1959Apj. . .130 . . 178W an INFRARED SURVEY of a REGION

1959ApJ. . .130 . . 178W o Q hm possible tofollowtheclassificationsystemof 4° prismCaseplates. in theUppsalaSchmidtspectraisabout2200A/mmatAband,whichmakesit with theUppsalaSchmidttelescopeatMountStromloObservatory.Thedispersion Spectroscopic plates.ForspectralclassificationmostoftheI-Nplateswerehypersensi- refer toWrattenfiltersand“RGl”theSchottfilter.Allplatesweretakenwith searched forcarbonstars.Onlyonewasfound.Thesurfacedistributionofthestarsshowsalatitude Schmidt telescopeoftheWarnerandSwaseyObservatoryexceptU70,whichwastaken has beenmadefortheM2-M4stars. larger distances.Thepresentanalysisdealswithstarsbeyondthisdistance.Atentativedensity effect fortheearlyandintermediateMstarswhichishardlyapparentlatestars.Thered mined byMcCuskey(1949).ThemethodofPaper Iwasusedtoderivetheinfrared types BandAforwhichphotographic(wg) red (wv)magnitudeshadbeendeter- tized asdescribedinPaperI. and ¿>=—8°(regionA),—6?5B),—5°C),respectively. Aquila. ThemethodsareidenticalwiththoseusedintheanalysisofaregionCygnus minus infraredcolorsshowamarkedreddeningat2.5kpcfromthesunbutnoadditional covering 2squaredegreeseach.Thewholefieldcoveredbytheplates,ofabout20degrees,was believed tobecomplete12.25fortheearlyMstarsand12.75latestars.Thesearch rectangles containafewstarssuspectedofS-typecharacteristicsandseveralredvariables. lel tothegalacticequatorandheightsequalI.Theyarecenteredat¿=12° Dec. =+6?9;/12°;£—7(Lundpole).Thethreerectangleshavetheirbasesparal- blue classificationweregivenbyMcCuskey(1949).LF1iscenteredatR.A.=1927; M starswascarriedoutinthreeareasatgalacticlongitude12°andlatitudes—8°,—6?5,—5°, 478 redstarsarepresented.Thelimitinginfraredmagnitudeofthesurveyisabout13.0.data by McCuskeyandSeyfert(1947)(1956).Theobservationaldataforthe each withintheregionLF1discussedfordeterminationofluminosityfunction infrared colorshavebeenmeasuredforthisinvestigation. magnitudes (wi)andtocorrectforthedifferences betweenfilters88Aand89. (Westerlund 1958;hereafterreferredtoas“PaperI”),withtheexceptionthatredminus P r © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The studywascarriedoutonred-sensitive103a-Eandinfrared-sensitiveI-NKodak The redandinfraredmagnitudesequenceswereprimarily basedon30starsofspectral Table 1givesthedataofplates.Inlastcolumn“88A,”‘W/’and“89B” In thewholeareaonlyonecarbonstarhasbeenidentifiedwithcertainty.Thethree The presentinvestigationdealswithastudyoftherelativelycoolstarsinregion The fieldsprimarilysearchedforredstarsarethreerectanglesof2squaredegrees Spectral classesontheCaseinfraredsystem,magnitudes,andredminuscolorsfor * NowatUppsalaSouthernStation,MountStromloObservatory, Canberra,Australia. III. APPARENTANDABSOLUTEMAGNITUDES:SPECTRAL CLASSIFICATION AN INFRAREDSURVEYOFAREGIONINAQUILA Warner andSwaseyObservatory,CaseInstituteofTechnology Received December4,1958;revisedFebruary1959 II. OBSERVATIONALMATERIAL B. Westerlund* I. INTRODUCTION ABSTRACT 178 1959ApJ. . .130 . . 178W 1 plates. FormostofthevariablesdetailsaregiveninTable6. brighter thanmi=12.0mag.and±0.10forthefainterones.Asinfrared mag. intheinfrared.Theerrorcolorforcataloguestarsis±0*07 by aidoftherelationderivedforthathalfstarsbrighterthanm=13. does notdeviateappreciablyfromtheirphotoelectric system,R.Themethodsusedfor M stars,—4.0mag.,inagreementwithPaperI.Thespectralclassificationfollowsthe absolute magnitudesoftheearlyMstars,—3.0mag.hasbeenadoptedand,forlate and Burger1946).Therefore,theextensionwascarriedoutforeachhalfofplate w —WirandRIlikely.Itthereforeseemsworthwhile totryobtaintheintrinsic vary fromoneplatetotheotherandhalfof(Nassau with aneutralhalf-filter.Ithasbeenshown(Westerlund1956)thatfilterconstantsmay a characteristiccurvecompletely coincidingwiththeextrapolatedline.Thismaybetaken asaproof and /,respectively,aresuchastomakeafairlyclose agreementbetweenthecolorindices the determinationofzeropointsandscales oftheinfraredmagnitudes,Wi Case system,referredtoinPaperI. of theaccuracyextension. present redplates,straightlines couldbeexpectedtow=16mag.Theextendedmagnitude scalegives colors (w—Wir)ofromthemoreaccuratephotoelectric measurements.Forthisthe magnitude intervalwhenmeasuredinasuitablysetHaffner-type iris-diaphragmphotometer.Forthe V pr r r pr r 1 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem According toKronandSmith(1951),thezeropoint oftheCaseredsystem(ra) The probableerrorofasinglemagnitudedeterminationwasfoundtobe±0.07 The magnitudesofmostthestarsaremeanvaluesfrommeasurementsonthree The redmagnitudescalewasextendedtow=15mag.byaidofoneplateexposed Experienceshowsthatthecharacteristiccurvesofplates willbestraightlinesoveraconsiderable r pr 3715. 3712. 2996. 4301-4. 4273-4. 4268-4 3710. 3709. 3457-2, 2708-2, 914-4.. 3706. U 70... Plate No. and Prism IV. THEINTRINSICCOLORS 1956, June9 1952, May29 1957, July18 1956, Sept.27 1956, June10 1956, July29 1956, June12 1947, June18 1956, July17 1956, June10 1953, July24 1951, Aug.10 1956, July17 INFRARED SURVEY179 Data ofthePlates TABLE 1 Spectral Plates Direct Plates Exposure (minutes) 88A 88A 89 RG1 RGl±neutral RG1 Filter 1959ApJ. . .130 . . 178W parts ofthe(full-drawn)curvesiscloseto0.6infields BandC,indicatingnoabsorption a redeterminationoftheabsorptioninside2.5kpc possible.Theslopeofthestraight M2-M4 stars.Theapparentlybrightstarsare too fewinthepresentcasetomake of light,constantstardensity,andthesameluminosity functionforsomedistance magnitude mi.Figure2showsthecorresponding cumulativeWolfdiagramsforthe stars forthethreeregions;N(m)=numberof persquaredegreebrighterthanthe from thesunof2.5kpc(McCuskeyandSeyfert 1947; McCuskey1956).Witharatio of totalinfraredabsorption(Ai)tothephotographic of3:8wefindA=1.05mag.at C aremostlikelydueto the increasingdistancesfromgalacticplane. (Bok 1937).Thedifferent slopeforregionAaswellthecurvedupperparts inBand that distance. and for28otherstarsshowingpronouncedvariationinspectraltypeormagnitude stars isdiscussedinSectionVII. or suspectedofvariabilityaccordingtotheGeneralCatalogueVariableStars(8stars) is limitedtothepresentationofavailabledataforstarsknownbevariables as wellmagnitudeandcolorvariationsoveralongerperiod.Atpresentthediscussion suspected variablesoftypeM6.5andearlier. magnitude; thefourth,redminusinfraredcolorindex.Thestarsarelistedinorder The firstcolumngivesthenumberofstarforitsidentificationoncharts(Figs, within therangeofluminositygiantclasshasbeentaken,only have beenidentifiedandmarked(Table5).Also,somestarscommontobothMcCuskey’s The meancolorsforordinarygiantstarsofclassesM2,M3,M4,andM5thusderived, asterisks indicateneworearlierknownvariables(relistedinTable6);thesymbolf catalogue (1949)andthepresentonearenotedin“Remarks”tocatalogue.The of galacticlongitude.FortheorientationchartsanumberbrightBDstars classification possibleintheCasesystembeingseparationofsupergiants. T (Table 6).MoststarsoftypesM7andlaterarecertainlyvariables(cf.PaperI). r ir la, 1£,1c);thesecond,spectraltypewithletterMomitted;third,infrared to theCasesystembyaidofrelationgivenNassauandvanAlbada(1949). red andinfraredmeasures,R§/e,areavailableforanumberofMgiants.The coigne, andWhite1957). Kxon 1953;KronandGascoigneKron,White,Gas- on theR,IsystemnomeasurementsforMgiantsareavailable(KronandSmith1951; colors {R—/)ecanbereducedto/byaidoftheÑPSstarsincommon value oíR—/isneededforunreddenedbrightstars.However,intheexistingcatalogues (R —/)o,aregiveninTable9,line4.Noconsiderationofeventualvariationsthecolor two systems.Thefollowingrelationhasbeenused: 180 B.WESTERLUND © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Table 7givestheobserveddistributionof M2-M4, M5-M6.5,andM7-M10 The totalphotographicabsorption(Ag)inLF1 amounts to2.8mag.atadistance The wholefieldseemsrichinvariablesandworthobservingforspectralvariations An independentdeterminationoftheintrinsiccolors(tn—Wi)oM2-M5 Tables 2,3,and4givethedataforallredstarsidentifiedinregionsA,B,C. The MountWilsonspectraltypesusedinthesix-colorphotometryhavebeenreduced P In thesix-colorphotometry(StebbinsandWhitford1945;StebbinsKron1956) xr VII. THEINTERSTELLARABSORPTION R —I=0.69{RI)6+0.24. V. THECATALOGUE VI. THEVARIABLES 1959ApJ. . .130 . . 178W © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem

Fig. la.—Identification chart for region A 1959ApJ. . .130 . . 178W © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem

Fig. \b.—Identification chart for region B 1959ApJ. . .130 . . 178W © American Astronomical Society : •K8 N I >•. 2" ^ fS •§. •to "roto s: *o '•vO 5 vO '■ r-. Jn i .5^ . ol ro g: .2. • '‘lo . rog: / n,; • R 9 r /! to in i ' -o •n • *4>(N •Í. ÍS^* -.S: ^? s •®oV!û oo ‘ \*-4) • tor '. Oo. \ , ^3 rM C?. ^.; .'- Z VJ \ •.•■• ci »3 x • ,\ N *• *.v> ss .: ^ § §if3 V ro •tf; % sr* ''O \ - 'g: '•'^y>V * ro H' SÍ. Si • m. S to ^ g ■••3 5ári-v. ^ .rs 5: • . u ÍC /'>*'>•>?9. •* .'>..-i®OQ•■ io.;.u^? •• >.< - to— . o 1 \ ’*~o•*.*0 O'* i/> >0I I \ ^ Oo •o s in /.vo^n ri- 5 ^ ✓ m ' io* oo ^ s VJ1 I ^ Ä Ul t QO a» 2 ■ S' VN 9 a?. ¿., ts f n« i?'

TABLE 3

RED STARS IN REGION B

m m No. Sp. iIAir No. Sp. mir mr-mir No. Sp. mir r" ir 1 3 10.45 1.89 51* 8 12.40 3.37 101 6.5 12.13 2.85 2 6 12.01 2.14 52 6 12.15 2.44 102 2 11.97 1.68 3* 4 10.87 1.88 53 2 11.69 1.77 103 6.5 9.40 2.93 4 7 12.84 2.49 54* 6 10.45 2.59 104 5 11.56 2.09 5 6 11.60 55 2: 12.41 1.44 105 4 11.76 1.88 6 6 9.53 2.57 56 6 12.27 2.52 106 4 12.01 1.99 7 + 4: 12.12 1.85 57 2 10.51 1.64 107 6.5 10.32 2.59 8 7 12.05 58 6.5 10.71 2.54 108 5 12.36 2.14 9 3 11.70 1.97 59 8 11.99 3.34 109 4 11.43 2.22 10* 5 9.48 2.22 60 7 12.11 2.93 110 4 10.87 1.96 11 5 12.18 2.13 61 7 12.63 111 2: 11.23 1.56 12 4 12.38 1.81 62 7 12.65 2.14 112 3 9.64 1.62 13 5 12.60 2.18 63 7 12.32 3.08 113 7 11.67 2.86 14 7 11.61 2.86 64 6.5 12.03 2.76 114 6.5 12.64 2.55 15 6 11.87 2.30 65 6.5 12.92 115 4 12.13 1.89 16 2: 12.50 1.77 66 8 12.89: 116 6.5 11.22 2.90 17 7 12.86 2.40 67* 7 11.18 117* 5 11.01 2.09 18 7 12.38 68 2 12.14 1.91 118 6.5 11.33 2.71 19 4 12.56 1.93 69 6 9.67 2.61 119* 6: 20 6.5 11.39 2.73 70 5 12.65 1.99 120 6.5 9.69 2.50 21 4 12.11 2.24 71 6 10.77 2.30 121 4 11.24 2.04 22 6.5: 11.53 2.29 72* 6 12.30: 122 6.5 12.11 2.57 23 8: 12.64 2.69 73 3 11.65 1.90 123 3 11.27 1.91 24 2: 10.64 1.41 74 4 12.23 1.90 124 4 12.34 2.03 25* 8 12.50 75 2 11.11 1.83 125 7 12.01 3.42 26 6 12.71 76 2 10.84 1.79 126 5 12.05 2.13 27 7: 12.03 2.72 77 6 12.30 2.22: 127 6: 12.22 2.45 28 3 12.75 78* 8 12.40 128 6 9.89 2.13 29 6 11.77 2.56 79* 6.5 8.63 129 8 13.12 1.77 30 7 10.51 2.99 80 6.5 9.71 130 3 11.67 1.66 31* 7 12.12 2.61 81 4 9.46 1.70 131 3 11.25 1.63 32 3:: 11.82 1.73 82 6 12.44 2.42 132 8: 12.02 1.81 33 3 11.26 1.80 83 7 11.88 3.04 133 7 12.06 2.51 34 2: 11.54 1.49 84 5 12.97 134 6 10.18 2.61 35 8 11.87 2.26 85 2 11.12 1.66 135* 9 11.56: 36 6 12.54 2.56 86 7 11.62 2.99 136 9 12.46 37 6.5 12.69 2.47 87 5: 12.83 2.07 137 7 12.71 2.61 38* 7 11.69 1.95 88 5 12.32: 1.90 138 6.5 10.62 2.41 39 7 12.45 89 2 10.68 1.53 139 7 12.53 2.95 40 6.5 11.51 2.36 90 3 10.84 1.72 140 6 11.62 2.61 41 7 12.19 2.50 91 6.5 10.18 2.82 141 2 10.87 1.52 42 3: 11.63 1.96 92 3 11.54 1.77 142 5 10.24 2.05 43 6.5 12.21 2.62: 93 5 11.62 1.99 143 + 6 11.24 2.43 44 5 10.01 2.37 94 6 10.71 2.39 144 6.5 10.29 2.61 45 4 11.74 1.75 95 4 12.63 1.89 145 4 12.04 1.90 46 4 12.52 1.90 96 5 13.00: 146* 6.5 12.13 2.88 47 7 12.56 2.67 97 3 11.07 1.54 147 5 12.80 2.45 48 7 12.48 2.58 98 4 11.88 1.90 148 6.5 12.31 49 6.5 10.75 2.31 99 2 10.62 1.47 149 7 10.54 2.59 50 4 10.30 1.96 100* 6.5 12.00 150* 7 11.27

182

TABLE 4

RED STARS IN REGION C

No. Sp. mir No. Sp. mir m-r-m ir No. Sp. mir mr-m^r 1 2 11.22 1.41 51 8 12.98 101 6.5 12.40 2 6.5 11.82 1.49 52 5 12.45 2.32 102 8 11.22 3.10 3 4 10.52 2.04 53 6.5 9.87 2.61 103 6.5 12.89 2.22 4 5 12.78 2.74 54 4 7.23 2.15 104 5 12.08 1.96 5 7: 13.02 55 7 12.35 2.49 105 8 12.41 3.13 6 5 12.68 56 5 12.86 106 3 12.22 1.69 7 6.5: 13.11 57 7 12.90 107 6 12.78 2.46 8 7: 13.04 58 4 12.46 1.97 108 6.5 12.40 2.72 9 4 11.73 2.20 59 2: 9.73 1.55 109 6.5 11.55 2.45 10 3 12.52 1.77 60 + 6 12.46 110 6 12.53 2.44 11 7: 12.81 61* 7 12.43 2.91 111 6.5 11.59 2.84 12 3 11.97 1.97 62 3 10.28 1.80 112 5 12.95 2.21 13 6: 12.83 63 7 11.92 2.83 113 6 13.11: 14 6.5 12.93 64 7 12.43 114 7:: 12.89: 15 5 10.29 2.49 65 7 13.00: 115 2 11.53 1.55 16 + 6.5 12.48 2.01 66 7 10.46 3.07 116 7 11.53 2.84 17 5 12.95 67 4 10.08 2.15 117 6 12.68 2.48 18 7 11.95 2.97 68 6.5 11.81 2.33 118 5 11.73 2.29 19 7: 13.00: 69* 7 13.00: 119 6.5 12.85 20 7 11.89 70 6.5 13.09 120 4 12.43 2.03 21 4 12.99 2.18 71 8 13.06 2.06 121 4 12.80 22 8 12.57 72 5 11.69 2.53 122 7 12.94 2.58 23 8 13.00 73 7: 12.81 2.66 123 6.5 11.65 2.61 24 8 13.00: 74 9 10.79 3.37 124* 8 12.37: 25 3 12.44 2.09 75 7: 12.86 2.29 125 6 13.00 2.61 26 4:: 12.55 2.13 76 2 10.66 1.49 126 6 13.16: 27 2 12.81 2.30 77 6 12.70 127 5 12.67 2.20 28 5:: 12.53 2.49 78 6.5 12.24 2.69 128 4 12.77 29 3 11.37 2.08 79 8 12.80 2.05: 129 2 10.86 1.87 30 6 12.36 2.13 80 3 11.39 1.80 130 4 12.31 2.35 31 5 12.87 2.50 81 6.5 11.46 2.54 131 7: 13.09 2.43 32 6.5 12.93 82 6 12.76 2.33 132 6.5 10.18 2.80 33 2 7.51 1.66 83 7 12.56 2.63 133 4 12.50 34 7 12.74 84 6.5 12.74 2.51 134 5 12.36 2.04 35 7 85 4 10.74 2.07 135 4 9.28 2.15 36 + 4 11.53 2.07 86 6.5 11.76 2.80 136 5 12.80 2.48 37 2 12.12 1.66 87 5 11.74 1.91 137 3 12.06 1.85 38 3 11.95 1.93 88 2 12.04 1.62 138 3 10.48 1.86 39 4: 12.44 2.21 89 6.5 12.40 2.68 139 7 12.91 40 8 12.97 90 6.5 11.69 2.94 140 6 10.59 2.53 41 4 12.56 91 6 12.81 2.52 141 6.5 12.92 2.41 42 7 12.94 92 + 6 8.98 2.26 142 6.5 12.98 43 6.5 13.13 93 2 11.20 1.36: 143 6.5 11.85 2.66 44 7 11.93 94 6.5 11.22 2.41 144 2 11.03 1.46 45 3 11.23 2.01 95 6 12.24. 2.33 145 7 12.98 1.92 46 8: 96 4 11.23 1.80 146 5 11.72 2.03 47 5 11.63 2.09 97 7 12.33 2.53: 147 6 12.84 1.40 48 6 11.67 2.52 98 7 12.97 148 7 10.86 2.60 49 6.5 11.62 2.60 99 8 149 7 12.70 2.56 50 8: 100 8 13.16 150 8: 12.74

183

© American Astronomical Society • Provided by the NASA Astrophysics Data System CO [■" o ^ TABLE 4 (Continued) RED STARS IN REGION C 0^1 CT)LO m m m No. Sp. m No. Sp. ir r- ir No. Sp. m j j" mr-m^r ir mr-mir 151 2:: 11.96 1.82 176 6 11.76 2.74: 201 7 13.00 152 7 12.83 2.17 177 6.5 11.33 2.71 202 6 12.34 2.29 153 3 11.55 1.83 178 3 9.93 1.64 203 6 12.39 2.51 154 8 12.56 1.61 179 4 11.90 1.93 204 5 12.12 2.21: 155 6 12.78 180 6.5 12.61 2.95 205 6.5 11.16 2.72

156* 7 9.58 3.04 181 8 12.45 2.57 Q 7R 206 7 12.45 2.11 157 7 182 6.5 12.86 2.63 207 6.5 11.75 2.47 158 6.5 11.90 2.63 183 5 12.13 2.42 208 5 10.85 2.34 159 5 12.80 184 3 10.69 1.82 209 7 12.19 160 6.5 11.51:: - 185* 9 11.60: 210 2 10.21 1.37

161 8 11.39 3.10 186 5 11.66 2.13 211 12.55 162 8 9.81 2.63 187 6.5 10.68 2.62 212 12.48 2.79 163 5 10.41 2.12 188 2: 11.61 1.61 213 12.26 164 6 11.54 2.03 189 4 11.92 2.17 3.47 10.12 3.08 214 12.45 2.51 165* 8 190 3: 11.89 1.89 215* 12.15 2.34 166 3 10.14 1.80 191 5 11.78 2.13 167 2 11.35 1.58 192* 4 11.33 1.96 216 8 13.11:: 168 2 11.46 1.72 193 4 11.19 2.03 217 7 10.93 169 6: 11.25 2.31 194 3 11.55 1.78 218 6 6.97: 2.58 170 6 10.01 2.23 195 4: 12.26 2.38 219 6.5 8.06 2.80 220 3 11.08 1.77 171 6 11.03 2.44 196 2::: 10.50 1.53 172 2 10.85 1.47 197 3 12.11 1.64 221 6.5 9.87 2.60 173 6 9.86 2.43 198 4 12.20 1.70 222 6 10.98 2.22 174 7 12.60 2.21 199 4 11.94 2.23 223 8 12.85 2.43 175 3 12.48 1.98 200 2: 11.59 1.67

184

In Paper I, we concluded that the M2-M4 stars show a high concentration to the galactic disk. Sanduleak’s study of the apparently bright M stars (1957) indicates only a slight tendency for the M2-M4 stars to increase in number as the longitude of the galactic center is approached. We may therefore compare the LF1 curves with those of corresponding (though positive) latitudes in LF2; the influence of the difference in longitude will be very small. The dashed lines in Figure 2 are based on the material in Paper I. The

TABLE 5 Reference Stars

BD Stars in Region Star No. on Charts

+4°4152 +5°4151 +6°4105 +5°4190 +6°4154 +6°4122 +5°4192 +6°4165 +7°4052 +5°4209 +6°4158 -f 7°4064 +6°4215 +6°4176 +7°4071

Fig. 2.—The cumulative Wolf diagrams for regions A, B, and C in the case of M2-M4 stars. For comparison the corresponding curves for regions (7) and (6-7 in) LF 2 are drawn (dashed).

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1959ApJ. . .130 . . 178W magnitude group);(3)thenumberoflateMstars is likewiselargerinLF1.Fortheratio LF1 thaninLF2atgreaterdistancesfromthe galactic plane(regionB,thesecond- ground absorption.Forthecomparisonofgroupsdifferenceinabsolutemagni- in regionC. good agreementwiththeresultforcorresponding (positive)latitudegroupinLF2 of M2-M4:M5-M6.5:M7-M10at5=—6?5 we haveapproximately4:2.5:1,in does notdiffermuchinthetwodirections;(2) numberofearlyMstarsislargerin parentheses. Thetableshowsthat(1)thedistribution oftheapparentlybrightMstars M6.5 andM7-M101mag.brighterthanthestars ingroupM2-M4(cf.Sanduleak for theM2-M4,M5-M6.5,andM7-M10groups,respectively,correctedfore- obvious isthehighnumberofM5-M6.5stars between Mi=10.26and10.74mag. done byregroupingthestarsinto2-mag.intervalsandtakingingroupsM5- tude betweenearlyandlateMstarshastobeconsidered.AsinPaperI,thisbeen Mir =10mag.andm^12.5Themeancolorsforthefourspectralclassesas Wir)ab, theintrinsiccolors{m—Wi)oinTable9,thirdline,areobtained.Theyagree line). The reddeninginCexceedsthatAandBbyabout0.1mag.Forfurtherdiscussion, Mir =11.8mag. (4:2:1). assumptions arecorrect. well withthosederivedinSectionIV(Table9,fourthline),thusprovingthattheadopted be derivedandtheratioA/E_idetermined.However,ithasbeenthoughtmore M3, M4,andM5,separately,itisfoundthatnoincreaseinreddeningappearsbetween Mir =9.75mag.fortheM2-M4stars,whereasinLF1centerisapproachedatabout region B;consequently,Ei=0.6mag.Bysubtractingfromthecolors{m— reasonable toreversetheprocedurebyadopting,fromStebbinsandWhitford’sabsorp- derived fromthismagnitudeintervalaregivenforregionsA,B,andCinTable8. the meancolors{m—Mí)abarecalculatedas(A+BC0.1):3(Table9,second the colorvariations.Byplottingcolorsm—MiagainstforspectraltypesM2, direction, l=32?5,theshortestdistancetogalacticcenterisreachedatabout geneous distributionoftheM2-M4starsin(lowerpartthe)galacticdisk.Thein- 1957). TheresultisgiveninTable11,withthecorresponding valuesfromPaperIwithin fluence oftheshorterdistancetocenterdirectionLF1isvisibleat£=—6?5 tion law(Whitford1948),Ai=1.7£-ir.TheWolfdiagramsgive1.0mag.for regions (seebelow).Thisfactmayalsobeused“inreverse^asaproofofthehomo- agreement withMcCuskey’sdata,aswellthecolordifferencesbetweentwo absorption. Thederivedvalues,Ai=1.0and1.2mag.,respectively,areinexcellent deviations ofthecurvesforregionsBandCfromdashedlinesyieldtotalinfrared V (region B)astheearlierappearanceofcurvedpartforLF2(Fig.2).In A isleftoutofcomparison,becauseareasonableextrapolationfromLF2notpossible. region Cisbetweenregions6and7.Inthiscase,aninterpolationhasbeenmade.Region modulus ofthelatituderegionBissameasthat7,whereas yr ir Vy vy tTr Yr r 186 B.WESTERLUND © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem There isverylittleindicationofclusteringin any ofthespectralgroups.Most Table 10givesthenumberofstars[A{m))persquaredegreeforJmag.intervals By aidoftheintrinsiccolorsderivedinSectionIV,colorexcesses£-irmaynow A confirmationoftheresultsdrawnfromWolfdiagramsisobtainedbystudying The LF2regions6and7werefoundfreefromabsorbingscreens.Consequently,the r VIII. THEDISTRIBUTIONOESTARSINSPACE 1959ApJ. . .130 . . 178W A105 11.30 B 310.81 B 109.46 B 3111.60 B 5too A 7511.15 B 2512.29 A 899.77 B 5112.11 B 3812.22 A 9410.73 A 6612.75 A 65overexposed B 5410.44 A 6310.00 A 5410.79 A 1511.80 Star m|and(m-m)on A 1411.30 ri No. 5-29-526-9-567-17-566-18-478-10-516-12-567-29-569-27-567-18-57 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem faint 12.22 10.62 11.09 10.22 12.26 12.91 12.12 11.02 10.64 10.40 12.22 10.81 10.22 12.04 10.73 9.65 2.90 2.43 2.28 3.22 9.82 2.57 2.63 2.60 1.95 1.66 1.94 2.19 2.75 1.27 2.64 VARIABLE STARSINREGIONSA,B,ANDC faint 10.34 too 12.87 11.75 12.49 10.78 10.34 11.07 10.56 11.71 10.56 10.86 2.69 2.95 2.04 2.61 3.85 8.48 2.66 2.82 2.61 9.28 2.90 2.89 2.60 9.96 1.93 8 6.5 8: TABLE 6 187 6.5 6.5 7 6.5 8 8 6 6.5 Spectral typeon 6.5 6.5 6.5 6.5(VO) 9 6.5 5: 6.5 6.5 6.5 8 orS 6.5 7 6.5 6.5 4 d.5 8 6.5 No. 4681 V386Aql V384Aql No. 4728 V621Aql V623Aql 1959ApJ. . .130 . . 178W C215 11.74 C192 11.42 C185 10.55 C165 11.28 C156 9.46 C124 11.70 C 6912.4613.08: C 6112.0212.55 B150 12.30 B146 too B135 too B119 10.96 Star and(m-m^.)on No. 5-29-526-9-567-17-566-18-478-10-516-12-567-29-569-27-56 B117 11.08 B 79 B 67too B100 11.85 B 7812.92 B 7213.13: r © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem faint faint faint 8.29 12.32 faint 12.41 11.30 too 10.90 faint too 11.82 12.11 2.03 3.63 9.48 1.86 2.88 10.89 9.90 12.84 10.87 12.46 11.72 2.30 2.88 2.10 3.11 3.24:: 8.90 2.13 1.71 1.25 VARIABLE STARSINREGIONSA,B,ANDC 12.38 faint too 11.25 11.84 13.08: 12.73 10.39 12.46 11.01 12.83 2.24 2.31 2.56 3.76 11.05 9.59 9.49 3.16 11.30 11.48 11.89 12.18 2.75 3.27 2.15 2.59 3.19 3.64 8.68 2.44 3.11 6.5 6.5 6.5 TABLE 6(Continued) 188 faint too 6.5 6 9 6.5 6.5 6.5 8 Spectral typeon 6.5 6.5 6: 6.5 faint too 6.5 6.5 6.5 8 7-18-57 R 10 4 9 8 6.5 V819Aql 7 9 7 9 3 6.5 7 6.5 V373Aql 9 7 5 1959ApJ. . .130 . . 178W 12.24. 12.74. 11.74. 13 24. 11.24. 10.74. 10.24. 9.74 9.24 8.74, 8.24 7.24, 7.74, © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem M4 M5 M3 M2 Sp. Type (Æ-/)o... • ( WMi)0• (m—m) r riAB 20.5 17.0 12.5 10 0 3 0 0 5 0 5 3.0 2 5 5.0 6.5 1.5 Mean Colors(m,—m)ab>andAdoptedIntrinsic ir 2 22+0.08(11) 1.79+ .07(6) 1.44+0 03(13) 1.91+ 05(10) Mean Colors,m-m,oftheM2-M5Stars The ObservedDistributionoftheStars M2-M4 iT Region 21.0 24 5 24 0 15, 4 0 0 0 0 0 9 1, 1 B Colors ofM2-M5Stars 24 5 32.0 30 5 18.0 12.0 4.0 0.5 2.0 7.5 1.0 1.0 1.0 1.0 0.89 0.95 1.49 M2 TABLE 9 TABLE 8 TABLE 7 15.5 13.5 19.0 10.5 2.5 0.5 N(m) 2.0 5.5 5.0 1 0 1.0 1.0 2.11+0 04(10) 1.78+ 04(13) 1 62±0.04(14) 1.92+ .04(17) Spectral Range 1.18 1.78 1.18 Region M3 Spectral Type M5-M6.5 Region B 29 0 22 0 31 5 11.5 15.5 3.5 0 0 0.5 0 9 0 0.5 6.0 B 1 35 1.95 1.28 M4 46.0 23.5 33.5 17.0 4.0 8.5 6.0 1.0 1.5 1.5 1 0 2.20+0.05 (15) 2.08 +04(19) 1.87+ .03(18) 1.58 +0.03(18) 11.0 2.12 3.5 2.0 1.62 1.52 0 5 0 0 0 0 0 5 9.0 7.5 1.0 MS M7-M10 Region 10.0 17.0 19 0 4.5 0 0 0 0 0 0 0 1 5 1.0 B 31. 17 4. 2 2. 0 0 0 0 0 9 0 6. 1959ApJ. . .130 . . 178W r beingthedistancefromsunandzgalacticplane. method usedinPaperI.ThederiveddensitiesaregivenTable12,afterconverting the initialdensitygradientsforeachlatitudeintodensitiesatcertain(r,z)points, any evidenceofanincreaseindensityuptothat point. However,thepresentmaterial sun. Also,thetentativecharacter ofthisanalysisshouldbeemphasized. does notalloweachzlayer tobefollowedoveragreatdistanceinthedirection fromthe 190 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem A densityanalysisoftheM2-M4starsinLF1hasbeencarriedout,following The pointclosesttothegalacticcenterisreachedat aboutr=5.5kpc.Thereishardly 9.75- 1 1.74 8.75- T .74 8.75- 1 0 74 6.75- 8.74 6 75-8 7.75- 9 Distribution ofStarsCorrectedforForegroundAbsorption 74 74 IX. THESPACEDENSITIESOESTARS Numbers ofStarsperSquareDegree 11 14 2.5 5 5 1.0 B. WESTERLUND 20 12 4 3 0 TABLE 10 TABLE 11 A(m) (4.0) (4) (2 0) (0.8) (0 8) (7.5) Region 23 (19.5) 18 (4.3) 3.0(1 2) 6 (23) 7 5(9) 1.5 (15) Spectral Range M5-M6.5 M7-M10 M5-M6.5 M2-M4 M7-M10 M2-M4 1959ApJ. . .130 . . 178W r. Theinvestigationoftwomorefieldsat/=12° havingó=0°andb+6°isbeing carried outfortheconsiderationofsucheffects. iris-diaphragm photometerattheMountStromlo Observatoryforthemeasurements. gestions. IalsowishtothankDr.B.J.Bokforthe opportunityofusingtheHaffner-type within thepresentlongitudeinterval(LF1:/=12°; LF2:/=32?5)atlargevaluesof galactic planeasfoundinLF2appearsconfirmed.ComparisonsofLF1andindicate Bok, B.J.1937,TheDistribution oftheStarsinSpace(Chicago:UniversityChicago Press). Kron, G.E.1954,Proceedings of theThirdBerkeleySymposiumonMathematicalStatistics andProbability it maybeofimportanceforthecomparisonfieldsatpositiveandnegativelatitudes by theLundpole(Schmidt1957;Westerhout1957)hasnotbeenconsidered.Admittedly, of r—2.5kpc.Thecompletelackreddeningatlargerdistancesindicatesthatthe ing distancefromthegalacticcenterisobviousfirstatgreaterheightsabove that ahomogeneouslow-latitudelayerofM2-M4starsmayexist.Theeffectincreas- plane. Finally, Igratefullyacknowledgeagrantfromthe SwedishNaturalScienceResearch direction fromabout2to8kpc,eveninthegalacticplane. analysis hasbeencarriedoutbetweenorabovethespiralarms.Thisisinagreementwith Council enablingthepurchaseofabinocularmicroscope fortheclassificationprogram. the radioastronomicaldata,sincedensityofneutralhydrogenislowinpresent absorption wasfoundtobebestdescribedbyobscuringscreenswhicharelikely connected with(blue)spiralarms,asdefinedbyOBstars. could eventuallybeinterpretedasthecrossingofa(red)spiralarm.Theinterstellar to thegalacticcenterisindicated. © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem I amgreatlyindebtedtoDr.J.Nassauforhis manyusefulcommentsandsug- The followingconclusionsmaybedrawnfromthepresentinvestigation: 3. InthedirectionofLF2adensitymaximumwasfoundforearlyMstarswhich (Berkeley: UniversityofCalifornia Press),p.39. 5. Theeventualdeviationofthemeangalactic(hydrogen)planefromthatdefined 4. ThereisnoevidenceofanyspiralarmbeingcrossedintheLF1directionoutside 2. InthecaseofM5-M10starsanincreaseinstarnumbertowarddirection 1. ThecomparativelyhighproportionofM2-M4starstothelateMnear Space DensitiesofM2-M4Stars 6 {D[r] per10CubicParsecs) INFRARED SURVEY191 REFERENCES X. SUMMARY TABLE 12 192 B. WESTERLUND Krön, G. E., and Gascoigne, S. C. B. 1953, ApJ., 118, 511. Krön, G. E., Gascoigne, S. C, B., and White, H. S. 1957, A.J., 62, 205. Kron, G. E., and Smith, J. L. 1951, Ap.J.y 113, 324. Kron, G. E., White, H. S., and Gascoigne, S. C. B. 1953, ApJ., 118, 502. McCuskey, S. W. 1949, ApJ., 109, 426. . 1956, ibid., 123, 458. McCuskey, S. W., and Seyfert, C. K. 1947, ApJ., 106, 1. Nassau, J. J., and Burger, V. 1946, ApJ., 103, 25. Nassau, J. J., and van Albada, B. 1949, ApJ., 109, 391. Sanduleak, N. 1957, A J., 62, 150. Schmidt, M. 1957, B.A.N., 13, 247. Stebbins, J., and Kron, G. E. 1956, ApJ., 123, 440. Stebbins, J., and Whitford, A. E. 1945, ApJ., 102, 318. Westerhout, G. 1957, B.A.N., 13, 201. Westerlund, B. 1956, Ark.f. astr., 1, 567. . 1958, Ap.J. Suppl., No. 37, p. 73. Whitford, A. E. 1948, Ap.J., 107, 102.