When Magnetic Fields Sculpt the Sky: The Riegel-Crutcher cloud in optical polarization

Fuente: arXiv
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Main Authors: Franco, Gabriel A. P., Gomides, Mayara, Li, Zhi-Yun, Santos, Fabio P., Tabatabaei, Farideh S.
Format: Preprint
Published: 2026
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author Franco, Gabriel A. P.
Gomides, Mayara
Li, Zhi-Yun
Santos, Fabio P.
Tabatabaei, Farideh S.
author_facet Franco, Gabriel A. P.
Gomides, Mayara
Li, Zhi-Yun
Santos, Fabio P.
Tabatabaei, Farideh S.
contents Filamentary structures are ubiquitous in the interstellar medium, yet the extent to which magnetic fields influence the morphology of cold atomic gas remains an open question. The nearby Riegel-Crutcher cloud, composed of long and narrow H I filaments observed in self-absorption, provides a critical test case. We present the most extensive optical polarimetric survey of this region to date, comprising more than 90,000 high signal-to-noise stellar polarization measurements combined with Gaia DR3 data. Using stellar polarization, extinction estimates, and archival Na I absorption data, we locate the cloud at a distance of $150 \pm 15$ pc, consistent with that of the Pipe Nebula. The plane-of-sky magnetic field traced by optical starlight polarization closely matches that inferred independently from Planck 353 GHz dust-emission polarization, revealing a coherent large-scale magnetic field across the region. A Rolling Hough Transform analysis shows that the H I filaments are tightly aligned with this field orientation. Together, these results provide strong observational evidence that the structure of the cold neutral medium in the Riegel-Crutcher cloud is closely linked to a highly ordered magnetic field. This level of coherence supports a scenario in which magnetic fields play a dynamically important role in shaping the cloud structure, and suggests that the Riegel-Crutcher cloud is part of a larger magnetized complex influencing gas flows in the solar neighborhood.
format Preprint
id arxiv_https___arxiv_org_abs_2605_08823
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle When Magnetic Fields Sculpt the Sky: The Riegel-Crutcher cloud in optical polarization
Franco, Gabriel A. P.
Gomides, Mayara
Li, Zhi-Yun
Santos, Fabio P.
Tabatabaei, Farideh S.
Astrophysics of Galaxies
Filamentary structures are ubiquitous in the interstellar medium, yet the extent to which magnetic fields influence the morphology of cold atomic gas remains an open question. The nearby Riegel-Crutcher cloud, composed of long and narrow H I filaments observed in self-absorption, provides a critical test case. We present the most extensive optical polarimetric survey of this region to date, comprising more than 90,000 high signal-to-noise stellar polarization measurements combined with Gaia DR3 data. Using stellar polarization, extinction estimates, and archival Na I absorption data, we locate the cloud at a distance of $150 \pm 15$ pc, consistent with that of the Pipe Nebula. The plane-of-sky magnetic field traced by optical starlight polarization closely matches that inferred independently from Planck 353 GHz dust-emission polarization, revealing a coherent large-scale magnetic field across the region. A Rolling Hough Transform analysis shows that the H I filaments are tightly aligned with this field orientation. Together, these results provide strong observational evidence that the structure of the cold neutral medium in the Riegel-Crutcher cloud is closely linked to a highly ordered magnetic field. This level of coherence supports a scenario in which magnetic fields play a dynamically important role in shaping the cloud structure, and suggests that the Riegel-Crutcher cloud is part of a larger magnetized complex influencing gas flows in the solar neighborhood.
title When Magnetic Fields Sculpt the Sky: The Riegel-Crutcher cloud in optical polarization
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2605.08823