G. Heald

Source finding in linear polarization for LOFAR, and SKA predecessor surveys, using Faraday moments

The optimal source-finding strategy for linear polarization data is an unsolved problem, with many inhibitive factors imposed by the technically challenging nature of polarization observations. Such an algorithm is essential for Square Kilometre Array (SKA) pathfinder surveys, such as the Multifrequency Snapshot Sky Survey with the LOw Frequency ARray (LOFAR), as data volumes are significant enough to prohibit manual inspection. We present a new strategy of Faraday Moments for source-finding in linear polarization with LOFAR, using the moments of the frequency-dependent full-Stokes data (i.e. the mean, standard deviation, skewness, and excess kurtosis). Through simulations of the sky, we find that moments can identify polarized sources with a high completeness: 98.5 per cent at a signal to noise of 5. While the method has low reliability, rotation measure (RM) synthesis can be applied per candidate source to filter out instrumental and spurious detections. This combined strategy will result in a complete and reliable catalogue of polarized sources that includes the full sensitivity of the observational bandwidth. We find that the technique can reduce the number of pixels on which RM Synthesis needs to be performed by a factor of ≈1 × 10 5 for source distributions anticipated with modern radio telescopes. Through tests on LOFAR data, we find that the technique works effectively in the presence of diffuse emission. Extensions of this method are directly applicable to other upcoming radio surveys such as the POlarization Sky Survey of the Universes Magnetism with the Australia Square Kilometre Array Pathfinder, and the SKA itself.

Broadband Radio Polarimetry of Fornax A. I. Depolarized Patches Generated by Advected Thermal Material from NGC 1316

We present observations and analysis of the polarized radio emission from the nearby radio galaxy Fornax A over 1.28--3.1 GHz, using data from the Australia Telescope Compact Array (ATCA). In this, the first of two associated papers, we use modern broadband polarimetric techniques to examine the nature and origin of conspicuous low-polarization (low-

A GBT Survey of the HALOGAS Galaxies and Their Environments. I. Revealing the Full Extent of H i around NGC 891, NGC 925, NGC 4414, and NGC 4565

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Reliable detection and characterization of low-frequency polarized sources in the LOFAR M51 field

) patches in the lobes. We resolve the low-

Investigation of the cosmic ray population and magnetic field strength in the halo of NGC 891

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Calibrating the relation of low-frequency radio continuum to star formation rate at 1 kpc scale with LOFAR

patches, and find that their low fractional polarization is associated with complicated frequency-dependent interference in the polarized signal generated by Faraday effects along the line of sight. The low-

The intergalactic magnetic field probed by a giant radio galaxy

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Magnetic fields on a wide range of scales in star-forming galaxies

patches are spatially correlated with interfaces in the magnetic structure of the lobe, across which the line-of-sight-projected magnetic field changes direction. Spatial correlations with the sky-projected magnetic field orientation and structure in total intensity are also identified and discussed. We argue that the low-

The POlarised GLEAM Survey (POGS) I: First Results from a Low-Frequency Radio Linear Polarisation Survey of the Southern Sky

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Combining Faraday Tomography and Wavelet Analysis

patches, along with associated reversals in the line-of-sight magnetic field and other related phenomena, are best explained by the presence of