CHANG-ES XXII: Coherent Magnetic Fields in the Halos of Spiral Galaxies
| Autor: | Krause, Marita, Irwin, Judith, Schmidt, Philip, Stein, Yelena, Miskolczi, Arpad, Mora-Partiarroyo, Silvia Carolina, Wiegert, Theresa, Beck, Rainer, Stil, Jeroen M., Heald, George, Li, Jiang-Tao, Damas-Segovia, Ancor, Vargas, Carlos J., Rand, Richard J., West, Jennifer, Walterbos, Rene A. M., Dettmar, Ralf-Jürgen, English, Jayanne, Woodfinden, Alex |
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| Rok vydání: | 2020 |
| Předmět: | |
| Zdroj: | A&A 639, A112 (2020) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1051/0004-6361/202037780 |
| Popis: | Context. The magnetic field in spiral galaxies is known to have a large-scale spiral structure along the galactic disk and is observed as X-shaped in the halo of some galaxies. While the disk field can be well explained by dynamo action, the 3-dimensional structure of the halo field and its physical nature is still unclear. Aims. As first steps towards understanding the halo fields, we want to clarify whether the observed X-shaped field is a wide-spread pattern in the halos of spiral galaxies and whether these halo fields are just turbulent fields ordered by compression or shear (anisotropic turbulent fields), or have a large-scale regular structure. Methods. The analysis of the Faraday rotation in the halo is the tool to discern anisotropic turbulent fields from large-scale magnetic fields. This, however, has been challenging until recently because of the faint halo emission in linear polarization. Our sensitive VLA broadband observations C-band and L-band of 35 spiral galaxies seen edge-on (called CHANG-ES) allowed us to perform RM-synthesis in their halos and to analyze the results. We further accomplished a stacking of the observed polarization maps of 28 CHANG-ES galaxies at C-band. Results. Though the stacked edge-on galaxies were of different Hubble types, star formation and interaction activities, the stacked image clearly reveals an X-shaped structure of the apparent magnetic field. We detected a large-scale (coherent) halo field in all 16 galaxies that have extended polarized intensity in their halos. We detected large-scale field reversals in all of their halos. In six galaxies they are along lines about vertical to the galactic midplane (vertical RMTL) with about 2 kpc separation. Only in NGC 3044 and possibly in NGC 3448 we observed vertical giant magnetic ropes (GMRs) similar to those detected recently in NGC 4631. Comment: 40 pages, 29 figures, 5 tables, accepted for publication by A&A. Conclusions in abstract abridged to meet ArXiv size limit |
| Databáze: | arXiv |
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