scholarly journals Some numerical experiments concerning the determination of the general velocity field of the Galaxy from proper motions

1981 ◽  
Vol 196 (3) ◽  
pp. 659-668 ◽  
Author(s):  
J. Byl ◽  
M. W. Ovenden
Keyword(s):  
Velocity Field ◽  
Numerical Experiments ◽  
Proper Motions ◽  
The Galaxy ◽  
General Velocity

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 Orbits of Galactic Globular Clusters from Schmidt Plate Astrometry

1994 ◽  
Vol 161 ◽  
pp. 453-459 ◽  
Author(s):  
M. Odenkirchen ◽  
R.-D. Scholz ◽  
M.J. Irwin
Keyword(s):  
Globular Clusters ◽  
Proper Motions ◽  
Mass Model ◽  
Orbital Parameters ◽  
The Galaxy ◽  
Galactic Globular Clusters

We present results from orbit integrations for the globular clusters M 3 and M 92. Absolute proper motions recently measured from Tautenburg Schmidt plates and a three-component mass model for the Galaxy have been used to derive the galactic orbits of these clusters. Orbital parameters and the influence of observational uncertainties on the determination of the orbits are discussed.

scholarly journals A New Absolute Proper Motion Determination of Leo I Using HST/WFPC2 Images and Gaia EDR3

2021 ◽  
Vol 163 (1) ◽  
pp. 1
Author(s):  
Dana I. Casetti-Dinescu ◽  
Caitlin K. Hansen ◽  
Terrence M. Girard ◽  
Vera Kozhurina-Platais ◽  
Imants Platais ◽  
...  
Keyword(s):  
Proper Motion ◽  
Milky Way ◽  
Proper Motions ◽  
Large Area ◽  
Field Of Study ◽  
Data Set ◽  
Polar Structure ◽  
The Galaxy ◽  
The Absolute

Abstract We measure the absolute proper motion of Leo I using a WFPC2/HST data set that spans up to 10 yr to date the longest time baseline utilized for this satellite. The measurement relies on ∼2300 Leo I stars located near the center of light of the galaxy; the correction to absolute proper motion is based on 174 Gaia EDR3 stars and 10 galaxies. Having generated highly precise, relative proper motions for all Gaia EDR3 stars in our WFPC2 field of study, our correction to the absolute EDR3 system does not rely on these Gaia stars being Leo I members. This new determination also benefits from a recently improved astrometric calibration of WFPC2. The resulting proper-motion value, (μ α , μ δ ) = (−0.007 ± 0.035, − 0.119 ± 0.026) mas yr−1 is in agreement with recent, large-area, Gaia EDR3-based determinations. We discuss all the recent measurements of Leo I’s proper motion and adopt a combined, multistudy average of ( μ α 3 meas , μ δ 3 meas ) = ( − 0.036 ± 0.016 , − 0.130 ± 0.010 ) mas yr−1. This value of absolute proper motion for Leo I indicates its orbital pole is well aligned with that of the vast polar structure, defined by the majority of the brightest dwarf spheroidal satellites of the Milky Way.

scholarly journals Masers and the Cosmic Distance Scale

1988 ◽  
Vol 129 ◽  
pp. 169-174 ◽  
Author(s):  
Mark J. Reid ◽  
James M. Moran ◽  
Carl R. Gwinn
Keyword(s):  
Sufficient Accuracy ◽  
Distance Scale ◽  
Proper Motions ◽  
Fundamental Parameters ◽  
The Galaxy ◽  
Nearby Galaxies ◽  
Extragalactic Distance Scale ◽  
Maser Sources ◽  
Better Than

Studies of H2O masers have demonstrated the power of VLBI techniques to measure relative positions with sufficient accuracy (∼ 10 μas) to determine proper motions and to estimate distances to maser sources throughout the Galaxy. The distance to four H2O masers have been determined, and the distance to the center of the Galaxy has been determined to be 7.1 ± 1.5 kpc from observations of the H2O masers in Sgr-B2. Proper motion distances for other H2O masers, and possibly for OH masers, may allow the determination of the fundamental parameters describing the size (Ro) and rotation rate (Θo) of the Galaxy with accuracies of better than 10%. Finally, the measurement of the proper motions of H2O masers in nearby galaxies (< 10 Mpc) is feasible and offers the possibility of direct calibration of the extragalactic distance scale.

scholarly journals The Tautenburg Part Of The Programme Studying The Main Meridional Section Of The Galaxy

1988 ◽  
Vol 133 ◽  
pp. 451-454
Author(s):  
E. Schilbach
Keyword(s):  
Proper Motion ◽  
Proper Motions ◽  
Schmidt Telescope ◽  
Meridional Section ◽  
Mean Error ◽  
The Galaxy ◽  
The Mean

The programme for the determination of proper motions with reference to galaxies for 6000 stars on 17 fields near the main meridional section of the Galaxy is presented. For each field there are 2 or 3 first-epoch plates taken with the Tautenburg Schmidt-telescope before 1970. In preliminary investigations the mean error of an individual proper motion was found to be per century both for bright (8m–12m) and for faint (16m–18m) stars.

scholarly journals The Determination of Absolute Magnitudes from Proper Motions

1973 ◽  
Vol 54 ◽  
pp. 11-17
Author(s):  
W. J. Luyten
Keyword(s):  
Proper Motions ◽  
Special Groups ◽  
Solar Motion ◽  
The Galaxy ◽  
Absolute Magnitudes

A brief review is given of the several ways in which stellar motions may be used statistically. In the case where the motions of all stars shown on plates of certain regions are measured these are generally used to determine kinematical relations in the Galaxy and only secondarily for the estimation of luminosities; when motions are measured for special groups of stars the solar motion is first determined and then used for the calculation of distances and luminosities.

scholarly journals Microarcsec Astrometry: The Gaia Mission

1998 ◽  
Vol 11 (1) ◽  
pp. 581-582
Author(s):  
L. Lindegren ◽  
M.A.C. Perryman
Keyword(s):  
Accurate Determination ◽  
Distance Measurements ◽  
Profound Impact ◽  
Individual Stars ◽  
The Galaxy ◽  
Direct Distance ◽  
Scientific Potential ◽  
Space Astrometry ◽  
Small Instrument

The Hipparcos mission demonstrated the efficiency of space astrometry (in terms of number of objects, accuracy, and uniformity of results) and the fact that a relatively small instrument can have a very large scientific potential in the area of astrometry. However, Hipparcos could probe less than 0.1 per cent of the volume of the Galaxy by direct distance measurements. Using a larger instrument and more efficient detectors, it is now technically feasible to increase the efficiency of a space astrometry mission by several orders of magnitude, thus encompassing a large part of the Galaxy within its horizon for accurate determination of parallaxes and transverse velocities. Such a mission will have immediate and profound impact in the areas of the physics and evolution of individual stars and of the Galaxy as a whole.

The electron transport that occurs within wurtzite zinc oxide and the application of stress

MRS Advances ◽  
2017 ◽  
Vol 2 (48) ◽  
pp. 2627-2632 ◽  
Author(s):  
Poppy Siddiqua ◽  
Michael S. Shur ◽  
Stephen K. O’Leary
Keyword(s):  
Monte Carlo ◽  
Zinc Oxide ◽  
Electron Transport ◽  
Velocity Field ◽  
Monte Carlo Simulations ◽  
Significant Role ◽  
Energy Gap ◽  
Device Application ◽  
The Impact

ABSTRACTWe examine how stress has the potential to shape the character of the electron transport that occurs within ZnO. In order to narrow the scope of this analysis, we focus on a determination of the velocity-field characteristics associated with bulk wurtzite ZnO. Monte Carlo simulations of the electron transport are pursued for the purposes of this analysis. Rather than focusing on the impact of stress in of itself, instead we focus on the changes that occur to the energy gap through the application of stress, i.e., energy gap variations provide a proxy for the amount of stress. Our results demonstrate that stress plays a significant role in shaping the form of the velocity-field characteristics associated with ZnO. This dependence could potentially be exploited for device application purposes.

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