October 5, 2025Open Access

Faraday Depolarization Study of a Radio Galaxy Using LOFAR Two-metre Sky Survey: Data Release 2

Key Points

Depolarization analysis reveals turbulence effects in a low-frequency radio galaxy's magneto-ionic medium.
The study utilized LOFAR's polarimetric data, yielding a rotation measure of -47 rad/m^2 and fractional polarization at 3.0%.
Bayesian fitting of five depolarization models identified a three-component model as the best, suggesting intricate Faraday effects.
Findings indicate the importance of multi-component modeling for understanding depolarization in radio galaxies.

Abstract

We present a detailed depolarization analysis of a radio galaxy ILTJ012215. 21+254334. 8, utilizing polarimetric data from the LOFAR Two-metre Sky Survey (LoTSS) Data Release 2 (DR2) catalogue. The selected source exhibits a rotation measure (RM) of ~ - 47 rad/m² and a projected linear size of 335 kpc at a redshift z ~ 0. 05. Depolarization model fitting was performed on LOFAR High Band Antenna data (120 - 168 MHz), with fractional polarization detected at 3. 0%. Five depolarization models were tested, and Bayesian qu-fitting revealed that the three-component model (1T+2ED) best describes the data, with a reduced chi-squared value of 2. 12 and a logarithmic Bayesian evidence of 1384. 82. This model includes a Faraday-thin component at RM ~ - 0. 3 rad/m² (instrumental leakage) and two external Faraday dispersion astrophysical emission at RM ~ - 47 rad/m². The results demonstrate that depolarization in low-frequency radio galaxies requires multi-component modelling and is driven by turbulence and inhomogeneity in the magneto-ionic medium. Our findings highlight the potential of LOFAR polarization studies for probing galactic and intergalactic magnetic fields with high precision.

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