Magnetic fields in our Milky Way Galaxy and nearby galaxies

TL;DR

This paper reviews the methods used to observe magnetic fields in the Milky Way and nearby galaxies, discusses their large-scale structures, and summarizes recent findings on their configurations and roles in galactic processes.

Contribution

It provides a comprehensive overview of observational techniques and recent discoveries regarding galactic magnetic fields, highlighting their structure and influence.

Findings

Magnetic fields in spiral galaxies follow spiral arms and may have reversals.

Galactic halos contain large-scale toroidal and poloidal magnetic fields.

Magnetic fields are preserved during star formation processes.

Abstract

Magnetic fields in our Galaxy and nearby galaxies have been revealed by starlight polarization, polarized emission from dust grains and clouds at millimeter and submillimeter wavelength, the Zeeman effect of spectral lines or maser lines from clouds or clumps, diffuse radio synchrotron emission from relativistic electrons in interstellar magnetic fields, and the Faraday rotation of background radio sources as well as pulsars for our Milky Way. It is easy to get a global structure for magnetic fields in nearby galaxies, while we have observed many details of magnetic fields in our Milky Way, especially by using pulsar rotation measure data. In general, magnetic fields in spiral galaxies probably have a large-scale structure. The fields follow the spiral arms with or without the field direction reversals. In the halo of spiral galaxies magnetic fields exist and probably also have a large-scale structure as toroidal and poloidal fields, but seem to be slightly weaker than those in the disk. In the central region of some galaxies, poloidal fields have been detected as vertical components. Magnetic field directions in galaxies seem to have been preserved during cloud formation and star formation, from large-scale diffuse interstellar medium to molecular clouds and then to the cloud cores in star formation regions or clumps for the maser spots. Magnetic fields in galaxies are passive to dynamics.