Detecting Magnetic Fields in Large-Scale Structure with Radio Polarization

TL;DR

This paper explores detecting magnetic fields in large-scale cosmic structures via polarized synchrotron emission, highlighting observational challenges and proposing cross-correlation techniques to improve detection amid foreground noise.

Contribution

It reports on new observations of potential magnetic field signatures in large-scale structures and discusses innovative methods to overcome foreground contamination.

Findings

Possible detection of Mpc-scale extension of the Coma cluster relic.

Foreground galactic emission significantly complicates detection of extragalactic magnetic fields.

Cross-correlation with optical data offers a promising statistical detection approach.

Abstract

We present our attempts to detect magnetic fields in filamentary large-scale structure (LSS) by observing polarized synchrotron emission emitted by structure formation shocks. Little is known about the strength and order of magnetic fields beyond the largest clusters of galaxies, and synchrotron emission holds enormous promise as a means of probing magnetic fields in these low density regions. We report on observations taken at the Green Bank Telescope which reveal a possible Mpc extension to the Coma cluster relic. We also highlight the major obstacle that diffuse galactic foreground emission poses for any search for large-scale, low surface-brightness extragalactic emission. Finally we explore cross-correlation of diffuse radio emission with optical tracers of LSS as a means to statistically detecting magnetic fields in the presence of this confounding foreground emission.