scholarly journals Correction to Absolute Proper Motion Using the IAS-Galaxy Model

1990 ◽  
Vol 141 ◽  
pp. 427-429
Author(s):  
Kavan U. Ratnatunga
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Theoretical Models ◽  
Galactic Structure ◽  
Coordinate Frame ◽  
Proper Motions ◽  
Software Interface ◽  
The Galaxy ◽  
Galaxy Model ◽  
Star Catalogs

The IAS-Galaxy model (Ratnatunga, Bahcall and Casertano 1989) is a software interface between theoretical models of the Galaxy and observed kinematic distributions. It has been developed for analysis of many kinematic catalogs to study global galactic structure. In addition, the IASG model can be used to estimate corrections needed to derive absolute parallax and absolute proper motion by evaluating, on a star-by-star basis, the expected mean motion of the reference stars.A theoretical Galaxy model is defined on an inertial coordinate frame. Proper motions are measured in a reference frame defined by a fundamental catalog. The observed distribution of proper motions in star catalogs can be directly compared with the expected distributions evaluated using IASG to check the accuracy of the adopted reference frame in realizing the inertial coordinate frame in the sky.

scholarly journals Progress Report on the Southern Proper Motion Program

1995 ◽  
Vol 166 ◽  
pp. 357-357
Author(s):  
I. Platais ◽  
T. M. Girard ◽  
V. Kozhurina-Platais ◽  
R. A. Mendez ◽  
W. F. Van Altena ◽  
...  
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Systematic Errors ◽  
Progress Report ◽  
Model Choice ◽  
Plate Model ◽  
Field Independent ◽  
The Status ◽  
First Results ◽  
Galaxy Model

We present the status of the Yale/San Juan Southern Proper Motion program (SPM) which is the southern hemisphere extension of the Lick Observatory Northern Proper Motion program with respect to faint galaxies (Platais et al., 1993). To date, measurements and reductions in the South Galactic Pole region comprising ≈ 1000 square-degrees on the sky have been finished. At this stage of the SPM program particular attention has been paid to the plate model choice along with an assessment of and accounting for systematic errors. For our establishing of a secondary reference frame we have noticed the presence of a potentially dangerous effect, so–called field–independent coma which is caused by lens decentering. We acknowledge the superb Hipparcos preliminary positions without which such analysis would be virtually impossible. The SPM data at the SGP region have also been used to constrain a multi–component Galaxy model. First results of this analysis are presented.

scholarly journals Proper Motions With Respect to the Extragalactic Reference Frame

1990 ◽  
Vol 141 ◽  
pp. 407-417
Author(s):  
A. R. Klemola
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Milky Way ◽  
Proper Motions ◽  
Stellar Proper Motions

The Lick proper motion program, one of several using galaxies as a reference frame, is summarized with a statement of work accomplished for the non-Milky Way sky. The problem of identifying relatively transparent regions at low galactic latitudes is discussed, with tabular results presented for 41 windows from the literature having observable galaxies. These fields may be helpful for attaching stellar proper motions directly to the extragalactic frame.

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 Galactic Structure with GSC-II Material

1998 ◽  
Vol 179 ◽  
pp. 228-230
Author(s):  
A. Spagna ◽  
M.G. Lattanzi ◽  
G. Massone ◽  
B.J. McLean ◽  
B.M. Lasker
Keyword(s):  
Stellar Populations ◽  
Galactic Structure ◽  
Proper Motions ◽  
The Galaxy ◽  
Photographic Photometry

Faint surveys of accurate colors and proper motions are fundamental for studying the physical and kinematical properties of the stellar populations in the Galaxy. A program designed to address such issues has been initiated on selected fields utilizing prototype material from the GSC-II project (see McLean et al. in this volume, p. 431). Photographic photometry V, B–V, V–Rc, is derived down to V = 18.5 with a precision of about 0.1 mag, together with absolute proper motions to σμ ≃ 3 mas/yr.

scholarly journals Report on the Herstmonceux I.N.T. Parallax Programme

1974 ◽  
Vol 61 ◽  
pp. 167-167
Author(s):  
B. F. Jones
Keyword(s):  
Proper Motion ◽  
Reduction Technique ◽  
Royal Greenwich Observatory ◽  
Proper Motions ◽  
Isaac Newton ◽  
The Galaxy ◽  
Visual Magnitude ◽  
Isaac Newton Telescope

In 1971 a pilot parallax programme was initiated on the 98-in. Isaac Newton Telescope at the Royal Greenwich Observatory. Nineteen stars between visual magnitude 15 and 19 and of high proper motion were put on the programme. The plates were taken at prime focus through the Wynne corrector. Observations are now complete for two of these stars. Because of time allocations and the desire to observe at maximum parallax factor, observations are made at large hour angles. All stars in each field are being measured on the GALAXY measuring engine and parallaxes and proper motions will be computed for all stars. The fields are being reduced using an overlap reduction technique.

scholarly journals Astrometry with Schmidt Telescopes for Probing the Galaxy

1995 ◽  
Vol 148 ◽  
pp. 234-240 ◽  
Author(s):  
C. Andrew Murray
Keyword(s):  
Proper Motion ◽  
Proper Motions ◽  
The South ◽  
Large Numbers ◽  
The Galaxy ◽  
Zero Points

AbstractThe use of proper motions and parallaxes for large numbers of stars, obtainable from a combination of Schmidt telescopes and automatic plate scanners, is discussed. The importance of deriving the zero points of both absolute proper motion, and of parallactic motion, is emphasised. Calibrations of proper motion and of parallaxes should be based on dispersions of proper motion. These methods are illustrated by results from a study in the South Galactic Cap.

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 Densifying the Optical Reference Frame: The Tycho-2 Catalog of 2.5 Million Stars

2000 ◽  
Vol 180 ◽  
pp. 75-79
Author(s):  
S.E. Urban ◽  
G.L. Wycoff
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Proper Motions ◽  
Naval Observatory ◽  
Optical Reference ◽  
The Mean ◽  
The U.S

AbstractSince the establishment of the Hipparcos Catalog as the defining source of the optical reference frame, densification beyond its ≈ 120,000 stars has been made possible by the utilization of the Tycho-1 Catalog. The ACT, combining the old Astrographic Catalog (AC) data with the Tycho-1 positions, is the best known example of this. The Tycho-2 consortium, led by E. Høg, has performed new reductions on the Tycho data. This not only has increased the astrometric and photometric accuracies of the original 1 million Tycho-1 stars, but also has added an additional 1.5 million stars. The U.S. Naval Observatory led the effort to compute the proper motions of these 2.5 million stars. They are based not only on the AC data but also include over 140 other ground-based catalogs, all directly reduced to the Hipparcos system. The result of these efforts is the Tycho-2 Catalog, available since February 2000. Positions, proper motions, and BT and VT magnitudes are given for 2.5 million stars. The catalog is 99% complete to V=11.0, and 90% complete to V=11.5. Positional accuracies at the mean epochs vary from < 10 mas for stars V < 9 to just under 100 mas for V > 12. Proper motion accuracies are estimated to be 1.3 mas/year to 3.0 mas/year for the same magnitude ranges. Photometric accuracies range from 0.02 magnitudes for the brightest stars to 0.25 magnitudes for the faintest.

scholarly journals The Distance to the Center of the Galaxy

1987 ◽  
Vol 115 ◽  
pp. 554-555 ◽  
Author(s):  
M. J. Reid ◽  
M. H. Schneps ◽  
J. M. Moran ◽  
C. R. Gwinn ◽  
R. Genzel ◽  
...  
Keyword(s):  
Proper Motion ◽  
Radial Component ◽  
Proper Motions ◽  
Star Forming ◽  
The Galaxy

The distance to a star forming region can be determined by measuring the proper motions within H2O maser clusters. If the motions of the maser spots are random, the distance can be determined by applying the technique known as statistical parallax. Alternatively, if organized motions are evident in the proper motions, one can model the source to estimate its the distance. Both methods rely on a comparison of the radial component of the motion (in km/s) and the proper motion on the plane of the sky (in milli-arcseconds/year).

scholarly journals Astrometry and Galactic Structure

1994 ◽  
Vol 161 ◽  
pp. 425-434
Author(s):  
S.R. Majewski
Keyword(s):  
Proper Motion ◽  
Globular Clusters ◽  
Milky Way ◽  
Galactic Structure ◽  
Proper Motions ◽  
Future Prospects ◽  
The Status ◽  
Galactic Globular Clusters ◽  
Remarkable Agreement

The application of astrometric surveys to understanding the structure and kinematics of the Milky Way is discussed, with particular emphasis on some of the issues expected to be addressed in the next decade or so. It is shown that the results of complete proper motion surveys of field stars at the Galactic poles are in remarkable agreement concerning the global kinematics of stars as a function of distance, but that significant differences exist in how these data are decomposed to derive the kinematics of individual Galactic components. The status and future prospects regarding the measurement of proper motions and orbits for Galactic globular clusters and satellites are also discussed.

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