The Optics of Refractive Substructure

Abstract

Newly recognized effects of refractive scattering in the ionized interstellar medium have broad implications for very long baseline interferometry (VLBI) at extreme angular resolutions. Building upon work by Blandford & Narayan (1985), we present a simplified, geometrical optics framework, which enables rapid, semi-analytic estimates of refractive scattering effects. We show that these estimates exactly reproduce previous results based on a more rigorous statistical formulation. We then derive new expressions for the scattering-induced fluctuations of VLBI observables such as closure phase, and we demonstrate how to calculate the fluctuations for arbitrary quantities of interest using a Monte Carlo technique.

11 Pages, 4 Figures, Accepted for publication in ApJ

References in corpus (11)

• RadioAstron -- a Telescope with a Size of 300 000 km: Main Parameters and First Observational Results
• Resolved Magnetic-Field Structure and Variability Near the Event Horizon of Sagittarius A*
• Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron. I. Imaging BL Lacertae at 21 microarcsecond resolution
• Modeling Seven Years of Event Horizon Telescope Observations with Radiatively Inefficient Accretion Flow Models
• RadioAstron Observations of the Quasar 3C273: a Challenge to the Brightness Temperature Limit
• Theory and Simulations of Refractive Substructure in Resolved Scatter-Broadened Images
• Persistent Asymmetric Structure of Sagittarius A* on Event Horizon Scales
• Imaging an Event Horizon: Mitigation of Scattering Toward Sagittarius A*
• Discovery of Substructure in the Scatter-Broadened Image of Sgr A*
• Extreme Brightness Temperatures and Refractive Substructure in 3C273 with RadioAstron
• The Intrinsic Shape of Sagittarius A* at 3.5-mm Wavelength

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• The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA
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• Quantifying Intrinsic Variability of Sagittarius A* using Closure Phase Measurements of the Event Horizon Telescope
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• The intrinsic structure of Sagittarius A* at 1.3 cm and 7 mm
• Persistent Non-Gaussian Structure in the Image of Sagittarius A* at 86 GHz
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• Direct VLBI Detection of Interstellar Turbulence Imprint on a Quasar: TXS 2005+403