PI: Norbert Zacharias, U.S. Naval Observatory, email@example.com
Address: Astrometry Department, 3450 Mass. Ave. NW, Washington, DC 20392, USA
CoI: Marion Zacharias, contractor with USNO
CoI: Charlie Finch, U.S. Naval Observatory
Title: Radio-optical reference frame link
Abstract: Aligning the optical reference frame (currently realized by the Hipparcos and Tycho-2 star catalogs) and the defining radio reference frame (ICRF2) is a high priority, particularly with the upcoming Gaia mission and its need to align this new optical system to ICRF2. Compact, extragalactic sources (mainly QSO) are used for this purpose. Recent results indicate much larger than expcted offsets between radio positions and their optical counterparts centroids. The proposed observations will allow to distinguish between systematic errors in the current optical reference frame and possible astrophysical ``real" offsets of centroids between radio and optical data. The solution of this problem has far reaching implications for the reference frame alignment procedures for the Gaia data and can shed some light on the morphology of QSO radio cores and host/merging galaxies.
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