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The Michigan/MIKE Fiber System Survey of Stellar Radial Velocities in Dwarf Spheroidal Galaxies: Acquisition and Reduction of Data
We introduce a stellar velocity survey of dwarf spheroidal galaxies,undertaken using the Michigan/MIKE Fiber System (MMFS) at theMagellan/Clay 6.5 m telescope at Las Campanas Observatory. As of 2006November we have used MMFS to collect 6415 high-resolution(R=20,000-25,000) spectra from 5180 stars in four dwarf spheroidalgalaxies: Carina, Fornax, Sculptor, and Sextans. Spectra sample therange 5140-5180 Å, which includes the prominent magnesium tripletabsorption feature. We measure radial velocity (RV) to a medianprecision of 2.0 km s-1 for stars as faint as V~20.5. Fromthe spectra we also are able to measure the strength of iron andmagnesium absorption features using spectral indices that correlate witheffective temperature, surface gravity, and chemical abundance.Measurement of line strength allows us to identify interlopingforeground stars independently of velocity and to examine themetallicity distribution among dSph members. Here we present detaileddescriptions of MMFS, our target selection and spectroscopicobservations, the data reduction procedure, and error analysis. Wecompare our RV results to previously published measurements forindividual stars. In some cases we find evidence for a mild,velocity-dependent offset between the RVs that we measure using themagnesium triplet and previously published RV measurements derived fromthe infrared calcium triplet. In companion papers we will present thecomplete data sets and kinematic analyses of these new observations.This paper includes data obtained with the 6.5 m Magellan Telescopeslocated at Las Campanas Observatory, Chile.
| Bright globular clusters in NGC 5128: the missing link between young massive clusters and evolved massive objects
Context: Globular clusters are the simplest stellar systems in whichstructural parameters are found to correlate with their masses andluminosities. Aims: To investigate whether the brightest globularclusters in the giant elliptical galaxies are similar to the lessluminous globular clusters like those found in Local Group galaxies, westudy the velocity dispersion and structural parameter correlations of asample of bright globular clusters in the nearest giant ellipticalgalaxy NGC 5128 (Centaurus A). Methods: The UVES echelle spectrographon the ESO Very Large Telescope (VLT) was used to obtain high-resolutionspectra of 23 bright globular clusters in NGC 5128, and 10 clusters wereobserved with EMMI in echelle mode with the ESO New TechnologyTelescope. The two datasets have 5 clusters in common, while one clusterobserved with UVES had too low a signal-to-noise ratio. Hence the totalnumber of clusters analysed in this work is 27, more than doubling thepreviously known sample. Their spectra were cross-correlated withtemplate spectra to measure the central velocity dispersion for eachtarget. The structural parameters were either taken from the existingliterature, or in cases where this was not available, we derived themfrom our VLT FORS1 images taken under excellent seeing conditions, usingthe ISHAPE software. The velocity dispersion and structural parametermeasurements were used to obtain masses and mass-to-luminosity ratios(M/L_V) for 22 clusters. Results: The masses of the clusters in oursample range from M_vir = 10^5-107 Mȯ, andthe average M/LV is 3 ± 1. The three globular clustersharbouring X-ray point sources are the second, third, and sixth mostmassive in our sample. The most massive cluster, HCH99-18, is also thebrightest and the largest. It has a mass (M_vir =1.4×107 Mȯ) that is an order ofmagnitude higher than the most massive clusters in the Local Group and ahigh M/LV ratio (4.7 ± 1.2). We briefly discusspossible formation scenarios for this object. Conclusions: Thecorrelations of structural parameters, velocity dispersion, masses, andM/LV for the bright globular clusters in NGC 5128 extend theproperties established for the most massive Local Group clusters towardsthose characteristic of dwarf elliptical nuclei and ultra-compact dwarfgalaxies (UCDs). The detection of the mass-radius and themass-M/LV relations for the globular clusters with masseshigher than ~ 2 × 106 Mȯ provides themissing link between “normal” old globular clusters, youngmassive clusters, and evolved objects like UCDs.Based on observations collected at the European Southern Observatory,Paranal, Chile, within the Observing Programmes 63.N-0229 and069.D-0169.
| Spectroscopy of Globular Clusters out to Large Radius in the Sombrero Galaxy
We present new velocities for 62 globular clusters in M104 (NGC 4594,the Sombrero Galaxy), 56 from 2dF on the AAT and 6 from Hydra on WIYN.Combined with previous data, we have a total sample of 108 M104 globularcluster velocities, extending to 20' radius (~60 kpc), alongwith BVR photometry for each of these. We use this wide-field data setto study the globular cluster kinematics and dark matter content of M104out to 10' radius (30 kpc). We find no rotation in theglobular cluster system. The edge-on nature of M104 makes it unlikelythat there is strong rotation which is face-on and hence unobserved;thus, the absence of rotation over our large radial range appears to bean intrinsic feature of the globular cluster system in M104. We discussways to explain this low rotation, including the possibility thatangular momentum has been transferred to even larger radii throughgalaxy mergers. The cluster velocity dispersion is ~230 kms-1 within several arcminutes of the galaxy center, and dropsto ~150 km s-1 at ~10' radius. We derive the massprofile of M104 using our velocity dispersion profile, together with theJeans equation under the assumptions of spherical symmetry and isotropy,and find excellent agreement with the mass inferred from the stellar andgas rotation curve within 3' radius. The M/LVincreases from ~4 near the galaxy center to ~17 at 7' radius(~20 kpc, or 4 Re), thus giving strong support for thepresence of a dark matter halo in M104. More globular cluster velocitiesat larger radii are needed to further study the low rotation in theglobular cluster system, and to see if the dark matter halo in M104extends beyond a radius of 30 kpc.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Radial velocities in the globular cluster ? Centauri
We have used the ARGUS multi-object spectrometer at the CTIO 4 m Blancotelescope to obtain 2756 radial velocity measurements for 1966individual stars in the globular cluster ? Centauri brighter thanblue photographic magnitude of about 16.5. Of these, 1589 stars arecluster members. A comparison with two independent radial velocitystudies, carried out by Suntzeff & Kraft and by Mayor et al.,demonstrates that the median error of our measurements is below 2 kms-1 for the stars brighter than B-magnitude 15, whichconstitute the bulk of the sample. The observed velocity dispersiondecreases from about 15 km s-1 in the inner few arcmin toabout 6 km s-1 at a radius of 25'. The cluster showssignificant rotation, with a maximum amplitude of about 6 kms-1 in the radial zone between 6' and 10'. In a companionpaper by van de Ven et al., we correct these radial velocities for theperspective rotation caused by the space motion of the cluster, andcombine them with the internal proper motions of nearly 8000 clustermembers measured by van Leeuwen et al., to construct a detaileddynamical model of ? Centauri and to measure its distance.
| Elemental Abundance Ratios in Stars of the Outer Galactic Disk. II. Field Red Giants
We summarize a selection process to identify red giants in the directionof the southern warp of the Galactic disk, employing VICphotometry and multiobject spectroscopy. We also present results fromfollow-up high-resolution, high signal-to-noise echelle spectroscopy ofthree field red giants, finding [Fe/H] values of about -0.5. The fieldstars, with galactocentric distances estimated at 10-15 kpc, support theconclusion of Yong and coworkers that the Galactic metallicity gradientdisappears beyond RGC values of 10-12 kpc for the older starsand clusters of the outer disk. We summarize the detailed abundancepatterns for 15 other elements for these stars and compare them withrecently obtained results for old open cluster red giants in the outerdisk. The field and cluster stars at such large distances show verysimilar abundance patterns, and, in particular, all show enhancements ofthe α-elements O, Mg, Si, Ca, and Ti and the r-process element Eu.These results suggest that Type II supernovae have been significantcontributors to star formation in the outer disk relative to Type Iasupernovae within the past few gigayears. We also compare our resultswith those available for much younger objects. The limited results forthe H II regions and B stars in the outer disk also suggest that theradial metallicity gradient in the outer disk is shallow or absent. Themuch more extensive results for Cepheids confirm these trends and thatthe change in slope of the metallicity gradient may occur at a largergalactocentric distance than for the older stars and clusters. However,the younger stars also show rising α-element enhancements withincreasing RGC, at least beyond 12 kpc. These trends areconsistent with the idea of a progressive growth in the size of theGalactic disk with time and episodic enrichment by Type II supernovae aspart of the disk's growth.This paper makes use of observations obtained at the National OpticalAstronomy Observatory, which is operated by the Association ofUniversities for Research in Astronomy (AURA), Inc., under contract fromthe National Science Foundation. We also employ data products from theTwo Micron All Sky Survey, which is a joint project of the University ofMassachusetts and the Infrared Processing and Analysis Center,California Institute of Technology, funded by the National Aeronauticsand Space Administration and the National Science Foundation.
| Stellar Kinematics of Boxy Bulges: Large-Scale Bars and Inner Disks
Long-slit stellar kinematic observations were obtained along the majoraxis of 30 edge-on spiral galaxies, 24 with a boxy or peanut-shaped(B/PS) bulge and six with other bulge types for comparison. Such B/PSbulges are identified in at least 45% of highly inclined systems, and agrowing body of theoretical and observational work suggests that theyare the edge-on projection of thickened bars. Profiles of the meanstellar velocity V, the velocity dispersion σ, as well as theasymmetric (h3) and symmetric (h4) deviations froma pure Gaussian are presented for all objects. Comparing these profileswith stellar kinematic bar diagnostics developed from N-bodysimulations, we find bar signatures in 24 of our sample galaxies (80%).Galaxies with a B/PS bulge typically show a double-humped rotation curvewith an intermediate dip or plateau. They also frequently show a ratherflat central velocity dispersion profile accompanied by a secondary peakor plateau, and numerous galaxies have a local central σ minimum(>~40%). The h3 profiles display up to three slopereversals. Most importantly, h3 is normally correlated with Vover the presumed bar length, contrary to expectations from axisymmetricdisks. These characteristic bar signatures strengthen the case for aclose relationship between B/PS bulges and bars and leave little roomfor other explanations of the bulges' shape. We also find thath3 is anticorrelated with V in the very center of mostgalaxies (>~60%), indicating that these objects additionally harborcold and dense decoupled (quasi-) axisymmetric central stellar disks,which may be related to the central light peaks. These central diskscoincide with previously identified star-forming ionized-gas disks(nuclear spirals) in gas-rich systems, and we argue that they formed outof gas accumulated by the bar at its center through inflow. As suggestedby N-body models, the asymmetry of the velocity profile (h3)appears to be a reliable tracer of asymmetries in disks, allowing us todiscriminate between axisymmetric and barred disks seen in projection.B/PS bulges (and thus a large fraction of all bulges) appear to be madeup mostly of disk material, which has acquired a large vertical extentthrough bar-driven vertical instabilities. Their formation is thusprobably dominated by secular evolution processes rather than merging.
| Radial Velocity of the Phoenix Dwarf Galaxy: Linking Stars and H I Gas
We present the first radial velocity measurement of the stellarcomponent of the Local Group dwarf galaxy Phoenix, using the FORS1instrument at the VLT's Unit Telescope 1 (Antu). From the spectra of 31red giant branch stars, we derive a heliocentric optical radial velocityfor Phoenix of Vsolar=-52+/-6 km s-1. On the basisof this velocity, and taking into account the results of a series ofsemianalytical and numerical simulations, we discuss the possibleassociation of the H I clouds observed in the Phoenix vicinity. Weconclude that the characteristics of the H I cloud with heliocentricvelocity -23 km s-1 are consistent with this gas having beenassociated with Phoenix in the past and being lost by the galaxy afterthe last event of star formation in the galaxy, about 100 Myr ago. Twopossible scenarios are discussed: the ejection of the gas by the energyreleased by the supernovae (SNe) produced in that last event of starformation and a ram pressure stripping scenario. We derive that thekinetic energy necessary to eject the gas isESNe~2×1051 ergs and that the number of SNenecessary to transfer this amount of kinetic energy to the gas cloud is~20. This is consistent with the number of SNe expected for the lastevent of star formation in Phoenix, according to the star formationhistory derived by Martínez-Delgado, Gallart, & Aparicio. Thedrawback of this scenario is the regular appearance of the H I cloud andits anisotropic distribution with respect to the stellar component.Another possibility is that the H I gas was stripped as a consequence ofram pressure by the intergalactic medium. In our simulations, thestructure of the gas remains quite smooth as it is stripped fromPhoenix, keeping a distribution similar to that of the observed H Icloud. Both in the SNe ejection case and in the ram pressure sweepingscenario, the distances and relative velocities imply that the H I cloudis not gravitationally bound to Phoenix, since this would require aPhoenix total mass about an order of magnitude larger than its totalestimated mass. Finally, we discuss the possibility that Phoenix may bea bound Milky Way satellite. The minimum required mass of the Milky Wayfor Phoenix to be bound is MMW(<450kpc)>=1.2×1012 Msolar, which comfortablyfits within most current estimates. Based on observations collected invisitor mode with the VLT UT1, Antu, at the European SouthernObservatory, Chile.
| Testing the Surface Brightness Fluctuations Method for Dwarf Elliptical Galaxies in the Centaurus A Group
We have obtained deep B and R-band CCD photometry for five dwarfelliptical galaxies that were previously identified on Schmidt filmscovering the region of the Centaurus A (Cen A) group. From a Fourieranalysis of the R-band CCD images we determined the surface brightnessfluctuation (SBF) magnitude mR for each stellar system. Allmagnitudes are similar, and, given the small color spread, they suggestthat these low surface brightness galaxies lie approximately at the samedistance, regardless of the assumed SBF zero point. Long-slit spectrahave been acquired to derive redshifts for two of the dwarfs, ESO269-066 and ESO 384-016. The velocities, vsolar=784 kms-1 and vsolar=561 km s-1,respectively, identify them unambiguously as Cen A group members. An age(HδA)-metallicity(C2λ4668) analysis of the spectra reveals anunderlying old and metal-poor stellar population in both cases.Combining photometric and spectroscopic results we find strong evidencethat indeed all dwarf galaxies are Cen A group members. Based onCepheid, TRGB, and PNLF distances published for the two main Cen A groupgalaxies, NGC 5128 and NGC 5253, we adopted a mean group distance of3.96 Mpc to calibrate the apparent fluctuation magnitudes. The resultingabsolute SBF magnitudes MR of the dEs correlate with thedereddened colors (B-R)0 as predicted by Worthey's stellarsynthesis models, using the theoretical isochrones of Bertelli andcollaborators. This good agreement allows a calibration of the SBFmethod for dwarf ellipticals in the color range0.8<(B-R)0<1.5. However, two branches of stellar populationsappear in the MR-color plane, and care has to be taken todecide which branch applies to a given observed dwarf. For dwarfs with(B-R)0<1 there is very little color dependence(MR~-1.2), in accord with our previous SBF analysis of faint,blue Sculptor group dEs. For red dwarfs, (B-R)0>1.2, theMR-color relation is steep, and accurate colors are needed toachieve SBF distances with an uncertainty of only 10%. One of thedwarfs, ESO 219-010, is located slightly behind the core of the Cen Agroup at about 4.8 Mpc, while the remaining four recover the mean groupdistance of 3.96 Mpc that was put into the calibration. The depth of thegroup is only 0.5 Mpc, which identifies the Cen A group as a spatiallywell-isolated galaxy aggregate, in contrast to the nearby Sculptorgroup.
| The shape and scale of Galactic rotation from Cepheid kinematics
A catalog of Cepheid variables is used to probe the kinematics of theGalactic disk. Radial velocities are measured for eight distant Cepheidstoward l = 300 deg; these new Cepheids provide a particularly goodconstraint on the distance to the Galactic center, R0. We model the diskwith both an axisymmetric rotation curve and one with a weak ellipticalcomponent, and find evidence for an ellipticity of 0.043 +/- 0.016 nearthe sun. Using these models, we derive R0 = 7.66 +/- 0.32 kpc andv(circ) = 237 +/- 12 km/s. The distance to the Galactic center agreeswell with recent determinations from the distribution of RR Lyraevariables and disfavors most models with large ellipticities at thesolar orbit.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Spectroscopy for E and S0 galaxies in nine clusters
Central velocity dispersions, Mg_2 line indices and radial velocitiesfor 220 E and S0 galaxies are derived on the basis of intermediateresolution spectroscopy. Galaxies in the following clusters have beenobserved: Abell 194, Abell 539, Abell 3381, Abell 3574, S639, S753,Doradus, HydraI (Abell 1060) and Grm 15. For 151 of the galaxies, thevelocity dispersion has not previously been measured. 134 of the Mg_2determinations are for galaxies with no previous measurement. Thespectra cover either 500 or 1000A, centred on the magnesium triplet at5177A. The observations were obtained with the Boller & Chivensspectrograph at the ESO 1.5-m telescope and with the OPTOPUS, amulti-object fibre-fed B&C spectrograph, at the ESO 3.6-m telescope.The data are part of our ongoing study of the large-scale motions in theUniverse and the physical background for the Fundamental Plane. TheFourier fitting method was used to derive the velocity dispersions andradial velocities. The velocity dispersions have been corrected for theeffect of the size of the aperture. The correction was established onthe basis of velocity dispersion profiles available in the literature. Acomparison with results from Davies et al. shows that the derivedcentral velocity dispersions have an rms error of 0.036 in logsigma.There is no offset relative to the velocity dispersions from Davies etal. The offset relative to data from Lucey & Carter is-0.017+/-0.011 in logsigma, with our velocity dispersions being thesmallest. The velocity dispersions derived from the B&C and theOPTOPUS observations, as well as the velocity dispersions published byDavies et al., Dressler, Lucey & Carter and Lucey et al., can bebrought on a system consistent within 3 per cent. The Mg_2 line indiceshave been corrected for the size of the apertures, transformed to theLick system, and corrected for the effect of the velocity dispersion.From comparison with data from Davies et al. and from Faber, we findthat the rms error of Mg_2 is 0.013. Comparisons of the radialvelocities with data from the literature show that our determinationsare accurate to within ~=35 km s^-1. The accuracies reached for theseobservations are adequate for the study of the large-scale motions inthe Universe and for investigations of the Fundamental Plane.
| A kinematic study of the Sculptor dwarf spheroidal galaxy.
We derive new, accurate radial velocity (V_r_) measurements for 23Sculptor K-giant stars from high-resolution echelle spectra made withthe ESO NTT and 3.6-m telescopes. Comparing our velocities with previousmeasurements (Armandroff & Da Costa 1986) for 15 stars, we show thatthe V_r_ measurements are reliable, and discover two V_r_ variable starswith large amplitudes (>17km/s). These variations are best explainedby binary orbital motions. As our sample is likely to contain manyadditional undetected binaries with smaller velocity amplitudes (due toless favorable orbit inclinations, smaller mass ratios, or longerperiods), the observations suggest a large binary fraction in Sculptor,possibly larger than ~20% within the period limits ~0.5 to ~20yrs. Thisresult is consistent with the recent discoveries of 2-3 large-amplitudevariable stars in Ursa Minor and Sextant. Previous kinematic studies ofdSph galaxies based on single-epoch measurements are consequently notfully reliable. Radial velocity-variable stars artificially inflate thevelocity dispersion and the mass-to-light (M/L) ratio estimates. Thisweakens the case for dark matter, at least in some of the dSph galaxies.In the case of Sculptor, a velocity dispersion of 6.2+/-1.1km/s and aM/L ratio of 13+/-6(M/L_V_)sun_ are derived from our sample.These results do not provide unambiguous evidence for a dominant darkmatter component in Sculptor, mainly because our sample is likely tocontain additional undetected V_r_ variables of lower amplitude.
| SANTIAGO 91, a right ascension catalogue of 3387 stars (equinox J2000).
The positions in right ascension of 3387 stars belonging to the Santiago67 Catalogue, observed with the Repsold Meridian Circle at Cerro Calan,National Astronomical Observatory, during the period 1989 to 1994, aregiven. The average mean square error of a position, for the wholeCatalogue, is +/-0.009 s. The mean epoch of the catalogue is 1991.84.
| Observational Data for the Kinematics of the Local Universe - Part Two - Second Set of Radial Velocity Measurements
This paper is the second one in a series dedicated to the study of thekinematics of the local universe. It gives 361 new optical and radioredshifts measured at ESO, OHP and Nancay Observatories.
| Dynamics of the Pavo-Indus and Grus clouds of galaxies
A study of groups of galaxies in the above regions was carried out byselecting a sample extending one magnitude deeper than previous work inthe area, complete down to 15 mag. We report new redshift determinationsfor 58 galaxies in the region and 13 other miscellaneous galaxies, basedon La Silla observations. Using a total of 266 galaxies with measuredredshifts in the Pavo-Indus and Grus clouds, we perform a new analysisof groupings following a well-tested algorithm. A total of 18 groups issingled out, most of them known from previous work, even though a fewadditional members are added. For all the groups, we have calculateddynamical parameters and M/L ratios. All groups are found to be boundaggregates, but only one group can be virialized. For the six mostpopulated examples, having at least five members, we also calculateseveral mass estimators and discuss the wide range of observed M/Lratios, which extends from nine to nearly 500 M(solar)/L(solar). Weintroduce two parameters to measure the presence of either a dominantgalaxy or internal subcondensations, respectively, and test whether anycorrelation with the M/L ratios can be detected. No clear correlationsare found.
| Observational data for the kinematics of the local universe. I - Radial velocity measurements
The study of the local velocity field requires the use of a very largesample to describe as accurately as possible some prominent features ofthe local kinematics. The problem of collecting a large sample is mademore difficult because of the Malmquist bias which plagues distancedeterminations. The present program aims at determining bias-freedistances for a complete sample in order to study the local velocityfield. The present paper gives 303 preliminary optical and radioredshifts measured for this program at ESO, OHP and NancayObservatories.
| The frequency of low-mass companions to K and M stars in the solar neighbourhood
The measurements of radial velocities of 200 stars from the Gliesecatalog during 5 years with an accuracy of 0.5 km/s indicate the absenceof substellar mass companions with periods less than 3000 d. Theprobability of companion detection is determined by numerical modeling.New data on spectroscopic orbits of late-type dwarfs are used toestimate the distribution of companion masses by the maximum likelihoodmethod. The statistical properties of low-mass binaries are differentfrom those of more massive main-sequence and giant systems: thefrequency of spectroscopic binaries is less (10 +/- 2 percent) while atleast half of them have a mass ratio exceeding 0.5. Evidence is foundfor a nonmonotonic distribution of the masses of secondary componentswith a deficit in the 0.2-0.3 solar mass range.
| Gamma velocities of 58 faint Milky Way Cepheids
Using new radial velocity measurements of 47 faint southern hemisphereGalactic Cepheids, together with additional velocity data from Metzgeret al. (1991), gamma velocities are found for 58 low galactic latitudeCepheids. The gamma velocity is determined by using the period of aCepheid to generate a 'typical' velocity curve, then fitting the curveto the velocity measurements using two free parameters, the gammavelocity, and the phase. The velocity curve is generated using a secondorder Fourier series with coefficients determined from the period. Forthe Cepheids with observations that sample the velocity curve over avariety of pulsation phases, gamma velocities are determined to betterthan 1.0 km/s. Good agreement between these gamma velocities andpreviously published values where they exist.
| NGC 6366 - The most metal-rich halo globular cluster?
Spectra have been obtained at the Ca II IR triplet of four giants in theheavily reddened Galactic globular cluster NGC 6366. These spectra, whencompared with similar spectra of giants in the globular clusters NGC6171 and NGC 1851, suggest, for an adopted reddening of E(B-V) = 0.70mag, that the Fe/H = -0.84 + or - 0.23 dex for NGC 6366. It is concludedthat the Fe/H abundance of NGC 6366 is = -0.85 + or - 0.10 dex. Thespectra also yield a heliocentric velocity of -123.2 + or - 1.0 km/s forthe cluster. This velocity, when analyzed following the precepts ofArmandroff (1989), unambiguously associates NGC 6366 with the slowlyrotating halo cluster system, albeit the most metal-rich member of thispopulation yet identified, rather than with the rapidly rotating disksystem of globular clusters. An improved heliocentric velocity of -34 +or - 3 km/s is also given for NGC 6171, resolving the uncertaintyconcerning the velocity of this cluster.
| Radial velocities for 28 southern young open clusters
Radial velocities for 83 OB-stars in 28 southern young open clusters arepresented. The internal and external accuracy of the data is in goodagreement with results obtained by Ardeberg and Maurice (1977) with thesame equipment. From a comparison with radial velocities existing in theliterature no systematic radial-velocity differences for stars in commonare found.
| Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL. II - Faint southern potential radial-velocity standards
Abstract image available at:http://adsabs.harvard.edu/abs/1984A&AS...57..275M
| The stellar aggregate surrounding HD 101205 (IC 2944).
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&A....54..233A&db_key=AST
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Osservazione e dati astrometrici
| Costellazione: | Sagittario |
| Ascensione retta: | 18h59m44.65s |
| Declinazione: | -34°28'15.8" |
| Magnitudine apparente: | 8.118 |
| Distanza: | 146.199 parsec |
| Moto proprio RA: | 40.6 |
| Moto proprio Dec: | -67 |
| B-T magnitude: | 9.329 |
| V-T magnitude: | 8.218 |
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INHABITED SKY
