منابع مشابه
Radio astrometry with chromatic AGN core positions
Aims. The effect of frequency-dependent AGN core positions (“core-shifts”) on radio Very Long Baseline Interferometry (VLBI) global astrometry measurements is investigated. Methods. The basic equations relating to VLBI astrometry are reviewed, including the effects of source structure. A power-law representation of core-shifts, based on both observations and theoretical considerations of jet co...
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Multiple-epoch phase-referenced VLBI observations of 11 radio-emitting stars have been conducted as part of an astrometric program to link the Hipparcos optical reference frame to the radio extragalactic reference frame. We present the VLBI positions, proper motions and trigonometric parallaxes from this program in the ICRF (International Celestial Reference Frame). These astrometric parameters...
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was found in an earlier investigation on dark matter in open clusters mainly situated in the northern sky. Taking into account the small number of clusters investigated as weil as the large mean errors, the result cannot be regarded as fully conclusive. It nevertheless gives an indication that the dark matter (dust) has been driven away from the cluster and that the remaining dark matter inside...
متن کاملOptical astrometry of Benchmark radio sources - IV. New results in the southern hemisphere
Optical positions relative to the International Reference Stars Catalogue (IRS), and therefore in the system of the FK5, have been obtained for the optical counterparts of 40 compact extragalactic radio sources south of δ ∼ +6◦. Many of these sources are being considered as possible Benchmark objects for the establishment of a quasi−inertial unified radio/optical reference frame. Precision leve...
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We propose a method to obtain accurate absolute astrometry of Hubble Space Telescope images. Ground based images are used to linkHST images to standard astrometric stars defining the optical frame of reference. The method has been used to register optical images of the Seyfert 2 galaxy NGC 5929 to the corresponding radio maps, allowing the exploration of the relationship between radio and optic...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1984
ISSN: 0074-1809
DOI: 10.1017/s007418090007844x