Speaker
Description
Quantifying the number density and physical characteristics of extragalactic polarized sources is crucial for future Faraday Rotation Measure studies to probe Galactic and intergalactic magnetic fields. We present a polarimetric study at 114.9–177.4 MHz of the ELAIS-N1 LOFAR deep field. An area of 25 deg^2 was imaged at 6”-resolution in the Stokes Q,U parameters. A 1σ sensitivity of 19 μJy/beam was reached in the central region by aligning the polarization angles and stacking datasets from 19 eight-hour-long epochs taken in two different observing cycles.
The depolarization level of sources known to be polarized at 1.4 GHz was quantified. Twenty-five polarized sources were detected above 8σ, five of which had not been detected in polarization at any other radio frequencies before. Seven additional polarized components were found by lowering the threshold to 6σ at positions corresponding to sources known to be polarized at 1.4 GHz. In two radio galaxies, polarization was detected from both radio lobes, so the final number of associated radio continuum sources is 31. The detected sources are weakly polarized, with a median degree of polarization of 1.75%. The sources previously detected in polarization at 1.4 GHz are significantly depolarized at 150 MHz. The catalog is used to derive the polarized source counts at 150 MHz. This is the deepest and highest-resolution polarization study at 150 MHz to date. A full characterization of the sources and an analysis of the catalog will be presented.
