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The Large Quasar Reference Frame (LQRF)- an optical representation of the ICRS

By A. H. Andrei, J. Souchay, N. Zacharias, R. L. Smart, R. Vieira Martins, D. N. Da Silva Neto, J. I. B. Camargo, M. Assafin, C. Barache, S. Bouquillon, J. L. Penna and F. Taris

Abstract

Context. The large number and all-sky distribution of quasars from different surveys, along with their presence in large, deep astrometric catalogs, enables the building of an optical materialization of the ICRS following its defining principles. Namely, kinematically non-rotating with respect to the ensemble of distant extragalactic objects; aligned with the mean equator and dynamical equinox of J2000; and realized by a list of adopted coordinates of extragalatic sources. Aims. The LQRF was built with the care of avoiding incorrect matches of its constituents quasars, homogenizing the astrometry from the different catalogs and lists in which the constituent quasars are identified, and attaining global alignment with the ICRF, as well as fully consistent source positions Methods. Starting from the updated and presumably complete LQAC list of QSOs, the initial optical positions of those quasars are found in the USNO B1.0 and GSC2.3 catalogs, and from the SDSS DR5. The initial positions are next placed onto UCAC2-based reference frames, following by an alignment with the ICRF, to which were added the most precise sources from the VLBA and VLA calibrator lists- when reliable optical counterparts exist. Finally, the LQRF axes are inspected through spherical harmonics, to define right ascension, declination and magnitude terms. Results. The LQRF contains 100,165 quasars, well represented across the whole sky, with 10 arcmin being the average distanc

Year: 1996
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