The SIMPLIFI Survey: Polarization of Dense Filaments with SOFIA III. Relative orientations of antenna temperature gradients with the magnetic field in the DR21 molecular cloud
Abstract
We investigate magnetohydrodynamic (MHD) turbulence in the DR21 molecular cloud using far infrared polarimetry from SOFIA HAWC+ and molecular spectroscopy from the Nobeyama 45~m telescope. The Velocity Channel Gradient (VChG) method is applied to thin velocity slices of the 12CO and 13CO J=1-0 emission to determine the antenna temperature gradients and their orientations in the plane of the sky. The relative orientations of the gradients with respect to the magnetic field position angles enable an evaluation of theoretically predicted alignment of elongated, turbulent eddies for Alfvenic, fast and slow modes and self-gravity. The projected Rayleigh statistic is calculated for both the full cloud and 6 regions of interest to provide a quantitative assessment of these alignments. Our analysis finds mostly parallel alignment of the gradient direction and the local magnetic field orientation in the Main Ridge of DR21 that comprises most of the cloud mass. While parallel alignment can result from fast MHD modes or cloud collapse, previous studies show spectroscopic evidence for the large scale collapse of the DR21 cloud, which supports self-gravity as the primary cause of the observed parallel alignment. One of the six sub-filaments that are connected to the Main Ridge exhibits mostly perpendicular alignment of the position angles of the gradient and magnetic field. These perpendicular relative orientations may be a product of Alfven and slow modes in a magnetized, sub-Alfvenic medium even if the sub-filament is accreting onto the Main Ridge.
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BibTeX
@misc{heyer2026simplifi,
title = {{The SIMPLIFI Survey: Polarization of Dense Filaments with SOFIA III. Relative orientations of antenna temperature gradients with the magnetic field in the DR21 molecular cloud}},
author = {Mark Heyer and Thushara G. S. Pillai and Jens Kauffmann and Juan D. Soler and Daniel Seifried and Laura M. Fissel and Gabriel A. P. Franco and Paul F. Goldsmith and Philip C. Myers and Helmut Wiesemeyer and Karl M. Menten},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.27090},
eprint = {2610.27090},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.27090},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The SIMPLIFI Survey: Polarization of Dense Filaments with SOFIA III. Relative orientations of antenna temperature gradients with the magnetic field in the DR21 molecular cloud
AU - Mark Heyer
AU - Thushara G. S. Pillai
AU - Jens Kauffmann
AU - Juan D. Soler
AU - Daniel Seifried
AU - Laura M. Fissel
AU - Gabriel A. P. Franco
AU - Paul F. Goldsmith
AU - Philip C. Myers
AU - Helmut Wiesemeyer
AU - Karl M. Menten
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.27090
UR - https://arxiv.org/abs/2610.27090
AB - We investigate magnetohydrodynamic (MHD) turbulence in the DR21 molecular cloud using far infrared polarimetry from SOFIA HAWC+ and molecular spectroscopy from the Nobeyama 45~m telescope. The Velocity Channel Gradient (VChG) method is applied to thin velocity slices of the 12CO and 13CO J=1-0 emission to determine the antenna temperature gradients and their orientations in the plane of the sky. The relative orientations of the gradients with respect to the magnetic field position angles enable an evaluation of theoretically predicted alignment of elongated, turbulent eddies for Alfvenic, fast and slow modes and self-gravity. The projected Rayleigh statistic is calculated for both the full cloud and 6 regions of interest to provide a quantitative assessment of these alignments. Our analysis finds mostly parallel alignment of the gradient direction and the local magnetic field orientation in the Main Ridge of DR21 that comprises most of the cloud mass. While parallel alignment can result from fast MHD modes or cloud collapse, previous studies show spectroscopic evidence for the large scale collapse of the DR21 cloud, which supports self-gravity as the primary cause of the observed parallel alignment. One of the six sub-filaments that are connected to the Main Ridge exhibits mostly perpendicular alignment of the position angles of the gradient and magnetic field. These perpendicular relative orientations may be a product of Alfven and slow modes in a magnetized, sub-Alfvenic medium even if the sub-filament is accreting onto the Main Ridge.
ER -