Interstellar Scintillation Observations of 146 Extragalactic Radio Sources

Abstract

From 1979--1996 the Green Bank Interferometer was used by the Naval Research Laboratory to monitor the flux density from 146 compact radio sources at frequencies near 2 and 8 GHz. We filter the ``light curves'' to separate intrinsic variations on times of a year or more from more rapid interstellar scintilation (ISS) on times of 5--50 d. Whereas the intrinsic variation at 2 GHz is similar to that at 8 GHz (though diminished in amplitude), the ISS variation is much stronger at 2 than at 8 GHz. We characterize the ISS variation by an rms amplitude and a timescale and examine the statistics of these parameters for the 121 sources with significant ISS at 2 GHz. We model the scintillations using the NE2001 Galactic electron model assuming the sources are brightness-limited. We find the observed rms amplitude to be in general agreement with the model, provided that the compact components of the sources have about 50% of their flux density in a component with maximum brightness temperatures $10^{11}$--$10^{12}$K. Thus our results are consistent with cm-wavelength VLBI studies of compact AGNs, in that the maximum brightness temperatures found are consistent with the inverse synchrotron limit at $3\times 10^{11}$ K, boosted in jet configurations by Doppler factors up to about 20. The average of the observed 2 GHz ISS timescales is in reasonable agreement with the model at Galactic latitudes above about 10\de. At lower latitudes the observed timescales are too fast, suggesting that the transverse plasma velocity increases more than expected beyond about 1 kpc.

arXiv comment32 pages, 16 figures. Submitted to ApJ

References in corpus (14)

• The Wisconsin H-Alpha Mapper Northern Sky Survey
• The discovery of a microarcsecond quasar: J1819+3845
• PKS 0405--385: the smallest radio quasar?
• Rapid Variability and Annual Cycles in the Characteristic Time-scale of the Scintillating Source PKS 1257-326
• Interstellar scintillation as the origin of rapid radio variability in the quasar J1819+3845
• First Results from MASIV: The Micro-Arcsecond Scintillation-Induced Variability Survey
• Interstellar Scintillation of the Polarized Flux Density in Quasar, PKS 0405-385
• Annual modulation in the scattering of J1819+3845: peculiar plasma velocity and anisotropy
• Annual modulation in IDV of quasar 0917+624 due to Interstellar Scintillation
• A Dual Frequency, Multi-Year Monitoring Program of Compact Radio Sources
• Intra-Day Variability and the Interstellar Medium Towards 0917+624
• Fitting Formula for Flux Scintillation of Compact Radio Sources
• The Extreme Scattering Event Toward PKS 1741-038: VLBI Images
• Diffractive Interstellar Scintillation of the Quasar J1819+3845 at 21cm

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