First uGMRT Constraints on Rotation Measure in the Radio-Quiet Seyfert Galaxy NGC 4235
Abstract
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±1.7 mJy at 1.3 GHz, 27.7±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 {∼200 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 ∼3×10−2 cm−3 for a characteristic perturbation scale of ∼0.3 parsec within an assumed magnetized region of size ∼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.
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BibTeX
@misc{ghosh2026first,
title = {{First uGMRT Constraints on Rotation Measure in the Radio-Quiet Seyfert Galaxy NGC 4235}},
author = {Salmoli Ghosh and Preeti Kharb and Janhavi Baghel},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.10726},
eprint = {2610.10726},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.10726},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - First uGMRT Constraints on Rotation Measure in the Radio-Quiet Seyfert Galaxy NGC 4235
AU - Salmoli Ghosh
AU - Preeti Kharb
AU - Janhavi Baghel
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2610.10726
UR - https://arxiv.org/abs/2610.10726
AB - 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±1.7 mJy at 1.3 GHz, 27.7±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 {∼200 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 ∼3×10^−2 cm^−3 for a characteristic perturbation scale of ∼0.3 parsec within an assumed magnetized region of size ∼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.
ER -