Magnetic Misalignment of Interstellar Dust Filaments

• Published in: arXiv.org 2023-04
• Main Authors: Cukierman, Ari J, Clark, S E, Halal, George
• Format: Article
• Language: English
• Subjects: Birefringence; Coherence; Cosmic dust; Dust; Filaments; Interstellar matter; Masking; Millimeter waves; Misalignment; Polarization; Robustness
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2208.07382

We present evidence for scale-independent misalignment of interstellar dust filaments and magnetic fields. We estimate the misalignment by comparing millimeter-wave dust-polarization measurements from Planck with filamentary structures identified in neutral-hydrogen (HI) measurements from HI4PI. We find that the misalignment angle displays a scale independence (harmonic coherence) for features larger than the HI4PI beam width (\(16.2'\)). We additionally find a spatial coherence on angular scales of \(\mathcal{O}(1^\circ)\). We present several misalignment estimators formed from the auto- and cross-spectra of dust-polarization and HI-based maps, and we also introduce a map-space estimator. Applied to large regions of the high-Galactic-latitude sky, we find a global misalignment angle of \(\sim 2^\circ\), which is robust to a variety of masking choices. By dividing the sky into small regions, we show that the misalignment angle correlates with the parity-violating \(TB\) cross-spectrum measured in the Planck dust maps. The misalignment paradigm also predicts a dust \(EB\) signal, which is of relevance in the search for cosmic birefringence but as yet undetected; the measurements of \(EB\) are noisier than of \(TB\), and our correlations of \(EB\) with misalignment angle are found to be weaker and less robust to masking choices. We also introduce an HI-based dust-polarization template constructed from the Hessian matrix of the HI intensity, which is found to correlate more strongly than previous templates with Planck dust \(B\) modes.