scholarly journals Proper-Motion Based Kinematics Study of Galactic RR Lyraes

2015 ◽  
Vol 11 (S317) ◽  
pp. 290-291
Author(s):  
Andrei K. Dambis ◽  
Leonid N. Berdnikov ◽  
Alexei S. Rastorguev ◽  
Marina V. Zabolotskikh
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Velocity Dispersion ◽  
Galactic Center ◽  
The Sun ◽  
Proper Motions ◽  
Galactocentric Distance ◽  
Rr Lyrae

AbstractWe use the UCAC4 and SDSS proper motions of about 7500 RR Lyrae type variables located within ~10 kpc from the Sun to study the dependence of their velocity ellipsoid on Galactocentric distance in the RG = 3–17 kpc interval. The radial velocity dispersion, σVR, decreases from ~190 km/s at RG = 3.5–5.5 kpc down to ~100 km/s at RG = 13–15 kpc, and the σVT/σVR ratio remains virtually constant (σVT/σVR ~0.54–0.64) in the Galactocentric distance interval from RG = 4.5 kpc to RG = 10.5 kpc increasing to ~0.9 both toward the Galactic center and beyond RG = 11 kpc.

scholarly journals Measurements of annual parallaxes and proper motions of the red supergiant S Per

2007 ◽  
Vol 3 (S242) ◽  
pp. 378-380 ◽  
Author(s):  
Yoshiharu Asaki ◽  
Shuji Deguchi ◽  
Hirishi Imai ◽  
Kazuya Hachisuka ◽  
Makoto Miyoshi ◽  
...  
Keyword(s):  
Water Vapor ◽  
Proper Motion ◽  
Galactic Center ◽  
Rotation Velocity ◽  
Galactic Rotation ◽  
The Sun ◽  
Proper Motions ◽  
Right Ascension

AbstractVLBI phase-referencing monitoring of water vapor masers around the red supergiant, S Per, was conducted over four years. We successfully obtained proper motions and an annual parallax of the masers and determined the distance to S Per of 2.51±0.09 kpc. The proper motion of the star itself was inferred from the maser proper motions, and it was −0.38 and −1.54 mas/yr for right ascension and declination, respectively. Assuming the distance from the sun to the Galactic center, R0, of 8.5 kpc and the rotation velocity around the sun, Θ0, of 220 km/s, the Galactic rotation velocity around S Per is 200 km/s.

scholarly journals Review of Observational Data on RR Lyrae Stars

1971 ◽  
Vol 2 ◽  
pp. 781-787
Author(s):  
G. van Herk
Keyword(s):  
Radial Velocity ◽  
Observational Data ◽  
Proper Motion ◽  
Point Of View ◽  
Proper Motions ◽  
Physical Point ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Complete Set ◽  
Lyrae Stars

The data on which my work on the secular parallaxes of RR Lyrae stars is based (Bull. Astron. Inst. Neth.18) were in many respects so incomplete that I have tried to interest astronomers to get a more complete set of data. The number of stars for which I had a proper motion was only 168, and for which a radial velocity was known, was 180, with an overlap of only 138 stars. The accuracy of the proper motions was certainly unsatisfactory for 43% of the total. The greatest trouble in dealing with such insufficient numbers arises when one wants to subdivide the material into groups which are homogeneous from a physical point of view. Many subdivisions, in making up my paper, were not tried at all, simply because the material was inadequate.In recent years plenty of work has been done by various investigators, of which I will at this point only mention the work on proper motions done at the Leander McCormick Observatory, and the great number of radial velocities determined by Dr. Clube and his associates. I do not, however, believe we are yet in a position to consider the whole subject as finished. Discussions about space motions, as given by Professor Oort in the book Stellar Structures, Volume V, will, at this time, be hardly improved upon. I still feel we should increase the number of stars substantially in order to get a better statistical discussion possible. This means we have to go to fainter stars. Plenty of these stars will be found on the plates which have served to make the Charts of the Carte du Ciel, which means we have at least one old position available for proper motions. At Leiden we are now engaged in the determination or redetermination of the proper motions of 430 RR Lyrae stars.

The circular velocity at the sun

1979 ◽  
Vol 84 ◽  
pp. 225-230
Author(s):  
G. R. Knapp
Keyword(s):  
Globular Clusters ◽  
Galactic Center ◽  
Solar Rotation ◽  
Center Of Mass ◽  
Rotation Velocity ◽  
Current Evidence ◽  
Galactic Rotation ◽  
The Sun ◽  
Galactocentric Distance ◽  
Rr Lyrae

The galactic rotation velocity at the Sun, , can be derived several ways, none of them direct and unambiguous - (1) the solar velocity can be found relative to the halo population (the RR Lyrae stars, globular clusters etc.), but may contain an unknown contribution from possible systematic rotation of the halo system (2) the product Ro ω(Ro) = Ro (A-B) can be calculated but is uncertain because of large uncertainties in each of these three quantities (3) the motion of the Sun with respect to the center of the Local Group can be found but includes the motion of the galactic center of mass and (4) the velocity-longitude dependence of the outer HI boundary can be examined to deduce the most likely value of . The incorporation of new data into analyses using methods (1) and (3) gives essentially the same answers as older studies. Examination of the accumulated current evidence suggests that the best values for the solar rotation velocity and the galactocentric distance Ro are 220 km s−1 and 8.5 kpc respectively.

scholarly journals Kinematics of the Galactic Globular Cluster System

1988 ◽  
Vol 126 ◽  
pp. 49-60 ◽  
Author(s):  
R. F. Webbink
Keyword(s):  
Angular Momentum ◽  
Velocity Distribution ◽  
Radial Velocity ◽  
Globular Cluster ◽  
Velocity Dispersion ◽  
Proper Motions ◽  
Galactocentric Distance ◽  
Residual Velocity ◽  
Globular Cluster System ◽  
Kinematic Properties

Constraints on cluster kinematics proper motions, radial velocities and tidal radii are reviewed. Analysis of the cluster radial velocity distribution suggests a rotation law for the system in which the specific angular momentum is nearby independent of galactocentric distance, and the residual velocity dispersion is isotropic. However, the absence of severely tidally truncated clusters indicates that nearly radial orbits are absent from this distribution. The kinematic properties of the remote halo clusters remain largely indeterminate. Absolute proper motions measured directly with respect to background galaxies and quasars are needed to determine the kinematics of these objects, and also to elucidate the process of tidal stripping.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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.

scholarly journals Testing for Dark Matter in the Outskirts of Globular Clusters

2021 ◽  
Vol 922 (2) ◽  
pp. 104
Author(s):  
Raymond G. Carlberg ◽  
Carl J. Grillmair
Keyword(s):  
Dark Matter ◽  
Globular Clusters ◽  
High Probability ◽  
Velocity Dispersion ◽  
High Redshift ◽  
Dark Matter Halo ◽  
The Sun ◽  
Proper Motions ◽  
Preliminary Results ◽  
Galactic Background

Abstract The proper motions of stars in the outskirts of globular clusters are used to estimate cluster velocity dispersion profiles as far as possible within their tidal radii. We use individual color–magnitude diagrams to select high-probability cluster stars for 25 metal-poor globular clusters within 20 kpc of the Sun, 19 of which have substantial numbers of stars at large radii. Of the 19, 11 clusters have a falling velocity dispersion in the 3–6 half-mass radii range, 6 are flat, and 2 plausibly have a rising velocity dispersion. The profiles are all in the range expected from simulated clusters that started at high redshift in a zoom-in cosmological simulation. The 11 clusters with falling velocity dispersion profiles are consistent with no dark matter above the Galactic background. The six clusters with approximately flat velocity dispersion profiles could have local dark matter, but are ambiguous. The two clusters with rising velocity dispersion profiles are consistent with a remnant local dark matter halo, but need membership confirmation and detailed orbital modeling to further test these preliminary results.

scholarly journals The Formation of Disk Galaxies

1988 ◽  
Vol 130 ◽  
pp. 301-310
Author(s):  
K.C. Freeman
Keyword(s):  
Radial Velocity ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Basic Structure ◽  
Disk Galaxy ◽  
Disk Galaxies ◽  
The Sun ◽  
Structural Components ◽  
General Review

In this talk, I will discuss a few particular topics, rather than attempting a general review of the formation of disk galaxies. First recall the basic structure and kinematics of a disk galaxy like the Milky Way. The Table below lists the four main structural components as they are presently understood, and gives typical masses, and (if known) the characteristic rotational velocities (at the sun) and the radial velocity dispersion for each component. For more details, see Freeman (1987).

scholarly journals Proxima’s orbit around α Centauri

2017 ◽  
Vol 598 ◽  
pp. L7 ◽  
Author(s):  
P. Kervella ◽  
F. Thévenin ◽  
C. Lovis
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Orbital Period ◽  
Triple System ◽  
Orbital Motion ◽  
The Sun ◽  
Proper Motions ◽  
Velocity Measurements ◽  
Degree Of Confidence ◽  
High Degree

Proxima and α Centauri AB have almost identical distances and proper motions with respect to the Sun. Although the probability of such similar parameters is, in principle, very low, the question as to whether they actually form a single gravitationally bound triple system has been open since the discovery of Proxima one century ago. Owing to HARPS high-precision absolute radial velocity measurements and the recent revision of the parameters of the α Cen pair, we show that Proxima and α Cen are gravitationally bound with a high degree of confidence. The orbital period of Proxima is ≈ 550 000 yr. With an eccentricity of 0.50+0.08-0.09, Proxima comes within 4.3+1.1-0.9 kau of α Cen at periastron, and is currently close to apastron (13.0+0.3-0.1 kau). This orbital motion may have influenced the formation or evolution of the recently discovered planet orbiting Proxima, as well as circumbinary planet formation around α Cen.

scholarly journals Kinematics of Galactic Globular Clusters from Schmidt-Plate Astrometry

1995 ◽  
Vol 164 ◽  
pp. 405-405 ◽  
Author(s):  
R.-D. Scholz ◽  
S. Hirte ◽  
M.J. Irwin ◽  
M. Odenkirchen
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Globular Clusters ◽  
Proper Motions ◽  
Large Numbers ◽  
Solar Motion ◽  
The Galaxy ◽  
Ursa Minor ◽  
Galactic Globular Clusters

From measurements of Tautenburg Schmidt plates with the APM facility in Cambridge we obtained absolute proper motions of the Galactic globular clusters M 3 and M 92 directly with respect to large numbers of background galaxies (Scholz et al. 1993, 1994). We have extended our work to the dSphs in Draco and Ursa Minor (Scholz & Irwin 1994) and to other Galactic globular clusters using Tautenburg, Palomar and UK Schmidt plates. Combining our absolute proper motion of a cluster with its known radial velocity and distance (using common parameters of the solar motion) we derive the cluster orbit in the Galaxy (cf. Odenkirchen & Brosche 1992).

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