Probing galaxy halos using background polarized radio sources

Abstract

Linearly polarized radio emission from synchrotron sources undergoes Faraday rotation when passing through a magneto-ionized medium. This might be used to search for evidence of ionized halos around galaxies, using polarized radio sources as a probe. In this thesis I analyze the polarization properties of background radio sources from the Taylor et al. (2009) catalog based on observations with the Very Large Array, and correlate these to the angular separation between the radio sources and foreground galaxies. I find a decrease in the amount of polarized radio sources near the galaxies, interpreting this as radio sources being depolarized by galaxy halos. I also investigate searching for polarization in data from the Low Frequency Array (LOFAR). To this end, I reanalyze the observation of the M51 field by Mulcahy et al. (2014), focusing on the background radio sources in the field. I find several polarized sources, many of which contain complex polarization.