Simulation of the Polarized Sky at 1.4 GHz

TL;DR

This paper simulates the polarized sky at 1.4 GHz using semi-empirical models and polarization data, predicting source counts and informing future radio telescope observations.

Contribution

It introduces a polarization model based on AGN luminosity dependence and star-forming galaxy contributions, improving predictions of polarized source counts at microJy levels.

Findings

Polarized source counts fit down to ~1 mJy for AGN.

Star-forming galaxies dominate below 1 mJy in total intensity.

Predictions for next-generation radio telescopes' polarized source detections.

Abstract

We present results from simulations of the extragalactic polarized sky at 1.4 GHz. As the basis for our polarization models, we use a semi-empirical simulation of the extragalactic total intensity (Stokes I) continuum sky developed at the University of Oxford (http://scubed.physics.ox.ac.uk) under the European SKA Design Study (SKADS) initiative, and polarization distributions derived from analysis of polarization observations. By considering a luminosity dependence for the polarization of AGN, we are able to fit the 1.4 GHz polarized source counts derived from the NVSS and the DRAO ELAIS N1 deep field survey down to approximately 1 mJy. This trend is confirmed by analysis of the polarization of a complete sample of bright AGN. We are unable to fit the additional flattening of the polarized source counts from the deepest observations of the ELAIS N1 survey, which go down to ~0.5 mJy. Below 1 mJy in Stokes I at 1.4 GHz, starforming galaxies become an increasingly important fraction of all radio sources. We use a spiral galaxy integrated polarization model to make realistic predictions of the number of polarized sources at microJy levels in polarized flux density and hence, realistic predictions of what the next generation radio telescopes such as ASKAP, other SKA pathfinders and the SKA itself will see.