منابع مشابه
Determination of optical positions for 23 extragalactic radio sources
AB S TRACT The optical counterparts of 23 extragalactic radio sources, of which 13 are in the southern hemisphere, have been observed by three telescopes equipped with CCDs. By reference to the Astrographic/Tycho (ACT) Reference, Carlsberg Meridian (CMC), Positions and Proper Motions (PPM), Hipparcos (HIP) and Lick Northern Proper Motion (NPM) catalogues, the positions of the 23 objects have be...
متن کاملThe Reconciliation of Optical and Radio Positions
Reconciliation of optical and radio postions is basically a matter of reconciling positional reference systems. For example, the question of whether, for a given source, there is a real physical off-set between the optical and radio centroid at a given frequency cannot be properly inves tigated until the reference systems have been securely established. In the more sophisticated case of the co...
متن کاملCelestial positions in radio and optical
We discuss the importance of the direct link between the most accurate radio and optical reference frames that will become possible with the next-generation space as-trometry missions in about a decade. The positions of more than 500 active galactic nuclei that are common in the precise Very Long Baseline Interferometry (VLBI) catalogues and the Sloan Digital Sky Survey (SDSS) Data Release 4 (D...
متن کاملEstimating the Number of Wideband Radio Sources
In this paper, a new approach for estimating the number of wideband sources is proposed which is based on RSS or ISM algorithms. Numerical results show that the MDL-based and EIT-based proposed algorithm havea much better detection performance than that in EGM and AIC cases for small differences between the incident angles of sources. In addition, for similar conditions, RSS algorithm offers hi...
متن کاملAstrometry of the Optical Images of Some Southern Radio Sources
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...
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ژورنال
عنوان ژورنال: Nature
سال: 1969
ISSN: 0028-0836,1476-4687
DOI: 10.1038/2211229a0