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 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.

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 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 Searching for Earth-mass planets around α Centauri: precise radial velocities from contaminated spectra

2014 ◽  
Vol 14 (2) ◽  
pp. 173-176 ◽  
Author(s):  
Christoph Bergmann ◽  
Michael Endl ◽  
John B. Hearnshaw ◽  
Robert A. Wittenmyer ◽  
Duncan J. Wright
Keyword(s):  
Binary System ◽  
Radial Velocity ◽  
Binary Systems ◽  
Angular Separation ◽  
Radial Velocities ◽  
The Other ◽  
Cross Contamination ◽  
Star System ◽  
Spectroscopic Binary ◽  
Ongoing Project

AbstractThis work is part of an ongoing project which aims to detect terrestrial planets in our neighbouring star system α Centauri using the Doppler method. Owing to the small angular separation between the two components of the α Cen AB binary system, the observations will to some extent be contaminated with light coming from the other star. We are accurately determining the amount of contamination for every observation by measuring the relative strengths of the H-α and NaD lines. Furthermore, we have developed a modified version of a well-established Doppler code that is modelling the observations using two stellar templates simultaneously. With this method we can significantly reduce the scatter of the radial velocity (RV) measurements due to spectral cross-contamination and hence increase our chances of detecting the tiny signature caused by potential Earth-mass planets. After correcting for the contamination we achieve RV precision of ~2.5 m s−1 for a given night of observations. We have also applied this new Doppler code to four southern double-lined spectroscopic binary systems (HR159, HR913, HR7578 and HD181958) and have successfully recovered radial velocities for both components simultaneously.

scholarly journals Are there carbon stars in the Bulge?

1999 ◽  
Vol 191 ◽  
pp. 545-550
Author(s):  
Yuen Keong Ng
Keyword(s):  
Star Formation ◽  
Radial Velocity ◽  
Velocity Dispersion ◽  
Dwarf Galaxy ◽  
Radial Velocities ◽  
The Other ◽  
Agb Stars ◽  
Carbon Stars ◽  
Other Hand

The Bulge carbon stars have been a mystery since their discovery by Azzopardi et al. (1991), because they are about too faint to be regarded as genuine AGB stars, if located inside the metal-rich Bulge . Part of the mystery can be solved if these carbon stars are related to the Sagittarius dwarf galaxy . They are in that case not old and metal-rich, but young, ∼0.1 Gyr, with SMC-like metallicity (Ng 1998).The σRV = 113 ± 14 km s−1 (Tyson & Rich 1991) radial velocity dispersion of the stars appears to be consistent with Bulge membership. On the other hand, a similar velocity dispersion could be the result from an induced star formation event when the SDG crosses the galactic midplane. It is suggested that the carbon stars are tracers of such an event and that they therefore are located at distances related to the SDG. However, the majority of the carbon stars are not member of the SDG, nor are they similar to the C-stars which are member of the SDG.The radial velocities can be used to determine a possible membership to the SDG. However, they do not give information about the distance of the stars. In particular, if the stars are located at a distance comparable to the SDG. This implies that only the period-luminosity relation (Groenewegen & Whitelock 1996) can be used to distinguish unambiguously if the carbon stars are located at Bulge-like or SDG-like distances. Thus far only carbon stars with reliable periods have been identified at a SDG related distance (Ng & Schultheis 1997; Whitelock 1998).

scholarly journals M Giant Kinematics in Off-Axis Fields Between 150 and 300 PC from the Galactic Center

1996 ◽  
Vol 169 ◽  
pp. 111-117
Author(s):  
R. D. Blum ◽  
J. S. Carr ◽  
K. Sellgren ◽  
D. M. Terndrup
Keyword(s):  
Radial Velocity ◽  
Velocity Dispersion ◽  
Galactic Center ◽  
Radial Velocities ◽  
Galactic Bulge ◽  
Mass Model ◽  
The Mean

We present radial velocities for approximately 40 stars in each of four optically obscured, off-axis fields toward the Galactic bulge. The mean heliocentric radial velocity and velocity dispersion are −75 ± 24 km s–1 and 127 ± 16 km s–1 2 ± 23 km s–1 and 127 ± 14 km s–1, −14 ± 22 km s–1 and 126 ± 14 km s–1, and −31 ± 28 km s–1 and 153 ± 17 km s–1 for fields located at 299, 288, 171, and 160 pc projected radius, respectively. The dispersions generally match Kent's (1992) axisymmetric mass model but may be higher than the model's predictions at small projected radius.

scholarly journals Triple Galaxies and a Hidden Mass Problem

1990 ◽  
Vol 124 ◽  
pp. 115-127
Author(s):  
I.D. Karachentsev ◽  
V.E. Karachentseva ◽  
V.S. Lebedev
Keyword(s):  
Velocity Dispersion ◽  
Absolute Magnitude ◽  
Mass Excess ◽  
Homogeneous Sample ◽  
Groups Of Galaxies ◽  
Triple Systems ◽  
Crossing Time ◽  
Dynamical Parameters ◽  
Virial Mass ◽  
Harmonic Radius

AbstractWe consider a homogeneous sample of 84 triple systems of galaxies with components brighter than m = 15.7, located in the northern sky and satisfying an isolation criterion with respect to neighboring galaxies in projection. The distributions of basic dynamical parameters for triplets have median values as follows: radial velocity dispersion 133 km/s, mean harmonic radius 63 kpc, absolute magnitude of galaxies MB = —20.38, crossing time τ = 0.04 H−1. For different ways of estimation the median mass-to-luminosity ratio is (20 – 30)f⊙.A comparison of the last value with the ones for single and binary galaxies shows the presence of a virial mass excess for triplets by a factor 4. The mass-to-luminosity ratio is practically uncorrelated with linear size of triplets or with morphological types of their components.We note that a significant part of the virial excess may be explained by the presence of nonisolated triple configurations in the sample, which are produced by debris of more populous groups of galaxies.

scholarly journals Astrometric Radial Velocities From Hipparcos

1998 ◽  
Vol 11 (1) ◽  
pp. 564-564
Author(s):  
D. Dravins ◽  
L. Lindegren ◽  
S. Madsen ◽  
J. Holmberg
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Radial Velocities ◽  
Radial Motion ◽  
Spectral Lines ◽  
Parallel Program ◽  
Stellar Surface ◽  
Space Astrometry ◽  
Stellar Motion ◽  
Surface Convection

Abstract Space astrometry now permits accurate determinations of stellar radial motion, without using spectroscopy. Although the feasibility of deducing astrometric radial velocities from geometric projection effects was realized already by Schlesinger (1917), only with Hipparcos has it become practical. Such a program has now been carried out for the moving clusters of Ursa Major, Hyades, and Coma Berenices. Realized inaccuracies reach about 300 m/s (Dravins et al. 1997). Discrepancies between astrometric and spectroscopic radial velocities reveal effects (other than stellar motion) that affect wavelength positions of spectral lines. Such are caused by stellar surface convection, and by gravitational redshifts. A parallel program (Gullberg & Dravins 1997) is analyzing high-precision spectroscopic radial velocities for different spectral lines in these stars, using the ELODIE radial-velocity instrument atHaute-Provence.

scholarly journals Kinematics of Disk Stars in the Solar Neighbourhood

1998 ◽  
Vol 11 (1) ◽  
pp. 574-574
Author(s):  
A.E. Gómez ◽  
S. Grenier ◽  
S. Udry ◽  
M. Haywood ◽  
V. Sabas ◽  
...  
Keyword(s):  
Dispersion Relation ◽  
Radial Velocity ◽  
Velocity Dispersion ◽  
Tangential Velocity ◽  
Thin Disk ◽  
The Other ◽  
Proper Motions ◽  
Velocity Data ◽  
Kinematic Data ◽  
Radial Velocity Data

Using Hipparcos parallaxes and proper motions together with radial velocity data and individual ages estimated from isochones, the velocity ellipsoid has been determined as a function of age. On the basis of the available kinematic data two different samples were considered: a first one (7789 stars) for which only tangential velocities were calculated and a second one containing 3104 stars with available U, V and W velocity components and total velocities ≤ 65 km.s-1. The main conclusions are: -Mixing is not complete at about 0.8-1 Gyr. -The shape of the velocity ellipsoid changes with time getting rounder from σu/σv/σ-w = 1/0.63/0.42 ± 0.04 at about 1 Gyr to1/0.7/0.62 ±0.04 at 4-5 Gyr. -The age-velocity-dispersion relation (from the sample with kinematical selection) rises to a maximum, thereafter remaining roughly constant; there is no dynamically significant evolution of the disk after about 4-5 Gyr. -Among the stars with solar metallicities and log(age) > 9.8 two groups are identified: one has typical thin disk characteristics, the other is older than 10 Gyr and lags the LSR at about 40 km.s-1 . -The variation of the tangential velocity with age(without selection on the tangential velocity) shows a discontinuity at about 10 Gyr, which may be attributed to stars typically of the thick disk populations for ages > 10 Gyr.

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