The Kinematic Structure of Magnetically Aligned HI Filaments

Abstract

We characterize the kinematic and magnetic properties of HI filaments located in a high Galactic latitude region ($165^{\circ }<\alpha <195^{\circ }$ and $12^{\circ }<\delta <24^{\circ }$). We extract three-dimensional filamentary structures using \texttt{fil3d} from the Galactic Arecibo L-Band Feed Array HI (GALFA-HI) survey 21-cm emission data. Our algorithm identifies coherent emission structures in neighboring velocity channels. Based on the mean velocity, we identify a population of local and intermediate velocity cloud (IVC) filaments. We find the orientations of the local (but not the IVC) HI filaments are aligned with the magnetic field orientations inferred from Planck 353 GHz polarized dust emission. We analyze position-velocity diagrams of the velocity-coherent filaments, and find that only 15 percent of filaments demonstrate significant major-axis velocity gradients with a median magnitude of 0.5 km s${}^{-1}$ pc${}^{-1}$, assuming a fiducial filament distance of 100 pc. We conclude that the typical diffuse HI filament does not exhibit a simple velocity gradient. The reported filament properties constrain future theoretical models of filament formation.

15 pages, 16 figures

References in corpus (26)

• HI4PI: A full-sky HI survey based on EBHIS and GASS
• Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
• Updated Gaia-2MASS 3D maps of Galactic interstellar dust
• CARMA Large Area Star Formation Survey: Observational Analysis of Filaments in the Serpens South Molecular Cloud
• Mapping the Magnetic Interstellar Medium in Three Dimensions Over the Full Sky with Neutral Hydrogen
• Magnetically Dominated Strands of Cold Hydrogen in the Riegel-Crutcher Cloud
• An application of an optimal statistic for characterising relative orientations
• Ubiquitous velocity fluctuations throughout the molecular interstellar medium
• The Physical Nature of Neutral Hydrogen Intensity Structure
• The magnetic field and dust filaments in the Polaris Flare
• Formation of HI Clouds in Shock-compressed Interstellar Medium: Physical Origin of Angular Correlation Between Filamentary Structure and Magnetic Field
• Evidence for Line-of-Sight Frequency Decorrelation of Polarized Dust Emission in $Planck$ Data
• Self-gravitating Filament Formation from Shocked Flows: Velocity Gradients across Filaments
• Large-scale periodic velocity oscillation in the filamentary cloud G350.54+0.69
• Initial Conditions for Star Formation: A Physical Description of the Filamentary ISM
• Striations in molecular clouds: Streamers or MHD waves?
• Extracting the cold neutral medium from HI emission with deep learning: Implications for Galactic foregrounds at high latitude
• Gravity Versus Magnetic Fields in Forming Molecular Clouds
• Starlight-polarization-based tomography of the magnetized interstellar medium: PASIPHAE's line-of-sight inversion method
• The relative orientation between the magnetic field and gradients of surface brightness within thin velocity slices of 12CO and 13CO emission from the Taurus molecular cloud
• Similar complex kinematics within two massive, filamentary infrared dark clouds
• The Magnetic Field in the Milky Way Filamentary Bone G47
• Probing the massive star forming environment - a multiwavelength investigation of the filamentary IRDC G333.73+0.37
• Gaussian decomposition of HI surveys. IV. Galactic intermediate- and high-velocity clouds
• Dust-to-Gas Ratios of the GALFA-HI Compact Cloud Catalog
• The physical and the geometrical properties of simulated cold HI structures

Cited by in corpus (2)

• On the evolution of the observed Mass-to-Length relationship for star-forming filaments
• Properties of 3D HI Filaments in the Smith High Velocity Cloud