Turbulent power distribution in the local interstellar medium

Abstract

Context: The interstellar medium (ISM) on all scales is full of structures that can be used as tracers of processes that feed turbulence. Aims: We used HI survey data to derive global properties of the angular power distribution of the local ISM. Methods: HI4PI observations on an nside = 1024 HEALPix grid and Gaussian components representing three phases, the cold, warm, and unstable lukewarm neutral medium (CNM, WNM, and LNM), were used for velocities $|v_{\mathrm{LSR}}|\le 25$ \kms. For high latitudes $|b|>20°$ we generated apodized maps. After beam deconvolution we fitted angular power spectra. Results: Power spectra for observed column densities are exceptionally well defined and straight in log-log presentation with 3D power law indices $\gamma \ge -3$ for the local gas. For intermediate velocity clouds (IVCs) we derive $\gamma =-2.6$ and for high velocity clouds (HVCs) $\gamma =-2.0$. Single-phase power distributions for the CNM, LNM, and WNM are highly correlated and shallow with $\gamma \sim -2.5$ for multipoles $l\le 100$. Excess power from cold filamentary structures is observed at larger multipoles. The steepest single-channel power spectra for the CNM are found at velocities with large CNM and low WNM phase fractions. Conclusions: The phase space distribution in the local ISM is configured by phase transitions and needs to be described with three distinct different phases, being highly correlated but having distributions with different properties. Phase transitions cause locally hierarchical structures in phase space. The CNM is structured on small scales and is restricted in position-velocity space. The LNM as an interface to the WNM envelops the CNM. It extends to larger scales than the CNM and covers a wider range of velocities. Correlations between the phases are self-similar in velocity.

23 pages, 33 figures, A&A in press

References in corpus (67)

• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• Interstellar Turbulence I: Observations and Processes
• The Neutral Atomic Phases of the ISM in the Galaxy
• 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
• Turbulent molecular clouds
• Thermal condensation in a turbulent atomic hydrogen flow
• Interstellar Turbulence II: Implications and Effects
• The Millennium Arecibo 21-cm Absorption Line Survey. IV. Statistics of Magnetic Field, Column Density, and Turbulence
• The outer scale of turbulence in the magneto-ionized Galactic interstellar medium
• Magnetically Aligned HI Fibers and the Rolling Hough Transform
• Planck intermediate results. XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes
• Planck Early Results XXIV: Dust in the diffuse interstellar medium and the Galactic halo
• Planck 2018 results. XI. Polarized dust foregrounds
• GASS: The Parkes Galactic All-Sky Survey. II. Stray-Radiation Correction and Second Data Release
• On the universality of interstellar filaments: theory meets simulations and observations
• The Effelsberg-Bonn HI Survey: Milky Way gas. First data release
• HIPASS High-Velocity Clouds: Properties of the Compact and Extended Populations
• A Fractal Analysis of the HI Emission from the Large Magellanic Cloud
• Dark matter in the Milky Way, II. the HI gas distribution as a tracer of the gravitational potential
• 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
• Characterizing Magnetohydrodynamic Turbulence in the Small Magellanic Cloud
• The link between molecular cloud structure and turbulence
• The 21-SPONGE HI Absorption Line Survey II: The temperature of Galactic HI
• Southern Galactic Plane Survey Measurements of the Spatial Power Spectrum of Interstellar H I in the Inner Galaxy
• Studying Turbulence using Doppler-broadened lines: Velocity Coordinate Spectrum
• Tracing magnetic fields with spectroscopic channel maps
• Power Spectrum of the density of cold atomic gas in the Galaxy towards Cas A and Cygnus A
• Obtaining Spectra of Turbulent Velocity from Observations
• The Local Volume HI Survey (LVHIS)
• Velocity Spectrum for HI at High Latitudes
• 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
• A New 1.4GHz Radio Continuum Map of the Sky South of Declination +25 deg
• The structure of the thermally bistable and turbulent atomic gas in the local interstellar medium
• Cold and Warm Atomic Gas around the Perseus Molecular Cloud. II. The Impact of High Optical Depth on the HI Column Density Distribution and Its Implication for the HI-to-H2 Transition
• Cold Milky Way Hi gas in filaments
• Probing interstellar turbulence in cirrus with deep optical imaging: no sign of energy dissipation at 0.01 pc scale
• The Physical Nature of Neutral Hydrogen Intensity Structure
• Properties of cold and warm HI gas phases derived from a Gaussian decomposition of HI4PI data
• MHD Turbulence as a Foreground for CMB Studies
• Modelling and simulation of large-scale polarized dust emission over the southern Galactic cap using the GASS HI data
• Optically thick HI does not dominate dark gas in the local ISM
• The Multi-phase Turbulence Density Power Spectra in the Perseus Molecular Cloud
• Loops and spurs: The angular power spectrum of the Galactic synchrotron background
• DHIGLS: DRAO H I Intermediate Galactic Latitude Survey
• A kinematic study of the neutral and ionised gas in the irregular dwarf galaxies IC 4662 and NGC 5408
• Magnetically aligned straight depolarisation canals and the rolling Hough transform
• HI anisotropies associated with radio-polarimetric filaments. Steep power spectra associated with cold gas
• Anisotropies in the HI gas distribution toward 3C196
• Cygrid: A fast Cython-powered convolution-based gridding module for Python
• HI Observations of an Ultra-Compact High-Velocity Cloud
• HI 21 cm opacity fluctuations power spectra towards Cassiopeia A
• Characterizing the Turbulent Properties of the Starless Molecular Cloud MBM16
• Tiny scale opacity fluctuations from VLBA, MERLIN and VLA observations of HI absorption toward 3C 138
• Angular Power Spectra with Finite Counts
• The galactic foreground angular spectra
• Physical properties of a very diffuse HI structure at high Galactic latitude
• Comment on Clark et al. (2019) "The Physical Nature of Neutral Hydrogen Intensity Structure"
• Sheets, filaments and clumps - high resolution simulations of how the thermal instability can form molecular clouds
• Gaussian decomposition of HI surveys. IV. Galactic intermediate- and high-velocity clouds
• Turbulent power spectrum in warm and cold neutral medium using the Galactic HI 21 cm emission
• Galactic Magnetic Turbulence from Radio data

Cited by in corpus (6)

• GASKAP-HI Pilot Survey Science I: ASKAP Zoom Observations of HI Emission in the Small Magellanic Cloud
• HI filaments are cold and associated with dark molecular gas. HI4PI based estimates of the local diffuse CO-dark H2 distribution
• Technique for separating velocity and density contributions in spectroscopic data and its application to studying turbulence and magnetic fields
• Small-Scale HI Channel Map Structure is Cold: Evidence from Na I Absorption at High Galactic Latitudes
• Neutral hydrogen filaments in interstellar media: Are they physical?
• Diagnosing Turbulence in the Neutral and Molecular Interstellar Medium of Galaxies