Anisotropies in the HI gas distribution toward 3C196

Abstract

The local Galactic HI gas was found to contain cold neutral medium (CNM) filaments that are aligned with polarized dust emission. These filaments appear to be dominated by the magnetic field and in this case turbulence is expected to show distinct anisotropies. We use the Galactic Effelsberg--Bonn HI Survey (EBHIS) to derive 2D turbulence spectra for the HI distribution in direction to 3C196 and two more comparison fields. Prior to Fourier transform we apply a rotational symmetric 50% Tukey window to apodize the data. We derive average as well as position angle dependent power spectra. Anisotropies in the power distribution are defined as the ratio of the spectral power in orthogonal directions. We find strong anisotropies. For a narrow range in position angle, in direction perpendicular to the filaments and the magnetic field, the spectral power is on average more than an order of magnitude larger than parallel. In the most extreme case the anisotropy reaches locally a factor of 130. Anisotropies increase on average with spatial frequency as predicted by Goldreich and Sridhar, at the same time the Kolmogorov spectral index remains almost unchanged. The strongest anisotropies are observable for a narrow range in velocity and decay with a power law index close to --8/3, almost identical to the average isotropic spectral index of $-2.9<\gamma <-2.6$. HI filaments, associated with linear polarization structures in LOFAR observations in direction to 3C196, show turbulence spectra with marked anisotropies. Decaying anisotropies appear to indicate that we witness an ongoing shock passing the HI and affecting the observed Faraday depth.

arXiv commentminor errors corrected, 15 pages, 29 figures, accepted for publication by A&A

References in corpus (29)

• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• Reconnection in a Weakly Stochastic Field
• The Anisotropy of MHD Alfvénic Turbulence
• The Millennium Arecibo 21-CM Absorption Line Survey. II. Properties of the Warm and Cold Neutral Media
• Velocity Modification of HI Power Spectrum
• GASS: The Parkes Galactic All-Sky Survey. I. Survey Description, Goals, and Initial Data Release
• 3D maps of the local ISM from inversion of individual color excess measurements
• The Millennium Arecibo 21-cm Absorption Line Survey. IV. Statistics of Magnetic Field, Column Density, and Turbulence
• Magnetically Aligned HI Fibers and the Rolling Hough Transform
• GASS: The Parkes Galactic All-Sky Survey. II. Stray-Radiation Correction and Second Data Release
• The Effelsberg-Bonn HI Survey: Milky Way gas. First data release
• On the origin of non self-gravitating filaments in the ISM
• Velocity and density spectra of the Small Magellanic Cloud
• GASS: The Parkes Galactic All-Sky Survey. Update: improved correction for instrumental effects and new data release
• FIRBACK: III. Catalog, Source counts, and cosmological implications of the 170 micron ISO Deep survey
• Astrophysical hydromagnetic turbulence
• Velocity centroids as tracers of the turbulent velocity statistics
• Southern Galactic Plane Survey Measurements of the Spatial Power Spectrum of Interstellar H I in the Inner Galaxy
• Magnetically Dominated Strands of Cold Hydrogen in the Riegel-Crutcher Cloud
• Linear polarization structures in LOFAR observations of the interstellar medium in the 3C196 field
• GHIGLS: HI mapping at intermediate Galactic latitude using the Green Bank Telescope
• High resolution 21 cm mapping of the Ursa Major Galactic cirrus: power spectra of the high-latitude HI gas
• The structure of the thermally bistable and turbulent atomic gas in the local interstellar medium
• Cold Milky Way Hi gas in filaments
• Interpreting Power Anisotropy Measurements in Plasma Turbulence
• Extending Velocity Channel Analysis for Studying Turbulence Anisotropies
• Galactic interstellar filaments as probed by LOFAR and Planck
• Cygrid: A fast Cython-powered convolution-based gridding module for Python
• Physical properties of a very diffuse HI structure at high Galactic latitude

Cited by in corpus (24)

• HI4PI: A full-sky HI survey based on EBHIS and GASS
• WALLABY -- An SKA Pathfinder HI Survey
• Mapping the Magnetic Interstellar Medium in Three Dimensions Over the Full Sky with Neutral Hydrogen
• IMAGINE: A comprehensive view of the interstellar medium, Galactic magnetic fields and cosmic rays
• On the formation of density filaments in the turbulent interstellar medium
• Atomic and Ionized Microstructures in the Diffuse Interstellar Medium
• Dust polarization and ISM turbulence
• Relative distribution of cosmic rays and magnetic fields
• TurbuStat: Turbulence Statistics in Python
• Anisotropies in Compressible MHD Turbulence: Probing Magnetic Fields and Measuring Magnetization
• Magnetically aligned straight depolarisation canals and the rolling Hough transform
• HI anisotropies associated with radio-polarimetric filaments. Steep power spectra associated with cold gas
• Faraday tomography of LoTSS-DR2 data: I. Faraday moments in the high-latitude outer Galaxy and revealing Loop III in polarisation
• The multiphase and magnetized neutral hydrogen seen by LOFAR
• Nature of Striation in 21 cm Channel Maps: Velocity Caustics
• Probing the cold neutral medium through HI emission morphology with the scattering transform
• First look at the multiphase interstellar medium with synthetic observations of low-frequency Faraday tomography
• Turbulent power distribution in the local interstellar medium
• Turbulent power spectrum in warm and cold neutral medium using the Galactic HI 21 cm emission
• A Comparison of Multi-Phase Magnetic Field Tracers in a High-Galactic Latitude Region of the Filamentary Interstellar Medium
• The physical and the geometrical properties of simulated cold HI structures
• Magnetized Filament Models for Diverging Plasma Lenses
• Associating LOFAR Galactic Faraday structures with the warm neutral medium
• Diagnosing Turbulence in the Neutral and Molecular Interstellar Medium of Galaxies