Advancing Astrometry: Revisiting the VLBA Calibrator Surveys

Abstract : The original VLBA Calibrator Surveys (VCS) were a series of 6 VLBA campaigns from 1994 to 2007 in which more than 2000 compact extragalactic radio sources were observed at X/S bands. The goals were to obtain precise positions (uncertainties ~1 mas or better) of many hundreds of new sources for use as VLBI phase referencing calibrators, and to make snapshot images of them for morphological studies. These VCS campaigns were highly successful, resulting in accurate positions and scientific-grade images maps for a majority of sources. These observations were later used to approximately triple the number of sources contained in the second realization of the International Celestial Reference Frame by VLBI (ICRF2). However, the VCS sources in ICRF2 represent a class of 'single epoch' sources with average position uncertainties ~5 times greater than the other ~1200 ICRF2 sources which are observed much more frequently in geodetic VLBI sessions. In an attempt to greatly reduce their position uncertainties, we are re-observing ~2400 VCS sources at X/S bands on the VLBA in 8 24-hr sessions. With the recent VLBA sensitivity upgrade, the sensitivity is now nearly 5 and 3 times greater at X and S bands than the original VCS sessions. Five of these sessions have been run so far, re-observing 1500 sources. Preliminary analysis shows an improvement in the average position uncertainties by a factor of ~3.2 times for these re-observed sources. We will present and discuss these improvements and their implication for ICRF3 development (planned for 2018). Images are also being produced and examples will be presented. Additional references: VLBA Calibrator Survey : Beasley et al. 2002 2002ApJS..141...13B ICRF1 : 2009ITN....35....1M ICRF2 : 1998AJ....116..516M ICRF3 : 2014rfag.confE...1J GAIA : 2008IAUS..248..217L
Type de document :
Communication dans un congrès
American Astronomical Society, AAS Meeting #225, #113.07, held 4-8 January 2015 at the Washington State Convention & Trade Center in Seattle, WA., Jan 2015, Seattle, United States. 225, 2015
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https://hal.archives-ouvertes.fr/hal-01112650
Contributeur : Marie-Paule Pomies <>
Soumis le : mardi 3 février 2015 - 13:40:21
Dernière modification le : jeudi 16 novembre 2017 - 17:14:19

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Anthony J., Beasley, David, Gordon, Christopher, Jacobs, Alison, Peck, Jackie, Hodge, et al.. Advancing Astrometry: Revisiting the VLBA Calibrator Surveys. American Astronomical Society, AAS Meeting #225, #113.07, held 4-8 January 2015 at the Washington State Convention & Trade Center in Seattle, WA., Jan 2015, Seattle, United States. 225, 2015. 〈hal-01112650〉

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