196lApJS....6..213D 12 6 -11 -1 for. However,thenewevidenceforanaccumulationofgroups,clouds,andclustersinequatorialplane distinct cloudsandgroupswithdifferentpopulationsvelocities,atdistances.Inparticular, relation tothemassesofindividualsubsystems. per ,9ÏÏ*«2X10O,arenotsignificantlyreducedcomparedwithpreviousestimates,andthe in variouswaysisfromthreetofourtimesitsprobableerror,andthevelocitydistributionseachcloud of theLocalSuperclusterandtowarditscentersuggeststhatobservedvelocitydispersionbearslittle are widelydifferent. elliptical andlenticulargalaxiescenteredatCj(12h26.5m,+13?2)withameanvelocity^ the Virgoclusteritselfmayconsistoftwooverlapping,butseparate,clouds:(1)aconcentrated discrepancy betweengalaxymassesderivedfromtranslationalorrotationalmotionsremainsunaccounted Local Grouptothedistant,mainlyellipticalandlenticular,galaxiesofgreatclusters mixed populationofgalaxytypes,itwasusedasasteppingstoneforthetransfer Zwicky 1942,1957;Holmberg1958).Asthenearestoflargeclusterswithawell- Mpc; (2)adiffusecloudofspiralsandirregulargalaxiescenteredatCfi(12h27.5m,+13?9)withmean velocities ofover200brightgalaxiesbetween12hand13h,0-f20°,indicatesthepresenceseveral extragalactic distancescalefromthenearby,mainlyspiralandirregular,galaxiesof of theorder11-12Mpc.ThedifferencebetweensystemicvelocitiesE-and5-cloudscomputed velocity ~+1450±120p.e.kmsecanddispersion/R\ofthemeanradialvelocity system inastateofdifferentialexpansionandrotation, then(1)itisnotcorrecttoderive (OB supergiantsinspirals,globularclustersellipticals),itplaysanessentialpartthe (de Vaucouleurs1959Ô).Becauseitisbothfarenoughtohaveasignificantredshiftand 1956; Holmberg1958;Sandage1958). 3 14 The Virgoclusterofgalaxieshaslongplayedanimportantroleinextragalacticstudies The massofeithercloudderivedfromvelocitydispersion,NÍÍJl*«2X10O,andthemean A discussionofthesurfacedistribution,morphologictypes,apparentmagnitudes,diameters,and These investigationsraiseanumberofquestions: (1)Howistheclusterdefined? Its locationinthedirectionofmaximumsurfacedensitybrightgalaxiesmarks These questionsareimportantbecauseiftheVirgo clusteristhenucleusofasuper- © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem STRUCTURE OFTHEVIRGOCLUSTERGALAXIES Department ofAstronomy,UniversityTexas Gerard deVaucouleurs Received November10,1960 I. INTRODUCTION ABSTRACT 213 196lApJS....6..213D diameters (deVaucouleurs 1959¿>),and79haveknownradialvelocities (Humasonetal. revised morphologicaltypes (deVaucouleurs19596),141havecorrected photographic group ismarkednear12h 17m,+6°. northernmost partoftheelongatedVirgocloud appears inthelowerhalf;asmall,dense and generallybrighterthanwg«13.5.TheVirgo clusterproper,12°indiameterand centered near12h27m,+13?5(1950),isinevidence intheupperhalfofmap; be confinedtotheregionbetween12hand13h, 0°and+20°(1950). 1956); thesedataarelisted inTable1. south oftheequatorarenotdirectlyrelatedto the originalVirgocluster,attentionwill distribution, classification,magnitude,diameter, andvelocitycriteria.Sinceanexamina- tion oftheShapley-Amesdistributionmapsleaves littledoubtthatcloudsandgroups “wing.” and +2?5to+18?5(1950),thusexcludingthe“southernextension”butincluding Local Supercluster. stance, Holmberg(1958)definestheVirgoclusterasextendingfrom12h08mto48m, so-called “wing”formedbyadensegroupcenterednear12h17m,+6°(1950).Forin- maps intheShapley-Amescatalogue(1932)showsthatsurfacedensityofgalaxies clouds) intheVirgoclusteris,however,notwarranted;aninspectionofdistribution members oftheVirgocluster,whileafewbetween12h33mand13h03m,—14?8 P related totheVirgoclusterproper,exceptinsofarasbotharegalaxycloudswithin cloudiscloselysimilartotheUrsaMajorandprobablynomoredirectly this southernextensionisverymuchlessthanintheclusteritself.Infact, definition oftheclusterarea.Forexample,inredshiftcatalogue(Humasonetal. of theComa-Virgosupergalaxy,”andthussomeuncertaintywasintroducedinto through Virgodownto—20°wasdescribedbyShapleyandAmes(1931)asan“extension described itasanellipticalcloudmeasuring12°X10°andcenteredat12h25m,+15?5 limits ata=12h03mto56m,5+5°+20°.HubbleandHumason(1931) Ames (1926),wholocateditscenteratapproximately12h20m,+13°(1900),and —3?5, arenotedasinthe“southernextension.”Inclusionofthiscloud(orstring Local Superclusterbutisactuallyanagglomerationofseveraldistinctgroupsorclusters 1956), objectsbetween12h10mand57m,+1°6+18?5(1950),arelistedas (1930). ThisdensestregionistheVirgoclusterproper. ferred fromplausiblemass-luminosityratios(deVaucouleurs1960). and distanceestimates.Thesevariouspointswillbeexaminedinthefollowingsections. velocities andvelocitydispersionstoevaluatetheeffectofthisseparationonmass lapping intheprojection,itismostimportanttoassesstheirindividualmeanradial at differentdistancesfromusinthedensercentralregionsofsupersystemandover- discrepancy betweenthemassestimatedthroughvirialtheoremandin- (2) itmaynotbecorrecttoderivethemassofclusterfromobservedvelocitydis- 214 GERARDDEVAUCOULEURS than byitsnucleusalone.Thismightbe,atleastinthisparticularcase,areasonforthe persion ifthelatterisgovernedmorebydynamicsofsupersystemasawhole Among thesegalaxies,143 arelistedintheShapley-Amescatalogue(1932), 198have Figure 1isaplotof212galaxieshavingequatorial co-ordinatesinthespecifiedrange In whatfollows,thestructureofthisregionisanalyzed throughthecombineduseof Another sourceofconfusionhasbeenthefrequentinclusioninVirgoclustera Later, theelongateddistributionofbrightgalaxiesstretchingsouthcluster The Virgoclusterwasoriginallydescribedasthe“Coma-Virgogroup”byShapleyand Further, iftheVirgoclusterisnotasinglenuclearcondensationatcenterof © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem m. DISTRIBUTIONANDCLASSIFICATION H. APPARENTDISTRIBUTION 196lApJS....6..213D circles: ellipticalsandlenticulars;crosses:typeunknown. Fig. 1.—Distributionof212galaxiesintheregion Virgocluster.Dots:spiralsandirregulars; © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 215 196lApJS....6..213D NGC 4152 4124 4123 4116 4073 4064 4045 4281 4273 4270 4269 4264 4262 4261 4260 4259 4257 4254 4247 4246 4241 4237 4235 4234 4233 4215 4193 4192 4189 4179 4178 4168 4165 4313 4312 4309 4307 4306 4305 4303 4302 4301 4299 4298 4294 4293 4277 4268 4267 4266 4224 4222 4216 4212 4206 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 20.1 20.0 19.7 19^5 17.8 17.4 17.3 17.2 17.0 16.8 16.8 16.6 16.3 14.9 14.7 14.6 14.6 14.6 10.3 10.2 09.8 09.7 05.6 05.1 01.9 OO^ 08.1 05.6 01.6 12 19.5 19.5 19.4 19.2 19.9 19.2 19.0 18.7 18.7 17.6 17.3 17.2 17.1 17.0 16.8 15.3 15.3 14.0 13.8 13.4 13.4 13.1 12.8 11.3 11.3 11.2 t 02°15 12 04 15 49 07 15 09 20 13 04 11 47 06 18 05 34 15 09 06 23 06 01 14 42 07 34 07 28 06 57 15 36 07 28 03 58 07 54 13 20 11 09 13 29 02 58 02 11 18 43 13 01 04 45 14 53 04 50 11 47 14 53 18 40 05 40 05 37 05 37 05 44 13 03 05 50 06 07 06 05 39 13 37 13 25 06 41 14 11 13 27 15 11 13 42 01 35 13 31 16 19 10 40 03 09 07 44 + + + + ELEMENTS OF212GALAXIESINTHEREGIONVIRGOCLUSTER (S) Revised Type SO: sp SB(s)c SO SB(s?)0" SB(s)a SA(s)c SAB(rs)bc SA(s)a sp SAB(rs)?cd SO sp E2 SB(r)dm SB(s)a:p SAab: sp SO/a: SAB(r)0 SO. sp S sp SB(rs)0 SB(s?)0" E2-3 SA:(s)a sp Sd :sp SAB(s)b SA(r:)0 sp SA(rs?)b SA:(s)bc SAB(s)?c SAB(s)ab SB(rjj)dm SAB: (r)0/a SAB(rs)c SA(r)0 SB(r)c SAB(r)a SAB(rs)bc Sc: sp SB?dp SA(rs)c SB(s)cd (R)SB(s)0/a + (SO+SO) (SO) (S: sp) (R?)SAB(s?)ab (Sa) (Im?) (SO orSa) (Sc+) (E?) (12.1) (13.9) (13.8) (14.2) (13.8) (14.8) (14.0) (14.0) (13.3) (13.6) (13.5) (15.3) (12.1) (13.6) (13.2) (12.9) (14.0) (14.9) (15.0) (13.8) 13.0 13.0 12.4 13.2 12.8 12.8 12.6 11.7 10.5 12.6 12.8 11.3 12.1 11.4 13.0 11.8 12.4 12.8 12.7 12.5 12.3 12.8 13.0 10.4 13.2 13.1 12.5 13.0 11.7 12.2 12.2 12.6 12.7 13.0 12.8 mR (12.7) (14,6) (12.4:) (12.5) 12.3 12.5: 12.3 12.0: 12.2: 10.9 12.6: 11.7 12.7 13.1 10.7 12.5 11.4 11.7 14.4 12.0 11.8 12.6; 13.8 11.7 12.1 11.3 12.1: 10.2 13.3 13.0 12.1 12.6 12.9 12.5 13.3 12.7 11.9 12.4 12.3 14.5 12.3 13.1 10.0 12.4 11.0 nvj. LogD TABLE 1 216 0.18 0.30 0.30 0.47 0.90 0.42 0.39 0.70 0.23 0.18 0.56 0.60 0.57 0.38 0.59 0.31 0.62 0.18 0.43 0.88 0.34 0.28 0.41 0.39 0.43 0.72 0.48 0.56 0.72 0.72 0.24 0.49 0.47 0.63 0.39 log D/d 0.24 0.06 0.51 0.17 0.27 0.25 0.45 0.06 0.43 0.69 0.48 0.22 0.51 0.06 0.40 0.44 0.03 0.09 0.20 0.69 0.01 0.19 0.41 0.01 0.37 0.07 0.47 0.70 0.03 0.72 0.01 0.29 0.41 0.47 0.38 log D(0) 0.53 0.46 0.28 0.41 0.28 0.70 0.42 0.23 0.52 0.17 0.13 0.16 0.36 0.23 0.34 0.18 0.26 0.60 0.11 0.38 0.26 0.12 0.41 0.35 0.28 0.69 0.29 0.28 0.71 0.43 0.24 0.37 0.31 0.44 0.24 +1149 + 143 +1175 + 967 +2047 +2094 +2390 +1557 + 693 +2492 +2191 +2236 +1179 km/s -202 V, -34 Member- WB WB WA WA WA WA WA WB WB WB X,NW WB w» X, NW X,NW? WA WA WA WA WA WA WA WB S S? S? E? S? S S S S S E E E S S s s S S S S E S (S?) (S?) (S?) ship 1 ( l< 5« <5« <5« < 5 Rem. <5« <5- <6° <5 >5°* <5° <5° *6' <5° <5‘ <5° <5°* <6< <50 <6° <50 <5°* 196lApJS....6..213D 4467 4464 4461 4459 4458 4457 4451 4450 4445 4442 4440 4436 4435 4431 4429 4425 4424 4421 4411 4411 4410 4406 4388 4452 4438 4420 4419 4417 4413 4402 4396 4394 4390 4387 4385 4383 4382 4380 4377 4374 4371 4365 4353 4352 4351 4343 4342 4341 4412 4379 4378 4370 4350 4340 4339 4326 4324 NGC 4334 4333 4321 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 27.0 26.8 26.6 26.5 26.4 26.4 26.2 26.1 25.9 25.7 25.6 25.4 25.3 25.2 25.2 24.9 24.9 24.7 24.1 24.0 23.9 23.3 23.7 23.6 23.5 23.4 23.3 23.2 23.1 23.0 22.8 22.9 22.8 22.7 22.6 22.4 22.4 22.0 21.5 21.4 24.6 24.5 24.4 24.4 24.3 24.0 22.8 20.6 21.5 21.1 21.1 21.3 21.0 24.0 21.0 20.8 20.6 20.8 20.6 20.4 12 08 26 14 15 12 36 08 16 13 28 13 31 03 51 12 02 09 32 17 21 09 42 12 34 13 17 13 21 12 34 11 23 13 01 09 42 15 44 02 46 15 19 09 52 12 53 04 14 09 09 09 18 13 13 24 15 57 10 05 18 29 10 44 12 56 13 05 00 50 16 45 18 28 10 17 15 33 07 43 11 29 05 12 15 02 13 10 11 59 07 36 08 05 12 29 16 58 07 16 07 22 07 23 17 00 06 22 07 45 06 19 05 31 06 21 16 06 + + + + + - + + + SB(s)0 : SA(r)0+ E0-1 SA(s)ab SB(s)0° SA(r)0 SO: sp SB(s)a: SB(s)0° SB(rs)a SA:(s)0/ap SB(r)bc SB(s)a sp SB(s)0: SB(r)0? SB(r)p E3 S:c SB:c sp SB(rs )0:. SA(s)0p SAO" SAa sp SA(s:)ab SAO sp Revised Type SA(rs?)b: E+l SB(r)0 E3-4 SA(rs:)b SO sp SB(r)0 E0 SA(r)0 (E2) SAB(s)bc (E3) (R)SAB(s)0/a (ÔO?) (SBa) (Sa) (SB) (SBA": sp) (SO?) (SC+) (Sc) (S+S) (S:) (R)SB(r)bc (SO:a) (SO/a?) (SBO:) (R)SA(s)a (I?) (S: sp) (SBO:c) (SB(s)ab) (SAB(r)ab?) sp l (14.7) (13.6) (12.5) (14.1) (14.2) (13.7) (13.1) (14.1) (12.3) (14.7) (13.4) (13.9) (12.4) (14.0) (13.6) (13.0) (14.2) (13.5) (13.3) (14.5) (15.1) (14.6) (15.3) 12.0 11.9 12.4 11.7 11.9 11.8 13.2 11.4 11.4 11.7 13.1 12.6 12'. 5 12.2 12.3 12.8 10.9 12.2 12.2 12.9 10.5 13.0 12.9 12.8 12.9 10.9 11.0 13.1 12.6 12.8 12.1 12.8 12.5 10.8 H TABLE 1--Continued (13.4) (12.4) (12.8) (12.4) (13.1) (12.5) 11.6 12.9: 11.9 11.6: 12.5: 10.8 11.5 10.9 11.5 11.1 12.3 12.2: 11.9: 12.1 13.7 10.0 12.5 10.0 11.8: 12.0 12.8 12.6: 12.9 13.5 11.5 11.7 12.7: 12.5 10.2 11.8 10.7 11.8 12.6 13.2 14.1 12.1 12.0: 13.5? 12.1 10.0 217 log D ■0.6 0.00 0.53 0.41 0.11 0.54 0.92 0.47 0.32 0.34 0.61 0.30 0.60 0.43 0.30 0.48 0.42 0.18 0.54 0.02 0.67 0.54 0.59 0.66 0.30 0.23 0.52 0.41 0.42 0.61 0.08, 0.48 0.26 0.81 0.42 0.35 log D/d 0.48 0.42 0.33 0*08 0.04 0.00 0.49 0.18 0.00 0.18 0.70 0.19 0.50 0.43 0.18 0.41 0.47 0.57 0.03 0.15 0.08 0.67 0.11 0.26 0.21 0.35 0.09 0.19 0.28 0.27 0.07 0.25 0.41 0.01 0.38 0.02 log D(0) ■0.7 • 0.02 • 0.03 0.00 0.33 0.34 0.11 0.25 0.34 0.59 0.40 0.37 0.06 0.53 0.75 0.23 0.44 0.24 0.30 0.17 0.48 0.56 0.39 0.13 0.49 0.34 0.51 0.26 0.45 0.26 0.29 0.19 0.17 0.19 0.20 0.80 +1379 +1104 +1813 +1042 + 309 +1995 + 493 + 796 +1809 +1628 +1027 + 721 +1130 +1122 +1173 +1605 +1551 - 105 - 418 km/s V 439 880 614 720 T f T T X, NW X, NW X, NW W’ W? W’ X,NW X,NW? W’ w? W’ X, NW? W’ ? W? X, NW Member- E E E E E S S’ S? S’ S S’ S’ W? E E E E E E E S S E E S’ S’ E s S E S’ E E S S? E E E? E E E S (S?) (S?) (S?) ship 1 < 5 < 6° < 5° < 5° < 5° < 5° < o < 5° < 5° < 50 < 5° <50 <50 <5< < 5‘ <5° <50 5 core core core core* core core Rem. core core core core core* core A, B A B 196lApJS....6..213D NGC 4630 4479 4478 4477 4476 4474 4473 4472 4469 4468 4506 4503 4501 4498 4496 4492 4491 4486 4483 4480 4623 4621 4612 4595 4584 4578 4571 4570 4564 4552 4539 4536 4527 4526 4523 4522 4519 4517 4517 4516 4497 4608 4607 4606 4596 4586 4580 4579 4576 4569 4568 4567 4561 4551 4550 4548 4540 4535 4532 4531 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 28.3 27.8 27.5 27.3 27.3 27.0 27.0 40.0 29.9 29.7 29.5 29.2 29.1 29.1 28.4 28.4 28.2 27.9 27.8 27.6 27.4 12 29.6 39.6 39.5 39.0 38.7 38.7 37.3 35.9 35.3 35.1 35.0 35.0 34.3 34.4 34.3 34.1 34.0 34.0 33.6 32.9 32.3 32.1 31.9 31.8 31.7 31.6 31.6 31.1 31.2 31.0 30.2 30.6 38.4 37.4 35.8 33.1 33.1 32.9 31.8 04 14 13 42 08 16 09 02 14 19 07 56 11 55 07 35 10 26 12 10 12 05 11 27 04 12 08 21 11 45 12 40 09 17 04 31 13 51 12 36 13 55 12 37 14 21 12 10 10 27 15 34 04 35 13 23 05 30 09 50 04 38 14 28 07 31 13 26 11 31 11 32 11 43 19 36 12 50 12 33 12 30 14 46 15 50 18 29 02 28 08 28 06 44 13 21 02 56 07 56 15 26 09 27 08 56 00 40 00 23 14 51 13 42 14 42 08 53 + (SB(s)a:) Revised Type SA(r:)0~ SB(s?)0/a sp E5 SB(r)0° SB(rs)m SB(s ?)0°: E2 SB(s ?)0° E5 E2 SB(s)? sp SB(s)a SB(r)0 SA(s)0/a: SAB(rs)a SAB(rs)b SA(r:)cd SO sp SAB (r^)ab SAB(rs)bc SAB(rs)bc SB(rs)dm SB(rs)b SAB(rs)cd SAB(s)bc SAB(s:)0° SAB(s?)cd SB(rs)d SB(rs)dm SA:(s)cd SBO": SA(rs)b EO-lp SO sp SAB(rs)bc SAB(s)c IBm E0 E3 (Pec) (E:5) (R)SABO° (Sa) (S) (Sc") (SO:) (SO orE) (Sc') (E7) (Sc?) (Sa) (Sep) (13.1) (13.1) (13.7) (13.9) (13.7) (13.9) (13.0) (13.9) (13.9) (13.2) (13.1) (14.4) (12.8) (13.0) '11.8 13.1 12.5 13.2 11.4 10.7- 13.3 12.5 13.2 12.9 11.7 10.1 12.6: 12.7 12.2 13.1 13.0 12.8 11.0 12.5 12.8 12.0 11.2 12.3 12.1 12.9 11.1 12.1 12.9 12.6 11.6 12.8 10.9 12.0 12.2 11.3 12.7 11.9 12.9 11.2 11.3 10.7 TABEE 1--Continued (11.7) (12.2) 9.3 12.0: 9.7 13.1: 12.5 11.1 10.1 11.9 13.0 13.5 12.1 11.,2 10.9 12.0: 12.6 11.6: 12.5 12.5 11.1 12.0: 12.0 13.7: 12.1 10.3 11.9 14.2 11.7 11.6 10.1 11.6 12.0 12.6: 12.3 10.9 12.6: 10.4 12.2 11.3 10.5 12.2 11.0 10.9 HLj 218 log D 0.64 0.54 0.54 0.06 0.11 0.50 0.08 0.29 0.42 0.78 0.58 0.11 0.46 0.24 0.41 0.36 0.98 0.41 0.53 0.30 0.62 0.44 0.49 0.51 0.89 0.60 0.39 0.25 0.35 O.O95 0.67 0.23 0.87 0.83 0.77 0.75 0.54 0.50 0.44 0.41 log D/d 0.52 0.11 0.08 0.03 0.06 0.03 0.06 0.25 0.40 0.27 0.83 0.27 0.14 0.24 0.02 0.20 0.40 0.44 0.39 0.20 0.52 0.09 0.11 0.19 0.51 0.58 0.61 0.14 0.12 0.03 0.13 0.02 0.51 0.32 0.00 0.17 0.57 0.20 0.44 0.43 log D(0) ■0.2 0.64 0.33 0.04 0.10 0.48 0.13 0.31 0.33 0.23 0.6/ 0.52 0.08 0.53 0.36 0.25 0.35 0.25 0.39 0.44 0.31 0.21 0.03 0.57 0.65 0.61 0.48 0.31 0.76 0.15 0.35 0.21 0.63 0.15 0.69 0.75 0.34 0.52 0.30 0.44 + 753 +1410 +1195 + 918 + 339 +1642 +1171 +1458 +2173 +1679 +2201 +1640 + 896 +2355 +2206 +1098 +2060 + 194 + 908 + 280 + 372 +1819 +1925 +1615 + 357 +1123 km/s V Member- X, SE XjNW X, NW X,NW X,NW? X,NW X jNW X, NW X,NW X,NW X*NW? S’ E E E E E E E E? E E? E S S E S S S S S S S? S’ S’ S’ E s E E S E E? E E E S S S? E S E ? ? ? ? ? (S?) ? ? ship A=R80 £ <6‘ Rem. core core core core core core core <5° <50 <6° <50 >6‘ <5* <5‘ <5‘ <5 <5‘ <5< <5‘ <50 <6° <5° <50 <5° <50 <50 <50 <50 <50 <5‘ <5° <50 <5° <50 <50 196lApJS....6..213D HA88- 4866 4845 4808 4795 4772 4762 4754 4809 4765 4734 4713 4710 4701 4698 4694 4654 4633 4632 4904 4900 4880 4810 4771 4689 4688 4665 4660 4651 4649 4647 4643 4639 4638 4637 4636 4634 NGC Membership intheseveralclouds discussedintext. mp =Totalphotographicmagnitudefromvarioussources (Holmberg, Sandage,deVaucouleurs). Remarks anddistancetocenters ofEorSclouds. n =numberofdiametersources. Revised morphologicaltype(deVaucouleurs1959c). NGC identification,Rightascensionanddeclination(1950). V =correctedradialvelocityfromred-shiftcatalogue (Humason etal.1956). 4192, 4216,foreground. 4178, nearbydwarf. 4342, 4365,4406,4438,4548,4713,foreground? log D(0)=logarithmofcorrected("faceon")apparent major diameterinminutesof log D/d=logarithmofaxialratiofromsamesources. log D=logarithmofapparentmajordiameterinminutes ofarcfromvarioussources ( *)Theentriesareasfollows: = HarvardmagnitudefromShaply-AmesCatalogue(H.A.88, 2),or,wheninparenthesis, © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem arc (deVaucouleurs1959b). reduced tohomogeneoussystem(deVaucouleurs1959b). similar system,generallyfromLunddata. 49.7 46.6 45.2 48.7 47.5 47.1 45.8 45.7 42.0 41.4 41.2 40.3 40.2 52.5 51.0 50.8 50.7 50.4 45.3 42.6 41.1 41.0 40.8 40.3 40.3 40.2 40.1 40.0 58.4 57.7 57.0 55.5 52.6 52.3 52.3 53.3 12 58.2 04 35 05 07 12 45 01 51 00 23 02 51 02 52 08 20 02 27 04 45 11 31 15 26 03 39 08 45 00 15 02 46 14 27 01 33 11 35 05 35 03 19 11 51 11 43 00 11 15 14 01 04 36 11 26 13 23 16 40 11 49 02 15 13 31 11 43 02 57 14 34 14 + + SB(s)cd SA(r)0: sp SA(s)ab SA(s:)cd SA(s)a SAd? SB?(r)0° sp SB(r:)0” SAB(rs)d SA(s)cd SA(s)ab SBOp Revised Type SB(rs)c SB(s)d Imp SA: (r)0sp SA(rs)bc SAB(rs)cd SA(rs)c SB(rs)0/a SO" sp Sd: Imp SB(s)0/a E2 SAB(rs)c E+0-1 SB(s)d: sp SAc (Sc:) (Sa orSm) (S?) (S?) (Sbc) (S) (E6 orSO'sp) (13.5) (13.6) (13.4) 12.8 11.8 11.8 12.8 13.1 12.1 12.6 12.9 13.1 12.6 12.9 12.9 12.3 12.0 12.2 12.0 12.5 12.0 12.6 13.0 11.8 11.8 10.6 12.0 11.6 12.3 12.2 10.8 12.1 12.3 11.7 mR TABLE 1--Continued Notes toTable1 (12.3) (12.8) (12.2) 11.8: 12.5: 11.8: 11.5 12.0: 11.5 12.0 13.1 12.2: 11.8: 11.9 12.5 12.1: 12.2: 11.1 11.4: 11.4: 12.0 11.0 11.2 11.5: 12.1 12.1 10.4 13.7 11.8: 11.8: 11.9: mr 9.9 219 log D 0.47 0.62 0.52 0.39 0.34 0.45 0.57 0.06 0.29 0.61 0.57 0.95 0.61 0.41 0.61 0.20 0.50 0.35 0.19 0.56 0.67 0.39 0.47 0.25 0.61 0.50 0.39 0.23 0.63 0.54 log D/d 0.48 0.14 0.69 0.16 0.36 0.44 0.48 0.47 0.90 0.36 0.09 0.25 0.04 0.31 0.08 0.34 0.41 0.12 0.67 0.55 0.18, 0.76 0.04 0.06 0.32 0.17 0.04 0.14 0.23 0.03 log D(0) -0.01 0.28 0.33 0.14 0.37 0.05 0.40 0.47 0.35 0.46 0.37 0.45 0.12 0.51 0.47 0.48 0.37 0.23 0.20 0.11 0.42 0.38 0.59 0.57 0.33 0.30 0.40 0.37 0.30 0.45 +1011 +1398 +1379 +1324 +1862 + 870 + 870 + 574 +1248 + 958 + 810 kra/s 955 950 684 858 Member- X, SE X, SE X, SE X, SE X, SE X, SE X,SE X, SE X, SE X, SE X, SE X, SE X, SE X, SE X, SE X, SE S? E S X,SE S X, SE E? E? S S? S E S E? E E S ? ship <5- <5‘ Rem. <5° No4 <5° <5° <5° <50 <50. <50 >6° <6° <50 <6° 220 GERARD DE VAUCOULEURS

Figure 2 is a plot of whose revised types are E or SO (called here the “ellipti- cals” for brevity) ; Figure 3 is a plot of galaxies having revised types Sa, b, c, d, m, or Im (the “spirals”). Some striking distributional differences are in evidence. In the proper the ellipticals are scattered mainly in two opposite fan-shaped sectors to the northwest and southeast of a dense central core of 19 systems, centered at C^(12h 26.5m, +13?2), and 2° in diameter. The spirals are more uniformly distributed in an elliptical cloud measuring 9° east-west by 5° north-south, with a vacant area 2° in diame- ter near its center at Cs(12h 27.5m, +13?9). The dense group of ellipticals is apparently the core of both distributions, but neither the shapes nor the orientations of the E-cloud and of the 5-cloud agree. The mean radial density distributions, given in Table 2, are also completely different. TABLE 2 Radial Distributions in Virgo Cluster

Center

C^(12h 26.5m, +13T2) Cs(12h 27.5m, +13?9)

N* N/AÏ N* N/A¡

o 0°-lo 17 5.4 1 0.32 l _2° 8 0.85 10 1.06 20-3° 3 0.20 14 0.89 30-4° 9 0.41 15 0.68 40-5°, 10 0.35 15 0.53 50-6° 9 0.26 6 0.17 60-7° 8 0.20 ±p.e. +962 + 69 +1362 + 128 ^ M 631 (38) 825 (19)

* Number of objects, t Number per square degree.

The Virgo cloud extension (Cloud X) is poor in ellipticals and rich in spirals. It may overlap, at least in the projection, with the southernmost fringe of the Virgo cluster. In addition, a conspicuous excess of both E and S systems is present in a region, about 3° in diameter, around the group near 12h 17m, +6° (Cloud W).

iv. distribution and velocity a) The E- and S-Clouds The velocity distributions also show remarkable differences set out in Table 2A. Within 6?5 from Ce there are 64 ellipticals, of which 38 have known velocities; the mean of this group is = +962 + 69 (p.e.) km sec-1, and the velocity dispersion is (Te = 631 km sec-1. Within 6° from Cs there are 61 spirals, of which 19 have known velocities; the mean radial velocity of this group is (Vs) = +1362 + 128 (p.e.) km sec-1, and the velocity dispersion is as = 825 km sec-1. The difference between the mean velocities of the two groups is 8V = (Vs) — (Ve) = +400 + 146 (p.e.) km sec-1. The probability that the mean radial velocities of the E- and 5-clouds are actually equal and that the observed difference 5F/p.e. ^ 2.8 is due to chance is only 6 per cent for Gaus- sian distributions. Further division of the material leads to the results summarized by Table 6. The E- cloud may be divided into three parts: (a) a core, including 19 objects within 1?25 from

© American Astronomical Society • Provided by the NASA Astrophysics Data System 196lApJS....6..213D © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem I3h 504030 20 10I2h Fig. 2.—Distributionofellipticalandlenticulargalaxies 196lApJS....6..213D © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Fig. 3.—Distributionofspiralandirregulargalaxies 196lApJS....6..213D 1 1 1-1 1 -1 1 -1 objects withnegativevelocitiesarerejected. whole cloudis(Vs}=+1362±128(p.e.)km sec“(n=19),or+1536±111iftwo velocity distributionreasonably symmetricalaboutitsmean,thevelocity distributionin mean as~750kmsec“. conclude that,exceptfor theapproximatecorrespondenceofcore the E-cloudwith a highlyasymmetricaldistribution byrandomsamplingofaGaussianvelocity distribu- and 0.01,respectively.However,asTable2^4 Figure4show,whiletheE-cloudhasa in thefirstcase,4.1timessecond. following half(NGC>4500),including19objectswithin4?5inR.A.fromCs-Themean the “hole”in thecenterof5-cloud, thesurfacedistributions, meanvelocities, and tion withmean~1000 kmsec“anda«550secisobviously verysmall.We the 5-clouddepartswidely fromaGaussiandistribution.Theprobability ofdrawingsuch ability thatthesedifferenceswereduetosampling fluctuationswouldbelessthan0.05 the restricted5-cloud.Includingallobjectswithin 6°fromCs,themeanvelocityof negative velocitiesarerejected. two Ssystemswithnegativevelocities).Thedifference, 5F,is2.9timesitsprobableerror the E-cloud,withameanve^550kmsec“,andfrom390to1090inS-cloud, are consistentlyhigherthanforthevariouspartsofE-cloud;meanvelocityis magnitudes, diameters,andvelocitiesofthetwohalvesarealsoincloseagreementbut ing half(NGC<4500),including23objectswithin4?5inR.A.fromCsand(b)the from Ce- mean velocityofthewholecloudsodefinedis=+935±70(p.e.)kmsec(n (Ve} =+427±146(p.e.)(norejection),or+524 ±128(p.e.)(rejectingtwoEand 4400),including21objectswithin6° Ce,' (b)thenorth-precedingsector(NGC<4400),including11objectswithin6°from =+1405±166(p.e.)kmsec(n13),or+1682128iftwoobjectswith 0 -1 The velocitydifferencebetweenthe5-andE-clouds sodefinedisdV=(Vs}— A smallgroup(S')of11spiralslies4-5°southCs(Fig.3);themeanvelocity The velocity-dispersionvaluesrangefrom258to720kmsecintheseveralpartsof If thefrequencydistributionsofvelocitiesin eachcloudwereGaussian,theprob- The inner,ellipticalpartoftheS-cloudmaybedividedintotwoparts:(a)preced- The meanmagnitudes,diameters,andvelocitiesofthethreepartsagreeclosely; © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem fl *r <6 Velocity DistributionsinVirgoCluster* VIRGO CLUSTER TABLE 2A 223 196lApJS....6..213D -1 -1 -1 velocity-distance relationislinearwithA=F/120(AMpc,Fkmsec;vandenBergh velocity distributionsoftheE-and5-cloudsaresomarkedlydifferentastomaketheir width isatleast(11.3—8.0)(0.8+1.1)=1.4Mpc. physical associationappearverydoubtful. are 0.8and1.1Mpc,respectively,theymaybeseparatedbyanear-emptygapwhose apparent radiiofthetwogroupsareR—6°,maximumlinearclouds ropy ofthevelocityfieldamongbrightgalaxies(deVaucouleurs1958,1959a)andderive A^ =8.0±0.7(p.e.)Mpc,andofthe5-cloudAs11.31.3Mpc.Since 224 GERARDDEVAUCOULEURS where larger thanontheassumption ofalinearvelocity-distancerelation. supergalactic longitudes Loand+15°,whichcovertheregionofinterest; throughthe with Ricoi=500kmsecandRiei1100 sec.ThecurvesinFigure5arefor the velocity-distancerelationindirectionof theVirgoclusterfromrelation As =(1.45±0.15)Ri, or 7.0and14.5Mpc,ifRi=10Mpc.Theseparation iseven curve forLothevelocities FeandVscorrespondtodistancesA=(0.70 ±0.10)Riand 1960a), themeanvelocities,takenatfacevalue,implythatdistanceofE-cloudis E To statetheresultsdifferently,ifinafirstapproximationoneassumesthat In asecondapproximationoneshouldtakeintoaccountthenon-linearityandanisot- We concludewithaprobability of95-99percentorgreaterthattheVirgo “cluster”is © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem F =Ri[œ(R)—o>i]sin(LLo)Ei[e(R) ej cos(L—L)+e(R)r, r 0 Ri ce (R)—o3oe~^/i)andou=0.368o>o, Ä/Ä-1 e(R) =€oo(l—e~i)andeie(le) =0.632€oo, Fig. 4.—^VelocitydistributionsintheE-and5-clouds e VIRGO CLUSTER 225 a chance superposition of (at least) two nearby, but separate, clouds aligned at different distances on the line of sight in the dense central regions of the Local Supercluster. If so, the center of gravity and of the presumed rotation and expansion of the system need not be identified with any particular cluster.

b) The X- and W-Clouds The Virgo extension (Cloud X) south of +7° includes 42 objects (9 E, 29 S, 4 unclassi- fied), of which 6 ellipticals and 8 spirals have known velocities; the mean velocity is

Fig. 5.—^Velocity-distance relations in the directions Lo of the Virgo cluster and Lo + 15°

(Vx} = +1185 ± 74 (p.e.) km sec-1. In this direction the velocity-distance relation is as shown by the curve Lo + 15° in Figure 5, and the corresponding distance is Ax = (0.9 ± 0.2) Ri, ot about 9 Mpc on the same distance scale. There are striking differences and apparent inconsistencies set out in Table 3 between the velocities, magnitudes, and apparent diameters of the northwest and southeast halves of Cloud X separated by its minor axis. Magnitudes and diameters indicate that the northwest half is the nearer, at about two-thirds of the distance of thë southeast half, while the velocities suggest the converse situation. The velocity differential, ÔF = F(NW) — F(SE) = +632 + 100 (p.e.) km sec-1, is apparently significant. On the as-

© American Astronomical Society • Provided by the NASA Astrophysics Data System 196lApJS....6..213D -1 11 r -1 -1 Largest S:(logD(0)}. all intheLocalSupercluster. if thetiltofequatorialplaneisabout45°andradius6°.Whenthismassdivided sumption thatitisduetorotation,astheellipticaloutlineofcloudmightsuggest 226 GERARDDEVAUCOULEURS among the42systemswithinoutlineofCloudX,theirmeanmasscomesout again resultsfromtheaccumulationalonglineofsightseveralindependentgroups, still highermasses.ItisthereforepossiblethatCloudXnotastablephysicalunit,but persion forthewholecloudisex=408kmsec,andvirialtheoremwouldleadto Brightest S:(m).■ Brightest S:{m). Mean velocity:(Fo). (Fig. 1),themassofcloudisorder (93Î) <5X10O,whichisalmostoneorderofmagnitudetoohigh.Thevelocitydis- or, moreprecisely,A*r=(2.03+0.03)i?i,about 20Mpc,accordingtoFigure5. which 3ellipticalsand1spiralhaveknown velocities; themeanvelocity,{Vw}= groups W-aandW-b. on”) apparentdiametersofthe4brightestor largestsystemsareaboutthesamein available, but,asshowninTable4,theapparent magnitudesandreduced(i.e.,“face- in frontofamoredistant group(VirgoW)of8spiralswhose4brightest membersaver- age {mn)—13.9.Noreduced diametersorvelocitiesareavailable,but, fromtheappar- tion of4ellipticals(NGC 4324,4339,4342,4365,(mu)=12.2, +1130 kmsec) +2253 +54(p.e.)kmsec,indicatesadistance abouttwicethatoftheVirgocluster, T H 12h 14m,+7?5(GroupW-b),whichincludes 7 objects(2E,55).Novelocitiesare * Foralinearvelocity-distancerelation, The compactgroupat12h17m,+6°(GroupW-a), includes12objects(7E,55),of t Forthevelocity-distancerelationofFig.5. The smallgroupingnear 12h21m,+7?5(Table5),resultsapparentlyfrom theprojec- This groupisapparentlyataboutthesamedistance asthenearbygroupcenterednear © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Largest 5,SO:(logD(0))... Listed inTable1 Brightest S,SO:(m) Mean velocity:(Fo) H * Near12h17m,+6°:NGC4257,4259,4260,4261,4264,4266,4268, 4269,4270,4273,4277,4281. f Near12h14m,-f7?5:NGC4215,4224,4233,4235,4241,4246,4247. 11-2.1X10-0 +1501 +70 0.65+0.02 11.1+0.2 10.8+0.2 NW half Elements ofCloudVirgoX Elements ofCloudVirgoW +2253 +57 12.5 tF-a 0.22 TABLE 4 TABLE 3 +869 +75 0.41+0.01 11.6 +0.1 11.8 +0.1 12 SE half 4 4 5 12.9 W-b 0.25 (1.73* or2.641) 0.57 0.69 0.72 196lApJS....6..213D -1 f -1 -1 5000 kmsec.ThisdistantgroupisclearlynotapartoftheVirgocluster. larity isobvious. cloud and34galaxiesoftheE-cloud.Thesystematicdifferencebetweenvelocities within 6°fromCeorCs,excludingmembersofcloudsVirgoX,W,andW. ent magnitudes,thepredictedvaluesare(D(0))=1Í0(4largest)and4000- E-cloud; ifso,thevelocity rangeisfrom+200to+1800kmsec. relation intherange10«+1,000,butthedistribution isnotsymmetrical.Onlyone objects. NGC4178,4192,and4216areprojected ontheprecedingedgeof5-cloud, panying table.NGC4178isclearlyadwarfirregularintheforeground;largeap- system, NGC4406,isoutstanding atmr=10.0,Fo—418;sinceitis alsooneofthe and, inparticular,4178iswelloutsidethemain cloud(Fig.3). parent diametersoftheothers(Sec.VI)alsosuggest thattheyareprobablyforeground others arelessthan+1850, thereisapossibilitythatthesesystemsare notpartofthe systems—NGC 4473and 4578—havevelocitiesinexcessof+2150km sec;sinceall distributions ofvelocitiesarecomparedinTable2^4andFigure4;theirgreatdissimi- area nearthecenterofdistributionat(mr)=11.2,

VI. VELOCITY AND DIAMETER Figure 7 shows plots of velocity versus log D(0) for 19 galaxies in the 5-cloud and for 38 galaxies in the £-cloud. Again, for the 5-cloud there is no concentration near the center of the distribution at (Vs) ~ +1500, (log = 0.54, but a weak correlation is indicated between diameter and velocity, as might be introduced by the inclusion of a few foreground and background objects affected by the velocity-distance relation. In par- ticular, the two outstanding objects with negative velocities—NGC 4192 and 4216— have above-average diameters, and they may be in the foreground. The mean reduced diameter of the four largest systems in the 5-cloud is D(0) = 5Í6. In the 2£-cloud the distribution is fairly symmetrical about the center at (Ve) « +1000, (log T>(0)> = 0.28. There is no correlation between diameter and velocity. Four systems are clearly outstanding: NGC 4406 and 4438 with F < 0 and NGC 4473 and 4578 with V > +2000. The mean reduced diameter of the four largest systems in the E-cloud is D(0) = 3 Í 9. The elements of the two clouds in the Virgo cluster are listed in Table 6. The reduced apparent diameters of spirals can be used to estimate relative distances (de Vaucouleurs 1956&, 19596). In Table 7, line 3, geometric distance moduli are com- puted for a mean reduced diameter of the four largest spirals equal to 20 kpc (cf. de Vaucouleurs 19596). For comparison, photometric distance moduli (rn — M — 0.2) are given in lines 8 and 9 for an assumed mean absolute magnitude of the four brightest galaxies, Mt = —20.0, or approximately Mr ~ —19.5. The major diameters of the various clouds are given in line 11 for the adopted dis- tances of line 10. The groups have diameters of the order of 0.5-1 Mpc (about equal to the diameter of the ) ; the larger clouds have diameters of the order of 1-2 Mpc. It is not possible to determine the relative distances of the E- and 5-clouds from the present data; however, it was shown previously (de Vaucouleurs 1958), from the residuals in the velocity-magnitude relation, that the dispersions of absolute photographic magni- tudes of giant E and 5 systems are very nearly equal and that, on the average, (Me) — (Ms) = +0.4 mag. If so, the relative distances of the E-cloud and of the ellipticals in the foreground of group Wf can be estimated as shown in Table 7. The reduced apparent diameters of ellipticals cannot be used at present for distance estimates because the cor- responding linear diameters have not yet been estimated; however, the ratio 15.5/7.1 = 2.2 of distances derived from magnitudes in Table 7 is in good agreement with the ratio 1.9 of the apparent diameters in the E-cloud and the Wf foreground group. The ratio of distances of the 5- and E-clouds, 11.0/7.1 = 1.55 in Table 7, is also in fair agreement with the ratio 1.4 (or 2.1) derived from velocities in Section IV. However, peculiar velocities of individual clouds and groups introduce a substantial scatter in the distances derived from velocities. Note, in particular, the low velocity of Cloud X(SE) in relation to its estimated distance and also the negative velocities of the group of fore- ground objects discussed in Section V. The picture emerging from this discussion is of an irregular distribution of groups, clouds, and clusters with diameters of the order of 0.5-2 Mpc and peculiar velocities of the order of 500 km sec-1 scattered in depth in the equatorial plane of the Local Super- cluster toward its center. The Virgo “cluster” itself is to some extent an appearance re- sulting from the superposition of at least two clouds, the E-cloud and the 5-cloud, with different populations and velocities and at different distances. An inspection of the Lick (Shane 1956) and Palomar (Abell 1958) charts of galaxy and cluster distributions indicates that similar conditions prevail in other, more distant super- clusters, outside the local supersystem.

© American Astronomical Society • Provided by the NASA Astrophysics Data System 196lApJS....6..213D © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 500 01000 2000 •600 010002000V Fig. 7.—Velocity-diameterdistributionsintheE-and5-clouds 230 V 196lApJS....6..213D n (r<6°) All E All S All S All Si,S (inner- ± 0 (outer- 0 cloud) cloud) (r <6°) Group Core Others np sf © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 2 rejectingnegativevelocitiesNGC4192,4216. 3 r<6°,butoutsideinnercloud. 1 rejecting2negativevelocitiesNGC4406,4438F. 11.05 12.26 10.67 12.15 12.36 11.58 12.32 12.02 11.00 12.38 10.48 12.24 11.20 12.3: 10.80 11.95 12.53 12.96 11.63 12.75 10.80 12.40 Mean magnitudes and 4brightest (10) (21) (17) (48) (13) (19) (32) (16) (48) (4) (4) (4) (4) (4) (4) (8) (4) (8) (4) (4) (4) (4) ELEMENTS OFTHEE-ANDS-CLOUDSVIRGOCLUSTER 10.20 11.66 10.15 11.44 11.25 12.01 11.81 11.96 11.67 11.89 10.35 10.45 11.7: 12.38 10.10 11.3: 11.85 10.95 12.13 11.96 10.10 9.73 (ID (18) (44) (18) (15) (16) (34) (15) (49) (4) (4) (4) (4) (4) (4) (8) (4) (7) (4) (4) (4) (4) log D(0)n 0.27 (20) 0.28 (16) 0.32 (9) 0.42 (14) 0.29 (45) 0.44 (26) 0.47 (12) 0.38 (6) 0.38 (7) 0.38 (13) 0.42 (39) TABLE 6 231 Mean logD(O) and 4largest log D(0)n 0.47 (4) 0.63 0.52 0.56 0.70 (4) 0.67 0.74 0.47: (4) 0.52 (4) 0.59 (4) 0.75 (4) (4) (4) (4) (4) (4) (1173 +103) (1012 +64) (1904 +132:) (1686 +126) (1536 +11]) 1230 +300: 1564 +187 1409 +166 1563 +158: 1258 +202 1362 +128 Velocity and p.e. 929 +87 981 +125 935 +70 886 +97 953 +370: Mean 1090: 6 (553 13) Velocity (390: 4) (523 31) (678 17) (632 11) Dispersion 258 4 538 14 595 33 720 15 406: 3 890 13 733 7 947: 3 732 6 825 19 rr' n Rem. 196lApJS....6..213D 12 -1 -2 14 14 where per galaxyisstilloftheorder—10O, asbefore. shown thatthemassisgivenby symmetrical toencourageanapplicationofthevirial theorem.Schwarzschild(1954)has virial theoremwouldbemeaningless.However, itmightbeestimatedfromthevelocity range, about3000kmsec(Fig.4),thatthe escapevelocityisprobablylessthan strongly suggestthatitisnotanequilibriumconfiguration,andapplicationofthe Diameter (Mpc) (tn—M)o (F)^ =1500kmsecandthatthemassisVSDîl =VIR/2G<3X10O(cf.Smith (f?i—M—0.2)7’. (tn—M)o 1936). Ifthetotalpopulationofgiantspiralsin the 5-cloudisns~100,meanmass A(Mpc) results fromtheseparationoftwocomponents. independent clustershavingdifferentmeanvelocities.Sinceatleasttwodistinctclouds virial theorem(deVaucouleurs1960)couldbeexplainedbythemixingoftwoormore seem tobeinvolved,itisinterestingseewhetheranyreductioninthemassestimate e normally highmassvalue,VSW*~6X10O,fortheVirgoclusterderivedfrom (fttn) (log D(0)) (ntr) 232 GERARDDEVAUCOULEURS -1 The surfaceandvelocitydistributionsoftheE-cloud aresufficientlyconcentratedand 9. 10.Adopteddistanceanddiameterinmegaparsecs. 8. Correctedphotometricmodulusfor(Mf)«—19.5(fourbrightest). 4. GeometricmodulusforV/A—120kmsecMpc. 3. Meanradialvelocity. The surfaceandvelocitydistributionsofgalaxiesinthe5-cloud(Figs.35) 5. Meantotalmagnitudeoffourbrightest. 2. Geometricmodulusfor(Z>(0))=20kpc. 6. MeanHarvard-Lundmagnitudeoffourbrightest. 7. Correctedphotometricmodulusfor(Afr)=—20.0(fourbrightest). 1. Meanlogdiameteroffourlargest. This studyoftheVirgoregionwasinitiallyundertakentofindoutwhetherab- © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Relative DistancesintheRegionofVirgoCluster 1450 30.2 30.0 30.4 30.4 11.2 10.2 10.9 0.75 2.3 VH. MASSFROMVELOCITYDISPERSION 1500 X(NW) 30.4 30.6 30.5 30.9 13.2 10.8 11.1 NOTES TOTABLE7 <¿0 =2 0.65 1.3 TABLE 7 870 X(SE) 32.1 31.1 31.4 29.3 16. ± 11.6 11.8 0.41 1.6 C/>0’ j/* R 2 0 ! Sdq 2250 Cloud FF-a 31.4 33.0 31.8 25. ± 12.5 0.22 0.4 32.9 32.2 32. ± 12.9 W-b 0.25 0.8 (60. ±) 33.4 13.9 W' 1.0 950 29.4 29.1 29.5 11.6 9.7 0.50 1.5 7.4 Notes 10 4 9 3 8 6 2 5 7 1 196lApJS....6..213D lö411 10 16 6 -1 -1 3-1 26 16 15 12 14 , 5DÎ* «3X!0/310=O,aplausible, thoughstillhigh,value. initial velocitiesgreater than Vwillhaveescaped,whileobjectswithvelocities lessthan mated maximumradius ofthesystem(deVaucouleurs1956,1958).Objects formedwith to dowiththemassof thesupersystem,forin10yearsagalaxywhose velocityis Väft* «3X10O.Thisresultisofthesame order ofmagnitudeasthevalueV9ÏΫ total populationofthesupersystemisV« lO^lO, themeanmasspergalaxyis if thevelocitydispersion,a^650kmsec,isassociated to~10Mpc,thenagain the escapevelocity,V—1500kmsec,should beassociatedwiththeaverageradius, tional potential,itmustbewiththepotentialof theLocalSupersystemasawhole;ifso, velocity dispersion(deVaucouleurs1960;vandenBergh19605). V willstillbefoundinside thesystem,irrespectiveofitsmass,aslong as itisnotlarge separate componentsdoesnotreducesignificantlythehighmassvaluesderivedfrom Ve =1.5X10kmsec willmove4.5X10cm=15Mpc,whichisequal totheesti- e 10 Oderivedfromthegeneralrotationof system(deVaucouleurs1958).Ifthe (R) «10Mpc,ofthesupersystem,anda'mass V3)î*«3X10Ofollows.Similarly, population Ne~100themeanmasspergalaxyis1.5X10O. The apparentmassoftheclusterisstillorderVüDîJ~1.5X10O,andfora or e eliminate possibleforegroundandbackgroundobjects.Inbothcasestheassumeddis- e results arecollectedinTable8for58EandSOgalaxieswithin6°fromCe,'values using aharmonicmeandistanceandlessarbitrarythantheoreticalmodel.The tance isAe=7.5Mpc(meanofestimatesinSecs.IVandVI).Thederivedmassesare also givenfor47objectswithin5°fromCe,rejectingNGC4406,4438,4473,and4578to if the5'(^)sare“stripcounts”(marginaldistributions).Thismethodissimplerthan It isalsopossiblethatthevelocitydispersionand escapevelocityhavelittleornothing If thevelocitydispersionandescapein twocloudsarerelatedtoagravita- We mustconcludethatresolvingthemultiplestructureofVirgoclusterintoits © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem 47. S3 58. Sa (S) Apparent MassoftheE-CloudfromVelocityDispersion S Sdq vm. DISCUSSIONANDCONCLUSIONS 14 14 NTll <2.3X10O(f*=33) im% >1.0X10O(n=26). 5?4 7?0