The influence of radio-extended structures on offsets between the optical and VLBI positions of sources in the ICRF2
Context. We investigate the differences between positions as determined by optical (direct imaging) and Very Long Baseline Interferometry (VLBI) techniques of extragalactic sources listed in the second realization of the International Celestial Reference Frame (ICRF2). Aims. We aim to verify the inf...
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Published in | Astronomy and astrophysics (Berlin) Vol. 532; p. A115 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Les Ulis
EDP Sciences
01.08.2011
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Subjects | |
Online Access | Get full text |
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Summary: | Context. We investigate the differences between positions as determined by optical (direct imaging) and Very Long Baseline Interferometry (VLBI) techniques of extragalactic sources listed in the second realization of the International Celestial Reference Frame (ICRF2). Aims. We aim to verify the influence of the source’s intrinsic structure on these differences. Methods. Instruments with mosaics of CCDs were used to acquire the optical positions presented here, which lead us to opt for overlapping techniques to build a virtual, continuous CCD over the whole angular size of the respective fields of view, whose translation of the resulting intrumental positions into positions that are consistent with those in the ICRF2 was obtained with the help of the UCAC2. Results. The differences obtained between the optical and VLBI positions of the observed sources can reach more than 80 milliarsec for some measurements and, considering that they can hardly be explained by statistical fluctuations or systematic errors in the optical reference frame used here only, we argue that these differences can be related to the sources’ X-band structure index (8.4 GHz). Conclusions. In this context, the presence of the intrinsic structure should be considered when comparing the optical and VLBI positions of ICRF2 sources in the future. |
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Bibliography: | dkey:10.1051/0004-6361/201016201 bibcode:2011A%26A...532A.115C istex:DC399F68660B5FCA0B2E1358FC946A8CEE17B8CB Based on observations carried out with the SOAR telescope. Associate researcher at Observatoire de Paris/SYRTE, 77 Avenue Denfert Rochereau, 75014 Paris, France. publisher-ID:aa16201-10 ark:/67375/80W-WWC2GVKB-H |
ISSN: | 0004-6361 1432-0746 |
DOI: | 10.1051/0004-6361/201016201 |