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The MASIV Survey - IV. Relationship between intra-day scintillation and intrinsic variability of radio AGNs


Koay, JY and Macquart, JP and Jauncey, DL and Pursimo, T and Giroletti, M and Bignall, HE and Lovell, JEJ and Rickett, BJ and Kedziora-Chudczer, L and Ojha, R and Reynolds, C, The MASIV Survey - IV. Relationship between intra-day scintillation and intrinsic variability of radio AGNs, Monthly Notices of the Royal Astronomical Society, 474, (4) pp. 4396-4411. ISSN 0035-8711 (2018) [Refereed Article]

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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society : 2018 the author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

DOI: doi:10.1093/mnras/stx3076


We investigate the relationship between 5 GHz interstellar scintillation (ISS) and 15 GHz intrinsic variability of compact, radio-selected active galactic nuclei (AGNs) drawn from the Microarcsecond Scintillation-Induced Variability (MASIV) Survey and the Owens Valley Radio Observatory blazar monitoring program. We discover that the strongest scintillators at 5 GHz (modulation index, m5 ≥ 0.02) all exhibit strong 15 GHz intrinsic variability (m15 ≥ 0.1). This relationship can be attributed mainly to the mutual dependence of intrinsic variability and ISS amplitudes on radio core compactness at ∼ 100 μas scales, and to a lesser extent, on their mutual dependences on source flux density, arcsec-scale core dominance and redshift. However, not all sources displaying strong intrinsic variations show high amplitude scintillation, since ISS is also strongly dependent on Galactic line-of-sight scattering properties. This observed relationship between intrinsic variability and ISS highlights the importance of optimizing the observing frequency, cadence, timespan and sky coverage of future radio variability surveys, such that these two effects can be better distinguished to study the underlying physics. For the full MASIV sample, we find that Fermi-detected gamma-ray loud sources exhibit significantly higher 5 GHz ISS amplitudes than gamma-ray quiet sources. This relationship is weaker than the known correlation between gamma-ray loudness and the 15 GHz variability amplitudes, most likely due to jet opacity effects.

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:Lovell, JEJ (Dr Jim Lovell)
ID Code:152429
Year Published:2018
Web of Science® Times Cited:9
Deposited By:Research Performance and Analysis
Deposited On:2022-08-18
Last Modified:2022-09-14
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