Magnetic contribution to outer-disk rotation in the spiral galaxy NGC 5055
Abstract
We test whether fields of galactic strength enhance NGC~5055's outer gas rotation. Finite analytic disk decompositions yield consistent rotation--density pairs and a blended gravitational reference approximately retaining inner rotation while its density approaches the measured outer HI+He profile. This reference is modelled, not an independently measured stellar curve. Its difference from fitted gas rotation gives the required purely toroidal field for circular, axisymmetric midplane motion. The prescribed field strength at the reconstruction's inner radial boundary is Bs. With hydrogen inertia, no pressure and Bs=0, constant exponential heights of 1~kpc and 250~pc give approximate peaks of 5.47 and 10.95~μG near 34.9~kpc; 0.2~kpc gives approximately 12.24~μG. Extrapolated flaring exponential and Gaussian profiles peak at approximately 5.25 and 5.96~μG, respectively, near 33.8~kpc. For Bs=8~μG, their fields decline overall to approximately 5.73 and 6.30~μG near 39.7~kpc. These estimates are conditional on the gravitational reference, vertical structure and prescribed boundary field. Comparison with total radio fields supports the field scale without establishing a magnetic origin for the rotation excess.
Versions
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BibTeX
@misc{wozniak2026magnetic,
title = {{Magnetic contribution to outer-disk rotation in the spiral galaxy NGC 5055}},
author = {Natalia Woźniak and Joanna Jałocha and Łukasz Bratek and Szymon Sikora},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.07332},
eprint = {2611.07332},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.07332},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Magnetic contribution to outer-disk rotation in the spiral galaxy NGC 5055
AU - Natalia Woźniak
AU - Joanna Jałocha
AU - Łukasz Bratek
AU - Szymon Sikora
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2611.07332
UR - https://arxiv.org/abs/2611.07332
AB - We test whether fields of galactic strength enhance NGC~5055's outer gas rotation. Finite analytic disk decompositions yield consistent rotation--density pairs and a blended gravitational reference approximately retaining inner rotation while its density approaches the measured outer HI+He profile. This reference is modelled, not an independently measured stellar curve. Its difference from fitted gas rotation gives the required purely toroidal field for circular, axisymmetric midplane motion. The prescribed field strength at the reconstruction's inner radial boundary is B_s. With hydrogen inertia, no pressure and B_s=0, constant exponential heights of 1~kpc and 250~pc give approximate peaks of 5.47 and 10.95~μG near 34.9~kpc; 0.2~kpc gives approximately 12.24~μG. Extrapolated flaring exponential and Gaussian profiles peak at approximately 5.25 and 5.96~μG, respectively, near 33.8~kpc. For B_s=8~μG, their fields decline overall to approximately 5.73 and 6.30~μG near 39.7~kpc. These estimates are conditional on the gravitational reference, vertical structure and prescribed boundary field. Comparison with total radio fields supports the field scale without establishing a magnetic origin for the rotation excess.
ER -