Letter to the Editor

Spectropolarimetry of NGC 1275 reveals a narrow-line radio galaxy with polarization parallel to its radio jet axis

¹ Université de Strasbourg, CNRS, Observatoire Astronomique de Strasbourg, UMR 7550, 11 Rue de l’Université, 67000 Strasbourg, France
² Nordic Optical Telescope, Apartado 474, E-38700 Santa Cruz de La Palma, Santa Cruz de Tenerife, Spain
³ Department of Physics and Astronomy, Aarhus University, Munkegade 120, DK-8000 Aarhus C, Denmark
⁴ Institute of Astrophysics, Foundation for Research and Technology – Hellas, Voutes, 7110 Heraklion, Greece
⁵ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
⁶ Department of Physics and Astronomy, University of Turku, Vesilinnantie 5, Turku FI-20014, Finland
⁷ Institut d’Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 19c, B5c, 4000 Liège, Belgium
⁸ Finnish Centre for Astronomy with ESO (FINCA), University of Turku, FI-20014 Turku, Finland
⁹ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland

^⋆ Corresponding author: frederic.marin@astro.unistra.fr

Received: 29 June 2025
Accepted: 7 October 2025

Abstract

Concomitant with the Imaging X-ray Polarimetry Explorer (IXPE) observation of the Perseus cluster, we obtained optical spectropolarimetry of its central active galactic nucleus, NGC 1275, using the Alhambra Faint Object Spectrograph and Camera (ALFOSC) on the Nordic Optical Telescope (NOT). While the total-light spectrum confirms its edge-on, core obscured (type-2) classification, the polarized spectrum shows a polarization angle aligned with the arcsecond radio jet axis – an exceptional behavior for type-2 objects. Our polarization analysis also reveals wavelength-dependent linear polarization at a level of 2−3% in the continuum, likely arising from a combination of variable synchrotron emission and scattering; this supports a narrow-line radio galaxy classification with characteristics of a jet-dominated source.