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Absolute Proper Motions of the Dwarf Spheroidal Galaxies in Draco and Ursa Minor

Published online by Cambridge University Press:  26 July 2016

R.-D. Scholz  and
M.J. Irwin
R.-D. Scholz
Affiliation:
WIP-Projekt Astrometrie bei der Universität Potsdam, Germany
M.J. Irwin
Affiliation:
Royal Greenwich Observatory, Cambridge, U.K.

Abstract

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Palomar and Tautenburg Schmidt plates with a base line of about 35 years have been measured with the Automated Photographic Measuring (APM) system in Cambridge (UK) in order to obtain the proper motions of the Galactic dwarf spheroidal satellites (dSph) in Draco and Ursa Minor with respect to a well defined extragalactic reference frame. The investigations were encouraged by the accuracy level achieved for the mean absolute proper motions of galactic globular clusters (0.05 arcsec/century from 25 years base line Tautenburg plate pairs) which is comparable to the expected proper motion of the Draco and Ursa Minor dSph assuming tangential motions of about 100 km/s. Different methods for the removal of systematic errors in the absolute proper motion introduced by the measuring and reduction process are discussed. The more accurate relative proper motions of individual stars in both dSphs obtained by Stetson (1980) and by Cudworth, Olszewski & Schommer (1986) provide an external comparison and are also used to obtain the mean absolute proper motion of the dSphs.

Type
Part Eleven: Local Group Dwarf Galaxies and LSB Galaxies
Information
Symposium - International Astronomical Union , Volume 161: Astronomy from Wide-Field Imaging , 1994 , pp. 535 - 539
Copyright
Copyright © Kluwer 1994 

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