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Papers by William Van Altena

Research paper thumbnail of A Deep Proper-Motion Survey in Kapteyn Selected Areas: I. Survey Description and First Results for Stars in the Tidal Tail of Sagittarius and in the Monoceros Ring

Astronomical Journal, 2006

We describe a high-precision, deep (to V ~ 19-21) absolute proper-motion survey that samples ~50 ... more We describe a high-precision, deep (to V ~ 19-21) absolute proper-motion survey that samples ~50 lines of sight in the Kapteyn Selected Areas along declination zones -15, 0 and 15 degrees. In many fields the astrometric baseline reaches nearly a century. We demonstrate that these data provide typical per star precisions between ~ 1 and 3 mas/yr to the above

Research paper thumbnail of Space Velocities of Southern Globular Clusters. IV. First Results for Inner-Galaxy Clusters

Astronomical Journal, 2002

We discuss the kinematics of these clusters and of three additional bulge clusters -- NGC 6522, N... more We discuss the kinematics of these clusters and of three additional bulge clusters -- NGC 6522, NGC 6528 and NFC 6553 -- whose proper motions with respect to bulge stars had been determined previously. We find that all of the clusters have velocities that confine them to the bulge region. Of the three metal poor clusters ([Fe/H] < -1.0), NGC 6522, and NGC 6723 have kinematics consistent with halo membership. The third cluster, NGC 6266 however, appears to belong to a rotationally-supported system. Of the four metal rich clusters ([Fe/H] >= -1.0), NGC 6304 and NGC 6553 also have kinematics consistent with membership to a rotationally-supported system. NGC 6528 has kinematics, metallicity and mass that argue in favor of a genuine Milky-Way bar cluster. NGC 6316's kinematics indicate membership to a hotter system than the bar.

Research paper thumbnail of The Southern Proper Motion Program. I. Magnitude Equation Correction

The Astronomical Journal, 1998

Research paper thumbnail of Space velocity of the globular cluster NGC 288 and astrometry with the CTIO 4 meter telescope

Astronomical Journal - ASTRON J, 1993

Research paper thumbnail of Astrometry with reconstructed hubble space telescope planetary camera (WF/PC 1) images

… Journal of Imaging …, 1995

... ACKNOWLEDGMENTS The authors acknowledge the ongoing contribution to this project by other mem... more ... ACKNOWLEDGMENTS The authors acknowledge the ongoing contribution to this project by other members of the Space Telescope Astrometry Team: Fritz Benedict, Barbara McArthur, Ed Nelan, Darrell Story, Art Whipple, Bill Jefferys, Peter Shelus, Paul Hemen-way, Ray ...

Research paper thumbnail of Absolute proper motion of the canis major dwarf galaxy candidate

The Astrophysical …, 2005

We have measured the absolute proper motion of the candidate Canis Major dwarf galaxy (CMa) at (l... more We have measured the absolute proper motion of the candidate Canis Major dwarf galaxy (CMa) at (l, b) = (240 • , −8 • ). Likely main-sequence stars in CMa have been selected from a region in the color-magnitude diagram that has very little contamination from known Milky Way components. We obtain µ l cos b = −1.47 ± 0.37 and µ b = −1.07 ± 0.38 mas yr −1 , on the ICRS system via Hipparcos stars. Together with the radial velocity of 109 km s −1 , and the assumed distance of 8 kpc, these results imply a space motion of (Π, Θ, W ) = (−5 ± 12, 188 ± 10, −49 ± 15) km s −1 . While CMa has in-plane rotation similar to the mean of thick disk stars, it shows significant (3σ) motion perpendicular to the disk, and differs even more (7σ) from that expected for the Galactic warp. The W velocity lends support to the argument that the CMa overdensity is part of a satellite galaxy remnant.

Research paper thumbnail of Division I/Working Group Astrometry by Small Ground-Based Telescopes

Proceedings of the …, 2008

Research paper thumbnail of Speckle Interferometry of Southern Double Stars. II. Measures from the CASLEO 2.15 Meter Telescope, 1995-1996

... Benav•çdez San Juan, Argentina ; lopez2283=infovia.com.ar AND J. GETHYN TIMOTHY Nightsen, Inc... more ... Benav•çdez San Juan, Argentina ; lopez2283=infovia.com.ar AND J. GETHYN TIMOTHY Nightsen, Inc., 30 Fresno Road, Warwick, RI 02886-1407 ... 0 coordinates, which is the same as the identi–cation number in the Washington Double Star Catalog (WDS; Worley &amp;amp;amp; Douglass ...

Research paper thumbnail of The Southern Proper Motion Program. II. A Catalog at the South Galactic Pole

The Astronomical …, 1998

... E. LOçPEZ Universidad Nacional de San Juan and Yale Southern Observatory, Avenida Benav•çdez ... more ... E. LOçPEZ Universidad Nacional de San Juan and Yale Southern Observatory, Avenida Benav•çdez 8175 Oeste, Chimbas, 5413 San Juan, Argentina RENEç A. MEçNDEZ Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile WEN-ZHANG MA Department ...

Research paper thumbnail of Space Velocities of Southern Globular Clusters. V. A Low Galactic Latitude Sample

Astronomical Journal, 2007

These are the first results of the Southern Proper-Motion Program (SPM) where the second-epoch ob... more These are the first results of the Southern Proper-Motion Program (SPM) where the second-epoch observations are taken with the CCD camera system recently installed on the double astrograph at El Leoncito, Argentina.

Research paper thumbnail of DIVISION I / COMMISSION 8 / WORKING GROUP DENSIFICATION OF THE OPTICAL REFERENCE FRAME

Proceedings of the International Astronomical Union, 2008

Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Research paper thumbnail of A Deep Proper-Motion Survey in Kapteyn Selected Areas: I. Survey Description and First Results for Stars in the Tidal Tail of Sagittarius and in the Monoceros Ring

Astronomical Journal, 2006

We describe a high-precision, deep (to V ~ 19-21) absolute proper-motion survey that samples ~50 ... more We describe a high-precision, deep (to V ~ 19-21) absolute proper-motion survey that samples ~50 lines of sight in the Kapteyn Selected Areas along declination zones -15, 0 and 15 degrees. In many fields the astrometric baseline reaches nearly a century. We demonstrate that these data provide typical per star precisions between ~ 1 and 3 mas/yr to the above

Research paper thumbnail of Space Velocities of Southern Globular Clusters. IV. First Results for Inner-Galaxy Clusters

Astronomical Journal, 2002

We discuss the kinematics of these clusters and of three additional bulge clusters -- NGC 6522, N... more We discuss the kinematics of these clusters and of three additional bulge clusters -- NGC 6522, NGC 6528 and NFC 6553 -- whose proper motions with respect to bulge stars had been determined previously. We find that all of the clusters have velocities that confine them to the bulge region. Of the three metal poor clusters ([Fe/H] < -1.0), NGC 6522, and NGC 6723 have kinematics consistent with halo membership. The third cluster, NGC 6266 however, appears to belong to a rotationally-supported system. Of the four metal rich clusters ([Fe/H] >= -1.0), NGC 6304 and NGC 6553 also have kinematics consistent with membership to a rotationally-supported system. NGC 6528 has kinematics, metallicity and mass that argue in favor of a genuine Milky-Way bar cluster. NGC 6316's kinematics indicate membership to a hotter system than the bar.

Research paper thumbnail of The Southern Proper Motion Program. I. Magnitude Equation Correction

The Astronomical Journal, 1998

Research paper thumbnail of Space velocity of the globular cluster NGC 288 and astrometry with the CTIO 4 meter telescope

Astronomical Journal - ASTRON J, 1993

Research paper thumbnail of Astrometry with reconstructed hubble space telescope planetary camera (WF/PC 1) images

… Journal of Imaging …, 1995

... ACKNOWLEDGMENTS The authors acknowledge the ongoing contribution to this project by other mem... more ... ACKNOWLEDGMENTS The authors acknowledge the ongoing contribution to this project by other members of the Space Telescope Astrometry Team: Fritz Benedict, Barbara McArthur, Ed Nelan, Darrell Story, Art Whipple, Bill Jefferys, Peter Shelus, Paul Hemen-way, Ray ...

Research paper thumbnail of Absolute proper motion of the canis major dwarf galaxy candidate

The Astrophysical …, 2005

We have measured the absolute proper motion of the candidate Canis Major dwarf galaxy (CMa) at (l... more We have measured the absolute proper motion of the candidate Canis Major dwarf galaxy (CMa) at (l, b) = (240 • , −8 • ). Likely main-sequence stars in CMa have been selected from a region in the color-magnitude diagram that has very little contamination from known Milky Way components. We obtain µ l cos b = −1.47 ± 0.37 and µ b = −1.07 ± 0.38 mas yr −1 , on the ICRS system via Hipparcos stars. Together with the radial velocity of 109 km s −1 , and the assumed distance of 8 kpc, these results imply a space motion of (Π, Θ, W ) = (−5 ± 12, 188 ± 10, −49 ± 15) km s −1 . While CMa has in-plane rotation similar to the mean of thick disk stars, it shows significant (3σ) motion perpendicular to the disk, and differs even more (7σ) from that expected for the Galactic warp. The W velocity lends support to the argument that the CMa overdensity is part of a satellite galaxy remnant.

Research paper thumbnail of Division I/Working Group Astrometry by Small Ground-Based Telescopes

Proceedings of the …, 2008

Research paper thumbnail of Speckle Interferometry of Southern Double Stars. II. Measures from the CASLEO 2.15 Meter Telescope, 1995-1996

... Benav•çdez San Juan, Argentina ; lopez2283=infovia.com.ar AND J. GETHYN TIMOTHY Nightsen, Inc... more ... Benav•çdez San Juan, Argentina ; lopez2283=infovia.com.ar AND J. GETHYN TIMOTHY Nightsen, Inc., 30 Fresno Road, Warwick, RI 02886-1407 ... 0 coordinates, which is the same as the identi–cation number in the Washington Double Star Catalog (WDS; Worley &amp;amp;amp; Douglass ...

Research paper thumbnail of The Southern Proper Motion Program. II. A Catalog at the South Galactic Pole

The Astronomical …, 1998

... E. LOçPEZ Universidad Nacional de San Juan and Yale Southern Observatory, Avenida Benav•çdez ... more ... E. LOçPEZ Universidad Nacional de San Juan and Yale Southern Observatory, Avenida Benav•çdez 8175 Oeste, Chimbas, 5413 San Juan, Argentina RENEç A. MEçNDEZ Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile WEN-ZHANG MA Department ...

Research paper thumbnail of Space Velocities of Southern Globular Clusters. V. A Low Galactic Latitude Sample

Astronomical Journal, 2007

These are the first results of the Southern Proper-Motion Program (SPM) where the second-epoch ob... more These are the first results of the Southern Proper-Motion Program (SPM) where the second-epoch observations are taken with the CCD camera system recently installed on the double astrograph at El Leoncito, Argentina.

Research paper thumbnail of DIVISION I / COMMISSION 8 / WORKING GROUP DENSIFICATION OF THE OPTICAL REFERENCE FRAME

Proceedings of the International Astronomical Union, 2008

Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.