Turbulence in the Ionized Gas of the Orion Nebula

Abstract

In order to study the nature, origin, and impact of turbulent velocity fluctuations in the ionized gas of the Orion Nebula, we apply a variety of statistical techniques to observed velocity cubes. The cubes are derived from high resolving power ($R\approx 40,000$) longslit spectroscopy of optical emission lines that span a range of ionizations. From Velocity Channel Analysis (VCA), we find that the slope of the velocity power spectrum is consistent with predictions of Kolmogorov theory between scales of 8 and 22 arcsec (0.02 to 0.05 pc). The outer scale, which is the dominant scale of density fluctuations in the nebula, approximately coincides with the autocorrelation length of the velocity fluctuations that we determine from the second order velocity structure function. We propose that this is the principal driving scale of the turbulence, which originates in the autocorrelation length of dense cores in the Orion molecular filament. By combining analysis of the non-thermal line widths with the systematic trends of velocity centroid versus ionization, we find that the global champagne flow and smaller scale turbulence each contribute in equal measure to the total velocity dispersion, with respective root-mean-square widths of 4-5 km/s. The turbulence is subsonic and can account for only one half of the derived variance in ionized density, with the remaining variance provided by density gradients in photoevaporation flows from globules and filaments. Intercomparison with results from simulations implies that the ionized gas is confined to a thick shell and does not fill the interior of the nebula.

arXiv comment24 pages, 21 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

References in corpus (31)

• The Stellar IMF from Turbulent Fragmentation
• Velocity Modification of HI Power Spectrum
• The Dynamics of Radiation Pressure-Dominated HII Regions
• Gravity or turbulence? II. Evolving column density PDFs in molecular clouds
• Velocity and density spectra of the Small Magellanic Cloud
• Radiation-magnetohydrodynamic simulations of HII regions and their associated PDRs in turbulent molecular clouds
• Kinematics of the Orion Nebula Cluster: Velocity Substructure and Spectroscopic Binaries
• Million-Degree Plasma Pervading the Extended Orion Nebula
• Dynamical HII Region Evolution in Turbulent Molecular Clouds
• Velocity centroids as tracers of the turbulent velocity statistics
• A new density variance - Mach number relation for subsonic and supersonic, isothermal turbulence
• Hydrodynamics of Cometary Compact HII Regions
• A method for reconstructing the variance of a 3D physical field from 2D observations: Application to turbulence in the ISM
• Radiation-magnetohydrodynamic simulations of the photoionisation of magnetised globules
• A MUSE map of the central Orion Nebula (M 42)
• A Census of the Carina Nebula -- II. Energy Budget and Global Properties of the Nebulosity
• On the use of fractional Brownian motion simulations to determine the 3D statistical properties of interstellar gas
• The three dimensional dynamic structure of the inner Orion Nebula
• A method for reconstructing the PDF of a 3D turbulent density field from 2D observations
• Velocity statistics from spectral line data: effects of density-velocity correlations, magnetic field, and shear
• Modification of Projected Velocity Power Spectra by Density Inhomogeneities in Compressible Supersonic Turbulence
• Spectrophotometry of the Huygens Region of the Orion Nebula, the Extended Orion Nebula, and M~43; Scattered Light Systematically Distorts Conditions Derived from Emission-Lines
• High Velocity Features in the Orion Nebula
• Velocity Structure in the Orion Nebula. I. Spectral Mapping in Low-Ionization Lines
• Mach number study of supersonic turbulence: The properties of the density field
• Large Scale Flows from Orion-South
• Turbulence in simulated HII regions
• The Nature and Frequency of Outflows from Stars in the Central Orion Nebula Cluster
• Velocity Structure in the Orion Nebula. II. Emission Line Atlas of Partially Ionized to Fully Ionized Gas
• Structure, Velocity Field and Turbulence in NGC 604
• Obtaining Statistics of Turbulent Velocity from Astrophysical Spectral Line Data

Cited by in corpus (23)

• Nebular spectroscopy: A guide on H II regions and planetary nebulae
• Winds and radiation in unison: a new semi-analytic feedback model for cloud dissolution
• Properties of magnetohydrodynamic modes in compressively driven plasma turbulence
• Radio Measurements of the stellar proper motions in the core of the Orion Nebula Cluster
• Synthetic observations of star formation and the interstellar medium
• Measuring Turbulence with Young Stars in the Orion Complex
• Magnetic fields in star forming systems (I): Idealized synthetic signatures of dust polarization and Zeeman splitting in filaments
• Bow shocks, bow waves, and dust waves. I. Strong coupling limit
• Empirical constraints on the turbulence in QSO host nebulae from velocity structure function measurements
• The classical D-type expansion of spherical H II regions
• Messenger Monte-Carlo MAPPINGS V (M^3) -- A self-consistent three-dimensional photoionization code
• Bow shocks, bow waves, and dust waves. II. Beyond the rip point
• Nature of Striation in 21 cm Channel Maps: Velocity Caustics
• Layers in the Central Orion Nebula
• Supersonic turbulence in Giant HII Regions: clues from 30 Doradus
• Turbulent magnetic field in the HII region Sh 2-27
• Multiline observations of hydrogen, helium, and carbon radio-recombination lines toward Orion A: A detailed dynamical study and direct determination of physical conditions
• Turbulence in compact to giant H II regions
• Anomalous Hydrogen Recombination-Line Ratios in Ultraluminous Infrared Galaxies
• Backscattering and Line Broadening in Orion
• Formation of Orion Fingers
• SDSS-V LVM: Resolving Physical Conditions in the Trifid Nebula
• Diagnosing Turbulence in the Neutral and Molecular Interstellar Medium of Galaxies