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Paper: The First Deep WSRT 150 MHz Full Polarization Observations
Volume: 407, The Low-Frequency Radio Universe
Page: 3
Authors: de Bruyn, A.G.; Bernardi, G.; the LOFAR EoR-team
Abstract: We present the first deep total intensity and full polarization observations with the WSRT at frequencies from 116−162 MHz. Under stable ionospheric conditions we can image regions as large as 20° diameter with a single direction independent selfcalibration without detectable non-isoplanaticity effects. Deep imaging at low frequencies, however, requires removal of the brightest northern hemisphere radio sources (the A-team). A noise level of about 3 mJy, limited by classical confusion, can be achieved in Stokes I with the WSRT within a single 12 h synthesis in this frequency band. Thermal noise levels of 0.5 mJy have been reached in 6×12 h syntheses. These images have dynamic range in excess of about 20,000:1. In one such deep synthesis of the FAN region we have detected strong linear polarization over a range of Faraday depths from −6 to +2 rad m−2. The properties of a 3° diameter ring-like structure, first studied in detail by Haverkorn, Katgert, & de Bruyn (2003), suggest that we are dealing with a spherical ‘Faraday bubble’, a region with strongly enhanced Faraday rotation. We have also detected, for the first time, structure on a scale of about 10′ in the diffuse Galactic synchrotron foreground.
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