2025AJ....170..265B

Despite the pervasive nature of interstellar dust and its impact on nearly all observations, most dust corrections employ line-of-sight averages over large angular scales. This neglects real variations on small angular and distance scales from discrete components of the interstellar medium (ISM). We use V-band polarimetry, public dust maps, and Gaia Data Release 3 distances of 25 stars along a 50' radius sight line toward the O9.5IV star ζ Ophiuchi (d ≈ 182 pc) to examine both dust and magnetic structures over the range d = 36-1176 pc and angular scales of <1°. Polarization and reddening data indicate two discrete dust populations having different magnetic field orientations along the sight line, one at d ≃ 86-127 pc and another at d ≃ 252-287 pc. After removal of the foreground, the more distant component exhibits alignment in polarization angle with 12 μm polycyclic aromatic hydrocarbon (PAH) striations seen in the field. This more distant dust population exhibits evidence of extreme starlight polarization efficiency, with an average of 14.1% mag^–1, greater than the canonical Serkowski limit of 9% mag^–1. The spatial coincidence with the PAH striations indicates the PAH-emitting grains and those responsible for the high polarization efficiency may be components of the same dust population. We find no evidence that ζ Oph's radiative influence affects the polarizing or reddening properties of the surrounding dust. Our study demonstrates that accurate distance-based foreground subtraction is vital to properly understanding superimposed dust and the magnetic field components in the ISM.