WIYN Open Cluster Study. XVII. Astrometry and Membership to<i>V</i>=21 in NGC 188

Platais, I.; Kozhurina-Platais, V.; Girard, Terrence M.; Altena, W. F. van

doi:10.1086/379677

Cited by 87 publications

(160 citation statements)

References 27 publications

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“…For example one could use the spectroscopic binary properties which Geller & Mathieu (2011) found for NGC 188 instead of the solar-type field binary properties. Furthermore one could set the probability for a star to be a cluster member f c to the membership probabilities derived from the proper motion analysis of Platais et al (2003). Finally one could use a model for the Milky Way (e.g.…”

Section: Discussionmentioning

confidence: 99%

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Characterizing a cluster’s dynamic state using a single epoch of radial velocities

Cottaar

Meyer

Parker

2012

A&A

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Context. Radial velocity measurements can be used to constrain the dynamical state of a stellar cluster. However, for clusters with velocity dispersions smaller than a few km s −1 the observed radial velocity distribution tends to be dominated by the orbital motions of binaries rather than the stellar motions through the potential well of the cluster. Aims. Our goal is to characterize the intrinsic velocity distribution of a cluster from a single epoch of radial velocity data even for a cluster with a velocity dispersion of a fraction of a km s −1 . Methods. We investigate a maximum likelihood procedure, which has been pioneered in the literature about ten years ago. Assuming a period, mass ratio, and eccentricity distribution for the binaries in the observed cluster this procedure fits a dynamical model describing the velocity distribution for the single stars and center of masses of the binaries, simultaneously with the radial velocities caused by binary orbital motions, using all the information available in the observed velocity distribution. We test the capability of this procedure to reproduce the velocity dispersion of an observed cluster, using radial velocity data of an open cluster and Monte Carlo simulations. Results. We find that the fits to the intrinsic velocity distribution depend only weakly on the binary properties assumed, so the uncertainty in the fitted parameters tends to be dominated by statistical uncertainties. Based on a large suite of Monte Carlo simulations we provide an estimate of how these statistical uncertainties vary with the velocity dispersion, binary fraction, and the number of observed stars, which can be used to estimate the sample size needed to reach a specific accuracy. Finally we test the method on the well-studied open cluster NGC 188, showing that it can successfully reproduce a velocity dispersion of only 0.5 km s −1 using a single epoch of the multi-epoch radial velocity data. Conclusions. If the binary period, mass ratio, and eccentricity distribution of the observed stars are roughly known, this procedure can be used to correct for the effect of binary orbital motions on an observed velocity distribution. This allows for the study of the dynamical state of a stellar cluster with a small velocity dispersion from a single epoch of radial velocity data.

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Section: Discussionmentioning

confidence: 99%

“…5. The literature values for these parameters, derived from a proper motion analysis (Platais et al 2003) and the multi-epoch radial velocity data (Geller et al 2008;Geller & Mathieu 2011) have been plotted as black dots. If the error bars are given, they have been plotted.…”

Section: Case Study: Ngc 188mentioning

confidence: 99%

Characterizing a cluster’s dynamic state using a single epoch of radial velocities

Cottaar

Meyer

Parker

2012

A&A

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“…A number of excellent studies have previously been performed for NGC 188 that have accurately determined its physical parameters (von Hippel & Sarajedini 1998;Sarajedini et al 1999;Platais et al 2003;Michaud et al 2004;Stetson et al 2004;. NGC 188 is used as a fiducial cluster, and a precise age is obtained for Berkeley 17 relative to NGC 188.…”

Section: Introductionmentioning

confidence: 99%

“…As the highest priority cluster in the WIYN Open Cluster Study, excellent, multicolor color-magnitude diagrams (CMDs) and proper-motion data have been published for this cluster (von Hippel & Sarajedini 1998;Sarajedini et al 1999;Platais et al 2003). In their UBVRI photometric study, Sarajedini et al (1999) found that NGC 188 has an age of 7:0 AE 0:5 Gyr, a reddening of E(B À V ) ¼ 0:09 AE 0:02, and a distance modulus of (m À M ) V ¼ 11:44 AE 0:08.…”

Section: Introductionmentioning

confidence: 99%

UBVICCD Photometry of the Old Open Cluster Berkeley 17

Krusberg¹,

Chaboyer²

2006

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Photometric UBVI CCD photometry is presented for NGC 188 and Berkeley 17. Color-magnitude diagrams (CMDs) are constructed and reach well past the main-sequence turnoff for both clusters. Cluster ages are determined by means of isochrone fitting to the cluster CMDs. These fits are constrained to agree with spectroscopic metallicity and reddening estimates. Cluster ages are determined to be 7:0 AE 0:5 Gyr for NGC 188 and 10:0 AE 1:0 Gyr for Berkeley 17, where the errors refer to uncertainties in the relative age determinations. These ages are compared to the ages of relatively metal-rich inner halo/thick-disk globular clusters and other old open clusters. Berkeley 17 and NGC 6791 are the oldest open clusters, with ages of 10 Gyr. They are 2 Gyr younger than the thick-disk globular clusters. These results confirm the status of Berkeley 17 as one of the oldest known open clusters in the Milky Way, and its age provides a lower limit to the age of the Galactic disk.

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“…NGC 188 is one of the oldest known open clusters of the Milky Way belonging to the old Galactic disk population (Platais et al 2003). The cluster's spatial location in the Galaxy (l = 122…”

Section: Introductionmentioning

confidence: 99%

2MASS photometry and kinematical studies of open cluster NGC 188

Elsanhoury

Haroon²,

Чупина

et al. 2016

New Astronomy

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In this paper, we present our results for the photometric and kinematical studies of old open cluster NGC 188. We determined various astrophysical parameters like limited radius, core and tidal radii, distance, luminosity and mass functions, total mass, relaxation time etc. for the cluster using 2MASS catalog. We obtained the cluster's distance from the Sun as 1721±41 pc and log (age)= 9.85±0.05 at Solar metallicity. The relaxation time of the cluster is smaller than the estimated cluster age which suggests that the cluster is dynamically relaxed. Our results agree with the values mentioned in the literature. We also determined the clusters apex coordinates as (281• .88, −44• .76) using AD-diagram method. Other kinematical parameters like space velocity components, cluster center and elements of Solar motion etc. have also been computed.

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WIYN Open Cluster Study. XVII. Astrometry and Membership toV=21 in NGC 188

Cited by 87 publications

References 27 publications

Characterizing a cluster’s dynamic state using a single epoch of radial velocities

Characterizing a cluster’s dynamic state using a single epoch of radial velocities

UBVICCD Photometry of the Old Open Cluster Berkeley 17

2MASS photometry and kinematical studies of open cluster NGC 188

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