Publications of the Astronomical Society of the Pacific 98:403-422, April 1986
SYSTEMATIC REINVESTIGATION OF THE RADIAL VELOCITIES OF THE GALACTIC GLOBULAR CLUSTERS: IMAGE-TUBE RESULTS
JAMES E. HESSER* Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V8X 4M6, Canada STEPHEN J. SHAWL*t AND JAMES E. MEYERti Clyde W. Tombaugh Observatory, University of Kansas, Lawrence, Kansas 66045 Received 1985
ABSTRACT
Radial velocities measured from ~ 260 image-tube spectrograms at 120 A mm-1 of 90 Galactic globular clusters and NGC 121 in the Small Magellanic Cloud are presented and compared with previous major surveys. Velocities are also deduced from 23 evolved stars in four globular clusters. The data base is the largest homogeneous one currently available. Taken in conjunction with our earlier work, as well as that of Zinn and West (1984), Table III provides velocities for 22 Galactic globular clusters previously lacking them. Furthermore, the precision with which an additional ~ 18 cluster velocities are known should be substantially improved by virtue of our second, independent measurements. Rest wavelengths are given for the spectral features analyzed, and approximate wavelengths are tabulated for other features measured but not used in the velocity analysis. Solid-body, solar-motion solutions are used to probe the impact of our homogeneous set of image-tube velocities on earlier studies; in spite of a larger data base and more uniform sky coverage, net differences are small. From our data alone the solar apex is found to lie at α = 21h10m ± 52m and δ = 44?9 ± 9?8 or € = 88?1 and b = — 2?2. Evidence for the G-type clusters rotating more rapidly than the F-type ones persists. The availability of new spectral classifications reveals more distinct differences in velocity dispersions from the solar motion solutions for F- and G-type clusters, ~ 128 km s-1 and ~ 86 km s-1, respectively, than heretofore recognized. The velocity dispersion for the cluster system as a whole is ~ 120 km s_1. Similar results were found in an extensive analysis by Zinn (1985) based on separating the clusters into two metallicity groups at [Fe/H] = -0.8. Key words: catalogs-clusters of stars: globular-galaxies: structure-galaxies: Magellanic Clouds-Milky Way system-radial velocities-spectroscopy
I. Introduction velocities of clusters close to the Galactic center are not Precise radial velocities are required for analyses of consistent with a simple steady-state model of the Galac- global properties—spatial, kinematical, and chemical-of tic halo; Rodgers and Paltoglou (1984) infer from their the Galactic globular clusters. For example, Hartwick derived Galactic rotation that the Galactic globular clus- and Sargent (1978), Frenk and White (1980), Lynden- ters originated from the coalescence of a small number of Bell, Cannon, and Godwin (1983), and Peterson (1985) galaxies; and Zinn and West (1984) and Zinn (1985) have analyze the velocities of outlying clusters and dwarf inferred abundance and spatial distribution patterns spheroidal galaxies for their implications about the mass within the Galactic globular-cluster system. Accurate ra- of the Galaxy; Clube and Watson (1979) suggest that radial dial velocities also find application to the search for gas in globular clusters (e.g., Klein 1976; Smith, Hesser, and Shawl 1976; Faulkner and Freeman 1977; Hesser and Shawl 1977; VandenBerg 1978; Troland, Hesser, and *Visiting Astronomer, Cerro Tololo Inter-American Observatory, Heiles 1978; Bowers et al. 1979) and for discriminating National Optical Astronomy Observatories, which is operated by AURA, Inc., under contract to the National Science Foundation. cluster members from field stars (e.g., Zinn, Newell, and tVisiting Astronomer, Dominion Astrophysical Observatory. Gibson 1972; Nemec 1978; Smith and Perkins 1982; Har- tPresently at San Diego State University. ris, Nemec, and Hesser 1983; Peterson 1984).
403
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 404 HESSER, SHAWL, AND MEYER
At the genesis of this project in 1975, radial velocities was installed on the CTIO/Yale 1-meter telescope, we were available for 76 clusters, 70 of which arose princi- decided to obtain spectrograms of as many clusters as pally from the work of Mayall (1946) and Kinman (1959a). possible. In addition to the previously mentioned need The monumental, pioneering work of Mayall (1946) for initial velocity values to interpret the Fabry-Perot largely relied on the 0.9-m Crossley reflector at Lick data, we felt that a general consistency check with the Observatory (latitude +37°) and its two-prism spec- velocities to be deduced from Fabry-Perot observations trograph, which gave a linear reciprocal dispersion of ~ was desirable, inasmuch as its previous use had been only 430 A mm1 at H7. As many clusters as possible were also on emission-line nebulae. This paper, then, reports the observed with the 0.9-m refractor at ~ 130 A mm"1 as a velocities deduced from — 260 image-tube spectrograms check on the velocity system of the lower-dispersion of 91 globular clusters, while the next paper in this series Crossley spectra. Although the southerly declinations of (Shawl and Hesser 1986) will present the Fabry-Perot the bulk of the Galactic globular clusters posed enormous velocity results. difficulties,1 Mayall nonetheless succeeded in obtaining four, and sometimes more, spectrograms of each cluster. II. Observations and Analysis Kinman (1959a) took advantage of the southern lati- Details of the observations are reported in our previous tude (—26°) of the Radcliffe Observatory at Pretoria to papers on spectral classifications (Hesser and Shawl measure clusters which could not be studied from Lick. 1985-Paper I) and on the establishment of the velocity He used the two-prism Cassegrain spectrograph with a system for the image-tube spectrograph as applied to dispersion of ~ 86 A mm-1 at H7 to obtain 69 spectro- ~ F0-~ K4 Population I stars (Shawl et al. 1985-Paper grams from 4000 Â-4400 A of 18 clusters and 64 spectra of II). Briefly, the spectrograms were obtained with the 41 giant stars in 13 clusters. Kinman's Table VIII compila- Boiler and Chivens Cassegrain spectrograph and RCA tion served as the standard reference on cluster velocities 33033, two-stage, magnetically-focused image tube on until Webbink s (1981) compilation appeared. the CTIO/Yale 1-meter telescope on 27 nights between While searching for ionized hydrogen in globular clus- June 1975 and May 1978. The important spectrograph ters using the AURA single-etalon Fabry-Perot interfer- parameters were as follows: 3.63 mm slit length (71 arc sec ometer (Smith, Hesser, and Lasker 1978), the potential of at the focal plane); 150 microns (2.9 arc sec) slit width (21 this instrument to provide precision, integrated-light ra- microns projected at the plate); 120 A mm-1 nominal dial velocities became clear (Smith et al. 1976; Hesser and linear reciprocal dispersion; 0.53 mm projected spectrum Shawl 1977). However, its ~ 150 km s-1 free spectral width. Exposure times ranged from a few minutes to range requires prior knowledge of the cluster velocity to more than three hours. Sampling of the composite light ± 50 km s1 to determine to which order a given line (described in Paper I) was achieved (with few exceptions) profile belongs. This poses problems when clusters lack- by trailing the in-focus image on the slit. Care was taken ing a previous velocity determination are observed, or to avoid very bright stars, or dwelling on obvious clumps when previous measurements are so uncertain that the of stars that might have dominated the resultant spec- order choice becomes problematical. Our initial experi- trum. (That the spectra obtained are, with rare excep- ences suggested that some velocities in the literature may tions, uniformly exposed (see Fig. 1 of Paper I) suggests be substantially in error. that our sampling process was successful.) All told, some Thus, when in 1975 a new image-tube spectrograph ~ 260 spectra of 91 globular clusters were obtained; 72% of the clusters were observed more than once (Fig. 1). In addition to the spectral observations of the integrated or a June 1985 letter to us Dr. Mayall writes: "My chief recollection of composite light of Galactic globular star clusters, individ- using the Crossley on the globulars is how often I had to reverse the tube ual giant stars were also measured in four clusters.2 and rotate the upper section with the spectrograph. I would disable the platform limit switch by manually keeping it closed until the lead-screw turned to the end of the thread, thereby getting several degrees more of minus declination. I would set the tube on the west side and wait for the 2As discussed in Paper I (see particularly Appendices 1 and 2), the lack cluster to drift in, and started the exposure as soon as it reached the slit. of sky subtraction capability in the equipment inevitably signifies in- When it came to the meridian, I put in the dark slide, paralleled the tube creased uncertainties for results derived from data for a few clusters of and polar axle for reversal, and started the exposure with the tube down low central surface brightness and/or projected against dense star fields. to the object. All this took only a few minutes, and I did it so much that I With the exception of those clusters noted in Paper I, we do not believe had to keep my eye on the oil and grease in the bearings of the polar and our integrated spectrograms (and velocities therefrom) are likely to be declination axles! systematically in error because we took particular care when sampling "Getting NGC 1851 was a risky business with the 36-inch refractor. the more difficult objects. The agreement between velocities from To reach the guiding eyepiece, I had to use the high ladder with a individual giant stars and from composite-light spectra for the very shorter one on top of it. The running up and down in the dark was open, low-latitude, G-type cluster NGC 6352 is encouraging (see Tables dangerous and foolish—but I was young. I exposed for the maximum II-IV, below). Zinn and West's (1984) study with the same equipment cover of the diurnal arc, reversing on the meridian as with the Crossley. (but nearer solar maximum) included spectra of background regions I'm thankful to my lucky stars, and glad that the refractor was helpful!" adjacent to some of the more challenging objects. Only for seven clus-
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System GALACTIC GLOBULAR CLUSTERS 405
TABLE I Effective Wavelengths Adopted For Cluster Velocity Determinations*
x(0) Principal Contributor(8); Notes
3887.501 0.5 H(8); F8 and earlier 3932.996 1.0 Call 3969.099 1.0 -0.049 Call + He 3996.208 0.5 FeljCol 4006.735 0.75 -0.037 Fel 4022.288 0.5 Fel, CrI 4031.103 1.0 +0.028 Fel, Mnl 4045.081 1.0 quadratict Fel 4066.149 0.75 -0.106 Fel 4076.817 1.0 -0.024 SrII 4101.697 0.5 Hd; F6 and earlier 4102.452 0.5 -0.050 Hd; later than F6 4130.137 0.75 +0.052 Fel 4143.995 0.75 Fel 4 8 12 4153.174 0.75 Fel, Zrll Number of Plates 4174.221 0.25 Fel Fig. 1-Histogram of the number of measurable plates per cluster. 4202.692 0.5 -0.139 Fel 4224.872 0.75 +0.055 Cal As detailed in Section II of Paper II, the spectrograms 4271.837 1.0 +0.016 Fel 4324.827 0.75 Fel were measured with the ARCTURUS oscilloscopic mea- suring engine at DAO and initially reduced to heliocen- 4340.146 1.0 Ηγ 4352.765 0.75 Fel tric velocities with a program kindly provided by J. B. 4384.675 0.5 Fel Hutchings. As done for the standard stars (Paper II), all 4404.627 0.75 +0.026 Fel 4456.518 1.0 +0.098 Cal lines visible between Ca π H and Κ and the Na D lines were measured, reduced, and individually examined; 4481.649 1.0 -0.016 Fel, Til, Mgll 4492.728 0.5 +0.048 Fe misidentifications were corrected and lines individually 4532.246 0.75 -0.085 accepted or rejected. Lines which were initially unidenti- 4551.531 0.75 Fell, Til, Till 4705.750 0.5 Fel, Til fied had their rest wavelengths calculated for later analy- sis (Section IV). 4729.837 0.5 Fel, Fell 4764.006 0.5 +0.030 Fel The rest wavelengths determined for the standard stars 4810.847 0.5 -0.072 Fel, Nil, Znl in Paper II formed the starting point for determination of 4861.318 1.0 HB effective wavelengths of lines in the globular clusters. 4920.734 0.5 Fel, CrI, Fell Effective wavelengths for the cluster spectra will differ 4957.210 0.75 Fel 4983.365 0.75 Fel, Til slightly from those of Paper II for individual stars because 5039.944 0.75 +0.017 Fel of both the composite nature of the cluster spectra and the 5170.243 0.75Φ Mgl "b" + MgH lower metallicities of the globular clusters. Therefore, as 5184.479 1.0 -0.032 Mgl "b" + MgH was done for the standard velocity stars, velocity residuals 5207.536 0.5 Fel, CrI 5228.612 0.75 -0.069 Fel, Till for the globular-cluster spectra were iteratively examined 5269.683 0.75 quadratict Fel, Cal; in detail before arriving at the consistent set of wave- 5328.297 1.0 quadratict Fel, CrI lengths presented in Table I. 5478.285 0.75 Fel As shown in Paper II, no corrections were needed for * λ·λ(0) + aS, where λ(0) is the rest wavelength for either hour angle or zenith distance. However, the small spectral subclasses later than AO. (A0»0, FO-10, "run" corrections from Table II of Paper II were applied. etc.) The coefficients are determined over the spectral-type range of the Galactic globular cluster A correction for atmospheric dispersion of the type advo- system. Three decimal points are retained for cated by Bassino and Muzzio (1984) and applied in Paper avoidance of roundoff errors, but clearly the results are less certain.) II to the stellar velocities is neither justified by the globu- t Quadratic fits were adopted for the following lines: 4045 λ-4045.1262 + 0.0132(8-22) - 0.0015(8-22)2 5269 λ-5268.2463 - 0.1167(8-22) + 0.0059(8-22)2 ters did they suspect the contribution from the background to be 5328 λ-5328.0694 - 0.0012(8-22) + 0.0006(8-22)2 significant. Rose and Tripicco's (1986) very careful photographic spec- trophotometry also appears to support our belief that contamination Φ The total width of the almost-resolved from background light is not likely to be introducing detectable system- λ5167 + λ5173 Mgl lines was measured. atic errors in our velocities for Galactic-bulge clusters.
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 406 HESSER, SHAWL, AND MEYER
TABLE II mP-l ^ Velocities for Individual Plates
NGC Plate # Exp. Ν V(wt) a Notes NGC Plate # Exp. Ν V(wt) σ Notes NGC Plate # Exp. Ν V(wt) σ Notes (min) (km s~^) (min) (km s~^) (min) (km s"^) (1) (2) (3) (4) (5) (6) (7) (1) (2) (3) (4) (5) (6) (7) (1) (2) (3) (4) (5) (6) (7)
104 E0024-4 1.5 -30.3 11.1 5286 E0516-2M 25.0 6 62.3 16.3 6287 E0524-6 90.0 6 -209.7 19.5 (11) 104 E0024-5 1.8 -35.9 9.8 5286 E0522-4M 28.0 6 52.9 11.5 6287 E2056-4 30.0 6 -203.8 28.4 104 E0513-3 5.0 -29.2 8.4 (1) 5286 E1180-3 7.0 8 69.2 12.1 104 E0513-4 7.0 -30.2 7.2 5286 E1187-1 5.0 18 48.1 12.8 6293 E1196-2 14.0 11* -143.0 17.1 104 E0519-8 14.0 -10.2 10.7 (2) 5286 E1193-9 20.0 11 61.2 12.3 104 E0526-3 6.0 -28.0 9.7 6304 E0518-2 79.0 14 -102.2 15.0 104 E0526-4 9.0 -13.3 14.9 5634 E1180-6 28.0 7 -27.7 11.0 104 E0531-1 2.0 -14.2 9.1 5634 E1187-4 30.0 12 -65.8 15.2 6316 E0510-6 63.0 15 74.6 12.0 (11) 104 E0531-2 1.0 -19.9 8.0 6316 E2056-6 16.0 5 85.5 29.7 104 E0538-5 20.0 -38.0 8.3 (3) 5694 E0105-5 75.0 9 -163.0 19.0 104 E0539-2 5.0 -17.4 9.9 (4) 5694 E0509-3M 65.0 11 -150.3 8.7 (8) 6325 E0624-4 83.0 16 7.1 12.0 104 E0541-5 3.0 -17.3 10.7 5694 E0517-5 59.0 11 -143.4 10.7 6325 E2056-7 71.0 10 9.8 18.6 104 E0541-6 5.0 3.0 7.9 5694 E0536-3M 44.0 5 -159.1 15.2 (9) 104 E0621-2M 4.0 5694 E0618-2 30.0 6 -158.4 7.6 6333 E0010-3 63.0 259.8 20.5 5694 E0623-8 21.0 8 -147.8 11.4 6333 E0624-2 12.0 267.4 13.7 121 E0024-6 110.0 15 138.3 14.6 5694 E1180-9 24.0 8 -167.1 21.2 5694 E2060-6 21.0 9 -139.4 11.2 6342 E1303-4 97.0 13 97.3 12.9 362 E0526-5 39.0 3 217.7 20.0 6342 E2061-6 46.0 23 75.9 10.1 362 E0531-3 4.0 15 214.2 11.3 (1) 5824 E0522-6M 22.0 6 -12.5 8.2 362 E0531-4 8.0 8 216.9 13.9 5824 E1181-3 10.0 5 -46.1 9.6 6352 E0010-5M 142.0 17 -119.8 12.7 362 E0539-3 10.0 19 220.4 12.3 (3) 5824 E1181-9 8.0 5 -49.0 21.5 6352 E0619-1 38.0 12 -92.0 15.6 362 E0621-3M 4.0 .. 5824 E1187-6 7.0 18 -55.2 12.5 6352 E2061-9 34.0 18* -131.4 11.4 5824 E1194-3 9.0 11 -85.7 17.0 1261 E0539-5 25.0 17 51.3 14.2 6355 E0619-4 62.0 16 -176.1 12.1 5897 E0015-3 240.0 10 30.9 12.0 6355 E2062-2 41.0 10 -189.2 9.9 1851 E1175-8 2.0 15 318.3 13.4 5897 E1181-5 70.0 6 -11.0 24.4 1851 E1175-9 1.0 10 320.7 19.3 5897 E2050-8 90.0 18 22.3 12.2 6356 E1322-5 114.0 4 18.7 5.5 (2) 1851 E1183-6M 3.0 14 296.7 12.3 1851 E1183-7M 3.0 13 301.9 9.3 5904 E0516-4M 4.0 9 42.5 14.7 6362 E1303-9 41.0 12 -14.7 13.9 1851 E1190-8M 4.0 11 310.4 10.2 (5) 5904 E0522-8M 12.0 18 52.5 8.8 1851 E2043-4 3.0 13 308.0 16.2 5904 E0536-5 7.0 7 65.0 14.2 6388 E0010-4 5.0 19 70.0 11.5 1851 E2049-2 3.0 10 296.6 13.2 5904 E1187-9 6.0 24 50.7 8.4 6388 E0012-2 10.0 8 75.3 12.2 (2) 1851 E2054-6 3.0 8* 300.0 15.0 5904 E1194-6 9.0 7 47.4 12.9 6388 E0012-3 11.0 12 89.8 16.7 (2) 1851 E2059-7 3.0 13 309.2 10.8 6388 E0014-2 8.0 14 56.1 11.1 5927 E1182-1 29.0 21 -90.8 11.9 6388 E0014-3 11.0 16 66.2 12.2 1904 E1176-2 5.0 12* 163.2 17.2 5927 E1188-1 24.0 29 -114.5 9.1 6388 E0015-2 4.5 20 72.6 9.5 1904 E1183-8M 7.0 13 209.2 13.3 (5) 6388 E0017-3 8.0 14 67.4 14.0 (10) 1904 E1191-1M 7.0 13* 199.4 16.3 (5) 5946 E1188-3 43.0 19 115.3 9.8 6388 E0509-6 7.0 15 93.9 14.7 1904 E2060-1 9.0 11 185.5 18.5 5946 E2051-1 20.0 11 146.6 13.0 6388 E0510-9 5.0 16 90.9 10.7 6388 E0515-6M 6.0 18 67.9 8.6 (2) 2298 E1176-4 24.0 14 102.0 16.5 5986 E0510-3 36.0 15 81.1 13.3 6388 E0524-8 5.0 28 79.7 9.4 2298 E1184-3 60.0 11 95.7 19.6 5986 E0517-7 29.0 15* 83.5 12.9 6388 E0528-4M 9.0 15* 64.2 11.9 2298 E2050-1 29.0 9* 123.8 16.4 5986 E0524-2 60.0 15 104.1 10.3 6388 E0534-4 5.0 17 85.6 11.3 5986 E2060-8 12.0 13* 108.1 14.0 6388 E0536-9 4.0 16 77.9 7.8 2808 E1175-6 3.0 11 78.2 15.6 6388 E0618-7 2.0 18 55.2 12.3 2808 E1175-7 6.0 10 82.5 11.3 6093 E0516-6M 4.0 15 0.9 11.1 6388 E0623-3 3.0 12 92.9 15.0 2808 E1176-7 2.0 21 93.6 10.8 6093 E0523-3M 10.0 15 12.5 10.8 6388 E1302-3M 2.0 14 83.8 11.9 (12) 2808 E1184-7 3.0 13 108.0 12.9 6093 E1188-7 3.0 19 1.7 11.9 (7) 6388 E1310-3M 3.0 23 70.7 9.5 (2, 12) 2808 E1191-3M 5.0 18 101.7 9.2 6093 E1194-8 10.0 7 -3.2 12.4 6388 E1319-9 3.0 28* 77.5 9.5 2808 E2043-5 3.0 16 102.7 9.4 6388 E1322-1 5.0 20 70.0 10.3 2808 E2043-6 2.5 11 106.2 11.6 6101 E1310-6 200.0 9 206.2 32.8 6388 E2047-5 2.5 19 88.5 12.2 6388 E2053-1 2.0 16 90.0 16.6 3201 E1176-9 20.0 6 484.5 18.6 6121 E1188-9 19.0 25 60.7 9.6 6388 E2062-4 2.0 24 94.6 8.3 3201 E1184-9 55.0 6 482.6 17.0 3201 E1192-8M? 70.0 10 478.4 19.9 (6) 6139 E1189-1 22.0 13 4.9 15.8 6397 E2045-7 8.0 16 1.7 14.9 3201 E2060-3 24.0 11 467.2 14.9 6139 E2055-9 14.0 12 2.8 17.4 6401 E1304-9 70.0 16 -64.9 15.6 (11) 4147 E1177-2 21.0 15 184.7 13.9 (7) 6144 E0024-2 160.0 10 175.6 18.6 (10) 6401 E2062-5 34.0 12 -58.0 16.0 4147 E1185-3 33.0 8 171.0 11.1 6144 E0537-3 150.0 9 162.3 20.5 4147 E2043-7 27.0 10 178.1 13.7 6144 E2051-4 89.0 12 155.7 12.2 6402 B2045-8 21.0 12 -24.8 13.6 4372 E1178-3 46.0 3 61.3 37.3 6171 E2045-1 44.0 8 -36.4 20.4 6426 E2046-1 120.0 5 -161.2 22.8 4372 E2044-4 90.0 17 44.7 9.2 6171 E2061-2 32.0 16* -17.6 11.2 4372 E2055-3 90.0 9 65.9 19.1 6440 E0534-7 30.0 10 -89.0 12.2 6218 E1195-1 67.0 11 -48.5 15.6 6440 E1302-8 39.0 22 -77.7 11.7 4590 E1177-7 21.0 9 -82.8 12.7 6218 E2061-4 25.0 12 -37.5 17.1 4590 E1186-1 33.0 8 -103.8 13.4 4590 E2060-5 27.0 10 -61.2 14.4 6235 E1304-4 51.0 14 83.5 13.9 6441 E0008-3 47.0 11 60.4 10.0 6235 E2056-3 60.0 11 90.7 20.5 6441 E0509-7 12.0 6 -30.2 18.5 4833 E1178-7 16.0 4 184.4 13.1 6441 E0511-1 10.0 19 ^5.9 8.8 4833 E1186-6 37.0 13 198.0 12.0 6254 E1195-3 22.0 6 75.8 18.3 6441 E0515-7M 10.0 16 28.8 10.0 (2) 4833 E1193-5 51.0 7 188.1 15.3 6441 E0524-9 8.0 26 17.8 8.2 6266 E0517-2 12.0 11 -83.9 12.7 6441 E0528-5 15.0 18* 28.5 10.7 5024 E1179-3 14.0 10 -85.5 15.1 6266 E0523-6M 11.0 17 -77.1 7.4 6441 E0534-5 8.0 16 -8.7 12.9 5024 E1185-7 14.0 9* -77.9 11.0 6266 El182-3 5.0 11 -80.9 17.7 6441 E0537-1 4.0 24 28.5 7.8 6266 E1195-5 9.0 11 -73.0 10.6 6441 E0618-8 3.0 18 -13.9 9.2 5139 E1179-8 7.0 6 216.8 12.0 6441 E0623-4 5.0 10 26.8 5.9 5139 E1186-9 7.0 19 227.0 13.0 6273 E0523-7M 26.0 13 120.8 14.7 6441 B1302-4M 4.0 13 8.4 11.2 (12) 5139 E2055-4 3.5 8 223.1 20.0 6273 E1195-7 15.0 7 145.3 17.5 6441 E1310-4M 5.0 18 14.4 7.2 (2, 12) 6441 E1320-1 4.0 24 33.5 10.7 5272 E2055-7 5.0 8 -140.8 10.4 6284 E2045-6 13.0 10 41.4 17.0 6441 E2047-6 2.0 11* 36.4 13.5
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System GALACTIC GLOBULAR CLUSTERS 407
NGC Plate # Exp. Ν V(wt) σ Notes NGC Plate # Exp. Ν V(wt) σ Notes NGC Plate # Exp· Ν V(wt) σ Notes (min) (km e"^·) (min) (km s-1) (min) (km s"1) (1) (2) (3) (4) (5) (6) (7) (1) (2) (3) (4) (5) (6) (7) (1) (2) (3) (4) (5) (6) (7) 6453 E1305-4 64.0 10* -73.7 16.1 (11) 6584 E1305-9 51.0 9 235.3 16.9 6752 E0518-7 55.0 5 -12.5 5.8 6453 E2062-7 24.0 13 -88.9 11.8 6752 E0620-2 6.0 8 -41.2 21.1 6624 E0619-7 7.0 20 43.1 10.7 6752 E1311-9 4.0 7 -15.9 19.4 (1) 6496 E1311-1 122.0 19 -81.7 13.5 (11) 6624 E0624-7 14.0 16 37.5 10.5 6496 E2062-9 123.0 10 -109.1 8.8 6624 E2052-9 13.0 31 74.1 8.5 6760 E0024-3 59.0 17 -35.5 9.8 6760 E1320-8 115.0 23 -20.3 9.5 6517 E1320-3 169.0 18* -36.8 9.5 6626 E0619-8 7.0 -2.0 13.1 6626 E1322-8 29.0 1.9 9.0 6809 E0538-3 33.0 4 162.6 11.3 6522 E0017-4 24.0 12 -36.2 9.3 (13) 6809 E0625-1 41.0 6 159.1 13.0 (10) 6522 E0511-7 22.0 14 -5.7 12.2 6522 E2063-3 8.0 14 20.0 11.0 6637 E1312-3 1.0 20 44.0 11.8 (14) 6838 E2052-4 32.0 12 -40.8 13.3 6637 E1322-9 31.0 7 24.6 8.1 6528 E0018-2 47.0 19 161.7 9.5 6864 E0529-8 13.0 13 -185.1 11.2 6528 E0528-8 53.0 23* 169.8 10.6 6638 E2046-8 15.0 12 24.4 8. 6864 E1311-8 15.0 10 -168.5 9.1 6528 E2063-4 14.0 19 141.0 13.9 6642 E0016-2 167.0 11 -71.1 16.2 6934 E2047-7 13.0 9* -386.8 14.0 6535 E2051-6 90.0 9 -159.0 15.4 6642 E0624-6 51.0 7 -31.8 10.7 6642 E2052-8 23.0 11 -52.2 11.8 6981 E2052-7 40.0 10 -309.0 17.0 6539 E0018-3 189.0 12 -51.8 15.7 (13) 6652 E2047-2 10.0 14 -80.4 14.0 7006 E0512-2 65.0 7 -375.4 13.9 6541 E0518-5 36.0 6 -165.9 9.7 7006 E0529-3 79.0 7 -350.5 15.1 6541 E2056-9 4.0 13 -149.3 10.5 6656 E0008-6 70.0 7 -167.8 13.4 7006 E2058-3 20.0 3 -330.0 21.3 6656 E0619-9 13.0 5 -155.9 19.2 6544 E2057-1 14.0 11* 6681 E1312-2 12.0 13 207.1 16.3 7078 E0519-3 11.0 11 -106.6 11.0 6553 E0018-6 35.0 14 -30.7 13,3 6681 E2047-3 7.0 10 227.9 7078 E0529-6 3.0 7 -108.4 20.4 6553 E0534-9 23.0 20 -24.8 10.3 7078 E0620-3 2.5 5 -106.8 22.3 6553 E0537-6 27.0 19 -22.3 9.3 6712 E2052-1 19.0 12* -80.8 27.1 7078 E0625-2 7.0 5 -86.1 12.9 6553 E2057-3 12.0 15 -18.7 15.1 6715 E1312-1 3.0 16 105.8 14.0 6558 E2046-6 22.0 16 -135.9 17.3 (11) 6715 E2047-4 3.0 16 151.2 11.7 7089 E0519-4 13.0 13 -11.8 14.0 6558 E2057-4 28.0 10 -155.4 16.6 7089 E0530-2 6.0 7 23.5 9.3 6717 E0018-7 52.0 13 -13.9 9.5 7089 E0620-4 5.0 5 -20.9 12.1 6569 E0018-5 38.0 9 -25.8 13.6 6717 E2057-7 40.0 14 7.3 12.5 7089 E0625-3M 4.0 7 -34.2 13.0 6569 E0535-3 43.0 19* -25.0 10.7 6569 E0537-8 32.0 21 -28.7 12.6 6723 E05H-8 58.0 11 -82.5 12.4 7099 E0512-3 10.0 13 -163.6 11.2 6569 E2057-6 18.0 20 -26.7 9.2 6723 E0525-4 50.0 17 -78.1 8.2 7099 E0530-3 21.0 5 -158.8 7.8
* Values given are the averages of repeated measurements of the spectrum. (7) Central cusp on slit during part of exposure. (1) One trail. (8) Moon set 10 min. after exposure began. (2) Cloudy (9) Moon (3 day old) plus thin cirrus. (3) Double exposure: 2 min. without and 18 min. with 1.25 mag. (10) Streaked spectrum. neutral density filter (preslit). (11) Rich star field noted at telescope. (4) 1.25 mag. neutral density filter. (12) Exposure taken at Moonset. (5) Equal duration sky exposure taken - no signal detected. (13) Badly underexposed. (6) Moon had set, but cirrus may have reflected some moonlight. (14) Exposure terminated by clouds. lar-cluster residuals themselves nor expected because of Our final velocities, weighted by the inverse square of the essentially uniform illumination of the slit provided the internal error calculated for each plate, are given in by our sampling of the light of these extended sources. Table III where, for purposes of the comparisons we will The final image-tube velocities derived from the inte- make in the next section, we also list data from other grated light measurements for 90 Galactic globular clus- major surveys or compilations. The first three columns of ters plus NGC 121 in the Small Magellanic Cloud are Table III contain identifications (NGC, other common presented in Tables II and III. The former records our names, and the IAU designation, respectively). Column individual measurements in order of NGC number. (4) is the spectral type from Paper I. All subsequent Column (2) has the plate number (which can be correlated columns except (10) contain pairs of numbers, the first with date through reference to Table II of Paper II). The being a velocity and the second its associated error, as exposure time (in minutes) in column (3) is followed by follows: column (5) is from Mayall's (1946) Tables 1 (Cross- the number of lines, Ν (column (4)), entering into the ley spectra, only) or 3 and 4 (including 36-in refractor weighted mean velocity, V (column (5)), and its weighted data). The errors (calculated by us following Mayall's standard deviation, σ (column (6)); the latter two quanti- suggestion to weight the 36-in refractor data three times ties are in km s-1. The weighting referred to in this table is more heavily) are the standard deviations of the mean for by spectral line using the weights given in Table I. A plate the velocity determinations he reported, and are indica- number followed by "M" indicates that the Moon was up tive of internal errors only; Mayall presented evidence for during part of the exposure. Additional notes on the larger external errors (see below). Column (6) from Kin- cluster spectra may be found at the end of the table as well man's (1959a) Table III contains the velocities and stan- as in Appendices 1 and 2 of Paper I. dard deviations he determined, while column (7) is from
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 408 HESSER, SHAWL, AND MEYER
TABLE III Summary of Radial Velocities and Associated Errors
Velocities (km 8^) NGC Other IAÜ SpT Mayall Kln(III) Kln(VIII) Webblnk Zlnn/West Ν HSM NGC (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
104 ... 0021-723 G4 - 24± 1 - 24± 4 - 14.10± 0.94 13 - 22± 3 104 121 ··· ········ F6 φ Φ Φ Φ φ Φ ······· 144 1 138 15 121 288 ... 0050-268 • · · · · - 47 4 - 47 10 - 48.2 5.0 288 362 ... 0100-711 F9 221 5 221 10 232.4 2.9 220 3 217 7 362 DEJC 1 0234+209 • · · · · .. DEJC 1261 ... 0310-554 F7 40 18 46 22 55. 12. 14 1261 Ρ 1 0325+794 • · · · · ι . . . · . • · · · · · 3. 32. • · · · · ...... • · · · Ε 1 0353-494 • · · · · • . . . . . • · · · · · • · · · · ...... ERID 1 0422-213 • · · · · • . . . . . • · · · · · - 40.5 9.7 • · · · · .. ERID Ρ 2 0443+313 • · · · · -133. 57.0 • · · · · 1851 ... 0512-400 F7 290 6* 317 3 309 12 318.6 2.7 9 306 4 1851 1904 79 0522-245 F5 224 10* 181 8 196 22 185.4 6.9 4 193 8 1904 2298 ... 0647-359 F5 64 22 64 30 44. 11.0 3 108 10 2298 2419 ... 0734+390 • · · · · 14 22 14 30 - 20. 10.0 ...... 2419 2808 ... 0911-646 F7 • · · · · · 101 101 10 104.1 4.4 77 7 98 4 2808 Ε 3 0921-770 • · · • · · · · · ...... ·. .... UKS 0923-545 • · · • · · · · · ...... Ρ 3 1003+003 • · · · · • · · · · · 22. 28...... ·. »... 3201 ... 1015-461 F6 493 493 7 494.0 5.0 4 477 9 3201 SAHB 1 1052+407 • · ...... SÁHB • · · · Ρ 4 1126+292 • · 168. 57...... 4147 ... 1207+188 F2/3 191 17 191 30 182. 10. 3 177 7 4147 4372 ... 1223-724 F5 • · · # 66 66 15 83. 11. 2 49 8 4372 4590 68 1236-264 F2/3 116 8 -116 30 -116.5 7.8 - 59 20 3-84 8 4590 4833 ... 1256-706 F3 204 204 15 216.6 8.0 186 20 2 194 9 4833 5024 53 1310+184 F6 89 8* • · · -112 22 - 78.9 4.6 • · · · · · 2-80 9 5024 5053 ... 1313+179 .... · • · · • · · · · · ...... 5053 5139 ... 1323-470 F5 • · · 231 230 10 228.3 1.7 ...... 3 222 8 5139 5272 3 1339+286 F6 161 6* -153 4 -147.11 0.47 1 -141 10 5272 5286 ... 1343-511 F5 45 45 15 48.6 6.0 62 20 5 58 6 5286 5466 ... 1403+287 ... • · · · · 119.9 2.5 ...... 5466 5634 ... 1427-057 F3/4 63 12 63 27 — 63. 12...... 2-41 9 5634 5694 ... 1436-263 F4 187 9 187 27 -183.8 7.5 -118 20 8 -152 4 5694 14499 ... 1452-820 .... · • · · • · · · · ·.·...· ...... ·...... 14499 5824 ... 1500-328 F4 58 16 58 30 - 58. 6. - 28 20 5-38 5 5824 • · · · Ρ 5 1513+000 • · · · · ...... 5897 ... 1514-208 F7 ... • · · · · ...... 3 23 8 5897 5904 5 1516+022 F7 58 11* 42 49 4 51.9 2.4 64 20 5 52 5 5904 5927 ... 1524-505 G2 • · · 96 30 78. 2. - 93 14 2 -106 7 5927 5946 ... 1531-504 F7/8 • · · .·.. 98 14 2 127 8 5946 5986 ... 1542-376 F5 2 44 2 30 - 35. 32. .... ·. 94 6 5986 • · · · Ρ14 1608+150 • · · · · ... .. 81.0 2.8 ...... 6093 80 1614-228 F6 15 5* 18 15 12.9 6.1 ...... 4 6 6093 6101 ... 1620-720 F5: ...... · . . ι ...... 193: 14 1 206 33 6101 6121 4 1620-264 F8 ... 66 5 65 7 64.3 4.6 66 20 61 10 6121 6139 ... 1624-387 F6/7 : ... 29 19 20 22 7.6 6.9 .. ·. 4 12 6139 6144 ... 1624-259 F5/6 ... • · · · # · • · · · · ».... ·...· 94 14 162 9 6144 • · · · Τ 3 1625-352 • · · · · ... • · · · Φ Φ • · · · · ...... 6171 107 1629-129 G0: -147 17 φ Φ Φ φ Φ φ -147 30 -147. 17. - 60 20 2 22 16 6171 6205 13 1639+365 • · · · · -225 3* Φ φ φ Φ Φ φ -241 12 -247.8 1.7 .... ·. ». » ·.. 6205
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System GALACTIC GLOBULAR CLUSTERS 409
TABLE III - continued
VELOCITIES (km s"1) NGC OTHER IAU SpT Mayall Kin(III) Kin(VIII) Webbink Zinn/West Ν HSM NGC (1) (2) O) (4) (5) (6) (7) (8) (9) (10) (11) (12)
6218 12 1644-018 F8 36± 8 36±37 - 43 5± 2 .... db .. 2 - 44± 12 6218 6229 ... 1645+476 • · · · · -154 10* -150 15 -154 2 7 ...... 6229 6235 ... 1650-220 F9: •...... ft ft ft ft 105 12 2 86 4 6235 6254 10 1654-040 F3 65 15 71 10 70 1 3 1 76 18 6254 6256 T12 1656-370 ft ft ft ft ft ft 6256 P15 1657-004 • · · · · · ft ft ft ft ft ft »...... 6266 62 1658-300 F9 - 91 15* - 75 15 - 60 9 4 3 - 60 20 4-78 5 6266 6273 19 1659-262 F7 117 12* 102 27 121 11 147 20 2 131 11 6273 6284 ... 1701-246 F9 22 14 22 30 22 14 1 41 17 6284 6287 ... 1702-226 F5 2 -208 16 6287 6293 ... 1707-265 F3 - 73 13 - 73 27 - 73 13 - 94 20 1 -143 17 6293 6304 ... 1711-294 G3 - 98 15 - 98 30 - 98 15 -110 20 1 -102 15 6304 6316 ... 1713-280 G2 • · · · · · 68 20 2 76 11 6316 6325 ... 1714-237 GO • · · ft · · ft ft ft ft ft ft ft ft ft ft ft ft · ft - 3 20 2 8 10 6325 6333 9 1716-184 F5/6 224 11 224 22 224 7 7 ...... 1 260 20 6333 6341 92 1715+432 -105 6* -118 7 -120 5 1 ...... 6341 6342 ... 1718-195 G3/4 75 20 2 84 8 6342 6352 ... 1721-484 G4 - 94 20 3 -118 7 6352 6355 ... 1720-263 GO -147 20 2 -184 8 6355 6356 ... 1720-177 G3 31 31 40 20 1 19: 6 6356 Τ 2 1724-307 ...... 6362 ... 1726-670 G3 - 10 20 1-15 14 6362 6366 ... 1725-050 ...... 6366 Τ 4 1727-315 ...... ft ft ft ft HP1 1727-299 ...... ft ft ft ft LILL 1 1730-333 ...... LILL 6380 ... 1731-390 ...... 6380 6388 ... 1732-447 G2 81 68 20 23 77 2 6388 • · · · Τ 1 1732-304 ft ft ...... PIS 26 1732-385 ft ft ...... PIS TON 2 1733-390 ft ft ft ft ft » ft ...... TON 6397 ... 1736-536 F4 11 19 ... .. 1 2 15 6397 6401 ... 1735-238 F9 ft ft ft ft 63 12 2-62 11 6401 6402 14 1735-032 F4 121 129 123 ... .. 1-25 14 6402 Ρ 6 1740-262 ...... 6426 ... 1742+031 Gl:: 1 -162 23 6426 • · · · Τ 5 1745-247 ft ft ft ft ft ...... 6440 ... 1746-203 G4: 125 133 65 14 2-83 8 6440 6441 ... 1746-370 G2 70 70 30 20 14 20 2 6441 Τ 6 1747-312 ...... 6453 ... 1748-346 F8 78 12 2-84 10 6453 • · · · UKS 1751-241 ..... ft ft ft ft ft ...... 6496 ... 1755-442 G4 103 12 2-95 9 6496 • · · · Τ 9 1758-268 ft ft ft ft ft ft ft ft ft ft ...... 6517 ... 1759-089 F8 47 14 1 - 37 10 6517 6522 ... 1800-300 F7/8 8 ... .. 3-11 6 6522 • · · · Τ10 1800-260 ft ft ft ft ft ft ...... • ft ft ft 6528 ... 1801-300 G3 101 160 20 3 160 6 6528 6535 ... 1801-003 GO -126 14 1 -159 15 6535 6539 ... 1802-075 G4: : - 35: 10 1-52 16 6539
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 410 HESSER, SHAWL, AND MEYER
TABLE III - continued
VELOCITIES (km β"1) NGC OTHER IAU SpT Mayall Kin(III) Kln(VIII) Webbink Zinn/West Ν HSM NGC (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
6541 ... 1804-437 F6 . . . . db. . -148± 8 -148±15 -152.8 ± 3.4 •... ί .. 2 -158± 7 6541 6544 ... 1804-250 F9: - 12 8 - 12 27 - 12.0 7.8 - 39 20 1 2 20 6544 6553 ... 1806-259 G4 • · · · · · - 32.6 6.0 - 5 12 4 - 24 6 6553 6558 ... 1807-317 F7 • · · · · · -135 14 2 -146 12 6558 11276 Ρ 7 1808-072 »...... · • · · · · · ·· ···· ·· 11276 T12 1809-227 ...... ···· ·■ ······■ ···»· ··«· ·· ·· ···· ·· ···· 6569 ... 1810-318 G1 : ...... ···· ·· ······· ····· 36 14 4 — 26 6 6369 6584 ... 1814-522 F6 ...... 160 37 180. 32.0 1 235 17 6584 6624 ... 1820-303 G4/5 69 12 69 27 69. 12. 43 20 3 55 6 6624 6626 28 1821-249 F8 - 3 9 1 18 1.8 6.2 ...... 1 - 2 13 6626 6637 69 1828-323 G2/3 95 19 95 30 50.1 7.1 37 20 2 31 7 6637 6638 ... 1827-255 GO - 14 14 - 14 30 - 14. 14. 2 20 1 24 9 6638 6642 ... 1828-235 F8 ...... - 90. 11. - 44 12 3-47 7 6642 6652 ... 1832-330 G3 -124 7 -124 27 -124.2 7.1 - 87 14 1-80 14 6652 6656 22 1833-239 F5 -162 6 142 -144 7 -152.5 2.6 2 -164 11 6656 Ρ 8 1838-198 • · · » · · ...... — 38 14 ...... 6681 70 1840-323 F5 198 15 198 30 198. 15 2 223 8 6681 6712 ... 1850-087 F9 -131 23 -131 30 -123.9 4.9 - 91 14 1-81 27 6712 6715 54 1851-305 F7/8 107 7* 130 122 10 131.0 3.7 129 14 2 133 9 6715 6717 Ρ 9 1852-227 F6 • · · · · · 34 12 2 - 6 8 6717 6723 ... 1856-367 F9 - 3 12 - 3 30 35. 15. - 90 14 2-79 7 6723 6749 ... 1902+017 • · · · · • · · · · · ...... 6749 6752 ... 1906-600 F4/5 • · · · · · 39 - 39 7 - 32.2 3.2 - 28 20 3-15 5 6752 6760 ... 1908+009 65 • · · · · · - 20 12 2-28 7 6760 Τ 7 1914-347 • · · · · · ...... 6779 56 1914+300 -182 18 -145 12 -138.1 7.6 6779 ΡΙΟ 1916+184 • · · · · · ...... • · · · Α 2 1925-304 ..... • · · · · · .... ·...... 6809 55 1936-310 F4 • · · · · · 170 170 12 166.6 4.4 160 20 1 159 13 6809 Τ 8 1938-341 • · · · · • · · · · · ...... Ρ11 1942-081 ...... —68. 10...... 6838 71 1951+186 G1 - 80 21 - 80 30 - 19.27 0.92 1 - 41 13 6838 6864 75 2003-220 F9 -222 6* 87 -198 16 -195.2 4.4 -182 14 2 -175 7 6864 6934 ... 2031+072 F7/8 -358 33 -360 22 -379. 13 1 -387 14 6934 6981 72 2050-127 F7 -274 18 -255 37 -278. 12. -285 20 1 -309 17 6981 7006 ... 2059+160 F6 -348 20 ...... -348 27 -384.8 7.3 2 -364 10 7006 7078 15 2127+119 F3/4 -118 8 - 98 2 -107 10 -112.1 1.9 -94 20 4-100 7 7078 7089 2 2130-010 F4 14 5 - 12 10 - 5 4 - 6.1 3.3 5 20 4 - 5 6 7089 7099 30 2137-234 F3 -166 10 -185 9 -174 15 -172.3 2.9 -160 20 2 -160 6 7099 Ρ12 2143-214 • · · · · · ...... 9. 35...... • · · · Ρ13 2304+124 • · · · · · ...... — 28. 37...... 7492 ... 2305-159 • · · · · · ...... —188.5 8.5 ...... 7492
* Velocity from either Table 3 or 4 of Mayall (1946).
his Table VIII compilation and homogenization of his, columns (5) and (7) shows the size of the effect. Webbink's Mayall's, and others' velocities. The errors take into ac- (1981) review of available velocity data resulted in the count Mayall's remarks regarding the magnitude of possi- weighted averages and errors in his Table 4 listed in our ble external errors in his data; comparison of the errors in column (8). Zinn and West's (1984) velocities are given in
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System GALACTIC GLOBULAR CLUSTERS 411 column (9), where the error estimates are based on scaling their estimate of 20 km s1 precision for a typical, single spectrum by the square root of the number of spectra measured. The number of spectra we obtained that had five or more measurable lines (see Table II for the number of _o Q. lines per spectrum) is listed in column (10) of Table III. The pair of numbers in column (11) contains our velocity
8 12 σ (Mean) km s"1 Fig. 3(b)-The histogram of the errors quoted in Table III (for the mean velocity) are shown.
almost certainly be larger. Table IV summarizes velocity measurements made and reduced exactly as in Paper II for individual giant stars in four globular clusters. The table is similar to the preced- ing one, and the source of the stellar identifications is 8 16 24 32 given in the footnotes to it. (For those stars where two Number of Spectral Lines spectra were obtained, the plate number and exposure Fig. 2-The histogram of the number of spectral lines used in an individ- time (in minutes) for the second plate is given under ual velocity determination shows that on average 13 spectral lines were "Remarks"; similarly, for NGC 1851 UV5 the UT of mid- used. exposure is found there.) The NGC 6352 spectrograms
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 412 HESSER, SHAWL, AND MEYER
TABLE IV homogeneity of our presentation, we have not combined the four mean velocities in Table IV with those in Table Velocities for Individual cluster stars. III; however, they should be considered when forming new mean velocities for the clusters in question. (Paper II Star Plate Exp. vCkms"^) Remarks NGC Ν may be consulted for more information on errors of indi- vidual star measurements.) 104 4- 1001 Ε 626-5M 19 1 - 11.2 11.1 104 4- 1005 Ε 626-6M 22 1 9.8 10.0 104 4- 1006 Ε 626-7M 32 1 -3.4 11.4 III. Comparison with Other Velocity Determinations 104 4- 1033 Ε 626-4Μ 29 1 -3.9 12.3 104 9006 Ε 621-5Μ 11 1 18.0 14.0 In this section the velocities presented in Table III are 104 9031 Ε 621-6Μ 24 24.5 14.0 compared with those given by Mayall (1946), Kinman 104 1-'9065 Ε 622-3Μ 20 21.5 21.4 104 1- 9051 Ε 622-2Μ 20 35.2 10.1 (1959a), Webbink (1981), and Zinn and West (1984). 104 1 9083 Ε 626-2Μ 25 29.2 16.3 Each basic comparison involves a four-part figure: (a - top 104 1 9085 Ε 626-3Μ 25 1 - 16.7 14.1 104 1 9405 Ε 541-4 36 25.1 9.7 (E 626-IM 33) row) and (b) compare velocities for F- and G-type clus- 104 1 9411 Ε 541-3 83 14.8 12.6 (Ε 621-9M 34) ters, respectively, using the spectral classifications of Pa- 104 1 9414 Ε 541-1 45 30.1 7.3 (E 622-IM 20) per I; (c) velocity comparison without regard to spectral Average (13 stars) -16.0 3.5 type; and (d - bottom row) plots the velocity differences (HSM—other). The solid line in each figure represents a 1851 UV5 Ε2049-3 30 315.5 24.5 (o. exp. 23:37) 1851 UV5 Ε2054-5 30 335.2 22.2 (23:12) least-squares fit to the data after points (labeled with their 1851 UV5 Ε2059-6 36 298.3 19.5 (23:25) NGC numbers) deviating by more than 40 km s~1 from Average (1 star) 314.7 12.7 the first regression were deleted. Errors are allowed for in both coordinates following York (1966). The regression 5139 151 E0009-3 104 219.1 13.7 coefficients are listed in Table V (below), while discrepant 5139 1 E0009-2 167 191.7 16.0 clusters are summarized in Table VI (below). Average (2 stars) 207.5 10.4 A. Mayall Comparison with MayalFs (1946) results is presented in 6352 37 E3559-3 42 1 -120.4 9.8 6352 55 E3559-2 39 1 -107.4 10.9 the left-hand portion of Figure 4(a). As noted in the 6352 113 E3559-1 47 1 -116.8 10.3 Introduction, Mayall obtained four or five spectrograms 6352 181 E3565-2 30 1 -96.8 10.8 6352 190 E3565-1 34 1 -117.9 11.8 for most of his clusters in spite of enormous observational Average (5 stars) -112.2 4.8 difficulties. Typically, five lines per plate were measured: Ca π Η and Κ, H7, Ηδ, and the CH "G" band. These lines were given weighting factors of 2 for Ca π Η and Κ, 1 for Identifications : Ηδ, and 0.5 for H7 and the G band (which does not have a NGC 104 (Hesser and Hartwick 1977, Figures 4a, 1); NGC 1851 (Vidal and Freeman 1975); stable effective wavelength for most velocity systems). To NGC 5139 (Wooley et al. 1966); quote Mayall: "Under these circumstances it is easy to see NGC 6352 (Hartwick and Hesser 1972). why globular-cluster velocities, determined by low dis- persion of their integrated light, are unlikely to be of high were obtained by G. L. H. Harris and we are indebted to accuracy." Mayall found an internal probable error of a -1 _1 her for allowing us to use them. Star UV5 in NGC 1851 single plate to be ± 22 km s (± 32 km s standard 1 1 was proposed early as a possible identification for deviation), or 11 km s (16 km s s.d.) for the mean of MX0513-40 (Vidal and Freeman 1975). While subsequent four plates. However, he suggested that the external position measurements (Jernigan and Clark 1979; Shawl errors, particularly of his low-dispersion Crossley data, and White 1980) eliminated UV5 as a viable candidate for were likely to be several times their internal errors. In the X-ray source, it remains an interesting star in its own addition to the general scatter of the points. Figure 4(a) right, since it is a member of the little-explored class of indicates that something appears to have induced greater- UV-bright globular cluster stars (cf. Zinn et al. 1972; than-average scatter in a few velocities, as we have noted Harris et al 1983). (Our data for UV5 from 7-9 (UT) May previously (Shawl et al. 1981). 1978 support the conclusions of Vidal and Freeman (1975) Although the Crossley spectrograph was very compact, and of Bolton and Mallia (1977) that this Β star has the the fact that many of the clusters lie far to the south as same radial velocity as the cluster. Intercomparison of viewed from Lick led us to look for evidence of a declina- velocity data suggests that the velocity of UV5 varies. On tion dependence. For example, NGC 6441 is a G-type our two, well-exposed spectra we did not notice any Η β cluster at —37° declination repeatedly observed by us; its emission.) The average difference between the mean ve- velocity difference (HS —Mayall), 90 km s-1, initially locities in Table IV less our velocity from integrated light alerted us (Smith et al. 1976; Hesser and Shawl 1977) to (Table III) is 1.7 ± 5.3 km s-1. In order to maintain the the validity of Mayall's suggestion that occasional larger
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System GALACTIC GLOBULAR CLUSTERS 413
errors might be present in the velocities from the low-dis- ter), with a dispersion about the regression line of 13 persion Crossley material. The differences between our km s"1. The increased scatter of the former comparison velocities and Mayall's as a function of declination, Figure (with all entries in Webbink's catalog) apparently arises 5, document that declination dependence alone does not largely from results based upon lower-dispersion spectra. account for the sometimes large ratio of external to inter- nal errors. (Similar plots as a function of declination for D. Zinn and West the other comparisons made below yield null results and Zinn and West (1984) have measured velocities from are not shown.) spectral material obtained with the same instrumental No statistically significant trends as a function of spec- configuration we used, although most of their spectro- tral type are seen in Figure 4(a), but a small zero-point grams were less than half as wide as ours. They observed difference is suggested between Mayall's system and ours 60 Galactic, and three Small Magellanic Cloud, globular in the sense that his velocities are, on average, ~ 12 clusters; slightly fewer than half the objects were ob- km s_1 more negative than ours. served more than once. Their spectra were digitized with a PDS microdensitometer prior to cross correlating them B. Kinman with 47 Tucanae spectra in the 3880 Â-4180 A and Kinman's (1959a) work, like Mayall's, is a tour deforce 4140 Â-4440 A regions. They adopted Webbink's (1981) of photographic spectroscopy, with four or more spectro- average velocity for 47 Tue, —14.10 km s_1, as their zero grams, each often of many hours exposure, having been point. (Note that their former spectral region includes a acquired for many of his objects. As noted in the Introduc- small portion of the UV G Ν bandhead while their latter tion, his spectrograms were at higher dispersion (89 A one includes the (strong) G band and the (weak) blue CN 1 -1 mm vs. 130 A or 430 A mm for M ay all), which enabled band. The effective wavelengths of these molecular fea- him to measure many more features and lessened the tures, which are quite pronounced in clusters of later problem of blending in the development of a reliable spectral type, are not stable functions of spectral type.) effective wavelength system. When our velocities are From plate-to-plate scatter they estimate an internal er- compared with those that he measured from his own ror of 13 km s-1, which is identical to our estimate. They spectra (his Table III), as in the central column of Figure found a dispersion of 24 km s1 when comparing velocities 4(a), the rms dispersion about the regression line drops to for 35 clusters (determined from 47 spectrograms) with 1 ~ 12 km s . The comparison also suggests that our those contained in Webbink's (1981) catalog. (For two image-tube velocity system is substantially the same as clusters, NGC 6101 and NGC 6539, they found unusually Kinman's non-image-tube one. No zero-point differences large plate-to-plate scatter.) In a comparison with our are evident, but the strong bias of the Kinman sample preliminary values (Shawl et al. 1981) they also found (on toward F-type clusters means these statements are excluding NGC 6101, NGC 6144, NGC 6496 and strictly valid only for them. (Note that the comparison NGC 6558) a dispersion of — 24 km s_1. ignores the zenith distance correction determined by In the right-hand panels of Figure 4(b) our final veloc- Feast and Thackeray (1963) and applied by Webbink ities are plotted against those of Zinn and West. The (1981) to Kinman's data. Application of that correction agreement is, as expected from their discussion, quite does not change the comparison in any substantive way, good. Following elimination of three high-residual clus- however.) ters, a small (~ 2 σ) zero-point difference of 5 km s_1 is Weighted means prepared by Kinman of his data and suggested. Had Mayor et al.'s (1984) CORAVEL velocity those of his predecessors, chiefly Mayall (1946) and Joy from 169 47 Tue stars, —19 ± 1 km s-1, been used in Zinn (1949), were the standard values in analyses of the Galac- and West's analysis, there would be no zero-point differ- tic globular-cluster system until Webbink's (1981) cata- ence between our two sets of data. Note also that our log. The right column of Figure 4(a) relates Kinman's value for 47 Tue, —22 ± 3 km s_1 (based on ten spectra), Table VIII velocities to ours; the increased scatter stems agrees better with the CORAVEL than the Webbink from the earlier work incorporated by Kinman in his value. The encouraging fact, that results from Zinn and attempt to produce a uniform system. West's digital scanning plus cross-correlation analysis ba- C. Webbink sically agree with those from our similar spectra measured Webbink (1981) thoroughly reviewed published clus- with the traditional approach, suggests that it is unlikely ter velocity determinations and formed new weighted that any substantial error exists in the globular-cluster means. In the left-hand panels of Figure 4(b) his values velocity system. It is, however, disquieting that the slope are compared with ours for all clusters in common, while between the velocities of the two sets of G-type clusters in the center panel only those velocities with weight >2.0 differ at the ~ 10% level. Perhaps this represents in part from Webbink's compilation are included in the compari- statistical fluctuations arising because the G-type clusters son. In the latter case the agreement is reminiscent of the are generally more difficult to observe, and in part from comparison with Kinman's own velocities (Fig. 4(a), cen- inclusion of the G H and CN bands in the Zinn and West
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 414 "Ί I ι I Γ 400 ΚΙΝΜΑΝ (TABLE "Hin
200 2298 5986- (/) 0 6402- χ 6712-1 > _ 200
-400
400
200
CO 0 χ ^ -200
-400 Η h 400 Τ( Λ ALL 200 Ε 2298- 5986- 6441 6441 —» Έ 0 6402 6402- ω 61716712- —Κ χ 6440-^ Η-6293 > -200
-400 -400 -200 0 200 400 -400 -200 O 200 400 -400 -200 0 200 400 V (MAYALL) (km s"') V(ΚΙΝΜΑΝ- ΠΙ) (km s"1) V (ΚΙΝΜΑΝ -ΥΠΙ ) (kms"') 150
100
> <
-100
-150 -400 -200 O 200 400 -400 -200 O 200 400 -400 -200 O 200 400 V(HSM) (kms"1) V (HSM) (km s"1) V (HSM) (km s"') Fig. 4(a)-Comparison of our velocities from the image tube with those of Mayall (1946) and with those of Kinman's (1959a) Tables III and VIII. A regression was initially fit to all data points in common, then those clusters lying > 40 km s1 from that regression were deleted and a new regression solution calculated. The latter is shown, but the points ignored (identified by their NGC numbers) have been included in the figure. Both sets of regression coefficients are given in Table V, and discrepant clusters are summarized in Table VI. The upper row in this diagram shows the results for clusters of spectral type (cf. Paper I) F, the second row for clusters of spectral type G, and the third row for all clusters regardless of spectral type. The bottom row plots the differences [V(HSM) — V(Other)] as a function of V(HSM).
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System GALACTIC GLOBULAR CLUSTERS 415
V (HSM) (km s-1) V (HSM ) (km s"') V(HSM) (km s-')
Fig. 4(b)-Comparison between our data and those from Webbink's (1981) compilation and from Zinn and West (1984); in the former case the second set of panels shows results for those clusters having assigned weights > 2.0.
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 416 HESSER, SHAWL, AND MEYER
their residuals are given (in parentheses) for comparison. Bearing in mind the cautionary remark in the preceding paragraph, we proceed to comment on some of these discrepancies. The bulk of them arise from comparisons with Mayall (1946), which are in turn frequently reflected in the subsequent tabulations of Kinman's (1959«) Table VIII and of Webbink (1981). They also sometimes arise from particular choices made in the process of homoge- nization in the latter catalogs. For example, when forming <>- new means for NGC 2298 and NGC 5986 Webbink chose < Έ to reject a single high Mayall value, which increased AV with respect to the direct comparison with Mayall. In the ω case of NGC 6144 Zinn and West (1984) measured two χ spectra (+94 km s"1) and we measured three (162 km s_1); > <3 we are unable to discern an error in our analysis. Zinn and West measured -60 km s"1 from one spectrum of NGC 6171, while we get -22 km s_1 from two spectra and we are again unable to explain the discrepancy. We note -20 0 20 Declination (°) that the hydrogen lines were specifically excluded from Fig. 5-The residuals from the least-squares fit to all the velocities in our solution because of the emission in them (see Paper I). common with Mayall (1946) are shown as a function of declination. The (Existence of a typographical error affecting the velocity Mayall velocities for NGC 1851 and NGC 6171 depend on 130 A mm 1 1 of NGC 6218 in Kinman's Table VIII has been noted data alone, whereas all other points include Crossley 430 A mnT data. previously (Hesser and Shawl 1977)). Although results from only one spectrum are quoted in Table III for cross-correlation analysis. (Analysis of low-dispersion NGC 6333, a second exposure with four lines (Table II) spectra of (relatively) low-velocity objects (such as the yielded a velocity in accord with the first. For NGC 6402 Galactic globular clusters) by cross-correlation tech- and NGC 6544 repeated measurements of the single niques is susceptible to difficult-to-detect errors arising spectrum available have given the value in Table III. The from the low contrast of the spectral features. ) The disper- difference between Webbink s value for NGC 6528 and sion about the regression line (ignoring NGC 6144, _1 ours would disappear if one of van den Bergh's (1969) NGC 6171, and NGC 6544) is ~ 16 km s (Table V). For measures were arbitrarily dismissed. Kinman's measures the 20 clusters for which no velocity measurement existed (cf. his Table VII) for NGC 6584 show large scatter, which before our work and that of Zinn and West, the average may account for the discrepancy between our value and difference between our determinations is —1.7 ± 24.8 _1 his. Most of the remaining discrepancies seem to arise km s (standard deviation). That this standard error is from the larger random errors that appear to occasionally somewhat larger than the mean dispersion in our two data affect some Mayall values (see Shawl et al. (1981), but sets (see Fig. 4(b) and Table V) probably reflects the fact note that subsequent analysis has resulted in reduced that faint, difficult clusters in the Galactic nuclear bulge discrepancies between Zinn and West's velocities and dominate the sample common only to our two studies. theirs for NGC 6101, NGC 6235, NGC 6496, and E. Discrepant Clusters NGC 6558). From the summary of the above comparisons in Table IV. Wavelengths of Other Lines Measured V, we conclude that the external error of an image-tube velocity determined from a single plate is ~ 20 km s 1. A separate file, containing 1892 measurements of fea- Although every effort has been made to minimize the tures that were "unidentified" at the time of measurement errors and to provide realistic evaluations of them, pe- from 207 spectra of 82 clusters, was produced in a rela- rusal of Table II for those clusters having multiple obser- tively systematic attempt to seek other, generally weaker, vations reveals the occasional, more discrepant plate. features whose suitability for radial-velocity determina- Such examples emphasize the caution to be exercised tions in globular-cluster integrated spectra might be sub- when using velocities based on a single plate. sequently explored. Histograms of these line measure- In Table VI we collect residuals (HSM minus the veloc- ments served to identify approximate wavelengths of ity predicted from the appropriate least-squares regres- those features which appeared repeatedly in our cluster sion) for those clusters which deviate by more than 40 spectra. Many wavelengths which proved to be stable km s_1 in the comparisons between our velocities and were incorporated into the velocity determinations. those of other investigators (the "all" comparison in Figs. However, for a variety of reasons, some of the lines were 4(a),(b)). Wherever other velocity determinations exist not carried to the same level of analysis. Since some of
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System GALACTIC GLOBULAR CLUSTERS 417
TABLE V Regression Coefficients* All Data Less Rejected Points Slope Intercept RMS Slope Intercept RMS Mayall F 0.98 ± 0.04 5.92 ± 5.49 38.40 35 0.97 ± 0.02 12.02 ± 3.80 18.80 26 G 0.53 ± 0.18 32.62 ± 14.56 41.70 10 0.77 ± 0.10 8.13 ± 7.89 18.50 7 All 0.97 ± 0.04 17.18 ± 6.31 42.61 45 0.97 ± 0.02 12.26 ± 3.49 19.56 33 AV 0.01 ± 0.05 17.64 ± 6.37 42.62 45 0.00 ± 0.02 6.54 ± 3.54 20.66 33 Kinman F 0.97 ± 0.02 2.22 ± 2.86 13.29 24 (Table III) G 0.94 ± 0.01 0.58 ± 0.27 0.98 3 All 0.97 ± 0.01 1.16 ± 1.92 12.39 27 AV -0.03 ± 0.01 1.04 ± 1.98 12.75 27 Kinman F 0.98 ± 0.02 3.63 ± 3.13 35.00 50 0.98 ± 0.01 2.79 ± 2.06 17.10 41 (Table VIII) G 0.82 ± 0.09 3.26 ± 4.99 38.92 14 0.93 ± 0.05 1.41 ± 2.74 20.38 10 All 0.98 ± 0.02 3.83 ± 2.72 38.17 64 0.98 ± 0.01 2.61 ± 1.76 20.89 51 AV -0.02 ± 0.02 3.73 ± 2.79 38.89 64 -0.02 ± 0.01 2.19 ± 1.70 17.86 51 Webbink (All) F 0.96 ± 0.02 2.85 ± 3.02 35.38 52 0.95 ± 0.01 2.52 ± 1.94 15.67 44 G 0.95 ± 0.07 -2.79 ± 3.67 38.78 16 0.97 ± 0.05 -3.93 ± 2.95 19.48 14 All 0.96 ± 0.02 0.22 ± 2.27 36.34 68 0.96 ± 0.01 -0.30 ± 1.57 16.96 58 AV -0.33 ± 0.02 -0.23 ± 2.28 17.63 68 -0.04 ± 0.01 -1.30 ± 1.57 17.30 58 (Weight>2) F 0.96 ± 0.01 1.50 ± 1.90 13.02 28 G 1.00 ± 0.07 -5.69 ± 3.68 9.91 6 All 0.96 ± 0.01 -1.46 ± 1.58 12.90 34 AV -0.04 ± 0.01 -1.85 ± 1.60 13.43 34 Zinn-West F 1.06 ± 0.04 -2.31 ± 3.86 21.10 34 1.03 ± 0.03 -5.42 ± 3.02 16.19 32 G 1.10 ± 0.05 -2.05 ± 3.52 16.77 24 1.11 ± 0.04 -3.13 ± 3.22 14.15 23 All 1.07 ± 0.03 -2.62 ± 2.61 19.46 58 1.05 ± 0.02 -5.10 ± 2.16 15.53 55 AV 0.07 ± 0.02 -2.44 ± 2.45 18.17 58 0.04 ± 0.02 -2.92 ± 1.95 14.32 55
*The regression equation is of the form: Ordinate (Fig.4) = Abcissa (Fig. 4) X Slope + Intercept
TABLE VI them do occur sufficiently frequently as to make them potentially valuable for the general problem of velocity Cluster Velocity Residuals Δν > 40 km determinations in globular clusters (and possibly in the nuclei of some galaxies), we have listed them in Table VII NGC Mayall Kinman Kinman Webbink Zinn-West along with the number of spectra on which the feature was (T. Ill) (T. VIII) measured.
1904 -43 (17) (-4) (-15) V. Discussion 2298 (27) 43 68 5986 75 89 128 The velocity and spectral-type coverage of the major 6144 • · · • · · 64 6171 104 119 119 45 surveys may be ascertained from inspection of Figure 4 and, somewhat more conveniently, from the histograms 6218 -96 -82 (-3) of Figure 6. The latter, as well as the numerical results 6293 -89 -75 -73 6333 (19) (36) 44 from it (see Table VIII), suggest that globular clusters of 6402 76 98 93 spectral type F have an {vr) tending to (statistically in- 6440 (28) 44 (16) significant) positive values, while the G-type clusters 6441 71 85 (5) (-9) show a 1 σ-2 σ preference for a slightly negative {vr). This 6528 • · · 63 (0) apparent difference probably reflects the small numbers 6544 (A) (18) (21) 46 6584 76 62 • · involved, arising in part from selective obscuration of 6637 -79 -65 (-18) (-5) G-type clusters by dust, as well as from differential rota- tion of the two cluster subsystems (see below). One also 6712 (27) 44 (37) (12) 6723 -94 -80 -113 (13) notices in Figure 6 and Table VIII the drop (by about a 6934 -56 (-36) (-23) factor of two) in the dispersion of the measured radial 6981 -60 -62 -43 7006 -43 (-30) (0) velocities (uncorrected for local solar motion) between clusters of type F and G, reflecting the long-established
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 418 HESSER, SHAWL, AND MEYER
* 0 ai ω ■400 -200 0 200 400 -400 -200 0 200 400 -400 -200 0 200 400
-400 -200 0 200 400 -400 - 200 0 200 400 -400 -200 0 200 400 VELOCITY (km s"1)
Fig. 6-Histograms of the velocities of the Galactie globular clusters as determined by each of the authors indicated at the top of each panel. The upper row in each portion shows the results for clusters of spectral type "F" according to Paper I, while the middle row contains the results for G-type clusters. Results irrespective of spectral class ("ALL ") are shown in the bottom row.
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System GALACTIC GLOBULAR CLUSTERS 419
TABLE VII TABLE VIII Statistical Summary of the Velocity Surveys in Figure 6 Approximate Wavelengths of Other Lines Occurring Frequently In Our Spectra MAYALL KINMAN (T.III) KINMAN (T.VIII)
WEBBINK ZINN/WEST 4250.71 ± 0.2 44 Fe I 4371.65 ±0.5 36 Gr I
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 420 HESSER, SHAWL, AND MEYER
TABLE IX Solar Motion Solutions
Source of Data: Kinman (1959a) Kinman (1959a) Hartwick and Sargent (1978) Source of Analysis: Kinman (1959b) HSM Hartwick. and Sargent (1978) Spectral Type: All G All F G All
V(χ) km s~ -73.6 ± 33 -77.6 ± 36.9 -47.3 ± 107.7 -73.6 ± 33.8 V(y) km s~ 93.4 ± 22 97.2 ± 26.6 53.3 ± 52.6 92.7 ± 22.2 V(ζ) km s~ -119.5 ± 28 -129.4 ± 31.5 -41.2 ± 79.1 -119.1 ± 28.2 u km s~ (2.3) (-15.9) (-22.9) (-17.2) -22.8 ± 29.2 -19.5 ± 21.4 -15.1 ± 18.5 v' km s" (167.4) (-178.5) (-78.1) (-166.9) -177 ± 36.4 -50.8 ± 62.9 -155. ± 28.9 w km s" (-13.5) (10.6) (-12.0) (8.2) -7.9 ± 37.1 2.7 ± 76.4 5.8 ± 29.5 V km s" 168.0 ± 27 179.5 ± 31.2 82.3 ± 81.0 168.0 ± 27.8 (178.6) (54.5) (155.8) σ km s"1 125.4 117.0 121.9 128 3* 101 ± 5* v ri 102.1 91.2 100.2 < I v pec I > ** ^ pec ^ 5-i -2.6 -6.3 -2.8 a(1950) 21 27 ± 26m 20h34in ± 61m 20h33m + 57m 6(1950) 4521 + 621 4621 + 1020 3020 ± 5525 4522 ± 920 1(°) 90.8 ± 7.5 84.9 73.7 84.1 (82.7) (69.0) (84.4) b(0) -4.6 ± 7.6 3.4 -8.4 2.8 (-2.5) (2.8) (2.1) 70 53 17 70 46 25 79
Source of Data: HSM Augmented HSM Source of Analysis HSM HSM Spectral Type: G ALL G All
V(x) km s-1 -95.6 ± 37.3 43.4 92.4 -87.6 1 33.6 -106.7 ± 28.6 43.4 ± 92.4 -98.3 ± 26.5 V(y) km s"1 95.1 ± 25.7 22.4 27.7 80.0 l 20.1 71.4 ± 20.8 22.4 ± 27.9 66.1 ± 17.1 V(z) km s"1 -149.6 ± 34.9 -8.7 45.2 -118.1 l 28.9 -120.3 ± 27.6 -8.7 ± 45.2 -100.1 ± 23.8 u km s-1 (-2.8) 18.2) (-5.5) (4.3) (-18.2) (-1.6) v' km s"1 (-201.3) (-4.8) (-167.2) (-174.2) (-4.8) (-152.8) w km s"! (3.9) (45.9) (-6.4) (-23.9) (45.9) (-26.7) V km s"1 201.4 ± 33.6 49.6 ± 82.1 167.4 i 28.6 175.9 ± 27.6 49.6 ± 82.1 155.1 ± 23.9 km s-1 127.9 86.0 119.7 122.5 86.0 116.1 v <1 pec I > km s" 104.1 66.7 96.6 99.4 66.7 93.3 ^ Vnec· ^ km s -2.3 -3.4 0.2 -1.1 -3.4 -0.9 α(1950) 21h01m ± 54m 13^9'm 21h101 ± 52 21h45m ± 42m 3 49 + 3¾ 21^41 40 6(1950) 4820 ± 925 1021 ± 5421 4429 ± 928 4321 ± 828 1021 ± 5421 4022 ± 828 1(°) 89.2 345.1 88.1 91.4 345.1 89.4 b(0) 1.1 67.7 -2.2 -7.8 67.7 -9.9 63 27 90 81 27 108
*Isotropic velocity dispersion from Hartwick and Sargent's Table 4 solution using Vq = 220 km s"*·.
337? 1, b = 66?0, which are similar to the values derived angle of the cluster to the apex. Mayall (his Fig. 3) specifi- from our data. Except for the minor numerical error cally notes those clusters which are important for solar- uncovered in Kinman's analysis, the net effect of all the motion solutions for which he lacked velocities; the cur- Table IX variants on our simplistic, straightforward recal- rent study includes 19 of those 22 clusters. Figure 7, culation of the solar motion is to underscore Kinman's corresponding to M ay all's Figure 3, Kinmans Figure 1, finding (on comparing his results with those of Mayall) and Zinn's (1985) Figure 6, plots the radial velocity (cor- that improvements in numbers of clusters and their distri- rected for the local solar motion) against cos A. The solar bution on the sky produce little change. motion of 167 km s"1 from the Table IX HSM solution is Discussions of cluster kinematics by Mayall (1946) and indicated. The velocities are evenly distributed on both Kinman (1959¾ ), and even the more recent ones of Frenk sides of zero. and White (1980) and Hartwick and Sargent (1978), were We further note that the velocity dispesion of ~ 120 limited by the number of clusters in the sample and by km s_1 computed from the solution for the HSM velocities their distribution relative to the apex of their motion. corrected for the local solar motion agrees well with the Both Mayall and Kinman, for example, discuss the distri- width of the velocity distribution in Figure 6 and Table bution of cluster velocities versus cos A, where A is the VIII, from which we find that 59% of the clusters are
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System GALACTIC GLOBULAR CLUSTERS 421
-1 -8 -.6 -.4 -.2 0 .2 Λ .6 .8 1 APEX DISTANCE
Fig. 7-The radial velocity (corrected for the local solar motion) is plotted versus the cosine of the apex angle, A. The solar-motion solution for 167 km s-1 is also shown. The arrow indicates the angle from the apex to the Galactic center. within ± 100 km s_1. Even with the large associated were individually measured and examined during the errors, the v' values from our solutions indicate smaller analysis of the globular-cluster spectra themselves. While solar motions for the G-type clusters, reflecting that they internal measuring errors are estimated to be ~ 13 km s_1 appear to rotate faster than the F-type clusters, as first per plate, we believe that internal plus external errors are found by Kinman, and subsequently by Hartwick and more nearly ~ 20 km s_1 per plate. Multiple observations Sargent (1978) and Zinn (1985). The latter paper reports a have been obtained for ~ 70% of the clusters. These new larger difference, as we have also found, between the measurements, summarized in Tables II and III, repre- calculated solar motion of the F- and G-type clusters than sent the largest, most homogeneous set of velocity data had been found by Hartwick and Sargent. Zinn s sugges- for our globular-cluster system. tion that 14 of the 25 G-type clusters in Hartwick and Comparisons between our velocities and those of May- Sargent's analysis might more appropriately be consid- all (1946), Kinman (1959«), Webbink (1981), and Zinn ered with the F-type clusters is correct: in Paper I we and West (1984) generally reveal excellent overall agree- classified spectra of eleven of those clusters as being of ment. Table V and Figure 4 show that all studies essen- spectral type F instead of G. tially share a common zero point regardless of spectral types, allaying a concern raised by Kinman (1959¾). As VI. Summary noted previously (Shawl et al. 1981), velocity discrepan- We have used a traditional approach of measuring indi- cies are more common when comparing with the lower vidual spectral lines on ~ 120 A mm1 image-tube plates dispersion results of Mayall (1946), in accordance with his taken with the Boiler and Chivens spectrograph at the predictions. A small zero-point difference between our Cassegrain focus of the Yale-Tololo 1-m telescope to de- velocities and those derived by Zinn and West from spec- termine radial velocities from the integrated light of 90 tral material obtained with the same instrument but ana- Galactic globular clusters and NGC 121 in the Small Mag- lyzed by cross-correlation techniques disappears on ellanic Cloud. Rest wavelengths were evaluated as a func- adopting Mayor et al. 's (1984) 47 Tue velocity as the zero tion of spectral type using as a starting point the results of point of the Zinn and West analysis. It is hypothesized Shawl et al. (1985) for Population I stars observed on the that an ~ 10% difference in slope between our and the same nights. All told, more than 4000 absorption lines Zinn and West velocity systems for G-type clusters might
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 422 HESSER, SHAWL, AND MEYER have arisen from application of cross-correlation tech- during many visits and by the Astronomy Department of niques to low-dispersion spectra of (relatively) low-veloc- the University of Galifornia at Berkeley during the time ity objects and inclusion of strong molecular features with when this paper was completed. unstable effective wavelengths in the cross-correlated REFERENCES regions. The net effect of our work (Shawl et al. 1981; this Basino, L. P., and Muzzio, J. C. 1984, Rev. Mexicana Astron. As- paper) and that of Zinn and West (1984) is to make avail- trofísica, 9, 165. able velocities for 22 Galactic globulars previously lacking Bolton, A. J., and Mallia, E. A. 1977, Astr. Ap. (Letters), 59, L23. them, in addition to substantially improving the velocity Bowers, P. F., Kerr, F. J., Knapp, G. R., Gallagher, J. S., and Hunter, precision for another ~ 18 clusters. D. A. 1979, Ap./., 233, 553. Clube, S. V. M., and Watson, F. G. 1979, M.N.R.A.S., 187, 863. Solid-body, solar-motion solutions based on the larger Faulkner, D. J., and Freeman, K. C. 1977, Ap./., 211, 77. data base with its improved sky coverage lead to minimal Feast, M. W., and Thackeray, A. D. 1963, Mem. R.A.S., 68, 173. statistical improvements over earlier solutions. From our Frenk, C. S., and White, S. D. M. 1980, M.N.R.A.S., 193, 295. data base alone we calculate the apex of the solar motion Harris, H. C., Nemec, J. M., and Hesser, J. E. 1983, Pub. A.S.P., 95, h ra m 256. to lie at α = 21 10 ± 52 and δ = 44?9 ± 9?8 (1950.0) or Hartwick, F. D. Α., and Hesser, J. E. 1972, Ap./., 175, 77. € = 88?1 and h = — 2?2. The velocity dispersion estimated Hartwick, F. D. Α., and Sargent, W. L. W. 1978, Ap. /., 221, 512. for the Galactic globulars following removal of the solar Hesser, J. E., and Hartwick, F. D. A. 1977, Ap./. SuppL, 33, 361. motion is ~ 120 km s"1 for the 90 clusters in the entire Hesser, J. E., and Shawl, S. J. 1977, Ap.]. (Letters), 217, L143. sample, and ~ 128 km s1 and ~ 86 km s1 for the 63 and 1985, Pub. A.S.P., 97, 465 (Paper I). Jernigan, J. G., and Clark, G. W. 1979, Ap. /. (Letters), 231, L125. 27 clusters of spectral types F and G, respectively. Like Joy, A. H. 1949, Ap./., 110, 165. our predecessors, we too find evidence from the solid- Kinman, T. D. 1959ö, M.N.R.A.S., 119, 157. body solutions that the G-type clusters are rotating more 1959Z?, M.N.R.A.S., 119, 559. rapidly than the F-type clusters. Indeed, evidence dis- Klein, M. J. 1976, Ap. Letters, 18, 25. cussed by Zinn (1985), Hesser and Shawl (1985), and in Lynden-Bell, D., Cannon, R. D., and Godwin, P. J. 1983, M.N.R.A.S., 204, 87P. this paper increasingly points to distinct differences be- Mayall, N. U. 1946, Ap.]., 104, 290. tween the F and G clusters, differences of considerable Mayor, M., Ibert, M., Andersen, J., Benz, W., Lindgren, H., Martin, importance for understanding the origin and subsequent N., Maurice, E., Nordström, Β., and Prévor, L. 1984, Astr. Αρ., evolution of the Galactic globular-cluster system, a sub- 134, 118. ject to which we shall return in future papers. Mihalas, D., and Binney, J. 1981, Galactic Astronomy, Structure and Kinematics, 2d ed. (San Francisco: Freeman Co.), chap. 6. Nemec, J. M. 1978, M.Sc. thesis. University of Victoria. We thank GTIO for their support throughout the ob- Peterson, R. C. 1984, Ap.]., 289, 320. serving phases of this project; our gratitude is indeed 1985, Ap. /., 297, 309. deep to E. Cosgrove, K. Gzuia, G. Martin, D. Maturana, Rodgers, A. W., and Paltoglou, G. 1984, Ap. /. (Letters), 283, L5. M. Navarrete, L. Pinto, G. Poblete, J. A. Rios, and M. Rose, J. Α., andTripicco, M. J. 1986, preprint. Russell, Η. N., and Bowen, 1. S. 1929, Ap./., 69, 196. Zemelman, who, as Night Assistants, provided superb Shawl, S. J., and Hesser, J. Ε. 1986, in preparation. support over the years. We are also indebted to the Shawl, S. J., and White, R. E. 1980, Ap./. (Letters), 239, L61. following people for their important contributions: J. B. Shawl, S. J., Hesser, J. E., and Meyer, J. E. 1981, in 1AU Colloquium Hutchings, P. Massey, andH. G. Harris (for sharing their 68, Astrophysical Parameters for Globular Clusters, ed. A. G. D. radial-velocity reduction programs); R. Day (for provid- Philip and D.S. Hayes (Schnectady: Davis Press), p. 191. Shawl, S. J., Hesser, J. E., Meyer, J. E., and van Heteren, J. 1985, Pub. ing us with his solar-motion program); J. van Heteren, S. A.S.P., 97, 519 (Paper II). G. Morris, and D. Tholen (for general software support); Smith, H. C., and Perkins, G. J. 1982, Ap. /., 261, 576. D. Andrews and W. G. Smyth (for their maintenance of Smith, M. G., Hesser, J. Ε., and Lasker, B. 1978, in GTIO Facilities the ARGTURUS measuring engine); and D. Growe, D. Manual, 2d ed., ed. J. Ε. Hesser (Tucson: AURA), p. [7].2. Duncan, and Y. Hurwitz (for help with the manuscript). Smith, M. G., Hesser, J. Ε., and Shawl, S. J. 1976, Αρ./., 206, 66. Troland, T. H., Hesser, J. E., and Heiles, C. Ε. 1978, Αρ./., 219, 873. We further thank F. D. A. Hartwick, T. D. Kinman, N. VandenBerg, D. Α. 1978, Αρ. /., 224, 394. U. Mayall, and S. van den Bergh for their encouragement van den Bergh, S. 1969, Αρ./. SuppL, 19, 145. over the years, G. L. H. Harris for permission to use her Vidal, Ν. V., and Freeman, K. C. 1975, Αρ. /. (Letters), 200, L9. spectra of NGG 6352 giants, and B. G. Reed for alerting Webbink, R. F. 1981, Αρ..]. SuppL, 45, 259. us to the York reference. S.J.S. acknowledges the role of Wooley, R. D. V., et al. 1966, Royal Obs. Annals, No. 2. York, D. 1966, Can.]. Phys., 44, 1079. extended support from both the NSF through grant No. Zinn, R. 1985, Ap.]., 293, 424. AST 80-00001 and the University of Kansas General Re- Zinn, R., and West, M. J. 1984, Ap.]. SuppL, 55, 45. search Fund, and the hospitality extended by the DAO Zinn, R. J., Newell, Ε. B., and Gibson, J. B. 1972, Astr. Αρ., 18, 390.
© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System