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VLBI Observations of Southern Hemisphere ICRF Sources. I
Citation
Ojha, R and Fey, AL and Johnston, KJ and Jauncey, DL and Reynolds, JE and Tzioumis, AK and Quick, JFH and Nicolson, GD and Ellingsen, SP and Dodson, R and McCulloch, PM, VLBI Observations of Southern Hemisphere ICRF Sources. I, The Astronomical Journal, 127, (6) pp. 3609-3621. ISSN 0004-6256 (2004) [Refereed Article]
DOI: doi:10.1086/421001
Abstract
We present 8.4 GHz very long baseline interferometry (VLBI) observations of 69 southern hemisphere extragalactic sources in the International Celestial Reference Frame. These are the first in a series of observations intended to image all such sources at milliarcsecond resolution in order to determine their continued suitability for reference-frame use based on intrinsic structure. We use the resultant images to calculate a core fraction, that is, the ratio of core flux density to total flux density, for all observed sources. The resulting distribution, with a mean value of 0.83, suggests that most sources are relatively compact. However, just over half the observed sources show significant extended emission in the form of multiple compact components. These sources are probably poorly suited for high-accuracy reference-frame use unless intrinsic structure and potential variability can be taken into account. Our observations represent the first large, comprehensive VLBI imaging survey in the southern hemisphere, significantly extending the existing limited VLBI surveys and, along with some well-known objects, containing many sources that have never been imaged at milliarcsecond resolution. The overlap with Very Long Baseline Array images of sources between 0° and -35° declination helps determine the limits to imaging with the southern hemisphere-accessible telescopes.
Item Details
Item Type: | Refereed Article |
---|---|
Research Division: | Physical Sciences |
Research Group: | Astronomical sciences |
Research Field: | Galactic astronomy |
Objective Division: | Expanding Knowledge |
Objective Group: | Expanding knowledge |
Objective Field: | Expanding knowledge in the physical sciences |
UTAS Author: | Ellingsen, SP (Professor Simon Ellingsen) |
UTAS Author: | Dodson, R (Mr Richard Dodson) |
UTAS Author: | McCulloch, PM (Professor Peter McCulloch) |
ID Code: | 30737 |
Year Published: | 2004 |
Web of Science® Times Cited: | 44 |
Deposited By: | Physics |
Deposited On: | 2004-08-01 |
Last Modified: | 2005-04-15 |
Downloads: | 0 |
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