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Title: Radial velocities of remote globular clusters - stalking the missing mass

Abstract

Measurements good to 25 km/s are presented of radial velocities of five remote galactic globular clusters, based on aperture-plate spectra of individual stars at 3.0 A resolution. Velocities with respect to the galactic rest-frame of two individual systems, Eridanus and Palomar 14, are large enough to suggest a total mass for the Galaxy of 1 trillion solar masses. A similar mass is inferred from the average of the galactocentric distance times velocity squared. 36 references.

Authors:
Publication Date:
Research Org.:
Lockheed Research Labs., Palo Alto, CA
OSTI Identifier:
5525214
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophys. J.; (United States); Journal Volume: 297
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; MILKY WAY; MASS; STAR CLUSTERS; RADIAL VELOCITY; GALAXY NUCLEI; GIANT STARS; MISSING MASS; GALAXIES; STARS; VELOCITY; 640105* - Astrophysics & Cosmology- Galaxies; 640102 - Astrophysics & Cosmology- Stars & Quasi-Stellar, Radio & X-Ray Sources

Citation Formats

Peterson, R.C. Radial velocities of remote globular clusters - stalking the missing mass. United States: N. p., 1985. Web. doi:10.1086/163529.
Peterson, R.C. Radial velocities of remote globular clusters - stalking the missing mass. United States. doi:10.1086/163529.
Peterson, R.C. 1985. "Radial velocities of remote globular clusters - stalking the missing mass". United States. doi:10.1086/163529.
@article{osti_5525214,
title = {Radial velocities of remote globular clusters - stalking the missing mass},
author = {Peterson, R.C.},
abstractNote = {Measurements good to 25 km/s are presented of radial velocities of five remote galactic globular clusters, based on aperture-plate spectra of individual stars at 3.0 A resolution. Velocities with respect to the galactic rest-frame of two individual systems, Eridanus and Palomar 14, are large enough to suggest a total mass for the Galaxy of 1 trillion solar masses. A similar mass is inferred from the average of the galactocentric distance times velocity squared. 36 references.},
doi = {10.1086/163529},
journal = {Astrophys. J.; (United States)},
number = ,
volume = 297,
place = {United States},
year = 1985,
month =
}
  • We report radial velocity measurements for 18 globular clusters and one dE galaxy in the field of the giant elliptical galaxy NGC 1399, the dominant galaxy of the Fornax Cluster. We also present radial velocity measurements for some possible young and super{endash}metal-rich globular clusters, which turn out to be foreground or background objects (viz., 28 stars and seven galaxies). The genuine globular clusters are selected, on the basis of their magnitudes and colors, to be metal-rich. For this cluster sample, we measure a mean radial velocity of {ital v}{sub rad} = 1353 {plus_minus} 79 km s{sup {minus}1} and a velocitymore » dispersion of {sigma} = 338 {plus_minus} 56 km s{sup {minus}1}. Using a few different mass estimators, this implies {ital M}/{ital L} values in the range 50{endash}130 within a radius of 28 kpc, consistent with {ital M}/{ital L} increasing with radius. Our velocity dispersion estimate ({sigma}) is intermediate between the value computed from the integrated stellar light at smaller radii and that computed at large radii from recent X-ray observations. {copyright} {ital {copyright} 1998.} {ital The American Astronomical Society}« less
  • Spectroscopic observations, obtained at 519 nm using an echelle spectrograph and reticon detector on the Multiple Mirror Telescope in 1986, are reported for four red giants in the Galactic globular cluster Palomar 15. The data are presented graphically and used to determine the weighted mean heliocentric velocity and galactocentric velocity of the cluster (+68.9 + or - 1.2 km/sec and +148 km/sec, respectively) and the perigalactic distance (20 kpc or more). It is inferred that the Galaxy has total mass of at least 2 x 10 to the 11th solar mass. 37 references.
  • We investigate the radial distribution of the low-mass X-ray binary (LMXB) population in the elliptical galaxy NGC 4649, using Chandra and Hubble data to separate the field and globular cluster (GC) populations. GCs with LMXBs have the same radial distribution as the parent red and blue GCs. The radial profile of field LMXBs follows the V-band profile within the D25 of NGC 4649. Using the spatial information provided by our data, we find that the global galaxy-wide relations among cumulative number and luminosity of LMXBs and the integrated stellar mass hold on local scales within D25. An excess of fieldmore » LMXBs with respect to the V-band light is observed in the galaxy's outskirts, which may be partially due to unidentified GC sources or to a rejuvenated field LMXB population caused by past merging interactions.« less
  • We have measured the absolute proper motions of nine low-latitude, inner Galaxy globular clusters, namely, NGC 6273 (M 19), NGC 6284, NGC 6287, NGC 6293, NGC 6333 (M 9), NGC 6342, NGC 6356, NGC 6388, and NGC 6441. These are the first determinations ever made for these clusters. The proper motions are on the International Celestial Reference System via Hipparcos. The proper-motion errors range between 0.4 and 0.9 mas yr{sup -1} and are dominated by the number of measurable cluster members in these regions which are very crowded by the bulge/bar and the thick disk. This sample contains five metal-poormore » ([Fe/H] < -1.0) and four metal-rich ([Fe/H] {>=} -1.0) clusters; seven clusters are located within {approx}4 kpc from the Galactic center, while the remaining two, namely NGC 6356 and NGC 6284, are in the background of the bulge at {approx}7.5 kpc from the Galactic center. By combining proper motions with radial velocities and distances from the literature we derive three-dimensional velocities. In a number of cases, distance uncertainties make the kinematical classification ambiguous. For the metal-poor group of clusters, we find that three clusters, namely NGC 6273, NGC 6287, and NGC 6293 are members of a kinematically hot system, the inner halo. As for the remaining two metal-poor clusters, NGC 6284 is located at {approx}7.5 kpc from the Galactic center and kinematically belongs to the thick disk, while NGC 6333, located in the inner {approx}2 kpc, has an uncertain membership (between halo and thick disk) due to the distance uncertainty. Within the metal-rich group of clusters, NGC 6356 and NGC 6342 have velocities compatible with membership in the thick disk; however, velocity uncertainties do not allow us to rule out their belonging to a hotter system. NGC 6342 is within {approx}2 kpc from the Galactic center, and thus it may belong to the bulge. NGC 6356 is at {approx}7.5 kpc from the Galactic center and thus its metallicity, kinematics, and location argue together in favor of thick-disk membership. The remaining two metal-rich clusters, NGC 6388 and NGC 6441, have velocities incompatible with membership in the thick disk or the bar of the Milky Way. They can be thought of as members of a kinematically hot system in the inner Galaxy. Curiously, both clusters have similar velocity components. Together with their similar Galactic location and peculiar but similar stellar-population characteristics, these two clusters may share a common origin. Their velocities are also very low indicating that the two clusters are now at apocenter, i.e., they will not leave the inner {approx}4 kpc of the Galaxy.« less
  • We present new radial velocity measurements for 82 stars, members of the Galactic globular cluster (GC) NGC 6388, obtained from ESO-VLT K-band Multi Object Spectrograph (KMOS) spectra acquired during the instrument Science Verification. The accuracy of the wavelength calibration is discussed and a number of tests of the KMOS response are presented. The cluster systemic velocity obtained (81.3 ± 1.5 km s{sup –1}) is in very good agreement with previous determinations. While a hint of ordered rotation is found between 9'' and 20'' from the cluster center, where the distribution of radial velocities is clearly bimodal, more data are needed beforemore » drawing any firm conclusions. The acquired sample of radial velocities has also been used to determine the cluster velocity dispersion (VD) profile between ∼9'' and 70'', supplementing previous measurements at r < 2'' and r > 60'' obtained with ESO-SINFONI and ESO-FLAMES spectroscopy, respectively. The new portion of the VD profile nicely matches the previous ones, better defining the knee of the distribution. The present work clearly shows the effectiveness of a deployable integral field unit in measuring the radial velocities of individual stars for determining the VD profile of Galactic GCs. It represents the pilot project for an ongoing large program with KMOS and FLAMES at the ESO-VLT, aimed at determining the next generation of VD and rotation profiles for a representative sample of GCs.« less