SOFIA/HAWC+ Far-Infrared Polarimetric Large-Area CMZ Exploration Survey. IV. Relative Magnetic Field Orientation Throughout the CMZ

TL;DR

This study uses polarimetric data to analyze the magnetic field orientations in the Galactic Center, revealing a pervasive vertical magnetic field component and its relation to molecular clouds and non-thermal filaments.

Contribution

It introduces statistical analysis of magnetic field orientations in the CMZ, showing a widespread vertical component and its implications for magnetic field strength and structure.

Findings

Magnetic fields in the CMZ range from parallel to perpendicular orientations.

A preferred perpendicular orientation exists between dust polarimetry and NTFs.

Estimated upper limit for vertical magnetic field strength is 4 mG.

Abstract

The nature of the magnetic field structure throughout the Galactic Center (GC) has long been of interest. The recent Far-InfraREd Polarimetric Large-Area CMZ Exploration (FIREPLACE) Survey reveals preliminary connections between the seemingly distinct vertical and horizontal magnetic field distributions previously observed in the GC. We use the statistical techniques of the Histogram of Relative Orientation (HRO) and the Projected Rayleigh Statistic (PRS) to assess whether the CMZ magnetic field preferentially aligns with the structure of the CMZ molecular clouds or the morphology of the non-thermal emission of the GC NTF population. We find that there is a range of magnetic field orientations throughout the population of CMZ molecular clouds, ranging from parallel to perpendicular orientation. We posit these orientations depend on the prevalence of gravitational shear in the GC in contrast with what is observed in Galactic Disk star-forming regions. We also compare the magnetic field orientation from dust polarimetry with individual prominent NTFs, finding a preferred perpendicular relative orientation. This perpendicular orientation indicates that the vertical field component found in the FIREPLACE observations is not spatially confined to the NTFs, providing evidence for a more pervasive vertical field in the GC. From dynamical arguments, we estimate an upper limit on the magnetic field strength for this vertical field, finding B less than or equal to 4 mG. A field close to this upper limit would indicate that the NTFs are not local enhancements of a weaker background field and that the locations of the NTFs depend on proximity to sites of cosmic ray production.