A New Method for Constraining Molecular Cloud Thickness: A study of Taurus, Perseus and Ophiuchus

Abstract

The core velocity dispersion (CVD) is a potentially useful tool for studying the turbulent velocity field of molecular clouds. CVD is based on centroid velocities of dense gas clumps, thus is less prone to density fluctuation and reflects more directly the cloud velocity field. Prior work demonstrated that the Taurus molecular cloud CVD resembles the well-known Larson's linewidth-size relation of molecular clouds. In this work, we studied the dependence of the CVD on the line-of-sight thickness of molecular clouds, a quantity which cannot be measured by direct means. We produced a simple statistical model of cores within clouds and analyzed the CVD of a variety of hydrodynamical simulations. We show that the relation between the CVD and the 2D projected separation of cores ($L_{2D}$) is sensitive to the cloud thickness. When the cloud is thin, the index of CVD-$L_{2D}$ relation ($\gamma$ in the relation CVD$\sim L_{2D}^{\gamma }$) reflects the underlying energy spectrum ($E(k)\sim k^{-\beta }$) in that $\gamma \sim (\beta -1)/2$. The CVD-$L_{2D}$ relation becomes flatter ($\gamma \to 0$) for thicker clouds. We used this result to constrain the thicknesses of Taurus, Perseus, and Ophiuchus. We conclude that Taurus has a ratio of cloud depth to cloud length smaller than about 1/10-1/8, i.e. it is a sheet. A simple geometric model fit to the linewidth-size relation indicates that the Taurus cloud has a $\sim 0.7$ pc line-of-sight dimension. In contrast, Perseus and Ophiuchus are thicker and have ratios of cloud depth to cloud length larger than about 1/10-1/8.

ApJ accepted, with 14 pages, 16 figures

References in corpus (10)

• Theory of Star Formation
• Radiation-Hydrodynamic Simulations of Collapse and Fragmentation in Massive Protostellar Cores
• The Mass Distribution and Lifetime of Prestellar Cores in Perseus, Serpens, and Ophiuchus
• The Effects of Radiative Transfer on Low-Mass Star Formation
• The COMPLETE Survey of Star-Forming Regions: Phase I Data
• The Five College Radio Astronomy Observatory CO Mapping Survey of the Taurus Molecular Cloud
• Probing the Turbulence Dissipation Range and Magnetic Field Strengths in Molecular Clouds
• The Kinematics of Molecular Cloud Cores in the Presence of Driven and Decaying Turbulence: Comparisons with Observations
• Outflows and Bubbles in Taurus: Star-formation Feedback Sufficient to Maintain Turbulence
• Molecular Clouds in the North American and Pelican Nebulae: Structures

Cited by in corpus (18)

• Probing accretion of ambient cloud material into the Taurus B211/B213 filament
• Star-Gas Surface Density Correlations in Twelve Nearby Molecular Clouds I: Data Collection and Star-Sampled Analysis
• Striations in molecular clouds: Streamers or MHD waves?
• Measuring Turbulence with Young Stars in the Orion Complex
• Turbulence in Milky Way Star-Forming Regions Traced by Young Stars and Gas
• Anisotropies in Compressible MHD Turbulence: Probing Magnetic Fields and Measuring Magnetization
• The SOFIA FEEDBACK Legacy Survey: Dynamics and mass ejection in the bipolar HII region RCW 36
• Measuring magnetization with rotation measures and velocity centroids in supersonic MHD turbulence
• Studies of Turbulence Dissipation in Taurus Molecular Cloud with Core Velocity Dispersion (CVD)
• Application of Convolutional Neural Networks to Identify Stellar Feedback Bubbles in CO Emission
• Physical and chemical structure of the Serpens filament -- fast formation and gravity-driven accretion
• Gas phase Elemental abundances in Molecular cloudS (GEMS) VI. A sulphur journey across star-forming regions: study of thioformaldehyde emission
• Projected velocity statistics of interstellar turbulence
• Turbulence in the Tail of a Jellyfish Galaxy
• QUIJOTE Scientific results. III. Microwave spectrum of intensity and polarization in the Taurus molecular cloud Complex and L1527
• Studying the chemical and kinematical structures of dense cores TMC-1C, L1544, and TMC-1 in the Taurus molecular cloud using the CCS and NH3 observations
• Robustness of Synthetic Observations in Producing Observed Core Properties: Predictions for the TolTEC Clouds to Cores Legacy Survey
• A Probabilistic Model to Estimate Number Densities from Column Densities in Molecular Clouds