Identify the physical origin of the optical polarization

Establish whether the linear polarization detected in the optical emission and continuum of the NGC 1275 filamentary nebula is produced primarily by dust scattering, magnetic-field-related processes, superposition of physically distinct filamentary structures, or another mechanism, through more extensive spectropolarimetric observations.

Background

The ESPaDOnS observations reveal low-level linear polarization and velocity-dependent features in the Stokes parameters of Region 1. Dust scattering is considered the most likely interpretation, but magnetic fields and the superposition of multiple emitting structures remain possible alternatives. Because the available polarimetric data cover only limited regions of the nebula, the observations do not establish a decisive physical explanation for the polarization.

References

Nevertheless, the lack of polarimetric observations across more extended regions of the filaments surrounding NGC 1275 and other BCGs prevents us from drawing a decisive conclusion on a tentative source of polarization.

— High Resolution Spectro-Polarimetric Observations of the Optical Filaments surrounding NGC 1275 with ESPaDOnS  (2610.13719 - Vigneron et al., 9 Oct 2026) in Section 3.3.2, “Potential Sources of Polarization”