First uGMRT Constraints on Rotation Measure in the Radio-Quiet Seyfert Galaxy NGC 4235

We present a multi-frequency polarimetric study of the radio-quiet Seyfert galaxy NGC 4235 using the upgraded Giant Metrewave Radio Telescope (uGMRT), aimed at constraining the Faraday rotation properties of its kpc-scale radio emission. This marks the first-ever analysis of polarization across two frequency bands of the uGMRT and the first constraints on rotation measure (RM) at lower frequencies for a weak radio source (17.1$\pm$1.7 mJy at 1.3 GHz, 27.7$\pm$2.8 mJy at 663 MHz). We detect linearly polarized radio emission associated with the core' and the extended lobes of NGC 4235. Broadband polarimetric analysis yields an RM value of {$\sim200$ rad m$^{-2}$} in the core’, indicating Faraday rotation by magnetized plasma external to the synchrotron-emitting regions. Using these RM constraints, we estimate an average electron density of the Faraday-rotating medium of $\sim$3$\times {10}^{-2}$ cm${}^{-3}$ for a characteristic perturbation scale of $\sim$0.3 parsec within an assumed magnetized region of size $\sim$1.3 kpc, consistent with a diffuse magnetized sheath or AGN-driven wind. These results extend classical Faraday rotation diagnostics to the low-power, radio-quiet AGN regime and demonstrate the potential of uGMRT broadband polarimetry for probing magnetized environments in and around such AGN.