A Comparison of Multiphase Magnetic Field Tracers in a High Galactic Latitude Region of the Filamentary Interstellar Medium

A Comparison of Multiphase Magnetic Field Tracers in a High Galactic Latitude Region of the Filamentary Interstellar Medium

TITLE
A Comparison of Multiphase Magnetic Field Tracers in a High Galactic Latitude Region of the Filamentary Interstellar Medium

INVESTIGATORS
J. L. Campbell, S. E. Clark, B. M. Gaensler, A. Marchal, C. L. Van Eck, A. A. Deshpande, S. J. George, S. J. Gibson, R. Ricci, J. M. Stil, and A. R. Taylor

ABSTRACT
Understanding how the Galactic magnetic field threads the multiphase interstellar medium (ISM) remains a considerable challenge, as different magnetic field tracers probe dissimilar phases and field components. We search for evidence of a common magnetic field shared between the ionized and neutral ISM by comparing 1.4 GHz radio continuum polarization and H i line emission from the Galactic Arecibo L-Band Feed Array Continuum Transit Survey (GALFACTS) and Galactic Arecibo L-Band Feed Array H i (GALFA-H i) survey, respectively. We compute the polarization gradient of the continuum emission and search for associations with diffuse/translucent H i structures. The polarization gradient is sensitive to changes in the integrated product of the thermal electron density and line-of-sight field strength (B∥) in warm ionized gas, while narrow H i structures highlight the plane-of-sky field orientation in cold neutral gas. We identified one region in the high Galactic latitude Arecibo sky, G216+26 centered on (ℓ, b) ∼ (216°, +26°), containing filaments in the polarization gradient that are aligned with narrow H i structures roughly parallel to the Galactic plane. We present a comparison of multiphase observations and magnetic field tracers of this region, demonstrating that the warm ionized and cold neutral media are connected likely via a common magnetic field. We quantify the physical properties of a polarization gradient filament associated with Hα emission, measuring a line-of-sight field strength B∥ = 6 ± 4 μG and a plasma beta $\beta ={2.1}_{-2.1}^{+3.1}$. We discuss the lack of widespread multiphase magnetic field alignments and consider whether this region is associated with a short-timescale or physically rare phenomenon. This work highlights the utility of multitracer analyses for understanding the magnetized ISM.
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Keywords: Interstellar Medium, publication. GALFACTS