Current Programs of Local Galactic Structure and Evolution

1984 ◽  
Vol 88 ◽  
pp. 171-176
Author(s):  
J. Andersen ◽  
B. Nordström
Keyword(s):  
Radial Velocity ◽  
Velocity Dispersion ◽  
Progress Report ◽  
Radial Velocities ◽  
Bright Star ◽  
Star Catalogue ◽  
Metal Abundance ◽  
F Stars ◽  
Near Future

AbstractWe present a progress report on some current radial-velocity observing programs aiming to provide complete data for selected samples of stars covering the whole sky. The velocities are based on ESO coudé spectra as well as CORAVEL observations obtained in both hemispheres. As a first step, the Bright Star Catalogue has been completed in radial velocities ( ~1500 stars or ~l/3 of the southern BS stars). Currently, we are approaching completion of some 4000 dwarf F stars from Olsen’s (1983) uvbyß photometric survey. The data will be used to study the velocity dispersion of these stars as a function of age and metal abundance from a kinematically unbiased sample. They will also provide a basis for an improved determination of Kz. Extension of the program to the G dwarfs is planned for the near future.

scholarly journals Radial Velocity Profiles for Anisotropic Spherically Symmetric Clusters: An Example

1988 ◽  
Vol 126 ◽  
pp. 691-692
Author(s):  
Herwig Dejonghe
Keyword(s):  
Distribution Function ◽  
Radial Velocity ◽  
Velocity Dispersion ◽  
Mass Density ◽  
Distribution Functions ◽  
Spherically Symmetric ◽  
Line Profiles ◽  
Anisotropic Models ◽  
The Family

A 1-parameter family of anisotropic models is presented. They all satisfy the Plummer law in the mass density, but have different velocity dispersions. Moreover, the stars are not confined to a particular subset of the total accessible phase space. This family is mathematically simple enough to be explored analytically in detail. The family is rich enough though to allow for a 3-parameter generalization which illustrates that even when both the mass density and the velocity dispersion profiles are required to be the same, a degeneracy in the possible distribution functions persists. The observational consequences of the degeneracy can be studied by calculating the observable radial velocity line profiles obtained with different distribution functions. It turns out that line profiles are relatively sensitive to changes in the distribution function. They therefore can be considered to be more natural observables when a determination of the distribution function is desired.

scholarly journals The Search for Dark Matter in Draco and Ursa Minor: A Three Year Progress Report

1987 ◽  
Vol 117 ◽  
pp. 153-160 ◽  
Author(s):  
M. Aaronson ◽  
E. Olszewski
Keyword(s):  
Dark Matter ◽  
Velocity Dispersion ◽  
Progress Report ◽  
Radial Velocities ◽  
Circumstantial Evidence ◽  
Dwarf Spheroidal Galaxies ◽  
Ursa Minor ◽  
Stellar Velocity ◽  
Atmospheric Motions ◽  
Matter Component

We report the cumulative results of an on-going effort to measure the stellar velocity dispersion in two nearby dwarf spheroidal galaxies. Radial velocities having an accuracy ≲ 2 km s−1 have now been secured for ten stars in Ursa Minor and eleven stars in Draco (including 16 K giants and 5 C types). Most objects have been observed at two or more epochs. Stars having non-variable velocities yield in both dwarfs a large (∼ 10 km s−1) dispersion. These results cannot be explained by atmospheric motions, and circumstantial evidence suggests that the effects of undetected binaries are also not likely to be important. Instead, it seems that both spheroidals contain a substantial dark matter component, which therefore must be “cold” in form.

scholarly journals The number of Be stars compared with the number of B stars, taking into account the specific physical characteristics of Be stars

1994 ◽  
Vol 162 ◽  
pp. 356-357
Author(s):  
D. Briot ◽  
J. Zorec
Keyword(s):  
Spectral Type ◽  
Bright Star ◽  
Physical Parameters ◽  
Emission Characteristics ◽  
Be Stars ◽  
Constant Mass ◽  
B Stars ◽  
The Past ◽  
Star Catalogue

It is very important for the understanding of the Be phenomenon, and particularly for locating a possible Be phase in the evolutionary track of B stars, to accurately determine the proportion of Be stars among all B stars. This type of study was already made several times in the past. Results obtained generally show a maximum Be frequency around spectral type B2 then a decrease towards late spectral types. Actually Be stars do not have the same characteristics as “normal” B stars and we have to take this into account in the determination of the ratio : number of Be stars / number of B stars. We use the Bright Star Catalogue (Hoffleit & Jaschek 1982) and the Supplement to the Bright Star Catalogue (Hoffleit, Saladyga & Wlasuk 1983) containing stars V= 7.10 and brighter. This study needed to be made separately for the different spectral types because:- Physical parameters of B stars are very different from B0 to B9;- Emission characteristics of Be stars vary very much, with a decrease from B0e to B9e.We successively consider three effects which can influence the frequency of Be stars:- The over-luminosity of Be stars as compared with B stars;- Spectral type changes during constant mass evolution;- Spectral type changes due to the fast rotation of Be stars.

scholarly journals Velocity Dispersion and Luminosity Function of Planetary Nebulae in the Nuclear Bulge of M31

1983 ◽  
Vol 103 ◽  
pp. 543-543
Author(s):  
D. G. Lawrie ◽  
H. C. Ford
Keyword(s):  
Maximum Likelihood ◽  
Radial Velocity ◽  
Luminosity Function ◽  
Velocity Dispersion ◽  
Planetary Nebulae ◽  
Image Intensifier ◽  
Interference Filter ◽  
Radial Velocities ◽  
Method Of Maximum Likelihood ◽  
Heliocentric Velocity

We used a sequence of velocity-modulated photographs to find and measure the radial velocities of faint planetary nebulae in the center of M31. The photographs were made with a Velocity Modulating Camera (VMC) which consists of a temperature-tuned 2.1 Å (FWHM) (O III) λ 5007 interference filter, a cooled, two-stage image intensifier, and a calibrating photomultiplier. The camera was mounted at the Cassegrain focus of the Shane 3 m telescope at Lick Observatory. We identified 19 new planetary nebulae, bringing the total number of known planetaries within 250 pc of M31's nucleus to 45. From the plate series, we derived radial velocities and relative brightnesses from 32 of the nebulae and placed radial velocity limits on the remaining nebulae in the field. By applying the method of maximum likelihood to the observed radial velocity distribution, we derive a mean heliocentric velocity of −309 (±25) km s−1 and a velocity dispersion of 155 (±22) km s−1 for the planetary nebulae.

scholarly journals Comparison of Different Methods for Determining Atmospheric Parameters of A and F Stars

1993 ◽  
Vol 138 ◽  
pp. 182-186 ◽  
Author(s):  
B. Smalley ◽  
M.M. Dworetsky
Keyword(s):  
Atmospheric Parameters ◽  
Spectrophotometric Methods ◽  
Profile Fitting ◽  
Standard Procedures ◽  
Highly Sensitive ◽  
Metal Abundance ◽  
The Subject ◽  
F Stars ◽  
Standard Techniques

AbstractThe atmospheric parameters of metallic-lined (Am) stars have been the subject of much debate. Using spectrophotometric flux fitting, Lane & Lester (1984) obtained values of Teff and log g for several classical Am stars that were systematically lower than those obtained by Dworetsky & Moon (1986), who used empirically calibrated uvbyß photometry. We have used the standard procedures of photometry, spectrophotometry and hydrogen-line profile fitting to determine the atmospheric parameters of many A and F stars, including several Am stars. Modifications to the standard techniques have been used to allow for the effects of cooler companion stars in the determination of such parameters. It is found that spectrophotometric methods give results for Teff and log g that are highly sensitive to the adopted metal abundance. This explains the anomalous results of Lane & Lester.

scholarly journals A Radial Velocity Dispersion Profile for the Fornax Dwarf Spheroidal Galaxy

2004 ◽  
Vol 220 ◽  
pp. 367-368
Author(s):  
Matthew G. Walker ◽  
Mario Mateo ◽  
Edward W. Olszewski ◽  
Michael Woodroofe ◽  
Xiao Wang ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Constant Velocity ◽  
Velocity Dispersion ◽  
Dispersion Model ◽  
Radial Velocities ◽  
Classical Analysis ◽  
Dispersion Profile

We have measured precise (± 3 km/s) radial velocities for 180 stars in the Fornax dwarf spheroidal galaxy, spanning the region R=0 to just beyond the nominal tidal radius. We perform a “classical” analysis of the resulting velocity dispersion profile. A mass-follows-light King model is ruled out, while a constant velocity dispersion model remains a good fit out to the limits of our dataset. For the constant velocity dispersion case, we calculate a velocity dispersion of 11.1 ± 0.7 km/s, which implies a central M/L/[M/L]⊙ ratio of 7.6 ± 1.0.

scholarly journals Southern triplets of galaxies

2000 ◽  
Vol 174 ◽  
pp. 11-24
Author(s):  
V. E. Karachentseva ◽  
I. D. Karachentsev
Keyword(s):  
Radial Velocity ◽  
Velocity Dispersion ◽  
Angular Separation ◽  
Absolute Magnitude ◽  
Radial Velocities ◽  
Dynamic Parameters ◽  
Sky Surveys ◽  
Triple Systems ◽  
Angular Diameters

AbstractUsing the ESO/SERC and POSS-I sky surveys we selected 76 isolated triple systems of galaxies with Dec. < −3°. For each triplet the equatorial coordinates, type of configuration, angular diameters, apparent angular separation of the components, morphological types, total magnitudes and some other characteristics are presented. 33 of 76 triplets have the measured radial velocities for all the components. The median values of basic dynamic parameters: a radial velocity dispersion, mean harmonic separation, an absolute magnitude of galaxies, mass-toluminosity ratio are very close to those obtained earlier for 83 northern isolated triple systems from the list of Karachentseva et al. (1979).

scholarly journals 30. Commission des Vitesses Radiales Stellaires

1936 ◽  
Vol 5 ◽  
pp. 188-196
Author(s):  
M. J. S. Plaskett ◽  
MM. Adams ◽  
Campbell ◽  
Frost ◽  
Guthnick ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Pacific Coast ◽  
Radial Velocities ◽  
University Of Michigan ◽  
University Of Texas ◽  
University Of Toronto ◽  
Visual Magnitude ◽  
Under Construction ◽  
The University

The three years that have elapsed since the Harvard meeting of the Union have witnessed steady progress in the determination of radial velocities. While the three large Pacific Coast Observatories have naturally been able to make the greatest additions to radial velocity work, the Yerkes Observatory, the Simeiz Observatory and the Observatory of the University of Michigan have also made valuable contributions. It is a pleasure to report that there will soon be three major accessions to the list of observatories capable of determining radial velocities. The David Dunlap Observatory of the University of Toronto with its 74-inch telescope, which should be in operation soon after the meeting, will have radial velocities as a prominent feature of its programme. The McDonald Observatory of the University of Texas with an 80-inch telescope now under construction should be ready to commence operations in 1936 and will undertake an extensive radial velocity programme. The Radcliffe Observatory at Oxford has now been granted permission by the Courts to remove to Pretoria, South Africa, and will establish there a 74-inch reflecting telescope, which will also be largely employed in the determination of the urgently needed radial velocities of the southern stars fainter than 5.5 visual magnitude. The Commission may, I believe, congratulate itself that substantial assistance in the preliminary steps leading to this permission of removal was provided by our action at the last meeting in presenting a resolution to the Union, duly passed by the General Assembly, pointing out the urgent need for additional radial velocities in the southern sky, and strongly supporting the project of the Radcliffe Observatory to establish a large telescope at Pretoria.

Heavy Remnants in Globular Cluster Cores

1984 ◽  
Vol 88 ◽  
pp. 393-396
Author(s):  
M. Mayor ◽  
G. Meylan
Keyword(s):  
Globular Cluster ◽  
Velocity Dispersion ◽  
Radial Velocities ◽  
The Core ◽  
Random Motions ◽  
Cluster Cores

With a mean precision of 0.6 km/s per measurement, the radial velocities of 169 giants in 47 Tue (published in Mayor et al., 1983) added to the further measures of 25 stars in the core, have permitted the determination of rotation V(r,z) and velocity dispersion σ(r) in this globular cluster. With a mean precison of 0.9 km/s per measurement, the radial velocities of 298 giants in ω Cen (to be published in Mayor et al., 1985), distributed up to the centre, have also permitted the determination of V(r,z) and σ(r) (for both clusters, see Meylan and Mayor, 1984).The ratios νo/σo of ordered to random motions and the ellipticities of ω Cen and 47 Tue point to a global isotropy of the velocity dispersion.

scholarly journals Radial Velocities for the Stars of the HIPPARCOS Mission

1992 ◽  
Vol 9 ◽  
pp. 433-436 ◽  
Author(s):  
Michel Mayor ◽  
Michèle Gerbaldi ◽  
Suzanne Grenier ◽  
Hugo Levato
Keyword(s):  
Radial Velocity ◽  
Chemical Evolution ◽  
Large Fraction ◽  
Space Mission ◽  
Radial Velocities ◽  
Solar Neighborhood ◽  
The Third ◽  
Crossing Time ◽  
Input Catalogue

A large fraction if not all of the programmes related to the study of the galactic structure, its kinematics and chemical evolution will require the knowledge of the third component of the velocity: the stellar radial velocity. But we will also need the radial velocity to be able to determine the true distribution of masses in the solar neighborhood (corrected by the crossing time of the stars in the sampled sphere). The radial velocity will allow the determination of the statistical parallax for a sample of stars lying beyond 100 parsec. At the very beginning of the development of the Hipparcos space mission, the very need for ground-based, complementary measurements has been recognized. However, in spite of the existence of new kinds of techniques or detectors, the task to provide radial velocities for the somewhat 118’000 stars of the Hipparcos Input Catalogue is quite enormous. All presently published stellar radial velocities determined since the beginning of this century represent at the most 20 to 25% of the total number of stars to be measured!

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