Faraday Complexity and Depolarisation in a High-Rotation-Measure Radio Galaxy from the Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) DR2

Faraday Complexity and Depolarisation in a High-Rotation-Measure Radio Galaxy from the Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) DR2
Debajyoti Mondal, Abhik Ghosh
arXiv:2606.07919v1 Announce Type: new
Abstract: We present a broadband spectro-polarimetric analysis of the extragalactic radio source texttt{RACS_0900-28_7036} using SPICE-RACS DR2 observations with the Australian Square Kilometre Array Pathfinder (ASKAP). The source was selected for its large rotation measure (${rm RM}=345.7pm0.2~{rm rad~m^{-2}}$), substantial excess relative to the local foreground ($Delta {rm RM}approx171~{rm rad~m^{-2}}$), and strong evidence of Faraday complexity ($sigma_{rm add}/deltasigma_{rm add}approx8.6$). Observations span 803–1083~MHz in 36 spectral channels, enabling detailed characterization of Faraday rotation and wavelength-dependent depolarization. One-dimensional $q$-$u$ fitting and Bayesian model selection identify a multi-component model comprising one Burn-slab component and two external Faraday dispersion components (1 Slab + 2 EFD) as the preferred description. The dominant astrophysical component exhibits ${rm RM}approx345.5~{rm rad~m^{-2}}$ with modest Faraday dispersion ($sigma_{rm RM}approx3~{rm rad~m^{-2}}$), while a secondary broader component at ${rm RM}approx131.5~{rm rad~m^{-2}}$ shows strong depolarization ($sigma_{rm RM}approx19.5~{rm rad~m^{-2}}$). The fractional polarization spectrum and $q$–$u$ plane evolution further confirm multiple Faraday-active regions along the line of sight. These results demonstrate that ASKAP broadband spectropolarimetry can resolve complex Faraday structures and probe turbulent magnetized environments, providing a framework for systematic depolarization studies across the full SPICE-RACS catalog and enabling statistical investigations of Faraday complexity in diverse extragalactic radio sources.arXiv:2606.07919v1 Announce Type: new
Abstract: We present a broadband spectro-polarimetric analysis of the extragalactic radio source texttt{RACS_0900-28_7036} using SPICE-RACS DR2 observations with the Australian Square Kilometre Array Pathfinder (ASKAP). The source was selected for its large rotation measure (${rm RM}=345.7pm0.2~{rm rad~m^{-2}}$), substantial excess relative to the local foreground ($Delta {rm RM}approx171~{rm rad~m^{-2}}$), and strong evidence of Faraday complexity ($sigma_{rm add}/deltasigma_{rm add}approx8.6$). Observations span 803–1083~MHz in 36 spectral channels, enabling detailed characterization of Faraday rotation and wavelength-dependent depolarization. One-dimensional $q$-$u$ fitting and Bayesian model selection identify a multi-component model comprising one Burn-slab component and two external Faraday dispersion components (1 Slab + 2 EFD) as the preferred description. The dominant astrophysical component exhibits ${rm RM}approx345.5~{rm rad~m^{-2}}$ with modest Faraday dispersion ($sigma_{rm RM}approx3~{rm rad~m^{-2}}$), while a secondary broader component at ${rm RM}approx131.5~{rm rad~m^{-2}}$ shows strong depolarization ($sigma_{rm RM}approx19.5~{rm rad~m^{-2}}$). The fractional polarization spectrum and $q$–$u$ plane evolution further confirm multiple Faraday-active regions along the line of sight. These results demonstrate that ASKAP broadband spectropolarimetry can resolve complex Faraday structures and probe turbulent magnetized environments, providing a framework for systematic depolarization studies across the full SPICE-RACS catalog and enabling statistical investigations of Faraday complexity in diverse extragalactic radio sources.