| Author(s) and Co-Author(s) with Affiliation: Salmoli Ghosh(National Centre for Radio Astrophysics (NCRA) - Tata Institute of Fundamental Research (TIFR), Pune, 411007, India), Preeti Kharb(National Centre for Radio Astrophysics (NCRA) - Tata Institute of Fundamental Research (TIFR), Pune, 411007, India), Elisa Costantini(Space Research Organisation Netherlands (SRON), Niels Bohrweg 4, 2333CA, Leiden, The Netherlands), Jack F. Gallimore(Department of Physics and Astronomy, Bucknell University, Lewisburg, PA 17837, USA), David Williams Baldwin(Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, Oxford Road, Manchester M13 9PY Lancashire, UK), Missagh Mehdipour(Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI, 48109, USA) |
| Abstract: Radio-quiet (RQ) active galactic nuclei (AGN) dominate the AGN population. Their radio emission is typically faint, compact, and morphologically complex compared to their radio-loud (RL) counterparts that exhibit large relativistic jets. "Feedback" from RQ AGN is generally attributed to radiatively driven outflows. The role of magnetic (B-) fields in launching and shaping these outflows remains poorly understood. We present new high-resolution radio polarimetric observations with the Very Large Array of the well-known Seyfert galaxy NGC 4151, which hosts radio emission on the 1-kpc scale. Our polarimetric imaging of NGC 4151 reveals a stratified B-field structure in an RQ AGN for the first time. The jet `spine' shows predominantly perpendicular B-fields consistent with shocks, while the jet `sheath' exhibits aligned B-fields indicative of shearing due to jet-medium interaction. This structure suggests the presence of a transverse velocity gradient and/or compositional stratification within the radio outflow. We detect a clear transverse rotation-measure (RM) gradient across the outer layer of the outflow, which we interpret as part of a larger, wide-angle biconical `wind' with perpendicular B-field. We further find that these AGN-driven magnetohydrodynamic winds are energetically modest (0.01 - 0.5% of the bolometric luminosity) compared to star-formation-driven galactic winds, limiting their ability to drive galaxy-scale feedback. However, their substantial mass content (10^3 M_sun) implies a significant impact on local circumnuclear environments. Overall, our results demonstrate that magnetic fields play an active role in launching and structuring outflows in RQ AGN. |
