http://arxiv.org/abs/2205.09069
The observational high-resolution data on the $HI$ gas disk rotation curve of the spiral galaxy $NGC\;6946$ at large radii and the recent increased amount and quality of data on linearly polarized radio continuum emission for this galaxy provide us to re-investigate the role of the regular magnetic fields in the rotation of gas and to test whether disk magnetic fields should be considered as a non-negligible dynamical ingredient. The spiral galaxy $NGC\;6946$ hosts two symmetric bright magnetic spiral arms which have been revealed in the radio polarization map. By taking into account the dynamical effect of the regular magnetic fields caused by two main magnetic arms, on the circular gas rotation and considering two dark matter mass density models, ISO and the universal NFW profile, the shape of the $HI$ gas rotation curve of this galaxy is fitted better, especially in the outer part. The contribution of the regular magnetic fields in the rotation velocity of the gas has a positive value and shows an ascending curve with a typical amplitude of about $ 7 – 14 \; km s^{-1}$ in the outer gaseous disc of the galaxy $NGC\;6946$. We also generate the map of the modeled regular magnetic field strength for the spiral galaxy $NGC\;6946$, which clearly shows two main inner contours with the spiral pattern and the highest magnetic field strength, with the field directed towards the galaxy’s center in both, almost compatible with two inner main magnetic arms detected in the polarized synchrotron intensity map.
M. Khademi and S. Nasiri
Thu, 19 May 22
8/61
Comments: 14 pages, 8 figures
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