Book contents
- Frontmatter
- Contents
- Preface
- Turbulence in the Interstellar Medium: a Retrospective Review
- Mechanism of Formation of Atmospheric Turbulence Relevant for Optical Astronomy
- Properties of Atomic Gas in Spiral Galaxies
- Turbulence in the Ionized Gas in Spiral Galaxies
- Probing Interstellar Turbulence in the Warm Ionized Medium using Emission Lines
- The Spectrum & Galactic Distribution of MicroTurbulence in Diffuse Ionized Gas
- Small Scale Structure and Turbulence in the Interstellar Medium
- What is the Reynolds Number of the Reynolds' Layer?
- Photoionized Gas in the Galactic Halo
- Turbulent Heating of the Diffuse Ionized Gas
- Cosmic Rays in Interstellar Turbulence
- Turbulence in Line-Driven Stellar Winds
- An Introduction to Compressible MHD Turbulence
- Turbulence in Atomic Hydrogen
- Supershells in Spiral Galaxies
- The Size Distribution of Superbubbles in the Interstellar Medium
- Large-Scale Motions in the ISM of Elliptical and Spiral Galaxies
- Vortical Motions Driven by Supernova Explosions
- The Intermittent Dissipation of Turbulence: is it Observed in the Interstellar Medium?
- Chemistry in Turbulent Flows
- Supersonic Turbulence in Giant Extragalactic HII Regions
- Turbulence in HII regions: New results
- Hypersonic Turbulence of H2O Masers
- Water Masers Tracing Alfvenic Turbulence and Magnetic Fields in W51 M and W49 N
- Turbulence in the Ursa Major cirrus cloud
- The Collisions of HVCs with a Magnetized Gaseous Disk
- The Initial Stellar Mass Function as a Statistical Sample of Turbulent Cloud Structure
- The Structure of Molecular Clouds: are they Fractal?
- Diagnosing Properties of Turbulent Flows from Spectral Line Observations of the Molecular Interstellar Medium
- Centroid Velocity Increments as a Probe of the Turbulent Velocity Field in Interstellar Molecular Clouds
- High-Resolution C18O Mapping Observations of Heiles' Cloud 2 – Statistical Properties of the Line Width –
- Observations of Magnetic Fields in Dense Interstellar Clouds: Implications for MHD Turbulence and Cloud Evolution
- The Density PDFs of Supersonic Random Flows
- Turbulence as an Organizing Agent in the ISM
- Turbulence and Magnetic Reconnection in the Interstellar Medium
- The Evolution of Self-Gravitating, Magnetized, Turbulent Clouds: Numerical Experiments
- Super–Alfvénic Turbulent Fragmentation in Molecular Clouds
- Decay Timescales of MHD Turbulence in Molecular Clouds
- Numerical Magnetohydrodynamic Studies of Turbulence and Star Formation
- Direct Numerical Simulations of Compressible Magnetohydrodynamical Turbulence
- Fragmentation in Molecular Clouds: The Formation of a Stellar Cluster
- Accretion Disk Turbulence
- List of participants
Diagnosing Properties of Turbulent Flows from Spectral Line Observations of the Molecular Interstellar Medium
Published online by Cambridge University Press: 04 August 2010
- Frontmatter
- Contents
- Preface
- Turbulence in the Interstellar Medium: a Retrospective Review
- Mechanism of Formation of Atmospheric Turbulence Relevant for Optical Astronomy
- Properties of Atomic Gas in Spiral Galaxies
- Turbulence in the Ionized Gas in Spiral Galaxies
- Probing Interstellar Turbulence in the Warm Ionized Medium using Emission Lines
- The Spectrum & Galactic Distribution of MicroTurbulence in Diffuse Ionized Gas
- Small Scale Structure and Turbulence in the Interstellar Medium
- What is the Reynolds Number of the Reynolds' Layer?
- Photoionized Gas in the Galactic Halo
- Turbulent Heating of the Diffuse Ionized Gas
- Cosmic Rays in Interstellar Turbulence
- Turbulence in Line-Driven Stellar Winds
- An Introduction to Compressible MHD Turbulence
- Turbulence in Atomic Hydrogen
- Supershells in Spiral Galaxies
- The Size Distribution of Superbubbles in the Interstellar Medium
- Large-Scale Motions in the ISM of Elliptical and Spiral Galaxies
- Vortical Motions Driven by Supernova Explosions
- The Intermittent Dissipation of Turbulence: is it Observed in the Interstellar Medium?
- Chemistry in Turbulent Flows
- Supersonic Turbulence in Giant Extragalactic HII Regions
- Turbulence in HII regions: New results
- Hypersonic Turbulence of H2O Masers
- Water Masers Tracing Alfvenic Turbulence and Magnetic Fields in W51 M and W49 N
- Turbulence in the Ursa Major cirrus cloud
- The Collisions of HVCs with a Magnetized Gaseous Disk
- The Initial Stellar Mass Function as a Statistical Sample of Turbulent Cloud Structure
- The Structure of Molecular Clouds: are they Fractal?
- Diagnosing Properties of Turbulent Flows from Spectral Line Observations of the Molecular Interstellar Medium
- Centroid Velocity Increments as a Probe of the Turbulent Velocity Field in Interstellar Molecular Clouds
- High-Resolution C18O Mapping Observations of Heiles' Cloud 2 – Statistical Properties of the Line Width –
- Observations of Magnetic Fields in Dense Interstellar Clouds: Implications for MHD Turbulence and Cloud Evolution
- The Density PDFs of Supersonic Random Flows
- Turbulence as an Organizing Agent in the ISM
- Turbulence and Magnetic Reconnection in the Interstellar Medium
- The Evolution of Self-Gravitating, Magnetized, Turbulent Clouds: Numerical Experiments
- Super–Alfvénic Turbulent Fragmentation in Molecular Clouds
- Decay Timescales of MHD Turbulence in Molecular Clouds
- Numerical Magnetohydrodynamic Studies of Turbulence and Star Formation
- Direct Numerical Simulations of Compressible Magnetohydrodynamical Turbulence
- Fragmentation in Molecular Clouds: The Formation of a Stellar Cluster
- Accretion Disk Turbulence
- List of participants
Summary
I describe the multivariate technique of Principal Component Analysis and its application to spectroscopic imaging data of the molecular interstellar medium. The technique identifies differences in line profiles with respect to the noise level at various scales. It is assumed that such differences arise from fluctuations within turbulent flows. From the resultant eigenvectors and eigenimages, a size line width relationship, (δv ∼ τα), can be constructed which describes the relationship between the magnitude of velocity fluctuations and the angular scale over which these occur for a given region. From a sample of selected molecular regions in the outer Galaxy, I find the power law exponent varies from 0.4 to 0.7. Thus, the turbulent flows within molecular regions of the Galaxy do not follow the Kolmogorov-Obukhov relation for incompressible turbulence. Implications of these results are discussed with respect to the injection and dissipation of kinetic energy in molecular regions.
Introduction
In the early, pioneering days of millimeter wave astronomy, the presence of turbulent flows within molecular regions of the Galaxy was inferred from the supersonic line widths of CO spectra. Since that time, telescope and detector technology has advanced such that one can now routinely construct detailed images of molecular emission from which the properties of interstellar turbulence can, in principle, be derived. In practice, statistical descriptions of the observations are required to fully exploit the available information.
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- Interstellar Turbulence , pp. 198 - 202Publisher: Cambridge University PressPrint publication year: 1999
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