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Published August 10, 2011 | Published
Journal Article Open

The Structure Function of Variable 1.4 GHz Radio Sources Based on NVSS and FIRST Observations

Abstract

We augment the two widest/deepest 1.4 GHz radio surveys, the NRAO VLA Sky Survey (NVSS) and the Faint Images of the Radio Sky at Twenty centimeters (FIRST), with the mean epoch in which each source was observed. We use these catalogs to search for unresolved sources that vary between the FIRST and NVSS epochs. We find 43 variable sources (0.1% of the sources) that vary by more than 4σ, and we construct the mean structure function of these objects. This enables us to explore radio variability on timescales between several months and about five years. We find that, on these timescales, the mean structure function of the variable sources is consistent with a flat structure function. A plausible explanation to these observations is that a large fraction of the variability at 1.4 GHz is induced by scintillations in the interstellar medium, rather than by intrinsic variability. Finally, for a subsample of the variables for which the redshift is available, we do not find strong evidence for a correlation between the variability amplitude and the source redshift.

Additional Information

© 2011 American Astronomical Society. Received 2011 March 6; accepted 2011 May 10; published 2011 July 27. We thank Orly Gnat for reading the manuscript and to Jim Condon, Heinz Andernach, and an anonymous referee for their comments. E.O.O. is supported by an Einstein fellowship and NASA grants. This paper is based on observations conducted with the VLA, which is operated by the National Radio Astronomy Observatory (NRAO), a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

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