Radial Velocity Studies of the Internal Kinematics of Open Clusters

1984 ◽  
Vol 88 ◽  
pp. 249-256
Author(s):  
Robert D. Mathieu
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Globular Clusters ◽  
Cluster Structure ◽  
Relaxation Times ◽  
Stellar Mass ◽  
Open Clusters ◽  
Radial Velocities ◽  
Order Of Magnitude ◽  
Motion Studies

The internal kinematics of open clusters are a particularly challenging subject for study with radial velocities. Our present sitate of knowledge concerning the structure and kinematics of open clusters has recently been reviewed (Mathieu 1985), so I will only summarize here several of the essential concerns. The most basic goal is to measure a central or global velocity dispersion. Comparison of such measured dispersions with dynamical models fit to the cluster structure is a direct test of our understanding of the dynamics of open clusters. Far more difficult but of great importance to our understanding of cluster dynamics is the observation of assorted differential effects in these clusters. Open clusters provide a unique opportunity to study velocity distributions as a function of stellar mass. Radial velocity studies of nearby clusters can in themselves span a factor 2 in stellar mass; when combined with proper-motion studies which include the earlier stars inaccessible to high-precision radial velocities, a mass spectrum of up to an order of magnitude can be studied. Also, as with globular clusters, anisotropie velocity distributions are to be expected in the halos of those open clusters which are more than a few relaxation times old. Proper-motion studies (Jones 1970, 1971; van Leeuwen 1983) have found that anisotropy exists to within 1 pc of the centers of the Pleiades and Praesepe, much nearer the center than has so far been found in globular clusters. Independent confirmation of these findings as well as an increase in the sample of clusters studied would be of real value. And finally, the very youngest open clusters allow us to study the state of clusters at formation and indeed the star-formation process itself.

Radial Velocities Without Spectroscopy

1999 ◽  
Vol 170 ◽  
pp. 77-81 ◽  
Author(s):  
Søren Madsen ◽  
Lennart Lindegren ◽  
Dainis Dravins
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Open Clusters ◽  
Radial Velocities ◽  
Motion Data ◽  
Hipparcos Parallax

AbstractWe discuss non-spectroscopic (astrometric) ways to determine radial velocities and their potentials in future astrometric missions. Radial-velocity accuracies are presented, based on Hipparcos parallax and proper motion data for several open clusters.

scholarly journals Astrometric Distances of Globular Clusters

1988 ◽  
Vol 126 ◽  
pp. 523-524
Author(s):  
Kyle Cudworth ◽  
Ruth C. Peterson
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Proper Motion ◽  
Globular Clusters ◽  
Small Distance ◽  
Radial Velocities ◽  
Proper Motions ◽  
Velocity Dispersions

With high-precision radial velocities and proper motions, one can equate the proper motion and radial velocity dispersions to obtain astrometric distances independent of any standard candles. We discuss the method and the small distance it yields to M 22.

scholarly journals Characterizing Blue Straggler Star Populations in Globular Clusters using HST Photometric Survey Data

2015 ◽  
Vol 11 (A29B) ◽  
pp. 149-150
Author(s):  
Mirko Simunovic ◽  
Thomas H. Puzia
Keyword(s):  
Detailed Analysis ◽  
Survey Data ◽  
Proper Motion ◽  
Globular Clusters ◽  
Stellar Mass ◽  
Evolutionary Models ◽  
Early Results ◽  
Blue Straggler ◽  
Age Estimates

AbstractWe present early results from a detailed analysis of the BSS population in Galactic GCs based on HST data. Using proper motion cleaning of the color-magnitude diagrams we construct a large catalog of BSSs and study some population properties. Stellar evolutionary models are used to find stellar mass and age estimates for the BSS populations in order to establish constraints related to the dynamical interactions in which they may have formed.

Open cluster study in LAMOST DR3

2017 ◽  
Vol 13 (S334) ◽  
pp. 391-393
Author(s):  
Jing Zhong ◽  
Li Chen ◽  
Chaoli Zhang ◽  
Zhengyi Shao ◽  
Jinliang Hou
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Open Cluster ◽  
Open Clusters ◽  
Projection Area ◽  
Distance Modulus ◽  
Membership Probability ◽  
Cluster Area ◽  
Large Projection ◽  
Cross Match

AbstractIn studying Galactic open clusters based on LAMOST DR3, we deliberately selected several nearby cluster, which have relatively large projection area and reliable proper motion measurements. For each cluster, we firstly determine the typical proper motion distribution profiles in the cluster-core and the outskirt region, respectively, and perform field-star decontamination on the cluster area. We then calculate kinematic membership probability for each star in the cluster area and cross-match the highly probable members with LAMOST DR3 spectral catalog. Based on enhanced signal of cluster-member radial velocity distribution emerging from the whole field, we have also obtained reliable radial velocity membership probability for each star. Finally, we perform isochrones fitting with MCMC technique to study basic properties of these cluster, including age, metallicity, and distance modulus.

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).

scholarly journals The Gaia-ESO Survey: The inner disc, intermediate-age open cluster Pismis 18

2019 ◽  
Vol 626 ◽  
pp. A90 ◽  
Author(s):  
D. Hatzidimitriou ◽  
E. V. Held ◽  
E. Tognelli ◽  
A. Bragaglia ◽  
L. Magrini ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Open Cluster ◽  
Open Clusters ◽  
High Resolution Spectroscopy ◽  
Distance Modulus ◽  
Chemical Abundance ◽  
High Confidence ◽  
Galactocentric Distance ◽  
Red Clump

Context. Pismis 18 is a moderately populated, intermediate-age open cluster located within the solar circle at a Galactocentric distance of about seven kpc. Few open clusters have been studied in detail in the inner disc region before the Gaia-ESO Survey. Aims. New data from the Gaia-ESO Survey allowed us to conduct an extended radial velocity membership study as well as spectroscopic metallicity and detailed chemical abundance measurements for this cluster. Methods. Gaia-ESO Survey data for 142 potential members, lying on the upper main sequence and on the red clump, yielded radial velocity measurements, which, together with proper motion measurements from the Gaia Second Data Release (Gaia DR2), were used to determine the systemic velocity of the cluster and membership of individual stars. Photometry from Gaia DR2 was used to re-determine cluster parameters based on high confidence member stars only. Cluster abundance measurements of six radial-velocity member stars with UVES high-resolution spectroscopy are presented for 23 elements. Results. The average radial velocity of 26 high confidence members is −27.5 ± 2.5 (std) km s−1 with an average proper motion of pmra = −5.65 ± 0.08 (std) mas yr−1 and pmdec = −2.29 ± 0.11 (std) mas yr−1. According to the new estimates, based on high confidence members, Pismis 18 has an age of τ = 700+40−50 Myr, interstellar reddening of E(B − V) = 0.562+0.012−0.026 mag and a de-reddened distance modulus of DM0 = 11.96+0.10−0.24 mag. The median metallicity of the cluster (using the six UVES stars) is [Fe/H] = +0.23 ± 0.05 dex, with [α/Fe] = 0.07 ± 0.13 and a slight enhancement of s- and r-neutron-capture elements. Conclusions. With the present work, we fully characterized the open cluster Pismis 18. We confirmed its present location in the inner disc. We estimated a younger age than the previous literature values and we gave, for the first time, its metallicity and its detailed abundances. Its [α/Fe] and [s-process/Fe], both slightly super-solar, are in agreement with other inner-disc open clusters observed by the Gaia-ESO survey.

scholarly journals Masses and Relaxation Times of Star Clusters in the SMC

1984 ◽  
Vol 108 ◽  
pp. 25-26
Author(s):  
M. Kontizas ◽  
E. Kontizas
Keyword(s):  
Globular Clusters ◽  
Relaxation Times ◽  
Star Clusters ◽  
Open Clusters ◽  
Schmidt Telescope ◽  
Density Profiles ◽  
Show Evidence

Plates taken with the 1.2m U.K. Schmidt Telescope and the 3.8 AAT Telescope have been used in order to derive the dynamical parameteres of 43 various clusters of the SMC by means of star counts. The clusters are divided into two main categories: (i) the disk, “blue” and “intermediate” in colour, young, mainly globulars and (ii) the halo, “red”, old globular clusters. The disk clusters have been found to be more massive and older than the galactic open clusters, whereas the halo clusters are at least 10 times less massive than the galactic globulars. The relaxation times of the disk clusters are larger than their evolutionary age while the observed density profiles always show evidence of well relaxed systems.

scholarly journals Bayesian Inference of Kinematics and Mass Segregation of Open Cluster

2015 ◽  
Vol 12 (S316) ◽  
pp. 265-266
Author(s):  
Z. Shao ◽  
X. Xie ◽  
L. Chen ◽  
J. Zhong ◽  
J. Hou ◽  
...  
Keyword(s):  
Bayesian Inference ◽  
Radial Velocity ◽  
Proper Motion ◽  
Open Cluster ◽  
Open Clusters ◽  
Membership Probability ◽  
Kinematic Data ◽  
Mixture Model Approach ◽  
Mass Segregation ◽  
Model Approach

AbstractBased on the Bayesian Inference (BI) method, the Mixture-Model approach is improved to combine all kinematic data, including the coordinative position($\vec{x}$), proper motion ($\vec{\mu}$) and radial velocity(v), to separate the motion of the cluster from field stars, as well as to determine the intrinsic kinematic status and dynamical effects of the cluster, such as the mass segregation, anisotropy etc.. Meanwhile, the membership probability of individual stars are estimated as by product results. This method has been testified by simulation of toy models and also successfully used for well studied open clusters, such as M67 and NGC188. It is expected to largely help the studies of open clusters while combine the coming GAIA data.

Complex study of the open cluster NGC 2281

2017 ◽  
Vol 12 (S330) ◽  
pp. 273-274
Author(s):  
Jaroslav Velčovský ◽  
Jan Janík
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Open Cluster ◽  
Open Clusters ◽  
Ccd Photometry ◽  
Complex Study ◽  
Colour Excess ◽  
Dynamical Parameters ◽  
Astrometric Data ◽  
Selection Of

AbstractWe present the complex study of the open cluster NGC 2281 where both traditional and newly developed methods for study of open clusters have been used. Morphological and dynamical parameters of the cluster were obtained from the accepted astrometric data. The new method “Superposition of Gaussian surfaces” along with proper motion of stars was used to determine membership probabilities which were helpful in selection of stars for further analysis. Metallicity and radial velocity of the cluster were obtained from spectroscopic measurements. Age, colour excess, and distance of the cluster were determined using absolute CCD photometry combined with previous results. The results were compared with those of previous studies.

scholarly journals Spectroscopic Radial Velocities: Photospheric Lineshifts Calibrated By Hipparcos

1998 ◽  
Vol 11 (1) ◽  
pp. 564-564
Author(s):  
D. Gullberg ◽  
D. Dravins
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Open Clusters ◽  
Radial Velocities ◽  
Radial Motion ◽  
Spectral Lines ◽  
Gravitational Redshift ◽  
The Sun

Wavelengths of stellar spectral lines depend not only on the star’s motion. Until recently, accurate studies of shifts not caused by radial motion were feasible only for the Sun. Solar lineshifts are interpreted as gravitational redshift (636 m/s) and convective blueshifts (~ 400 m/s; caused by velocity-brightness correlations). In other stars, such effects may be greater (Dravins & Nordlund 1990). Accurate astrometric radial velocities are now available from Hipparcos (Dravins et al. 1997a; 1997b), permitting studies of such shifts also in some other stars. For such stars in the open clusters of Hyades, Ursa Major and Coma Berenices, a spectroscopic program is in progress, analyzing wavelength shifts in groups of lines with different strengths, excitation potentials, etc., using the ELODIE high-precision radial-velocity instrument (Baranne et al. 1996) at Haute-Provence Observatory.

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