The Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey. II. The First Four Epochs
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https://doi.org/10.1086%2F592485
http://hdl.handle.net/11603/18497
https://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Search&refcode=2008ApJ...689..108L
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http://hdl.handle.net/11603/18497
https://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Search&refcode=2008ApJ...689..108L
http://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2008ApJ...689..108L
http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=J/ApJ/689/108
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Date
2008-12-10
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Citation of Original Publication
J. E. J. Lovell et al,The Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey. II. The First Four Epochs, The Astrophysical Journal, Volume 689, Number 1, https://doi.org/10.1086%2F592485
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law
Public Domain Mark 1.0
This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law
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Abstract
We report on the variability of 443 flat-spectrum, compact radio sources monitored using the VLA for 3 days in four epochs at ~4 month intervals at 5 GHz as part of the Micro-Arcsecond Scintillation-Induced Variability (MASIV) survey. Over half of these sources exhibited 2%-10% rms variations on timescales over 2 days. We analyzed the variations by two independent methods and find that the rms variability amplitudes of the sources correlate with the emission measure in the ionized interstellar medium along their respective lines of sight. We thus link the variations with interstellar scintillation of components of these sources, with some (unknown) fraction of the total flux density contained within a compact region of angular diameter in the range 10-50 μas. We also find that the variations decrease for high mean flux density sources and, most importantly, for high-redshift sources. The decrease in variability is probably due either to an increase in the apparent diameter of the source or to a decrease in the flux density of the compact fraction beyond z ~ 2. Here we present a statistical analysis of these results, and a future paper will discuss the cosmological implications in detail.