII),butalsomay to asFHBstars—seePier1983;Beersetal.1988;Preston ocular microscope.Thevastmajorityofimagesexhibit stars turnouttobequitemetaldeficient;othersaresimply essentially continuousspectraatA3950Â.Someofthese signed theclassificationA/MP.Anumberofstarsexhibit the fieldhorizontal-branchpopulation(hereafterreferred or A-typestars.Thiscategoryisdominatedbymembersof absent CanKandstrongHe,identifyingthemtobeAB- Three tofivetimesthisnumberofspectraexhibitweakor metal-poor (hereafterreferredtoasMP)candidates. exhibit weakCailHandKlineswhichidentifiesthemas K stars.Asmallfractionofstars(roughly1in1000) stellar CailK line,weintroducearather severe the lowestmetallicitystars,based onthestrengthof number ofemission-lineobjects whicharealsoidentified objects. Beersetal.(1992b) discuss spectraofthesmall didates withcontinuousprismspectraareQSOsorBLLac Follow-up spectroscopyindicatesthatahandfulofthecan- on thesurveyplates. 150 AcenteredonA3950Â.Becauseoftheinterference ~ 11.0.Weareintheprocessofextendingsurvey Tables 1(a)and1(b)listthesurveyplateswhichhave The platesarevisuallyinspectedwithalow-powerbin- By choosingtooptimizeour survey techniquetofind 1988 1992AJ 103.1987B 1989 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE © American Astronomical Society • Provided by the NASA Astrophysics Data System 16027 1312.2 15620 1454.7 16029 1602.9 16026 1226.1 16023 1358.2 15627 1531.9 15625 1146.1 15624 1418.6 15623 1358.3 15622 1252.2 15621 1017.9 16033 1314.2 16032 1249.1 16031 1230.1 15626 1336.2 16076 1255.1 16034 1544.0 Plate RA(1950)Dec\bRepeats¡/ 16078 1335.2 16077 1140.0 16545 1109.9 16079 1559.3 16082 1358.3 16081 1203.0 16080 1639.4 16543 1316.1 16542 1625.3 16474 1029.8 16472 1458.0 16471 1358.4 16470 1213.0 16088 1646.8 16086 1519.1 16085 1234.1 16084 1619.1 16083 1500.7 16541 1518.1 16479 1316.1 16478 1055.8 16477 1438.1 16475 1134.0 16473 0849.4 16469 1003.7 16468 0911.6 16467 1337.2 16090 1429.6 16089 1358.2 16087 1620.7 16466 1246.2 +25 10208.0 +45 0876.8 +25 1123.9 +25 12218.3 +45 0983.8 +25 1028.8 +25 11321.3 +50 0678.3 +30 1163.2 +30 12182.4 +25 1028.8 +50 0780.6 +20 12314.4 +55 0686.7 +25 1113.1 +30 12122.1 +25 12239.4 +30 12198.4 +60 0692.1 +30 1151.1 +30 12194.7 +60 0489.9 +35 13186.5 +20 12345.2 +00 09357.1 +40 1179.2 +40 11181.5 +35 1065.0 +45 0370.3 +65 0597.0 +60 0895.7 +55 0584.3 +50 0884.2 +30 1047.5 +20 0536.9 +10 0814.1 +20 12345.2 +35 13182.3 +45 08175.6 +40 11179.9 +15 12266.8 +40 09182.4 +20 112.4 +50 0989.7 +20 12276.9 +40 12176.9 +05 10356.9 +35 13127.3 Table 1(a).Burrell-Schmidtobjective-prismsurveyplatelog. +51.7 +59.4 +87.2 +85.2 +46.9 +84.2 +84.3 +74.3 BS15623 +79.2 +75.7 +64.8 +74.3 BS16023 +87.7 +56.2 +48.1 +83.9 +82.7 +74.7 +67.5 +80.5 BS16479 +40.3 +48.8 CS30301 +70.8 +39.5 +44.2 +79.5 +50.9 +80.5 BS16543 +63.4 BS16553 +72.2 +58.6 +75.2 +53.7 +43.8 +76.8 +60.2 +73.2 +56.2 +74.6 +79.6 +55.8 CS30317 +39.8 +82.2 +40.1 +40.0 +48.6 +82.0 +43.3 16547 1518.0 16546 1418.1 16557 1118.0 16556 1639.5 16555 1458.0 16553 1055.8 16551 1517.9 16550 1358.1 16549 1158.0 16548 1634.0 16921 1426.5 16920 1214.0 16559 1518.0 16558 1218.0 16554 1358.2 16552 1646.6 16922 0847.2 17142 1021.6 17141 1240.0 16926 0917.4 16924 1334.2 16923 1013.5 17140 1121.8 17139 0858.5 17137 1045.7 17135 0917.1 16990 1217.9 16984 1234.0 16981 1437.9 16972 1316.0 16968 1458.0 16942 1255.0 16941 1147.9 16940 0933.6 16939 1538.1 16938 1306.1 16927 0937.5 17138 1422.3 17136 0845.4 16986 1157.9 16945 1045.7 16936 1151.9 16935 0945.5 16934 1337.0 16933 1213.0 16930 1433.7 16929 1310.1 16928 1222.0 +40 12176.9 +35 0457.3 +15 11359.2 +35 13174.1 +50 0477.1 +10 11357.9 +45 1082.0 +40 13150.2 +00 082.0 +30 0450.6 +20 1112.2 -09 47290.5 -09 47269.2 -04 51352.0 -09 52352.3 -04 51356.9 +50 08169.1 +35 12189.7 +35 1274.8 +45 11172.5 +40 13130.6 +40 13171.9 +15 13286.3 +40 10182.3 +45 10175.3 +30 09195.3 +35 1060.2 +35 12188.7 +35 08188.3 +55 10161.6 +10 13278.5 +10 13265.6 +00 10351.4 +15 12331.6 +05 092.9 +35 12188.7. +15 12309.9 +40 13163.6 +35 10189.8 +10 0717.9 +40 12108.6 +20 13238.8 +45 10174.4 +15 11347.9 +20 13252.2 +55 1095.9 +35 1294.3 +35 13157.7 +39.9 +45.2 +72.6 +63.4 BS16478 +38.1 +69.8 +42.0 +41.7 +62.9 +63.7 +75.3 +45.1 CS22890 +52.1 +46.8 +39.4 +76.6 +39.3 +54.5 +57.8 +77.0 +67.9 +40.0 +77.3 +52.2 +48.8 +44.7 +77.6 +68.7 +62.7 BS16945 +38.2 +43.1 +71.3 +69.0 +76.3 +52.1 CS30325 +62.7 BS17137 +77.7 +48.0 +46.7 +76.7 +75.1 +49.7 +56.4 +81.0 +80.3 +72.0 +73.5 +79.1 1989 1992AJ 103.1987B 1990 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE © American Astronomical Society • Provided by the NASA Astrophysics Data System 22166 0059.3 22173 0405.2 22172 0321.5 22171 0200.0 22170 0040.2 22169 0404.2 22177 0411.0 22174 0118.6 22184 0238.1 22183 0057.6 22182 0417.4 22181 0300.0 22180 0137.6 22189 0240.2 22186 0421.3 22185 0322.9 22190 0344.4 22873 1957.9 22872 1623.6 22871 1439.2 22191 0436.0 22877 1318.3 22876 2357.7 22874 1438.7 22878 1638.9 22875 2227.9 22879 2045.9 22880 2043.8 22167 0317.3 22892 2207.9 22891 1916.8 22890 1517.5 22889 1339.5 22888 2310.7 22887 2241.0 22886 2218.2 22885 2019.9 22884 1538.2 22883 1419.4 22882 0027.9 22881 2204.4 22175 0219.4 22168 0318.2 22894 2339.0 22893 2259.2 22176 0339.8 22898 2105.3 22897 2116.4 22896 1930.5 22179 0040.3 22178 0533.2 22188 0044.3 22187 0044.3 Plate RA(1950)Dec/bRepeats| —13 11133.1 -10 05194.7 -10 22170.9 -09 47115.9 -14 43207.7 -04 53176.9 -04 55187.3 +04 58199.5 -09 47177.7 -09 54146.1 -19 38214.1 -24 55221.8 -10 02198.0 -10 22159.2 -05 09117.3 -38 09307.6 -38 09307.6 -35 56237.7 -15 12202.2 -10 19184.6 -04 58128.6 -30 05229.4 -MO 03190.0 -15 15205.6 -15 12193.4 -19 43335.5 -40 13243.8 +09 4926.7 -60 08337.1 -03 3510.8 -40 20358.6 -25 02332.2 -09 52314.8 -35 10354.4 -40 012.3 +10 18358.4 -20 0126.4 +00 502.7 -35 146.4 -10 0351.7 -30 111.1 -40 131.6 -09 58322.9 -10 0956.6 -40 061.5 -09 47356.7 -00 3088.1 -10 1261.3 -15 1542.6 -60 03336.7 -20 2028.1 -65 03329.1 -55 01342.7 Table 1(b).Curtis-Schmidtobjective-prismsurveyplatelog. -75.6 -68.1 -41.5 CS31067 -48.2 -44.6 CS30494 -50.2 -72.3 -43.0 -44.8 -46.3 -62.4 -71.2 -67.7 -14.2 -67.5 -44.6 -54.6 -69.5 +35.9 -79.2 CS22187 -59.2 +52.1 +31.3 +29.8 -42.0 -47.6 -61.5 -79.2 CS22188 -44.6 -52.3 +33.3 -32.0 -76.6 -58.3 -38.9 +34.7 +62.7 -53.9 -33.9 -84.6 +45.6 BS16559 +50.7 -34.0 -67.7 CS30493 -55.3 -50.5 -58.3 -50.8 -28.0 -59.0 -26.9 -38.8 -39.9 22943 2021.0 22942 0053.2 22941 2334.8 22940 2039.7 22938 2253.5 22937 2112.0 22946 0117.7 22945 2339.7 22944 2145.7 22949 2319.8 22948 2139.5 22947 1914.7 22952 2338.0 22951 2148.7 22950 2023.9 22953 0119.2 22958 0158.9 22957 2357.3 22955 2028.2 22954 0238.5 22960 2215.7 22959 1854.0 22956 2202.4 22965 2158.4 22964 1953.5 22963 0300.7 22968 0310.8 29493 2144.9 29495 2133.9 29504 0134.3 29503 0008.1 29501 2109.7 29499 2346.1 29496 2340.1 22936 1850.8 22939 1927.1 29506 2124.9 29512 2208.1 22961 0003.2 22962 0138.3 22966 2340.4 29494 2317.0 29491 2230.9 22967 0118.4 29502 2218.1 29500 0158.4 29498 2058.5 29497 0030.2 29505 0322.7 29508 2238.1 29507 2125.0 29509 0049.2 29510 0220.3 -40 032.6 -34 441.7 -65 29314.2 -15 0439.5 -45 15355.1 -24 53143.8 -34 503.4 -60 10336.6 -29 469.4 -65 28320.4 -49 50347.8 -19 59166.0 -04 4675.8 -39 562.7 —60 16296.2 -04 4183.2 -44 46354.8 -15 0229.7 -04 48177.0 -05 0791.8 -65 08325.8 -25 0619.2 -44 53352.8 -55 08283.2 -05 09153.1 -30 0914.8 -65 02330.7 -04 58183.4 -05 0853.9 -39 571.1 -54 52269.8 -05 09141.8 -30 0918.5 -25 0924.4 -30 1119.6 -30-09 17.7 -3011 19.4 -00 1063.5 -35 089.3 -30 10227.5 -25 1138.3 -30 0815.3 -25 1159.6 -30 1118,4 -15 0936.6 -20 0930.3 -45 07253.5 -35 10254.6 -25 1144.2 -30 11301.8 -00 1168.0 -25 09212.0 -10 1049.6 -15.5 -45.8 -34.8 -87.3 -72.5 -37.2 -20.9 -47.9 -43.9 CS30492 -50.4 -59.0 -24.6 -80.1 -56.7 -61.7 -50.3 -27.7 -49.1 -32.2 -55.5 -64.5 -44.1 -25.1 -59.5 -79.6 -55.0 -64.8 -51.5 -52.4 -66.7 -74.7 -43.8 -29.0 -49,8 -59.8 -69.7 -75.8 -40.0 -85.3 -74.7 -46.5 -43.1 -74.6 -48.5 -41.3 -43.1 -54.8 -77.6 -80.6 -44.7 -69.4 -87.2 -48.5 1990 1992AJ 103.1987B 1991 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE same ashotterstarsofnear-solarabundance. test whichmakesuseofthe19 fields[listedinTable1(a) deficient starswhoseCailKlineequivalentwidthsarethe temperature-related biasagainstselectionofcoolmetal- in oursurveyweexpectany metallicity biastodecouple tained. However,overtherange oftemperaturesexplored follow-up requiredtoapplythis testhasnotyetbeenob- and 1(b)as“repeats”]toidentify theregionin[Fe/H], ^eff phasespacewherethisbias enters.Thespectroscopic © American Astronomical Society • Provided by the NASA Astrophysics Data System We havedesigned(butnotyetcarriedout)anempirical 29513 2322.0 29514 0114.2 29517 2352.1 29521 2258.2 29529 0359.3 29515 0244.4 29516 2218.2 29518 0112.3 Plate RA(1950)Dec/bRepeats|l 29519 0229.7 29520 0439.4 29525 0136.1 29526 0326.4 29528 0219.3 29527 0034.2 30301 1458.1 30312 1538.1 30302 1945.2 30303 2121.8 30304 2352.1 30305 1318.1 30306 1518.1 30307 1917.4 30308 2049.5 30309 2348.0 30310 0106.3 30311 1318.1 30313 1831.3 30314 2045.6 30315 2324.0 30316 0110.3 30317 1438.1 30318 1811.3 30320 1358.1 30321 1833.3 30322 2117.5 30325 1458.1 30324 0013.1 30323 2302.0 30328 0051.3 30327 2157.8 30326 1854.3 30329 1538.0 30331 2111.8 30332 2238.1 -40 11351.9 +04 4968.7 -25 11193.1 -30 08226.1 -15 1172.9 -50 09269.7 -30 11243.0 +09 4883.4 -60 04269.9 -25 10203.8 -25 07218.5 +00 08357.0 -20 09198.6 -20 1197.1 -60 05272.1 -50 05348.6 +00 11318.6 -30 0916.6 +05 077.7 -20 1258.9 -40 04358.1 -40 12343.6 -45 08355.5 +00 076.3 +05 11321.6 -40 11288.5 -34 010.5 +05 09357.3 -35 088.4 -25 1234.8 +10 10349.7 -35 11274.1 -30 002.2 -32 012.5 +05 083.0 -45 09355.3 -25 1132.1 -34 022.5 -20 1272.4 -35 1010.1 -70 11302.6 +09 4878.0 -04 521.5 -25 0922.7 -68.0 -83.9 -64.6 -41.4 -72.0 -84.2 -60.2 -39.5 -44.1 -79.1 -54.8 +48.7 BS16472 -82.0 -44.2 -68.1 -29.4 +61.9 -44.9 +48.1 -75.1 -22.4 -39.8 +66.7 -72.1 +41.1 -76.7 -11.6 -38.2 +55.8 BS16477 -70.9 -81.0 +66.3 -11.1 +52.1 BS16968 -44.8 -66.0 -79.1 +38.0 -15.9 -52.9 -47.2 -41.7 -41.1 -6.0 Table 1(b).(continued) 30339 0022.1 30492 2111.3 30493 2309.5 30494 0405.2 30333 2338.1 30335 1323.4 30336 2035.7 30337 2207.9 30338 2318.1 30342 1815.5 30343 2133.7 30345 0046.2 30344 2245.9 31060 0013.0 31061 0238.0 31062 0034.0 31063 0238.0 31064 0246.1 31065 0055.0 31066 0158.1 31068 0559.3 31067 0318.0 31069 0018.0 31070 0018.0 31071 0317.5 31073 0055.0 31072 0519.2 31075 0333.3 31074 0237.5 31077 0014.0 31078 0258.0 31079 0258.0 31082 0116.0 31081 0116.0 31080 0446.5 31084 0317.5 31083 0317.5 31085 2358.0 31086 0137.1 31088 2338.0 31087 0338.0 31089 0137.0 where theCaIIKlineequivalentwidthsofcandidatestars 31090 0137.0 lution opticalspectroscopyfor some1500ofthesecandi- didates havebeenidentified.We haveobtained1Areso- survey plates(135of270).On theorderof4200MPcan- are <5Â,approachingtheresolutionofprismspectra. from temperatureintherange—2.25<[Fe/H]<2.0, dates todate.The1044stars confirmedtobe“normal” with colorsredwardofthehalo main-sequenceturnoff) dwarfs andgiants(thatis,stars withoutemissionlinesand We havecompletedvisualscansfor50%oftheextant +09 4795.8 -44 48309.4 +09 4789.3 -30 1018.7 -30 0714.0 -35 12337.6 -12 0018.5 -35 099.8 -35 11307.1 -35 118.8 -40 092.3 +04 50166.3 -35 116.5 -15 1286.7 -20 05214.7 +04 50166.3 -15 12106.3 -65 09285.1 -20 10192.1 -15 12129.9 +04 51176.8 +04 47108.7 -60 0026.8 +04 47108.7 +14 51168.1 +09 50162.1 -60 02268.8 -20 12134.3 +04 51171.9 -65 07280.2 +04 51171.9 -40 12330.1 -45 03250.2 +09 51172.2 +09 51172.2 -15 11151.6 +09 47102.8 -15 11151.6 +04 52181.2 +04 4792.2 -20 11182.3 -15 11167.9 -15 11167.9 +17.3 -49.0 -35.2 -46.8 -54.8 -80.3 -48.0 -62.7 -82.2 -43.8 CS22937 -44.7 CS22173 -67.5 CS22888 -48.3 CS31063 -75.2 -77.3 -47.9 -48.3 CS31061 -77.7 -72.6 -41.6 CS22168 -29.5 -56.9 CS31070 -56.9 CS31069 -34.4 -34.5 -82.6 -44.3 -75.3 -44.3 -45.1 CS31079 -40.1 -45.1 CS31078 -76.2 CS31082 -76.2 CS31081 -38.1 CS31083 -38.1 CS31084 -76.8 -50.8 -37.9 -73.4 CS31090 -53.5 -73.4 CS31089 +1.6 1991 1992AJ 103.1987B 1992 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE the orderof20%number ofmetal-deficientstars which shouldbeavailablewhen observationsofthecandi- paper. Ifwetakethesenumbers toberepresentativeofthe sample asawhole,thesubsetdiscussed hererepresentson with metalabundances[Fe/H]<0.0 arediscussedinthis © American Astronomical Society • Provided by the NASA Astrophysics Data System boxes aredrawnroughlytoscale.Thefilled itudes 6=—15°,—45°,and—80°,respectively.The sphere. sitions oftheplatesinnorthernGalactichemi- catalog aredrawn,(b)Asimilarplotindicatingpo- indicate fieldsfromwhichtheMPstarsinpresent lactic rotation.ThedashedlinesindicateGalacticlat- Galactic center;/=90°,¿=0°isthedirectionofGa- the solarposition;/=0°,b=0°isdirectionof southern Galactichemisphere.Theplotiscenteredon interference filtersurveyplatesonapolarplotofthe Fig. 1.(a)LocationsoftheHKobjective-prism/ South GalacticHemisphere North GalacticHemisphere 270 90 -1 1 A3700-A4500 À.Observationsof55starsreportedhere dates containedontheextantsurveyplatesareeventually detectors wereused,thedual-channelReticon(Shectman were obtainedwiththeCassegrainspectrographon our candidateMPstarshavebeenobtainedwiththeCas- able uponcompletionoftheentiresurvey. completed, or10%ofthenumberwhichshouldbeavail- tra withboththeReticonand2D-Fruttidetectors; ignated F.Foralimitednumberofstars,weobtainedspec- tions aredesignatedR;the2D-Fruttiobservationsdes- duction proceduresaregiveninBPSIandBeersetal segrain spectrographonthe2.5mDuPontTelescopeof these starsareindicatedbythedesignationR/Fincolumn Hale 5mtelescopeofPalomarObservatory.Twodifferent Las CampanasObservatory,overthewavelengthrange HP (Balmerline),andGP{Gband),inÁ,respectively. bands andsidebandsaredefinedslightlydifferentthanin description inBeersetal.(1990).Theresults,kms, cross-correlation orline-averageprocedure,followingthe widths forthebandslistedinTable2(notethatline are listedincolumn(11)ofTable5. from themeasuredequivalentwidthsfollowingband- listed linebandsandsidebandsattheappropriatewave- yield indiceswhichareaccuratetoontheorderofÔKP The moderatesignal-to-noiseratioobservations(S/N ences inresolutionbetweenthetwodetectorsused.Col- length. Indicesofabsorptionlinestrengthareobtained BPS I).Theradialvelocityofeachstarisusedtoplacethe by thesidebandsiscorruptedhostsofweakermetallic most metal-richstarsinoursample[(B—V)q somewhat lower(S/N^7-10).Forthecoolestand more metal-deficientstars,hencetheirsignaltonoiseis tegration timesfortherelativelymetal-richstars umns (13)-(15)ofTable5listtheindicesKP(CaIIAT), Reticon observations,takingintoaccounttheslightdiffer- set oflineindicesareputonasystemconsistentwiththe switching schemedescribedinBeersetal.(1990).Thefull indices forcool,metal-richstars isdegradedbyasmuch ration, andthecorrespondingpseudo-continuumdefined obtain atemperaturecalibration forthosestarswithout absorption lines.Asaresultthe accuracyofderivedline (1990). Incolumn(12)ofTable5,theReticonobserva- (Shectman 1984).Detailsoftheobservingsetupandre- 1981), andthetwo-dimensionaldiodearray2D-Frutti available photometry. Balmer lineindex,HP,asweare forcedtousethisindex a factorof2.Corruptionis particularconcernforthe 10 kms“,areobtainedforeachprogramstarfroma (12). Heliocentricradialvelocities,accuratetobetterthan ( —0.5<[Fe/H]<—1.5)weretypicallyshorterthanforthe =0.2 Â,3HP=0.\Á,andÔGP=0.3A,respectively.In- ~ 10-15)availableforthemajorityofourprogramstars ^ 1.0;[Fe/H]>—1.0],theCaHKindexapproachessatu- Moderate-resolution (1A)spectraforthemajorityof For eachstar,weobtainmeasuresoftheequivalent 3. SPECTROSCOPY 1992 1992AJ 103.1987B based onaplotofKPvsHP.Thebroadband(B—V) for themostmetal-deficientstarsinoursurvey,(B—V) our metal-poorprogramstarsscalesquadraticallywiththe color inthetemperaturerangespannedbymajorityof We adoptthislimitfortheblueendofselectioncriteria abundance (seeSec.4).Themain-sequenceturnoffcolor Balmer lineindexHP,tofirst-orderindependentofmetal for ourprogramstars. to beamixtureof(1)hotdegeneratestars,(2)sub- main-sequence Astars,andlikelyfieldbluestragglers,(4) dwarfs withweakorabsentCallAT,(3)blueHBstars, probable binarystarswithsufficientlystrongbluefluxto 1993 BEERSETAL.-.STARSOFVERYLOWMETALABUNDANCE vealed tobecoolKandMstars,someofwhichexhibit objects. AsmallnumberofcandidateMPstarsarere- weak CaIIKinemissionatthecoreofline,typical 0 typical ofMira,RSCVn,andBYDravariables.Spectro- dK anddMstars,orstarswithstrongCailKemission “fill in”theCaIIKline,and(5)afewQSOsBLLac based onavisualinspectionoftheindividualspectra. cool starswithCaIIKlineemissioninoursampleisdis- are discussedinBeersetal.(1992a).Spectroscopyofthe scopic observationsofthehotstarsdetectedinoursurvey the presentstudy,thesestarsrepresentunwantedcontam- cussed inapaperpreparation(Beersetal.1992b).For ~ 0.33,correspondstoaBalmerlineindexHP^4.0A. 0 signatures, whichweusetoremovethemfromoursample hot andcoolstarshavereadilyrecognizablespectroscopic cupied bybonafidemetal-poorstars.Fortunately,boththe ination ofoursampleintheregimeKP,HPspaceoc- TO magnitude. Table 3.CorrelationbetweenbrightnessclassandapparentV The initialselectionofbonafidemetal-deficientstarsis The spectraofanumberMPcandidatesrevealthem © American Astronomical Society • Provided by the NASA Astrophysics Data System The selectionofstarsbasedontheBalmerlineindexHP Brightness Class 13.16 (0.73) 12.42 (0.84) 13.84 (0.55) 14.31 (0.53) 14.73 (0.44) 15.02 (0.27) Complete Sample 12.00 {B -V)<0.5> 0 13.36 (0.48) 12.42 (0.84) 13.90 (0.54) 14.44 (0.45) 15.04 (0.25) 14.82 (0.33) 12.00 Call K18 Call K12 Call K6 G-band Line H H5 7 Table 2.Lineindexwavelengthbands(A). 12.73 (0.23) 13.54 (0.39) 13.97 (0.58) 14.41 (0.32) 3930.7 -3936.7 4095.8 -4107.8 3927.7 -3939.7 4297.5 -4312.5 3924.7 -3942.7 4334.5 -4346.5 « 12.00 ~ 12.42 « 15.04 Line Band 3903.0 -3923.0 4000.0 -4020.0 3903.0 -3923.0 4247.0 -4267.0 3903.0 -3923.0 4247.0 -4267.0 Blue Sideband tion couldclearlybeimprovedbyobtainingphotometry is regrettablysomewhat“fuzzy,”particularlyneartheends main-sequence turnoff(likelybluestragglersorFHB already underway.Thepresentsamplemayincludeafew for theentiresample;aprogramtoaccomplishthisgoalis of oursamplecutoff(AfP^O.5Â;HP~^.0A).Theselec- bounds ofourHPcutoff.Figure2isaplotKP'{KP poor main-sequencestarsneartheturnoff,whereerrorsin stars), andmayexcludeasmallnumberofquitemetal- stars whichare,inreality,somewhathotterthanthehalo the determinationofHPindexplacethemoutside corrected forinterstellarCailKcontaminationasde- scribed below)versusHPforthe1044acceptedprogram lowing theproceduredescribedinSec.5below.Theupper this plot,correspondingtovaluesof[Fe/H]derivedfol- stars. Linesofconstantmetalabundanceareindicatedin envelope inFig.2ispopulatedbystarswithabundances been adjustedslightlytotakeadvantageofadditionalob- with inferredmetalabundances[Fe/H]<—2.0,hasbeen the presentsampleofMPcandidates,primarilythosestars tometry havehadtwoormoremeasurements.Theresults latter reference.)Thebulkofthestarswithreportedpho- servations andtoconformthephotometricsystemof Campanas ObservatoryasdescribedinBPSIandFHBII. the 1.0mSwopeand2.5DuPonttelescopesofLas reported inFHBII.Theobservationswereobtainedwith estimates areavailableweadopttheFHBIIreddening either FHBIIorBurstein&Heiles(1982).Whereboth rections, listedincolumn(9)ofTable5,areobtainedfrom are listedincolumns(6)-(8)ofTable5.Reddeningcor- c —0.5 <[Fe/H]0.0. (Note thatthecolorsofstarsreportedinBPSIhave c Broadband UBVphotometryforroughlyone-thirdof 4. PHOTOMETRYANDINITIALDISTANCEESTIMATES Table 4.LinearfitstoCailKindicesforhotstars. [Fe/H] (B-V)RegionDwarfs 0 -1.5 -1.0 4000.0 -4020.0 4357.0 -4377.0 4144.0 -4164.0 4000.0 -4020.0 4000.0 -4020.0 4357.0 -4377.0 Red Sideband 0.33 -0.39 0.33 -0.44 0.33 -0.51 -9.12 -8.03 -7.67 -7.08 -8.53 -8.39 29.4 26.3 30.3 29.9 31.2 29.5 Giants 1993 1992AJ 103.1987B form V=—3.2E_. and B—Fcolordistributions,respectively,forthestarsin rected forreddeningandabsorptionasabove.Starsnear our samplewithavailablebroadbandphotometry,cor- value. Weadoptaninterstellarabsorptioncorrectionofthe with availablephotometry.Inthefullsample,fraction the main-sequenceturnoff[bluerthan(B—V)=0.45]ac- this conclusionmaybeextendedtoincludethemajorityof rather thanforegrounddwarfs.InFHBII,wearguethat survey arelikelytobedistantsubgiantsorgiantstars, ity ofMPstarswith(B—F)>0.5selectedintheHK strung outalongthehaloasymptoticgiantbranch(AGB) close to50%.Theremainderofstarsinoursampleare of starswithmeasuredorestimatedcolorsinthisrangeis count forroughlytwo-thirdsofthestarsinoursample available photometryandreddening estimates\E_\ tification ofadwarfstarassubgiant. abundances willnotbegreatly affected byamistakeniden- sequence turnoff(Beersetal.1990),andinferredmetal classified belowasmain-sequenceturnoff(TO)maybe objects nearthemain-sequenceturnoff.Manyofstars and giantbranch(G).InBPSI,wearguethatthemajor- dened (B—V)colorforthe275 MPprogramstarswith corrected magnitudesBandV asafunctionofthedered- strongly gravitydependentintheregionofmain- slightly evolvedsubgiants.Fortunately,theKBindexisnot 1994 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE 0bv 0 0 BV 0 0 0 Figures 3(a)and3(b)areplotsoftheVmagnitudes, © American Astronomical Society • Provided by the NASA Astrophysics Data System In Fig.4weshowthedistribution oftheabsorption- > corresponds tothelocationofmain-sequenceturnoffformetal-weakhalopopulation. parameterized by[Fe/H],areindicated.NotetheconcentrationofstarsinregionÄ'/<4,HP^>'b,which line index,HP,forstarsinthelowmetallicitysample.Theapproximatelocationoflinesconstantmetallicity,as Fig. 2.CaIIKlineindex,KP,correctedforassumedinterstellarIIKcontamination,asafunctionoftheBalmer c 0 1234 HP (A) bluer starsareobservedtofaintermagnitudesthanredder between apparentmagnitudeandcolor,inthesensethat i?(yl4400 Á)andF(À5500bandpassesusedforthe stars. Toagreatextentthisapparentcorrelationmaybe There areothereffectswhichmightcontributetothiscor- closely mimicsthesurveypassbandthanVpassband. edly shallowerthanthatinFig.4(b),astheBbandmore weighted regressionlines{lowess;seeCleveland&Devlin photometry. ThesolidlinesinFig.4arerobustlocally due tothemismatchbetweenprismsurveybandpass stronger CaIIKlineofcoolerstars,highersignal-to-noise relation, forexample,theenhancedblueresponseof brightness classesareused:(1) verybright,(2)(3) as metal-deficientcandidates.ThestarsinFig.4(b)with objective-prism spectraarerequiredtoidentifysuchstars exposed aregroupedintobrightness class(4);stars and (7)veryfaint.Starswhich arejudgedtobeideally medium bright,(4)medium, (5) mediumfaint,(6) densities ofthespectraoneach individualplate.Seven signed discreteestimatesofbrightness basedontherelative dian apparentmagnitudeF=13.8. < 0.03.Asisclearfromthefigure,thereexistsacorrelation 103a-O emulsion.Inaddition,becauseoftheintrinsically 1988). NotethattheslopeoflineinFig.4(a)ismark- (centered on>13950Â)andthecentralwavelengthsof (B—V)q <0.5haveamedianapparentmagnitudeF = 14.3.StarsinFig.4(b)with(B—F)>0.5haveame- 0 0 0 For thegreatmajorityofcandidatestarswehaveas- 1994 o oo O'! oo r" PQ 1995 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE © American Astronomical Society • Provided by the NASA Astrophysics Data System

Table 5. Observational data and derived distancs and abundances. s co oo ^ oT H a - 1 Q ^ •-i CT > — ^ 0 CQ ^ tq r¿S CQ & Q £ I ^ 05 lOO00 CS¡ CSCO1—4 00 T}405OpTf O CO-oo1—IOOtPi—I00®®®I>*CN O Ö®®®®®®®®®®® ® ®®®®®®®®®® ® to P 1-4®p COOOtPOOCO® 1—11—4®®COCOtO®pTp 1—4 rHiHi—4 ■^P CNtO 888883 tO TP® ® 05CNtOiH rH ¿OCOtOi—4CN tP ®torHtd p 05®P^ CO ci> ü I ' TjîCOr-H^Tf • lOCO^r-l I O CNCS O CN Ö O t-H rHr-H ^ lOLOT-I CO LOOí r—4 1—11—4CD O rK xr oqcqo 1 H cq as05 lO OOCO 1-H 1—4toCNCO 1-4 Tp1-1®t- t- t>-r>- I I I‘ I CNCO 1—4 cooi CN CO ■ ® • ® I I 1 COCOCSCNCSCSCOCOCO® COCNJ t^CNt^- rH O CO TP I 88 S8 I I II III I I cs pcq CS CO 1—4 r-4CN 1-4 ® ® t- H TP COTfCS CO P 1-4TP oo ® p tP ® <® ® o ® CO TP ® tO tP^ p PTp ® 05COtOTP 5; rH iH® ® 05 I I I I ® CN 1-4 O(TO O H Eh CN (CNtO ® CO00 ^ I ® ®®® ®®®®®®® ® CN iH tO '»P^P 1-4 05 00 051-4 p CN ® I I I » TpI I TP. • ® : p O ® o I I g to cqr-4ptpoqeq Ö CNCS1-4O TP ®1—Iio 1-4 TPp® CO CN TP ® co !.Tp Tp ^P CO ®totpTP ® pt-Pp.p iH rH CN rH tHiH Tp cóCOCN1-4rH ® PTPp1-4 CN iH ® OOi>-00 s § CN COtPtp05TpVH I ^ I I tP to1—Ioo ® 1-4 ,51 , enHEh : Oo C^l CS1—I CS 1—4 ® ® CN)co TP P® 1-4 ® CO ^TP <© <35CNi—I CN I ® ® P rHp CN OOtO1—1 I lili 1 till CNTT I ®^4

22 04 01 37.7 -18 45 25 212.6 -45.1 ... 0.00 0.40 4 F 7.04 3.09 2.71 25 04 01 31.1 -20 51 59 215.4 -45.9 ... 0.00 0.37 65 F 5.13 3.88 1.83 TO 4.52 0.6 0.09 -0.59 -0.72 26 04 01 47.4 -21 34 50 216.4 -46.0 ... 0.00 0.39 5 R 6.20 3.36 1.77 ... 1995 1996 BEERSETAL.\STARSOFVERYLOWMETALABUNDANCE © American Astronomical Society

Table 5. (continued) H 'S X 'S Ü r* Pi ^ 00 Ó? oq ^ tq oq C. ^ o' Q w S Ph

Table 5. (continued) 0 N O S : W o' PU Q H ^ > w i-P CT Sí c/o £3 ü^-v GQ ^ Q a ^ GQ OQ^ I 0 I o® ¿ oSo *OOoogootí Ö cóo 00 OC5 CS CQCO es CS CO1—IrHT-Hcses CS rH05cóCO es cooorHeo tó tíqsPtfPÍPípeífefa o < P 1-HTfLO05t-O O COPrHOO05eo1-Hb-t-p. co LO CSo CO 00LO.-_ 22 ^ eo rHescs LO OO051-Heo LO rHcs“— t- Tÿ00coLOCO es cs co eo 05 uoeo00t-rHco CO LOloes ooooooo p P1-H05 o O ÖCO ppppppp ooooooo cs n I I I I I O Xfocs■ Tf rf I coCO J ^p LO co lili • T-irj5 • po . UOb-1-H : oes • 05eooo , «—ICSIOt-HCS^-It-ICSi—I I ©eo rH CS Ö ÖÖÖÖÖÖÖ CSi—íes 05CSI>-^ eó esco oq p Ö ^ p o LOco o I I CS 1-H I 1 T—t CSCOCNr-l Tf COO Ö r-iOT—5»-HLOr-H P b-;p»-Jes ^ coTfeo LO O^rHoCS LO rHoOCOeo cs i>-rHeoes 05 00C75 ö oóloes tH csI1-HrH CO OO^05It- 00 rHcsCSl>-051—1 rH rH HtPo co COLO CÓ r-íÖ1-Hö05 Tf pPr-Ho co eoustp ÖÖÖÖÖÖÖ rH 05oLOO rH eo pcorf 05 ooPcoeseo ooooooo 00 rHcoP^ rH OI-HesPCS I I liliII I Il III i cseoes 1 I I i COCScsoo I 5! I CS Provided bythe NASA Astrophysics Data System I ¿ CSOTfCS COOOOOTfCSrHOOi-Hi-Hes CO 05O CO Tfp LO eoo P CO00 P O O co pppp tnppp pppp co COLO p o Ö lili * fa • ffi . CQ • Ö , CS , «o : es : es o I I I ^ Tt : ö , lO 05 I co eocscocoocso5ocot—o oo eseor-icsoot^T^escoco^lo oppoq prHi-npppppp ^ 05COPPLOCOrHOt^PO pppp r-í ^coes O PrHo öööö oööööoöö oppp pppppppp Tf ^ ^ ^ es1-Hö oooo oooooooooooooooo oooo oooooooo lili . ppPQ • Pow I pTJHP^ , ICS1-HrH , CO00Tf05 ; cs- n O LOTf1-H Ö 1-1 es I I o co I I CS T-Î o es lO Tf rH escs 0505rHO00rHOO eococococoeococo cococoeocococoeo Ö^^^COLOt^Ö OqppprHPptH cococóiot^^eó^ cococoeocococoeo 05 esrHco + H--f-f-h I I I CO ; ör-iest-ío . p1—j , 1-H^0rH , CO1-Hi—It—Ir-l , 1-H«OC—1—I

, 00 ^ 05 . rf o CO LO COCi ^ COtF COr-t OOCO CN- CO TF p p t-. ' CÓ Ö Ö CO Ö O ^F CO rH TF CO CO CÓ ^ CO O TF ^

P-< O ■oooo o o B o o “2§ ; ;o82aH H <í Cmä2oo 1 : H H H H H H S H H ppppOTF^Fb-r-npCiTF^FOOr-HCOOOrHCOCO oS OCOOtF OOCS^HOCSCSCN' Or-HCS^HCOr-HOTFOCO Or w ^ tFlO pCO CiT-H rHF- pCO COCSCOCOCS CO CO CM O CO ' ICSCOOCOCOO CO CO ' I CS CS — I I rH I CM I rH I | CM | CM | I I I o' ttlc, ooooo oooooooooooo oooooooooo ooooo i-Ht- r-Ht- r—^t- r-Ht— i—Ht- r¿E Ö Ö Ö Ö Ö oooooooooooo oooooooooo ooooo QQ ^ CMrH CDO .• OTF OCM OCi O rH CM LO CMO CirH 00O I o o o Ö Ö ' Ö Ö o Ö Ö Ö Ö Ö Ö Ö I I I I I I I I

1 £ , p TF p cq Ö Ö o oooo CO LD .CO . CO p CO LC TH rHCOpOpt^pppppp pp^Fppppppp COrHCMTFOi öCO oCO öCO ciCM qoCM cococococococoeococococoOrHrHrHOrHCMCMCMCMCMTF COCOCOCOCOCOCOCOCOCOÖCMCMrHÖr-HrHÖrHrH LOLOLOLOLOCO t>- b— OO b- + H-H- + + I I I I I I I I I I I I + + + + + + + + + + I I I I I tF P P p tF TF t>- P p P P p p p p p p ppppb- CM CM CÖ r-H cm t^t^t^t^LOoooocioooót^LO ciOrHOCMCOCOTFTFTFTF^pb-jp^TFpTFp Ci rH oô o Ö cococococococoeococococococococococococococococo eocococococococococoCMCOCOCOCOCOCOCOCOCO COlO COlO O^-v t— CO b- lO lO ’ w «S co TF "«F TF LO ■ Q oooooCM rH rH CM CO lOlOlOlOCOlOlOlOlOlOlOCOCî Cî Ci Ci rH 0O 0O b— OO Ci Ci rH CM CM CM CM TFO CiCO rHTF CiCO CiCO I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I CM b- LD tF pOpb^ppppTFpprH CM rH CM CM CM CM OO CO p b- p p CMTFrHCO^COCOOLOCMHFOrHCMr-H-rFr-HLOCOrHCDOOTFCO OLO CO^F CM OOrH oco 00rH OCM COCM OOCM LOCM CO CO CO CD CD ^H ^1 ^ tF 29 22 26 30.0 -39 13 11 2.0 -58.2 13.68 0.40 0.00 0.39 70 R 1.90 3.39 0.46 FHB 0.60 4.1 0.22 -2.45 -2.88 38 22 35 33.6 -39 28 15 0.8 -59.9 0.00 0.41 -86 R 5.30 3.01 1.64 TO 4.33 0.11 -1.02 -1.10 43 22 39 28.6 -41 47 34 355.9 -60.0 0.00 0.40 -18 R 7.43 3.16 2.27 I b- b-LO 00CM OO

CS O CS cs CS CS C** ' O rH r-H CM CS CM ® CO CM i I CM CM CO CM rH : CM CM : CM CM I I I I I I I I I I I I I I I I I I I I I I I I I I I I 05 00 05 CO COiO O CO ^05 '< 05 lO rH lO Si W o T-l o -I CC CN CS CM CS CM r-i CM fa < O CM fa CM CM O ; cm i ; CM CM farV ^ I I III III till I I I I I I I I I I I I I I I I LO t- . ® 05 oT 1-Ht- CMr-H 051-H Ot-H CO1-H rH1—I TFt-H i, rHto toi—H COrH LOT—( Or-H 1-H . CM CM o o o o o O Ö Ö Ö Ö Ö o ■ O Ö O O O o ® o o o o o • O ® H 05 CM U- t>; «pÇOrHO-T-HOOCM CM rH U- • CO CO CO lO CO CM • O OO • 05 rH W 00 ööfaöfa fa CM CM O fa O fa fa fa Ö : fa CO CO fa fa to ; fa ö ! fa to . O rH LO O lO I ® rH CO ® . 05 CO • Tf< © Ooôoo^ LO 05 <£> 05 couocococotô® LL*/t— O O W’WCM CM Vw^lO OOO 05 05to ■ TtJ tr. 05 cq co i cq oo cq • tH. © • cq fa fa CO CO CO fa fa CO fa fa fa CO CO CO CO CO fa co CO o o ’ fa o có co ö CO fa CO O I , m CQ OOOOO c5 c5 O P O O O : p O • o o - nP W p •og HHHHH . H H : h h ’ ^ fa «ä fatóPÍtíCtífafaDÍfafa tótfctfoáctfctíodaíoápá K » ©rH00©©lOO5rHl>.© kJ c? ©©CMÍH©©©©©CM ©t—«^©©'^©©Tr^tOrHtr©^- rHOOfarHt^tqrH©rHTjH©t^ ^©^lOT^CMb-COCOCM fa 3 ©rH©©rH CM rH rH© Tjl| CMU- ©CM CM CM CM CM CO I 11^1 > ^ I I I I I I I I I I s © rH O rH CM rH rH © to © OO OO CM © 0 Tr2 22cq 22cq SO; 2Scq - • oqt^rH -©t^tH;CM © ©oq ©CO • ©CM CM oo • cq oq © CO Tf Tf Tf co cô ! to fa ^ 5> rHCO ; farH rHCM rHto . 1-HCO TfrH COrH fa fa co ! fa fa ; fa fa có rHrHrH©rH,^©Oqiqi>;CqrHrHtr- oqoqt^CM©©©05©t^ OOÔrfU- COOOCMCM©T^CM©tqt^ ©©©t^tî>ôóoó©oó u—co © © u-fa fa O CM CO CO CO CO CO O © CM cocococococococococoeocococofa fa tO fa © fa CO fa fa fa fa CM CM CM eocococococococococo I I I I I + + + + + + + + + + + + + + + + + + + + + H-4- + I I I I I I I I I I 00 rH CO t- ©TfCMCMcqoqrHTfO'^ b-h-ooôqo5rHtq©©i^CMTr© T^T^©oq^ft>-©05©oq fa CM fa CM CM © fa tO tO 00 rHcocococoeocococococo rH rH rH rH rH rH rH rH rH I © © rH CM Ü ^ ©©rHCO©CM©Tf^CM^fCMCOT^©rH©©U~QOCM©©0'^00©Tfl fa «2 00 CX) 00 00 Q CO CO CO CO CO CO CO CO ^ ^ CO I I I I Il I I I I I I I I I I ++++++++++++++ I I I I I I I I OO © © U- CM © © © o oo © oocM©©©Tro5©oqoqt-;©05tq © © CM to ' © CO © ©fa©tôóto©eo^-facM CO CO © CM CM rH © CO & cococococococoeococo ©©©©©©©©©©©©©© CM CO CO ^ I

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© American Astronomical Society • Provided by the NASA Astrophysics Data System Table 5. (continued) w J o Q W «S ^ o' « ^ 3 ^ 5^ DQ Oh ÇD M S' U I ^ I £ o gg ;000;O-o o • CN CN 00 © OOLOTfCNTfCNCNOOCN©CNt^©CN©t^© Ö CN O CN LO O ©oooooooooooo© OOOOOO ©©©©©©©OOOOOOOOOOOOOOOOO©©©O©O S! Tt rHco00OS OStOI>-CNuOt>- Pi oítí^>tí CO ^ to t'- o cs ^3;ot-î pr-HCOpp©©CNCO'iti—I 1—1 CO ^ Oi.a>CO Tt LOCNCO O pTi : Il 17 I lililí lililí II III I ICNCOCNCOCO COCOCOCOCNCNCOeOCOCN' O CNi-H CO NfîCN s?g5!S :hhh :ei:h ■ ^ ■ TfCOO•CN ■ oOI-os ! T-ÎT-i1-ÎÖ ■ CNO•O- : o- I I CN lo Ttcó:t^í CO 1-HOOTt rH CN©.p I > cot>*i—icocN eot^Ttooososcoo cococococococococococococoeo eôcNi-HCNCNCNcôcoeôtOTicÔTtco o ^ OSCOi—itO0OCNi—I00t-O Ttr-HCOTtt-t-t^lOrHTHCOCNi-HTt HtCOCOtOCN' OOr-Hi-HCOTtCNr-ÎÔOàOÔOrH Pi-Hpppppr-HT-Hpí^ppp CN 00 00 CNCNrHi—IrHi—ICNCNCNCNCNiHiHCN rHOOOOOOO©OrHiHrHrHQO©CN CN cÓLOb-3t^r^coTtTtHtHtLoi>3t>3Tt ppt^PPPpT^rHpOt^-t^Tf r-HLOO^LOCOCOOOlOOOOOO I I I 7 1111117i : ö 00 O I : gog|ggo||gO|g •ooooooo oooooooooooo : Ör-4C5CNT—¡ Ht TilCOCN^ «Opt^OSrHCOl^- O ^HCOCNCSi-H I • o o Tt lOCOT^HIO p ©CNTt r-H CMCNo III I I I COCN©00 CO CN I 1 LOtOtOLOtOLO©©©iHi—IrH lO©©CN©©TÍ©©iHeOCO TtTiTtCOTt^^^CO^P^^ iHrHrH©rHrH©©©0©© co LO lo CNCNCNi-ÍCNCNCOTjHHtLOLOLO oooooooooooo s: tíCNCNtílOlOlOCOtí LO lo ©©OCNO©OOiHi-h©iH Pppt^ppppr-Hi-Hpp OOOOOOOOOOOO oooooooooooo co ooicoocotoo-cooscNi TfOOOOi—!tOLOOTFCOt>-©tO TtOCOOCOCOCOOOCOCOO oooooooooooo oooooooooooo 1-H ^r-HI1-1 rH CNi—HCOr—t I I I IIIII I i Ttco’ I CNi—IOi-Hi I CN' © LOTi “lOCOCNOiOrHOSi-HTtTt I I ilOr-JcNt-HOOTtT-H^HLO I T-H1-HCNCO' 1 I I COCN 1 I LOrHCOOOOCOO CO©CN> i CNOCO' ©OOOO ©COCN CN I CO CNTir-3lO CN COb-1-1co OO 1-HOSCN©LO CO OS00^ CN CO1-3 00 ooOOO0 1-3 CNcoCOLOlo 05 O.rHcopCO 1-H CNpT?Pt>; P 1-jTtCN OS PO00CO Ö r-î1-3OrH1-H Tt p»-H rH Ti©CN CO CN iH ©00 © P p CO Ttb-OCN Ö OS CN © TiCN■ CO LO 1-HrH( CN CO t» CO1-HrH00< I I I 1 I I II 3 CNr-3i—Î • TtrHOCN • Ö . CNOÎOCO ; CNr-t ' CNCÔCOCÓTt ■ COOOpt-;O , TtT^iOLO , O1^T-lrH o O CN T-H lili I I !SSSS LO ©00 2000 2001 BEERS ET AL. : STARS OF VERY LOW METAL ABUNDANCE 2001

LO1-H Tf05 00ÎO CS »-H CS CS CS r-l CN CO cocsi-hcsococscs CM CM O to to I I I I I I I I I I I I I I I I I I I I I I I I I I I I I oqSO loTP oqCO 1-1os 00co- < to to to to c-O05CMi-ji-HCOrHCMCOrH ..COCMi—l CO 05 LO Ö Ö Ö Ö O Ö OOOO ööööo oöööööoö • Ö Ö Ö fe OSCMCM^fCOCM 1-HLOCMcq 05 CM 00 O 05^TfCOt^-050CO • LO t- 1-1 . CO CM 05 O 1—t 1—I rH r-H 1—( rH i-H r*H to CM to Ö to to tototoiOOCMtoto ! co co to : ö to 0 00 O CO rH S : 05 LO 1-J TJH •. 00CO CM00 ^ co co ^ eó co to o o co tt co co coeocooTfOi—ico CO CO

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lO^T^TfeqrH rH Tf CO LO^eqcqTiHcqTrTfCMcoLOrHTflCOrHCMOOCO^t^i—llOCMCO o OOrHOOO rH^TOrH to ö cp CM Ö Ö CM CM-TfOCOOCOCMxfO1 CO O O O CO O !>. lo tjh cq rH^ CO COrH 05 1—! LOOCOCOO'^ 05 CO OO rH I CM 08 ^ CO ^H CO CO CM CO CO CO CM to CO CO tocoeocMco co co to to cm ’ CO CM Ö o CO co co co co cm co co CM CO CO CM rH CM CO 00 CO CO rH CM CM iH iH CO LO LO b- • LO CM QO LO O CM LO CO CM CM t'» CM CO Pen Pm Pd pd Pd Pd Pd pd Pd Pd Pd Pd Pd Pd Pd Pd Pd Pd Pd pd pm pm ph pm pm pm to ^ QO rH t- ^ 05 O OOrHrHl^-TfrHCMLOLOC^TrCM CO Tf rH CM 05 rH 1—I to m t>- rH CO O CM LO 05 CO CO COCM CM COrH CM CO CM CO 00■ 10■ 00■ Tf 1I CM rH05 i i I 7 1 7 1 I I I I I I I I I I I I I ^ o' 00cq OT}^ cq05 CO00 LO cq05 COQO 000000 OOOO 00000 000000000000 Ö O O O Ö Ö Ö is. OOOO Tf Tf Tfrl Ttft ¿S OOOOOO OOOO rH rH iH rH rH to 0 0 o o 0 0 Ö O Ö Ö OOOOO OOOOOOOOÖÖÖÖ ÖÖÖÖÖÖÖ CM rH COrH rHTf C?tH rHCO CM i Q OOOOOO 0 o o 0 o o 0 0 0000 o 000 o o I I I I I I I I I I I I I I I I I I I O LO O Tf O 05 IH t- ^ 1 £ LO rr CO o ; ^ cm to OOOOOO Ö Ö Ö OOOOO o Ö Ö Ö Ö Ö O Ö lo oq 00 cm to LO CO co to to to to to to cô to co to to lo TT co CO . CO Tfi TP : to to co 05 Tf Tf TT CO in cq cm 00 t- LO t^-rHT^LOcqiocqcqcqb-coc? «Ô lO CO CM CO CO cq oq ^ rH cm to o CO CO CO CO cocococococococococococoCMcoeococococotototoLOio to00 00to 00to 00to ‘oóto 00to 05^ I I I I I I + + + + -I- + + + + I I I I I I I I I I I I I I I I I I I ^ lo cq oq lo 05 CO CM 00 ^ Ttj cq o cm CO C5 rH LO LO CO CO 05 CO rH lO cm to LO CO CO 05 O CM o co LO to co to to lo ö to CO lo 0Ó to 05 COCMÖOsÖtocMCMtoCMCMto 05 Ö rH rH CM to CM COLO ^CO CO COTT LOCO COLO coLO LOco coLO LOco LOco LOco coLO COLO to LO LO LO LO LO LO CMCO iHCO Tji05 coCM CMÍH CM05 O^s i?: 10 -- - ^ ^ ^ ^ ^ w O O CM rH O rH 05 05 rH rH rH o IH O 05 Q CO CO CO co CO co O O IH IH rH o rH o coeoTfTfTfTfcocococococo00 05rHrHOO00 00^-05 05t^ rHO o05 O00 O05 00O O 00O LOo' I I I I I I + + + + I I I I I I I I I I I I I I I I I I I I I I I I o I CO QO !>• O 00 Ih CM CO LOOSCOLOOCO^ft^CMOTfO tH to cq to co lo cm rHto tolo toIh cmto to ot>* to10 , CM CM rH rH rH CM 00 OiH OrH 05 rH torH COrH to to to to LO LO LO LO LO iH to CO 05 o CO 26 22 16 03.9 -09 57 44 51.4 -50.0 14.89 0.43 -0.19 0.03 0.38 -70 R 3.45 3.67 1.33 TO 4.05 1.4 0.16 -1.71 -1.98 28 22 15 30.3 -10 16 54 50.8 -50.1 15.49 0.40 -0.15 0.03 0.37 -192 R 1.88 3.75 1.06 TO 3.90 2.0 0.19 -2.12 -2.58 29 22 13 32.1 -10 21 37 50.3 -49.7 0.03 0.50 -19 F 8.15 2.18 4.17 TO 4.35 1.0 0.13 -0.98 -0.70 CM CM CM CM CO CO ’ S? SS ! 31 22 12 19.3 -10 40 52 49.7 -49.6 ... 0.03 0.37 -33 R 5.62 3.96 2.42 <¿1 ct 00 00 00 CM CMs

© American Astronomical Society Provided by the NASA Astrophysics Data System 2002 BEERSETAL.-.STARSOFVERYLOWMETALABUNDANCE © American Astronomical Society • Provided by the NASA Astrophysics Data System

Table 5. (continued) s w % S’0 ^CS Ë s' w ^ o Q oq ^ CU o' Q S s DQ * ¿S I ^ i £ 1 O OS«O1-H00 CN| CS00.COo iO Tfio00b- ©©©©©©©©©© P ^ CS IrHCO1 rH ©^(_. Oh PítóPmfePdOdEmCmEiHpdodPC^C£h tocoiooicssooóoósouó b^CS^CSb^lOCO^COCSeÔrHSOiOrHCOT^CScÔOSCSCS P^rHppppb^'Sjb^ p^pb-;pp©pb^p-^pp^ppb-ppT^p© 00p©©00©CS00T£t'- ©T^CO©CSCS©©©CO©©CO©©b-rHCS©CS^rH rHCOCSCSCOrHCSCSCOCO CSCOCSCSrHCOCOCOCSCSCOCOrHCSCOCOrHCSCSrHCOCO COrHCSlOOCS^LOCSCS TrpOrHOppOrHO ppp©p©©pTT't^t^-p^pCOCSpOOt'-CSOCS ©©©©CO©CSrfrH© ©’SfCS^brtTCSt"-©COtrrHb-©CS©rHlO©CO©CO o|g :go;::giggggggggOë © o CS rH o4 »-Hr-îICSr—i lo o;.poq CS csiT-4:rH ©©©©©©©©©© rHrHrHrHrHCSCSCSCSCS b-©b»©©CSCO©SOTF "^F ©COrHCS S0©CS03©rHC0©C003 ©pb^prHpprHHtp ©©©pb^pp^b^CSpTFprH- rHrH©©©©rH©©© ©©©©©©rH©©© ©©©b-©b»©©©CS CO Tí? © b- ©rH ©rHrHCSTFCÓCÓTF©© 00TFb-©r-lTF©O3TFSO ©©©©TF©©©©© ©rHÖÖoirHCSrHrH© b-rHCOCS©rH©eO©b- b- Tf© COCS©CSrHCS©TFCO© ©©©©©©©©©© III II III II I III I I T— • © • ’"’ij . © .00 .SOCO03OOT—I : o : o 00 COOSi-H-'tfb-COCO I I rHCOO©©CSOOCS ©©to©©TrTrt>- CO ©CS' OÖÖOÖOÖÖ ©©©©©©©© cocococococococo ©©©©OOO© ©©©©©©©©©©©©©© rH rHO©©OrHrHrH ¿ ©©©©©©©© COCOTFrFiOSOLOb^ pb-ppppprF ©©©©©©©© tF côCO^SOb“ b-b^pppppp I ^ I I • PrH©p * CO^ , rHCSC5CO , rHCS , ©COCSrH©©COTÍ<©^©TÍ<00©^eO©^ ; CSr-îesrHoO . CSp^ : «O OCObr SCS ©rHpb* Ö Oooooooooooooo© I I ^ rH«p O rH I CS© ©©©©COrHOrHCS©©^rH eoeo^cocSTt.CSTFrH ©©©SC3brb*-b-b-b-03©©03 b^ppr-HppCSppprHpp © t>TfTjH © -©o©©©© b-©COCOb-©©COCOTFTF©© Tjî ^TFrjî I I I I I I tF xFrF ©©©©©© I CO rHCSo rH COO©CSb~ I CO ©b-©' 1 ^Il I ©cs I rH©CO . © © I © ^F 29 13 39 28.3 -11 41 56 322.0 +49.0 ... 0.03 0.44 15 F 3.83 2.67 1.28 TO 3.98 1.2 0.14 -1.91 -2.12 38 13 40 08.5 -08 31 47 323.8 +52.0 ... 0.03 0.45 -53 F 2.92 2.60 1.00 TO 3.82 1.3 0.15 -2.29 -2.57 45 13 41 07.7 -08 25 23 324.3 +52.0 ... 0.03 0.41 2 F 3.69 3.04 1.13 TO 4.06 0.9 0.12 -1.67 -1.92 2002 2003 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE © American Astronomical Society

Table 5. (continued) s s S’ 0 S’; CO 00 ►¿i oT H ^' CO SiS té Q ^ 0 Ö CO oq °Q ^ ciS I I £ Tb corbcs’eo ot^p b^t^co-ppo rH CS00IOCO•OOTbTbcs b-1 IßLßTbCOb^ Tb CO p Tb o COCOCOCOißißLßCOCOCOCOCOkß -HH-ll-f-4-+ lllllllllllll I III I I COTbCSrHOOCOOCOOOt^COCSCSCOCOCOCOb-co' CO Tb ooo . OS£ : cs I I S TbOUOOTbTbbÔOi-HOOO co cs oo COCSrHßOOßrHTbTbOCOCSrH CSrHrHOb-OOOSOCSrHrHrHCS CSCSCSCSCSCSCSCSCSCSCSCSCS rHppppptr-pppppp ÖOoÖÖÖÖOOOOOO Tbpt¿pTbTbb-Tbpb^pb-;p COb-oOSOOOSCSOSOSlOOSr-HrH 05 kocócócócob^b^b-ôóoócscsoó I I ; rH»-H'OCOCSC^COCSCSCN .!> .IO.tÔt^rHOCSOSiO :g Í cs CO 00LOrHlOíOi-HOCOrH OOC51—iTbßt>-00C5OOOCS rHißLßcookßCscsob-ooco I ! rH CSI looseoi—tcocsoocs Tbt^b^rHOSOOUO«OOSTbl Provided bythe NASA Astrophysics Data System •ö -ÖÖÖÖÖÖÖÖ*0000 .Tb .rH^COrHCOrHCOCS.rHt—Hr-H . 1-H. ö I I I

52 22 14 18.9 -16 54 26 41.1 -52.8 13.18 0.78 0.14 0.02 0.77 -75 R 3.77 0.71 5.49 G -0.23 4.7 0.23 -3.00 -2.92 56 22 16 29.9 -16 22 18 42.3 -53.1 14.11 0.46 -0.19 0.02 0.44 55 R 4.50 2.66 1.37 TO 4.06 1.0 0.13 -1.68 -1.82 2003 2004 BEERS ET AL. : STARS OF VERY LOW METAL ABUNDANCE 2004

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05 CO O CO 1-H ÇSI r-H Ö CO CO 1-H CO co co eo co t-H CO o rHOr-HOCOrHr-HCOOOCOCOrH I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

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Table 5. (continued) BEERS ETAL.:STARSOFVERYLOWMETALABUNDANCE 05 U] W o P-I io > ^ h-3 CT ^ o' Si ÛQ ^ 0Q ^ ¿S I 0 I CN OrH. OOOOOOOOOrKOOOOOOOO CMi—<*—li-HCMOCMCMOCMi—iCMCMCOO*-it--i COT^THTfCO^COCOTÔ^COCOCM^Tf^CO oooooooooooooooooo oooooooooooo r-ii-Hr-Hi-Hi—JÖÖÖÖoi' ^pî-HuooqîM-oop' CM It-H1-Hi-HIt-HCMi-H OlO |i-Hl00550t^05rHOCOCMt>-r-H05 O00CMt-CMi-HOOO05OC0i0Or-HO05t>« coeococococococococoeccocococococceo pt^-ppT^pOppXfpppt^-pi-Hpp oooooooooooooooooo pppTj^pT^p^Ttp CM CM s; tî-Ht^pHtpt-pi-Hpppppt-.pt'-CM LOiOkOtOLOkOkOkOLOkOLOLOLOkOkOkOkOiO t^lOiOHÿcÔCMcÔcCcÔ’^’^t^t^tÔ’^lOO coeococococococococococococococococo côc<5côcô'^kr5iokC’^TfTfTfTfkOkOkôoo oooooooooooooooooo oooooooooooooooooooo TfCMt^lOpi-HOOTrOOtÔOLOCOTfT^^bcMTf tÎ^HtppppCMppt^ppppppp _05O1-HCO I I I I i i05CÔOkOOCMCMkbtÔCMCMr-HTfeOCOi-3 Il I'’ 1-H OCNCS CM O I I CMCOOCMCMCOCMCOCMCOCO CMpr^pppppt^pCMp CO CMO' I ¡ rHCMö1-Í ! CMlOO05 CM COO(M I J - O CO :s

53 32.9 -62 56 48 313.5 -53.3 2007 2008 BEERS ETALr. STARS OF VERY LOW METAL ABUNDANCE 2008

CO »-Hco 05lO©l>^l ^ to © o I

rH ©!> © © © ëg © rH, rH © © TT CS rH Tjî © CO©©©CSI>CO^CS©rHTr©rH©eO©COCO CS © rH CO CO © ^ © w 3^ COCSCSCOCO CS rH CO rH © CS CS rH CS ’ rH CO CS CO CS CO CÓ CS CS CO ©rH «5© ©CS ©b*; rH© S©©©rH©TH©00©©rH©t^-rHTÇ'CSrHCOococot^-oo^cOLOoqcscocooqcoco©©© äs rH CO © CS CO © CO CO CO © t^Tji©Tiî©co©©©csTfoôcs©cs©©côi>^ cs © © CO tó tí ptf p£ ptf fe fe fe fe fe tí tí tí tí tí tí tí tí tí tí tí tí tí tí tí tí ^>tí tí títítítí © cs © © ©COrHT^Ttl HCS©t>-©l>-CS©rH©©©C^rH © © cs © ö S CS IH © © © rH b- I1 © (H rH t>- rH © CO ^ © © © © © rH^ ©CS CSrH rHCO > w I 7 I I II I I ’T I 1^1 ^ I lili s ^ 0 CO ^ Tf co Tf<© "TTrH ©HH © ©rH M ^ ^ CQ^ © © © © © © © © © © © © © © © ©O©©©©©©©©©©© © © © © © © © © tq © © © © © © © © © © ©©©©©©©©©©©©©©©©©©© © © © © OQ^ CSLO rH ©rH cs© rH© -H© ©^ ©rH © © rrf © I O O © O © © © © © © © © © © © © © © © © © © I I I I I I I I I I I lili lili © © © cs , © rH © © I £ > TJH Tf CO Tf CO © CO to oq © © © © © © © © © ■ © © © © © © o o t- rHCS ©tO 00© Tf Tf Tf Tfl Tjl ^ CÓ CS CO . CO ’Tf © CO CO © © © CO rH rH rH © © OO CO'«CCSrHOOCSrH©t^-t^rHO©©rHÇO©0© CS tH rH ooCS ooCS t-© OÓ 0Ó csCS csCS cocs ^cs cócs Tjr-rCTf^fTtiTfrrC-rrt>^tHtHOÖtHOÖo0aio6©OÖCrioÖÖÖrHtHlTfTfi©©TtltO©©©©xrl © © © © I I I I I I I I I I I I I I I I 1 I I I I I I I I I I I I lili rHOOT^t^CS ©©©©CS t^00rH©Tf©©©00©Tf©©CS©-r^CSCO© CO rH CD OO !>« OO 00 © © cscs©©coco©ooco©©©r^TttC(-,050l0^( coTf coTf eoTf eo© coTfl co© co© co©

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© American Astronomical Society • Provided by the NASA Astrophysics Data System 2009 BEERS ET AL. : STARS OF VERY LOW METAL ABUNDANCE 2009

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Fig. 3. (a) Histogram of the distribution of visual magnitudes, corrected for interstellar absorption, for stars in the present sample with available photometry. Bins are 0.25 mag in width, (b) His- togram of the distribution of broadband color, corrected for interstellar reddening. Bins are 0.05 mag in width. Fig. 4. (a) Apparent B magnitudes, corrected for interstellar absorption, as a function of dereddened color, for stars in the present sample with available photometry and with reddening estimates brighter or fainter than the ideal case are divided into the Eb_ y < 0.03. The solid line is a lowess regression line, (b) As before, remaining classes. Clearly, the true apparent magnitudes of but for absorption-corrected V magnitudes. Note the shallower slope the catalog stars within any given brightness class will vary of the relation in (a) compared to (b), primarily a result of the closer match of the B photometric band to the bandpass of the somewhat from plate to plate. objective-prism survey. Although the correlation between assigned brightness class and apparent magnitude is expected to be coarse, some information can be recovered. Figure 5 presents box with colors bluer and redder than (B—V)0 = 0.5, respec- plots of the observed apparent V magnitude for the subset tively. Note that there were not a sufficient number of the of 371 stars in the present sample with available photom- blue stars in brightness class 1 to draw a box plot in Fig. etry plotted as a function of their assigned brightness class. 5(a). Insufficient numbers of stars also exist for brightness Figure 5(a) pertains to the subsample of 275 stars with classes 1, 2, and 7 among the red stars in Fig. 5(b). We (2?— F)o < 0.5; Fig. 5(b) pertains to the remaining 96 stars have assigned both blue and red stars in brightness class 1 with {B— V)0 > 0.5. From the interquartile range of the a median apparent V magnitude of 12.0, which is the value individual boxes, we judge the 1er scatter in apparent mag- obtained for the sample as a whole. For red stars in bright- nitudes estimated from assigned brightness class to be ness classes 2 and 7, we have adopted the values of appar- roughly 0.4 mag. As is evident in the figures, the stars with ent F magnitude obtained from the blue sample of stars. (B—V)0 redder than 0.5 have apparent V magnitudes In Fig. 6 we show a two-color diagram for stars in the which are on the order of 0.5 mag brighter than those of present sample with available photometry. At least two the same brightness class but bluer than (B—V)0 = 0.5. obvious sequences are evident in this diagram. The upper The numerical results are summarized in Table 3. The envelope corresponds to the position of a highly deblan- second column of this table indicates the median apparent keted two-color line for main-sequence turnoff stars, sub- V magnitude corresponding to each brightness class, along giants, and giant branch stars, plotted as filled circles. A with the interquartile range in parentheses. The third and few of the stars are identified as members of the upper fourth columns list these quantities for the subsets of stars sequence even though they fall well below the bulk of the

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1992AJ 103.1987B 2024 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE contained inthephotometricsamplewithmetalabun- remaining membersinthefigure.Thesestarsarefew lower envelopeiscomprisedofstarswithgenerally deblanketing oftheremainingstarsinsequence.The dances [Fe/H]>—1.5,whichdonotexhibitthestrong els fortheevolutionofhorizontal-branchstarsbyLeeetal. surface gravity,plottedinthefigureasopencircles.Mod- c horizontal-branch (FHB),orasymptotic giantbranch(AGB) open circlesareRRLyraestars(RR), membersofthefield ple withavailablephotometry.The darkcircleswith(B—V) stars. circles with(B—V)>0.5aresubgiants (SG)orgiants(G).The Fig. 6.Dereddenedtwo-colordiagram forstarsinthepresentsam- <0.5 arepredominantlymain-sequence turnoff(TO)stars;thedark 0 0 © American Astronomical Society • Provided by the NASA Astrophysics Data System the orderof0.5magbrighterwithinagivenbrightnessclassthanbluestarsin(a). points notconsideredoutliers,(b)Asabovebutforstarswith(£—F)>0.5.Notethattheredareon the medianapparentmagnitude.Theverticlelinesoneithersideofboxextendtoincludelastdata within which50%ofthedatalie.Thehorizontallineinmiddleeachboxisdrawnatlocation photometry andwith(B—V)<0.5.Foreachbrightnessclass,theboxindicatesinterquartilerange, Fig. 5.(a)BoxplotofthemeasuredVmagnitudesforcandidateMPstarswithavailablebroadband 0 0 (B-V)o Brightness Class buming stageforHBstarsinmetal-weakglobularclusters branch population.Starswhichlieonthelowersequence, 0.60. StarswhichlieonthelowersequenceofFig.6,and in Table5.Forthecoolerstars,differencesurface Table 5,indicatingmembershipinthefieldhorizontal- with colors(B—F)<0.55,areassignedtotypeFHBin corresponds toa(B—V)colorofapproximately0.55- and withcolors(B—V)>0.55,areassignedtotypeAGB (1990) indicatethattheterminationofcore-helium- 0 0 0 HP forstarsinthepresentsamplewith availablephotometryand resistant leastmedianofsquaresfit. interstellar reddeningestimatesE_ <0.03.Thesolidlineisa Fig. 7.Dereddenedcolorasafunction oftheBalmerlineindex Bv 2024 1992AJ 103.1987B 2 2vM1 branch issmall,andtheassignmentofeachstartoase- tometric follow-up(seeFHBII)allowsustoclassifythem HP>3.5. Thestarsredderthan(B—V)=0.7andlying line indexHPwithobservedcolorforthesubsetofstars ments. However,wecanobtainanestimateof{B—F) not yethaveavailablebroadbandphotometrymeasure- RR inTable5. as likelyhaloRRLyraestars.Thesestarsareassignedtype stars, variabilityinthebroadbandcolorsnotedduringpho- quence mustberegardedastentative.Inthecaseofsix by there-weightedleastmedianofsquaresanalysis.The well offtheregressionlineareflaggedasprobableoutliers The relationshipiswelldefinedforHP>1.0[(i? of squaresregressionanalysis(Rousseeuw&Leroy1987). with photometry.InFig.7weplot(i?—F)oasafunction from inspectionoftheempiricalcorrelationBalmer gravity betweenthegiantbranchandasymptotic resistant quadraticfitbasedonareweightedleastmedian of HPforthestarswith\E_\<0.03.Thesolidlineisa 2025 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE adopted fitis by thecorrelationof(B—V)withHP.Thesetesti- where 6isthepredictionerroroffit.Thecoefficient BV, andthebrightnessclassofeachstarfrom listed incolumn(10)ofTable5. determination forthisfit,R=0.93,indicatesthatallbut which aresomewhattoobluetothosestarswithinferred is minimal.However,itlikelythatweassigncolors mated colorindices,BV,obtainedfromtheabovefit,are 7% oftheobservedvariancein(B—V)canbeexplained for theprogramstarswithavailablephotometryaredi- ciated withdeblanketingforstarsabundancesthislow with availablephotometryhaveinferredmetallicities[Fe/ colors. However,thegreatmajorityofstarsinoursample of thestars,duetodeblanketingeffectonobserved limit ontheexpectedstrength oftheinterstellarCaIIK initial estimatesoftheexpected contributionofinterstellar stars withoutphotometry,weusetheestimatedcolorindex rectly obtainedusingof(pc)=\çp^o-v)+]pthose abundance [Fe/H]=—2.0.Initialestimatesofdistances each programstarisobtainedasdescribedinBeersetal. abundances [Fe/H]>—1.0. H] <—2.0.Theresidualeffectonthe(B—V)colorasso- feature. Bowen (1991),thismodelis likely torepresentanupper described above.Fromtheinferred distances,weobtain objective-prism plates,toobtainapparentVmagnitudesas 0 0 — F)<0.7],althoughitapproachesanasymptotefor Ca IIKusingthemodelofBeers (1990).Aspointedoutby BV 0 (1990), usingtypeassignmentsappropriateforametal (B—V)o withHPwoulddependonthemetalabundance 0 star bycomparingthecorrectedCaIIindexKP'and imate abundancesforhotmain-sequenceAandHBstars following manner.AsdiscussedinNorris(1986),approx- with [Fe/H]>—1.5,wehavechosentopatchthepolyno- the mixingofpopulationswhichmustoccurforstarswith which wouldplacethemoffofthisgrid,presumablydueto Norris werebasedonanadoptedheliumabundanceY al. (1992a)discusspossibleproblemswiththeNorrispro- widths asafunctionofbroadband(B—V)qcolor.Beerset can beobtainedfrommodelsoftheCaIIKlineequivalent mial fitslistedinTableIIIofBeersetal.(1990)the obtain reasonableestimatesofmetalabundanceforstars metallicities [Fe/H]>—1.5.Sothatwemightbeableto stars withobserved(orinferred)colorsandmetallicities from themain-sequenceturnoffcolorslistedinTableIIof cedure, butunfortunately,nobetterestimatesareavailable at present.Weobtainlinearfitstothepointsextending calibrations adoptedbyNorris(1986).Theresultingfits Beers etal.(1990)totheredwardsideofFHB/A region in(B—V)overwhichthelinearpatchisvalid.The are listedinTable4.Thesecondcolumnof4liststhe is thecoefficientA;secondnumber/fj.Theselines The firstnumberlistedincolumns(3)and(4)Table4 fits fordwarfandgiantstars,respectively,intheform third andfourthcolumnslistthecoefficientsoflinear lute magnitude,distance(inkpc)andpredictedequivalent patches arerequiredforstarswith[Fe/H]<—2.5. for theprogramstarswithout photometry,distancesfor and AGBstarsata(2?—F)colorof0.55,ratherthan0.45 function ofcoloraregiveninTableIIBeersetal. and thered-startypesofG(thusmistypinganumber stars typesofTO(thusmistypinganumberFHBstars), which lackphotometry,weareforcedtoassigntheblue columns (16)-(19)ofTable5,respectively.Forthestars width oftheinterstellarCailKline(inA)arelistedin et al.(1990).Ourfinalestimatesofthestellartype,abso- strength isiterateduntilconvergenceasdescribedinBeers tance, andinterstellarcontributiontoobservedCailKline shown inFig.4ofBeersetal.(1990).Notethatno are graftedontothemodelsavailablefordwarfsandgiants Norris models,[Fe/H],areindicated incolumn(20)of these starsareaccuratetono better than25%. tance estimatesshouldbeaccurate toontheorderof10%- AGB stars).Theprecisedivisionoftypeassignmentasa =0.25 andanageof15Gyr.Ourpresentsamplecontains as before.Forthestarswithavailablephotometry,dis- 0 0 15%. Becauseofthe0.4mag scatter intheestimateofV (1990), withtheexceptionthatwedividebetweenFHB 0 0 K We obtaininitialestimatesof[Fe/H]foreachprogram KP^Ao+A^B-Vh. (2) The determinationofmetalabundance,stellartype,dis- The valuesofabundanceas specified bythepatched 5. ESTIMATIONOFMETALABUNDANCE 2025 1992AJ 103.1987B 2026 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE © American Astronomical Society • Provided by the NASA Astrophysics Data System •1 a boxcarsmooth. o L dex. AllspectrahavebeensmoothedwithaGaussianofbreadth2.5A,and flattenedwith inferred metallicity,[Fe/H],intherange-0.5<[Fe/H]<-4.5,steps of roughly0.5 Fig. 8.Typeexamplesofmain-sequenceturnoffstarsinthepresentsamplewith decreasing 3 c g C (g) 22953-37 (f) 22177-10 (d) 22896-28 (c) 22185-2 (e) 22896-136 _i IL_ -J l_ H5 H+He (B-V) =0.40[Fe/H]-2.99 (B-V) =0.37[Fe/H]-2.54 (B-V) =0.36[Fe/H]-1.56 (B-V) =0.37[Fe/H]-3.50 (B-V) =0.38[Fe/H]-2.12 0c 0c 0c 0c 0c Hr _j_ |_ 2026 1992AJ 103.1987B corrected metallicityestimates,[Fe/H],listedincolumn Table 5.Afinalcorrectiontotheinferredmetallicity,de- K indices,KP,consistentwithabundance[Fe/H]>—0.5 begin tobreakdownfor[Fe/H]>—1.0,weexpectthatthe metal abundancesforstarsintherange lation ofthepatchedNorrismodelsallowustodetermine abundance range—4.0<[Fe/H]<—1.0.Aslightextrapo- provide reasonableestimatesofmetallicityforstarsinthe scribed indetailBeersetal.(1990),isusedtoobtainour 2027 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE must beusedwithcaution,duetovariationinthestrength unrecognized) RRLyraestarsobservedatrandomphases umns. Themetallicitieswereportforknown(aswellas are indicatedinTable5bydotstheappropriatecol- than forthosestarswith[Fe/H]<—1.0.StarsCaII abundances wedetermineinthisrangewillbelessaccurate of theCailKlinewithphase. temperature effectshasbeeneliminated.Asseeninthe that mostofthevariationinstrengthCaIIKdueto have similarmeasured(orinferred)(B—V)colors,so roughly 0.5dexin[Fe/H].Thesestarswerechosento sequence turnoffareshowninFigs.8(a)-8(h),stepsof ples arevirtuallyindistinguishable.Notethecollapseof figure, theBalmerlineprofilesofalleightTOtypeexam- bandhead atA3883Âisonlyseenforthemostmetalrich A4300 Áwithdecreasingabundance.AdetectableCN wings ofthestellarCaIIKfeatureinpassingfrom based. ThegiantCS22968—14,forexample,hasanas- K indexasafunctionof[Fe/H]discussedbyBeersetal. hibits adepthsimilartotheblendCaIIIf-¡-HeatA3969 to thelackoflate-typestarsincalibrationCaII of ourtypeexamples.Theabundancesweassignforgiants lowed bythecollapseofcorestheselinesatlower measured (orinferred)(B—V)colorsareshowninFigs. abundances areobtained. of thestellarCaIIKfeaturedecreasesquicklyaslower A. Forthestarswithabundances[Fe/H]<—2.5,core have metallicitiesupto0.5dex lowerthanourreported higher thanthevaluereportedbyNorrisetal.(1992).The signed abundance[Fe/H]=—3.52,whichis0.2dex with [Fe/H]<—3.0mustbeconsideredpreliminarydue abundance. NotethegradualreductionofGbandat collapse ofthewingsCailKandHfeaturesfor (21) ofTable5.Weexpectthatourcalibrationshould values. tremely lowmetalabundance late-type starsinoursample tion. Itwouldappearlikelythat anumberofotherex- analysis isavailable,CS22885 —96[Fig.9(g)],isassigned most metal-deficientgiantforwhichahigh-resolution stars inthemetallicityrange—0.5<[Fe/H]<—2.0,fol- 9(a)-9(g), instepsofroughly0.5dex[Fe/H].Notethe c — 1.0<[Fe/H]<—0.5.BecausethepatchedNorrismodels a metallicity0.6dextoohighbased onthepresentcalibra- [Fe/H]= —0.5to—2.0,wherethisfeatureex- c c c 0 c (1990) uponwhichthepresentabundanceestimatesare 0 c c c c c c c © American Astronomical Society • Provided by the NASA Astrophysics Data System Type examplesofmetal-deficientstarsnearthemain- Type examplesofmetal-deficientgiantswithsimilar bourg. Theentiresimbadstellarcatalogwassearchedfor was carriedoutbyuseofthesimbadhidatabase,main- Table 6.Incolumn(1)welistthestarnameinpresent identifications. measured orestimatedapparentmagnitudesintherangeof Table 5(duetotheapproximatecoordinateslistedfor stars withinafewarcminutesofthepositionslistedin tained bytheCentredeDonnéesAstronomiqueStras- which havebeenpreviouslyidentifiedbyotherworkers majority ofpreviousdiscoveriesarevariableorsuspected name listedinSIMBAD.Itisperhapsnosurprisethatthe obtained inthepresentwork,andcolumn(3)stellar our objective-prismcandidateswereacceptedaslikely coordinates within2arcminofoursurveystarsandwith some starsinthesimbaddatabase).Onlythosewith variable stars,orwerediscoveredasaresultoftheirhigh survey, incolumn(2)thespectroscopictypeassignment proper motions.ThestarCS22942—19(CD—26304)is a highGalacticlatitudeCHstarreportedbyFeastetal. been notedbeforeforstarsinglobular clusters(Zinn1973, importance ofthedeterminationrelativeabundance present paperhavehadhigh-resolutionspectroscopicanal- proportional toitsG-bandstrength,parameterizedbythe sample willsoonbeavailable(Petersonetal.1992). number ofadditionallow-metallicitygiantsinthepresent tion forlate-typegiants.High-resolutionspectroscopyofa we shallbeabletobetterconstrainthemetallicitycalibra- the CailKcalibration.Theresultsavailabletodateare stars arerequiredtoverifythelow-metallicityregimeof of variouselementsforextremelymetal-weakstars,these yses carriedoutbypreviousworkers.Inadditiontothe weak G-bandeffectseemstobe theresultofmilddepletion Fig. 7,butwitheachstarplottedasacircleofdiameter errors. Asabundanceanalysesofoursampleaccumulate ture, ourestimatesof[Fe/H]allagreewiththehigh- termination perturbedbyalargeinterstellarCaIIKfea- summarized inTable7.NotethatwiththeexceptionofCS of carbonduetothemixing carbon-poor(andnitrogen- along thesubgiant-giantbranchsequence.Thiseffecthas 7 appeartoexhibitgenerallyweakerGbandsthanstars resolution estimatesof[Fe/H]towithinthereported 22885 —96,whichislikelytohavehaditsmetallicityde- stars (Bond1980).Brileyet al.(1990)arguethatthe GP index.StarswhichliealongtheAGBsequenceinFig. (1977) anddiscussedinmoredetailbelow. 1986; Brileyetal.1990),aswell asinmetal-deficientfield 1977; Norris&ZinnCarbon etal.1982;Langer c 0 6.2 AvailableHigh-ResolutionAbundanceDeterminations The resultsofoursimbadhisearcharesummarizedin An automatedsearchforstarsinthepresentsample A subsetofthelowestabundancestarsdiscussedin In Fig.10weshowthesametwo-colordiagramasin 6.1 PreviousIdentifications 6.3 CHandCNAnomalies 6. DISCUSSION 2027 CM O'! oo r" PQ 2028 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE © American Astronomical Society • Provided by the NASA Astrophysics Data System

Relative Counts dex. Allspectrahavebeensmoothed with aGaussianofbreadth2.5Á,andflattenedboxcar decreasing inferredmetallicity,[Fe/H] , intherange—0.5<[Fe/H]<4.0,stepsofroughly0.5 Fig. 9.Typeexamplesofgiantbranch andasymptoticgiantbranchstarsinthepresentsamplewith smooth. c (d) 22937-42 Wavelength (B-V) =0.61[Fe/H]-2.07 0c _l l_ 2028 1992AJ 103.1987B 2029 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE has beenexaggeratedforAGBstarsasaresultoftheirlow surface gravities. rich) CNprocessedmaterialtothestellarsurface,which ble 8.Inthistable,column(1)indicatestherangeofmetal these starshaveGbandswhicharesomuchstrongerthan are strongfortheircolors.Weidentifystarswithenhanced there areanumberofstarsinoursamplewithGbandsthat tion ofG-bandstrengthwithinapatchisbimodal.Thelist tification asoutliers.Inseveralcasestheobserveddistribu- others withinagivensubsettoallowforstatisticaliden- those starslocatedinthehightailsofeachsubset.Many abundance andcolor.Foreachpatchonthegridwithan of starswithanomalouslystrongGbandsisshowninTa- distribution ofGPindiceswithineachpatch,andidentify the GPindex.Themedianvaluesofindexfor adequate numberofstars,weobtainthemedianvalues sample ofstarsintosubsampleswithroughlysimilarmetal grid patchesareshowninFig.11(b).Wethenexaminethe G bandsbyconsideringthedistributionof[Fe/H]vs 10(a). ThegridshowninFig.11(a)isusedtodividethe {B—V)q (whichincludesthestarswithestimatesof {B—V)q basedontheirderivedBVindices)showninFig. c report largeinterstellarNaDabsorption;Norris,Peterson, andBeers(1992)reportastronginterstellarCall Notes -(a)Nissen(1989)showsthisstartobeaspectroscopic binary,(b)MolaroandBonifacio(1990) K line. CS 22884-108 CS 22881-39 CS 22876-32 CS 22885-96 CS 22968-14 © American Astronomical Society • Provided by the NASA Astrophysics Data System As isevidentfromthetwo-colordiagraminFig.10, STAR (5-V)oTYPE[Fe/H] { Table 7.Availablefineanalysisresultsforcandidatestars. CS 22951 CS 22180-14 CS 22876- CS 22873- CS 29512-32 CS 22937- CS 22937- CS 22881- CS 22875- CS 29514-18 CS 29512-13 CS 22942- CS 29517-29 CS 22189- CS 29514-7 Table 6.Previousidentificationsofprogramstars. 0.39 0.36 STAR 0.66 FHB -3.86 111 TO -3.28 46 45 32 52 71 17 19 7 -3.52 -3.75±0.20Norris,Peterson,andBeers(1992) —3.64 —4.21±0.20MolaroandBonifacio(1990) TYPE -4.29 ±0.19MolaroandCastelli(1990) -4.13 ±0.20Norris,Peterson,andBeers(1992) —3.29 ±0.20Norris,Peterson,andBeers(1992) —5:53 ±0.30MolaroandBonifacio(1990) —4.27 ±0.20Norris,Peterson,andBeers(1992) [Fe/H], FHB FHB TO TO TO TO TO TO RR TO TO TO TO SG G V* UYGRU V* TYGRU V* FVAQR V* YZAQR V* SXGRU V* GKPAY V* ANMIC V* ASMIC BPM 70728 BPM 46930 CD-26 304 PHL 8412 EGM 608 GD 1287 DRIL 35 OTHER G272-44 GD 678 SB 467 SB 44 ID value oftheGPindicesforstarswithparametersinthese A4077 AandA4215A,consistentwiththeiridentification ranges. Column(4)liststheextremeG-bandstars.Col- abundance ofthepatches,column(2)range umns (5)-(7)listtheobservedorestimated(B—V)col- measurement oftheradial velocityforthisstar latitude CHstarpreviouslyby Feastetal.(1977).Our metallicity regimesofoursample, itispossiblynocoinci- ing derivedmetalabundance.Althoughselectioneffects Type examplesof6the50subgiantCHstarsin ors, derivedvaluesof[Fe/H],andobservedGPindices, star 22942—19[Fig.13(c)]was notedasahighGalactic type starswithderivedmetallicities [Fe/H]<—3.0.The dence thatfiveofthesixstars with enhancedCNarelate- stars withenhancedCNfeaturesindifferentcolorand complicate theinterpretationofrelativenumbers we showspectraofthesestars,plottedinorderdecreas- deficient bariumstarsdiscussedbyLuck&Bond(1991). line (A4554Â)orontheCbands.Thus,ourenhanced ward enoughtorefineouridentificationsbasedontheBaII interest tonotethat,forstarsofafixedtemperature,the present sampleareshowninFigs.12(a)-12(f).Thestars in theliteraturesurveyofSleivyte&Bartkevicius(1990). of subgiantCHstarsnotedbyBond(1974),andcontained strong CNbandheadsatA3883Âand/orA4215À. respectively. ThosestarswithanXincolumn(8)exhibit strong CNfeaturesintheirspectra.InFigs.13(a)-13(f) exhibiting anomalouslystrongGbands,havemoderateto as CHstars.Unfortunately,ourspectradonotextendred- the enhancedG-bandsubsample)exhibitstrongSrllat number ofthestarsinFig.12(andthroughoutrest than 2ordersofmagnitudeindecreasingmetallicity.A derived metalabundance—0.5<[Fe/H]<—3.0.Itisof chosen areofsimilartemperature,butcoverarangein G-band subsamplemayalsoincludeexamplesofthemetal- G-band strengthremainsroughlyconstantevenovermore {B—V)q colorofthepatches,andcolumn(3)median 0 c c 2 c plotted withasymbolofareainproportiontoitsG-bandindexGP. sample withavailablephotometry,asinFig.6.Hereeachstaris Fig. 10.Dereddenedtwo-colordiagramforstarsinthepresent ¡3 CQ There aresixstarsinoursamplewhich,additionto The enhancedG-bandstarsinTable8augmentthelist I 0.4 0.60.8 (B-V)o 2029 r"PQ O'!oo 2030 BEERS ETAL.-. STARS OF VERY LOW METAL ABUNDANCE 2030 ooo Table 8. Stars with unusually strong G bands and CN features. [Fe/H] {B~V) Median GP STAR (B ~V) [Fe/H] GP CN (1) c (2) 0 (3) (4) (5) 0 (6) c (7) (8) CM (S\ 1.29 22172- 25 0.40 -0.79 2.25 22945- 43 0.38 -1.47 2.43 29506- 57 0.40 -0.65 2.59 29517- 4 0.37 -1.31 2.35 29529- 26 0.38 -0.61 2.68 0.4 to 0.5 2.10 22940-111 0.50 -0.58 5.44 29529- 39 0.50 -0.75 4.67 30493- 64 0.49 -1.00 4.92 0.5 to 0.6 4.34 22955-169 0.59 -0.99 5.43 22959- 35 0.60 -0.66 5.65 0.6 to 0.7 4.99 22180- 13 0.61 -0.75 6.25 1.5 to -2.5 0.3 to 0.4 0.76 22875- 26 0.40 -1.84 1.86 22879-144 0.38 -2.20 1.97 22887- 48 0.37 -1.83 2.02 22880- 74 0.48 -2.38 5.70 (B-V)o 22885- 54 0.41 -2.17 2.46 22897- 17 0.42 -2.25 3.27 22953- 31 0.46 -1.84 3.40 29495- 80 0.50 -1.53 2.43 29503- 10 0.44 -1.77 3.84 22888- 26 0.60 -1.62 3.47 22898- 62 0.60 -1.70 3.58 29513- 33 0.57 -1.58 4.98 29529- 21 0,56 -1.52 3.65 29529- 28 0.51 -1.99 5.83 30492- 34 0.59 -1.84 5.12 > 0.7 3.20 29513- 40 -1.52 -2.5 to -3.5 0.3 to 0.4 0.50 22896-136 0.37 -2.54 1.69 22943-201 0.40 -2.85 2.24 22945- 17 0.38 -2.56 2.51 22956- 17 0.40 -2.93 1.34 22958- 42 0.39 -3.34 29504- 6 0.37 -3.02 22879- 29 0.42 -2.52 3.37 22881- 36 0.48 -2.96 5.44 22884- 97 0.46 -2.81 2.46 22898- 27 0.47 -3.10 4.52 22949- 8 0.45 -2.72 2.91 22956-102 0.42 -2.77 4.74 22964-161 0.44 -2.62 2.71 0.5 to 0.6 1.16 22947- 49 0.55 -2.51 2.75 (B-V)o 22947-187 0.59 -2.55 4.05 22948-104 0.59 -2.61 3.31 29512- 73 0.55 -2.51 5.02 Fig. 11. (a) Distribution of derived metallicity, [Fe/H] , as a func- 0.6 to 0.7 2.21 22877- 1 0.61 -2.82 4.54 c 22958- 83 0.70 -2.62 3.86 tion of the observed (or inferred) dereddened color, for stars in the 30312-100 0.65 -2.52 3.49 present sample with [Fe/H]c<—0.5. The grid represents regions of > 0.7 3.31 22891-171 0.81 -3.01 7.15 X the sample for which we obtain measures of the median G-band 22892- 52 0.76 -2.92 5.49 indices GP. (b) Median indices of G-band strength, GP, obtained 22942- 19 0.86 -3.13 7.52 X 22945- 24 0.81 -2.88 7.57 for the indicated regions of the [Fe/H]c vs (B— V)0 plane. 22948- 27 1.13 -3.16 7.79 X 22960- 53 0.79 -3.38 6.03 X 29493- 90 0.74 -2.70 3.99' -1 29495- 42 0.72 -2.68 6.07 X VT= —230 km s , is consistent with the velocity reported by these authors ( — 239 kms“1). < -3.5 > 0.6 1.22 22957- 27 0.77 -3.95 5.99 X Metallicity-dependent mixing of the products of CNO processing within red giants has been explored by Sweigart & Mengel (1979), who argue that the interior regions of stars in which CN and ON processing has occurred are farther removed from the center in stars of low metal abun- ular cluster giants to result in the wide range of observed dance, and hence that mixing to the surface can proceed CN and CH variations among member stars (Smith 1987). more readily than for more metal-rich stars. Such a model, The importance of the present sample is that it is apparent in the absence of any additional effects, would predict that that similarly large variations of CNO elements also occur stars of low metallicity should be CN poor in their outer in extremely metal-deficient field stars, which may have atmospheres. Comparisons of CN and CH variations in formed (or in any case have spent most of their lives) metal-rich vs metal-poor globular clusters seems to confirm outside of the globular cluster environment. such an effect (see Smith et aL 1989, and references It should be noted that we have assumed, following the therein). Note, however, that the stars shown in Fig. 13 lead of many previous workers, that the late-type CH- and have both strong CH features and enhanced CN bands, CN-enhanced stars in our sample are distant giants. Green similar to the CH stars identified in the moderately metal- et al. (1991) have shown that a number of high-latitude poor globular cluster M2 (Smith & Mateo 1990). At carbon stars have measurable proper motions, and hence present it is certainly unclear what processes, and with must be identified as nearby dwarfs. It is possible that some what relative degree of importance, are operating in glob- of the stars in Table 8 fall into this category as well. In-

© American Astronomical Society • Provided by the NASA Astrophysics Data System CM o oo O'! oo r" PQ 2031 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE © American Astronomical Society • Provided by the NASA Astrophysics Data System A4300 Âfeatures.Allspectrahavebeen smoothedwithaGaussianofbreadth2.5A,andflattenedboxcar smooth. Fig. 12.Typeexamplesofstarsinthe vicinityofthemain-sequenceturnoffwithanomalouslylargeCH((7-band) Relative Counts 2031 (S\ CM o oo O'! oo r" PQ 2032 BEERSETAL:STARSOFVERYLOWMETALABUNDANCE © American Astronomical Society • Provided by the NASA Astrophysics Data System 24215 A,andanomalouslylargeCH(C-band) 24300Áfeatures.AllspectrahavebeensmoothedwithaGaussian Fig. 13.Typeexamplesofstarsinthe presentsamplewithmoderatetostrongCNbandheadsat2,3883Àand/or of breadth2.5A,andflattenedwitha boxcarsmooth. Relative Counts I1 1 U 3800 39004000410042004300 4400 4500 Wavelength 2032 1992AJ 103.1987B previous calibrationofthestrengthCaIIAasa dwarf carbonstar,publishedbyDahnetal.(1977). cal spectraoftheCHstarspresentedinBothunetal. spectra oftheCN-enhancedstarsFig.13withopti- metallicity for874starswithderivedabundanceslessthan function ofbroadbandcolor,wehavereportedestimates Ca IIK,HyandHÔ,theCHGband.Basedona velocities andlineindicesbasedontheequivalentwidthsof prism/interference-filter survey.Wehavereportedradial didate metal-poorstarsselectedfromtheHKobjective- spectroscopic andphotometricfollow-upofover1000can- this abundanceregimecontainedintheextensive with previousspectroscopicallydeterminedmetallicitiesin dances [Fe/H]<—2.0(A=446)equalsthetotalofstars deed, itisofsomeinteresttocomparethenature proper-motion starswithmeasuredabundancesofLairdet literature-based catalogofNorris(1986)andinthehigh 2033 BEERSETAL.:STARSOFVERYLOWMETALABUNDANCE al. (1988)andRyan&Norris(1991).Thesampleofstars with [Fe/H]<—3.0issufficientlylarge(A=70)toenable licity estimates[Fe/H]<—4.0,wehavearguedthaterrors though onlythreestarsinthissamplehavederivedmetal- concerning theearlychemicalevolutionofGalaxy.Al- detailed investigationsofahostfundamentalproblems [Fe/H]= —0.5.Thenumberofstarswithmetalabun- band photometryisevensmaller.Amongtheimmediate obtain metallicitiesthislow. in theextantcalibrationforabundancesofcoolergi- priorities forthisprogramarethedeterminationofUBV survey todatehaveavailablemoderate-resolutionspectros- have beenidentifiedasmetal-poorcandidatesbasedonthe above \b=45°.Onlyaboutone-thirdofthestarswhich provide nearlycompletecoverageoftheGalacticcaps plates whichweenvisionforthefullsurvey,should the identificationofasubstantialnumbermost ants wouldallowatotaloffivetotenstarsinthesample (1991), andwiththespectrumofG77—61,original in oursamplewillbepresented induecourse. is nowunderway.Ananalysis of thekinematicsstars function (MDF)forthestarsin thepresentsample,andin telescopes. way, thoughitistimeconsumingwithpresentlyavailable of starsintheabundancerange[Fe/H]<—2.5isunder- gravities andtemperatures.High-resolutionspectroscopy stars asanaidinthedeterminationofappropriatesurface Strömgren andIRphotometryofthemostmetal-deficient photometry forthepresentspectroscopicsample,and copy. Thefractionofcandidatestarswithavailablebroad- mains. Wehaveonlyobtainedroughlyfiftypercentofthe metal-deficient starsintheGalaxy,butmuchworkre- combination withprevioussamples ofmetal-deficientstars, c c c c c © American Astronomical Society • Provided by the NASA Astrophysics Data System In thispaperwehavepresentedtheresultsofapartial A detailedinvestigationofthe metallicitydistribution Clearly, theHKsurveyhasbeenextremelysuccessfulat 7. SUMMARYANDCONCLUSIONS ternal specifiers”forthestars,e.g.,CS22876—32,which to suggestnamesforourstarswhichfollowtheIAUspec- indicates star32onplate22876obtainedwiththeCurtis ifications. Althoughweintendtocontinuetheuseof“in- The BindicatesBesselian(1950)coordinates. ignation HKIreferstotheHKinterference-filtersurvey. We suggestthefollowing:eachstardiscoveredasaresult that aunique“externalspecifier”beassignedtoeachstar. Schmidt telescope,orBS15621—123,whichindicatesstar tion (indegrees,minutes,andsecondsofarc)foreachstar. hours, minutes,anddecimalsecondsoftime)declina- HHMMSS.S±DDMMSS refertotherightascension(in of theHKinterference-filter/objective-prismsurveywillbe scope, othersmaynotchooseto,anditseemsappropriate given thenameHKIBHHMMSS.S±DDMMSS.Thedes- 22876-32 becomesHKIB000504.7—354757. For example,undertheseconventions,thestarCS several additionalidentificationsofHKsurveystarswhich were notpresentinthesimbadhidatabase.Theseare:CS with photometryisthepreferredvalue. the valueof[Fe/H]listedinTable5foridentification multiple identifications.Inmostcaseswehavephotometry 22874—6=KS HYA,CS22879-143=AAMIC,and available foroneofthetwoidentifications.Inthesecases, checked forrepeatswithinTable5.Thefollowingstarsare 22876-16=NSV 14743. 123 onplate15621takenwiththeBurrellSchmidttele- photometric follow-upwhichhas culminatedinthepresent paper. Theauthorswouldalso like tothankananonymous able assistanceduringthe10 years ofspectroscopicand Las CampanasandPalomarObservatories fortheirinvalu- c CS 22937-73=29501-52 CS 22937-42=30492-76 CS 22173-7=30494-20 CS 22173-2=30494-4 CS 29513-16=30493-74 CS 22888-39=30493-56 CS 22886-42=29512-51 CS 22886-29=29512-27 CS 22886-22=29512-18 CS 22886-13=29512- CS 22937-72=30492-10229501-51 CS 22937-34=30492-56 CS 22173-21=30494-33 CS 22173-15=30494-40 CS 22173-14=30494-15 CS 22888-14=30493-23 CS 22886-8=29512-6 We havebeenencouragedbytherefereeandeditor Dr. WilliamBidelmankindlycalledourattentionto Also duetoapromptingfromDr.Bidelman,we The authorswouldliketothank thesupportstaffsof Multiple IdentificationsinTable5 Notes AddedinProof 2033 1992AJ 103.1987B Luck, R.E.,&Bond,H.E.1991,ApJS,77,515 Gilroy, K.K.,Sneden,C.,Pilachowski,C.A.,&Cowan,J.1988,ApJ, Feast, M.W.,Catchpole,R.M.,&Warren,P.1977,Observatory,97, Cleveland, W.S.,&Devlin,S.J.1988,Amer.Stat.Assoc.,83,596 Lee, Y.W.,Demarque,P.,&Zinn,R.1990,ApJ,330,155 Laird, J.B.,Rupen,M.P.,Camey,B.W.,&Latham,D.W.1988,AJ,96, Hobbs, L.N.,Welty,D.E.,&Torbum,J.A.1991,ApJ,373,L47 Hartwick, F.D.A.1976,ApJ,209,418 Green, P.J.,Margen,B.,&MacConnell,D.J.1991,ApJ,380,L31 Gratton, R.G.,&Sneden,C.1990,preprint Gilmore, G.,Edvardsson,B.,&Nissen,P.E.1991,ApJ,378,17 Dahn, C.C.,Liebert,J.,Kron,R..G.,Spinrad,H.,&Hintzen,P.M. 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